New Simplified Chemistry Class 6 ICSE Solutions – Air and Atmosphere

New Simplified Chemistry Class 6 ICSE Solutions – Air and Atmosphere

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

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Exercise

Question 1.
State what do you understand by the term ‘air’. Explain its importance to mankind.
Answer:
Air is a mixture whose composition varies at different intervals of time and different places of the world.
Man cannot survive without air and water and hence air is very essential for survival.

Question 2.
Give a brief account of the discovery of air and the scientists involved.
Answer:

  1. John Mayow (1674) proved air has two components – active and inactive components.
  2. Lavoisier (1789) named active component as oxygen and inactive component as nitrogen
  3. Other scientists (1800’s) discovered noble gases, CO2, water vapours.

Question 3.
What is meant by the term ‘atmosphere’. State the role played by the atmosphere for the survival of mankind.
Answer:
A blanket of air around earth is called atmosphere. Without atmosphere life would not be possible as atmosphere protects us from harmful gases. We could not live without air present in atmosphere. In absence of the atmopshere, the earth would get so cold at night that we would not be able to survive. No CO2 and N2 for plants without atmosphere.

Question 4.
Explain in brief the different layers of the atmosphere and the basic functions of the main layers.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 1
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 2

Question 5.
Describe a simple experiment with the help of a diagram to show that :

(a) Air occupies space
(b) Air has mass
(c) Air exerts pressure
(d) Air is highly compressible

Answer:
(a) Air occupies space :

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 3

  • Press an inverted glass
  • Tilt the tumbler to one side, tumbler over the water.

Observation : On tilting the tumbler, bubbles of air are seen coming out.
Water slowly enters the tumbler to take place of the trapped air in the tumbler.
Conclusion : Air occupies space (the space in the tumbler was occupied by air).

(b) Air has mass :

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 4

  • An inflated balloon is placed on one side of the scale.

Observation : It is seen that the scale moves towards one side.
It moves on the side on which the inflated balloon was placed.
Conclusion : Air has mass.

(c) Air exerts pressure :

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 5

  • Take an open can, fill it with water and heat it. On formation of steam, place the cap on tightly and keep the can aside.

Observation : On condensation of the steam the pressure inside the can reduces.
The air outside, exerts pressure on the can which crumples slowly.
Conclusion : Air exerts pressure.

(d) Air is highly compressible :

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 6

  • A leak proof syringe filled completely with air only (i.e. empty) is taken.

Observation : On pressing the piston of the syringe, the piston moves inwards.
Air (gas) inside the syringe has maximum inter-molecular space and is highly compressible.
Conclusion : Air is highly compressible.

Question 6.
Name the components of air with their approximate percentage by volume in air. Does the percentage by volume of each component remain the same, in the atmosphere of different parts of the world. Explain with reasons.
Answer:
Main components of air are :

  1. Nitrogen
  2. Oxygen

Composition of air by volume :

  1. Nitrogen – 78% or 4/5 th
  2. Oxygen 21% or 1/5 th
  3. Carbon dioxide 0.03 – 0.04%
  4. Inert gases 0.9%

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 7

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 8

Air is a mixture whose composition varies at different intervals of time and different places of the world.

Question 7.
With the help of a labeled diagram, describe a simple experiment to show the presence of oxygen and nitrogen in air using a piece of white phosphorus.
Answer:
Activity to show the presence of oxygen and nitrogen in air using a piece of white phosphorous.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 9

  1. A trough is taken and fdled with water.
  2. Over it is placed a bell-jar marked with five equal parts.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 10
  3. A crucible containing white phosphorus is placed on a cork.
  4. The cork is made to float on the water.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 11
  5. A heated iron rod is them taken.
  6. The phosphorus is ignited with the heated rod.

Observation : Dense white fumes of phosphorus pentoxide (P2O5) are formed when the phosphorus (P) burns in the active component of air (oxygen).
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 12
The rise in the level of water in the bell-jar is by – 1/5
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 13
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 14
The active component of air i.e. oxygen (1/5 of air) is used up in burning.
The remaining inactive component of air i.e. nitrogen (4/ 5 of air) is not used up in burning.

Question 8.
You are given a test tube with two outlets and a bottle of lime water. Using the same, how would you demonstrate experimentally the presence of carbon dioxide in air.
Answer:
Procedure :

  1. Take lime water in a test tube with two outlets ‘A’ and ‘B’ as shown above.
  2. Air is sucked slowly through the outlet ‘B’.
  3. Air moves in through end ‘A’ and passes through the lime water.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 15

Observation : The line water in the test tube turns milky.
Conclusion : Air which is sucked in from and ‘A’ contains carbon dioxide which turns the lime water milky. Hence, air contains – carbon dioxide.

Question 9.
Give a reason why water droplets appear on the outer surface of a tumbler containing ice.
Answer:
Water vapour present in air, condenses on the cooler surface of the tumbler. Hence they condenses into tiny water droplets.

Question 10.
Explain the importance of nitrogen of the air for plant growth.
Answer:
Nitrogen of air is converted to soluble nitrogenous compounds in the soil in the presence of air and moisture. These are absorbed by plants and converted to plant proteins.

Question 11.
Give a reason why nitrogen is filled in food packets and not oxygen.
Answer:
Nitrogen being inert or unreactive is filled into food packets to drive out the oxygen and reduce bacterial growth. The food package then stays well preserved.

Question 12.
State what would happen, if the air above the earth contained mainly oxygen and no nitrogen.
Answer:
Nitrogen is utilised by plants for their growth and development.
Free nitrogen of the air is converted to nitrogen compounds which are absorbed by the plants and converted to plant proteins. In the absence of nitrogen no plants will be survived on the earth.

Question 13.
State the utility of oxygen for respiration in

(a) living organisms
(b) plants.

Answer:
(a) Respiration in living organisms :
Respiration— It is a process whereby living things

  1. Use oxygen from their air to oxidize food substances mainly glucose, in their body cells.
  2. Release energy in the form of heat.
  3. Carbon dioxide and water vapour are also produced and released in the exhaled air.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 16
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 17

Process—

  1. Inhaled air — Oxygen from inhaled air dissolves in the blood stream in the lungs. It is carried to the cells where the food materials i.e. glucose is oxidized by the oxygen.
  2. Exhaled air — Carbon dioxide, water vapour and heat energy diffuse out of the lungs as exhaled air.
  3. Energy liberated — The energy liberated is utilized for metabolic activities and maintains the body temperature.

(b) Respiration in plants :

  1. Plants respire during the day and night.
  2. Plants— Respire through tiny pores on the surface of the leaves called ‘stomata’.
  3. The stomata help in taking in oxygen of the air and giving out carbon dioxide. Thus, they function as respiratory organs.
  4. Plants do not perform bodily activities and hence need less energy than animals. The rate of respiration in plants is thereby slower than in animals.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 18

Photosynthesis in plants :
Photosynthesis is a process by which green plants prepare their own food in the presence of sunlight and chlorophyll.

  1. In the leaf of a green plant are present leaf cells which contain chloroplasts in which is present a green pigment called chlorophyll.
  2. During photosynthesis which occurs during daytime, carbon dioxide and water in the presence sunlight and chlorophyll is changed into glucose and oxygen is released out.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 19
  3. Hence oxygen in the air is renewed by photosynthesis and therefore the amount of oxygen in air does not get depleted or removed from air.

Question 14.
Compare respiration and combustion-both involving oxygen of the air.
Answer:
Respiration is a process whereby living organisms

  1. Use oxygen from the air to oxidize food substances mainly glucose, in their body cells.
  2. Release energy in the form of heat.
  3. Carbon dioxide and water vapour are also produced and released in the exhaled air.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 20

Combustion or burning, involves oxidation i.e. combination of substances like fuels with oxygen or air generally resulting in production of heat and light.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 21
Carbon dioxide is released into the air as a result of all burning.

Question 15.
Explain the importance of carbon dioxide for
(a) photosynthesis (b) warming the earth’s environment. State what would happen if excess carbon dioxide as a pollutant is released into the atmosphere.
Answer:
(a) During photosynthesis which occurs during daytime, carbon dioxide and water in the presence of sunlight and chlorophyll is changed into carbohydrates and oxygen is released out.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 22
Hence oxygen in the air is renewed by photosynthesis and therefore the amount of oxygen in air does not get depleted or removed from air.
(b) Infrared (I.R.), visible rays and ultra violet (U.V.) rays are present in the earth’s surface.
The reflected U.V. rays from the earth’s surface pass through the carbon dioxide in the atmosphere, but the
I. R. rays are prevented by the carbon dioxide from being radiated out of the earth’s surface. This results in the earth’s environment staying warm.
The thick CO2 layer prevents the heat radiations from being radiated out which reason :
Reason : It results into rise in global temperature.

Question 16.
State in brief how water vapour in the atmosphere determines the climatic conditions.
Answer:
Water vapour in the atmosphere in excess :

(a) Minimizes the rate of evaporation.
(b) Produces rain, mist etc. thereby determining climatic conditions.

The rain serves as a natural source of water for plants and animals.

Question 17.
Give a reason why two different rare (inert) gases find application in advertisement signs and fluorescent bulbs.
Answer:

  1. Neon – In neon sign advertisements
    A brilliant red glow is seen on passage of an electric current through neon gas at low pressure.
    The colour can be changed by mixing mercury vapour and argon with neon.
  2. Xenon – In fluorescent bulbs flash bulbs and lasers. It emits intense white light in discharge tubes.

Question 18.
A mixture has a variable composition. Give three other reasons why air is considered a mixture and not a compound.
Answer:
Air is a mixture because :

  1. Air has no formula, a mixture has no formula whereas compound has a formula.
  2. No energy changes are involved to form air from various gases.
  3. When air is formed out of its constituents no change in mass nor change in volume takes place.
  4. Properties of air vary from place to place and time to time. i.e. there is more CO2 in towns as compared to villages where more oxygen prevales as compared to towns.
  5. Components of air can be separated by simple physical methods.

Question 19.
State a reason why there is a balance in the amount of carbon dioxide in the air, even though carbon dioxide is released into the atmopshere by various processes.
Answer:
By the way of photosynthesis in plants which which occurs during daytime, carbon dioxide and water in the presence of sunlight and chlorophyll is changed into carbohydrates and oxygen is released out.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 23
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 24
Hence, oxygen in the air is renewed by photosynthesis and therefore the amount of oxygen in air does hot get depleted or removed from air.

Question 20.
Name three different appliances where air is utilized.
Answer:

  1. Vehicles – Run on tyres which are inflated with air.
  2. Brake mechanisms – Of trains and other machines, work on compressed air.
  3. Pumps and siphons – Work on air pressure.

Objective Type Questions

Q.1. Match the statements in List I with the correct answers in List II.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 25
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 26
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 27

Q.2. The diagrams below represents an experiment to show the presence of a – component of air.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 28

Question 1.
State why air is sucked from – outlet ‘B’ and not from outlet ‘A’.
Answer:
Because if we suck from ‘A’, lime water will be sucked out.

Question 2.
State why the air is sucked ‘slowly’ from the outlet ‘B’
Answer:
Because if air is sucked fast, lime water will also be sucked out.

Question 3.
State the observation seen after completion of the experiment.
Answer:
Lime water turns milky.

Question 4.
State the reason for the above observation seen.
Answer:
The reason is the formation of CO2.

Question 5.
Name another component which if present in air as a pollutant – would have given a similar observation.
Answer:
Sulphur dioxide.

Q.3. Complete the statements given below by filling in the blanks with the correct word/s from the word/s in bracket.

Question 1.
The ____ [atmosphere /troposphere/stratosphere] is a layer which extends upto about 10-50 kms. above the earth.
Answer:
The stratosphere is a layer which extends upto about 10-50 kms. above the earth.

Question 2.
____ [helium/hydrogen sulphide] is an example of a pollutant present in air.
Answer:
Hydrogen sulphide is an example of a pollutant present in air.

Question 3.
The component of air used in photosynthesis is ____ and the products of photosynthesis is ____ [oxygen/carbon dioxide/nitrogen].
Answer:
The component of air used in photosynthesis is carbon dioxide and the products of photosynthesis is oxygen.

Question 4.
The product formed which is common to both combustion and respiration is ____ [oxygen/ carbon dioxide/nitrogen dioxide]
Answer:
The product formed which is common to both combustion and respiration is nitrogen dioxide.

Question 5.
The component of air which is variable in air above sea level and in air in general ____ [oxygen/ nitrogen/water vapour].
Answer:
The component of air which is variable in air above sea level and in air in general water vapour.

Q.4. Name the following :

Question 1.
The product formed when phosphorus burns in oxygen.
Answer:
Phosphorus pentoxide (P2O5).

Question 2.
The layer of atmosphere which contains the ozone layer.
Answer:
Stratosphere.

Question 3.
The active component of air which supports combustion and is used up in burning.
Answer:
Oxygen.

Question 4.
The main, rare (inert) gas present in air.
Answer:
Argon.

Question 5.
The component of air which is present more in industrial areas.
Answer:
Carbon monoxide, sulphur dioxide, oxides of nitrogen, hydrogen sulphide, dust particles.

Question 6.
The type of bacteria which directly absorb nitrogen from the air and converted soluble nitrates in the soil.
Answer:
Symbiotic bacteria.

Question 7.
The product of respiration released in exhaled ajr, other than carbon dioxide.
Answer:
Water vapour and energy.

Question 8.
An inert gas which has a low boiling point and is used for producing very low temperatures.
Answer:
Helium.

Question 9.
A process which removes carbon dioxide from the air.
Answer:
Photosynthesis.

Question 10.
The component of air which does not support combustion.
Answer:
Nitrogen.

Q.5. State whether the following statements are ‘true’ or ‘false’. If false write the correct statement.

1. The mesosphere in the atmosphere, contains most of the air, fit for respiration.
Ans. False.
Correct : The troposphere in the atmosphere, contains most of the air, fit for respiration.

2. The percentage of carbon dioxide in the air is between 0.2 to 0.4%.
Ans. True.

3. Carbon dioxide, water vapour and energy in the form of heat are evolved during respiration.
Ans. True.

4. Photosynthesis is a process by which green plants prepare their own food in the presence of sunlight and chlorophyll.
Ans. True.

5. Air is a mixture and not a compound since the components of air cannot be separated by physical methods.
Ans. False :
Correct : Air is a mixture and not a compound since the components of air – can be separated by physical methods.

Q.6. Give word equations for the following conversions.

Question 1.
Nitrogen of the air to nitric oxide.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 30
The nitric oxide reacts with oxygen to give nitrogen dioxide.

Question 2.
Nitric oxide to nitrogen dioxide.
Answer:
Nitric oxide + Oxygen → Nitrogen dioxide
The nitrogen dioxide further reacts with oxygen and water vapour of the air to give nitric acid.

Question 3.
Nitrogen dioxide to nitric acid.
Answer:
Nitrogen dioxide + Oxygen + Water → Nitric acid
The nitric acid formed comes down with the rain and combines with the carbonates in the soil to form soluble nitrates.

Question 4.
Nitric acid to soluble nitrates in the soil.
Answer:
Calcium carbonate + Nitric acid → Calcium nitrate + water + carbon dioxide
The water soluble calcium nitrates are absorbed by the plants and converted to plant proteins.

Question 5.
Carbon dioxide in air to carbohydrates in plants.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 5 Air and Atmosphere 29
Carbon dioxide and water in the presence of sunlight and chlorophyll is changed into carbohydrated and oxygen is released out.

New Simplified Chemistry Class 6 ICSE Solutions – Water

New Simplified Chemistry Class 6 ICSE Solutions – Water

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

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Exercise

Question 1.
State the sources of water

(a) on the earth’s surface
(b) below the earth’s surface.

Answer:
(a) Sources of water on the earth’s surface are —

  1. Snow, frost — Snow and frost are the natural forms of water present. They are found in the solid state.
  2. Rain water — The purest form of natural water almost free from impurities is rain water.
    Rain water may dissolve oxygen, nitrogen & carbon dioxide gas forming weak acids. In industrial regions, nitrogen dioxide and sulphur dioxide evolved may dissolve in rain water forming nitric acid & sulphuric acid which causes acid rain.
  3. River water — It is one of the impure forms of natural water since most forms of surface water enters into river water. It contains impurities such as sand partides, organic matter, bacteria, mineral salts which dissolve after soil erosion & dissolved gases.
  4. Lake water — It is another impure form of natural water which also contains impurities and other soluble salts.
  5. Sea water — The most impure form of natural water containing over 3% soluble salts including sodium chloride. It also contains salts of calcium & magnesium.

(b) Sources of Water below the earth’s surface are —

  1. Well water — Above the impervious rocky layers, of the earth’s surface is well water which contains soluble impurities.
  2. Spring water — Natural water accumulated above the rocky layers of the earth which forcefully comes out under pressure from the earth’s surface is spring water & contains soluble salts & minerals.

Question 2.
Give the importance of water in

(a) life processes
(b) household purpose
(c) fire fighting
(d) transportation.

Answer:
The importance of the Water is as follows :

(a) Life processes — Water is used by all plants, animals & humans for carrying out various metabolic processes including photosynthesis by plants & excretion by animals & humans.
(b) Household purposes — Water finds numerous applications, such as watering plants, washing clothes, cooking, bathing, cleaning etc.
(c) Fire fighting — Water is used for extinguishing fires either directly or as a constituent in a fire extinguisher.
(d) Transportation — Water serves as a habitat for marine life i.e. preferred place for an organism to live.

Question 3.
Explain how water plays an important role in

(a) industry
(b) agriculture.

Answer:
(a) Uses of Water in Industry :

  1. Water generates electricity in hydroelectric power stations.
  2. Water generates steam in boilers, used for various industrial purposes.
  3. Water finds application in chemical & other industries for cooling & cleaning operations.

(b) Uses of Water in Agriculture :

  1. In agriculture water finds importance in irrigation, production of crops & as a medium for spraying pesticides.

Question 4.
Give the occurrence of water in the three different states i.e. solid, liquid and gaseous.
Answer:
The Occurrence of water in three different states are :

  1. Solid state — As snow and frost.
  2. Liquid state — In sea water, river water and lake water.
  3. Gaseous state — As water vapour in air the amount depending on climatic conditions.

Question 5.
Draw a labelled diagram to show the change of state of water from solid state to liquid state to gaseous state starting from ice.
Answer:

New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 1

Question 6.
Explain the term water cycle. State the main points to show how water moves from the earth’s surface to the atmosphere and back to the earth’s surface as rain.
Answer:
The water cycle is a natural process by which the circulation of water takes place from the earth’s surface to the atmosphere and back to the earth’s surface as rain water.
The Process of water cycle is discussed below :
From The Earth’S Surface – To The Atmosphere

  1. Evaporation — The sun’s rays fall on the earth & warm its surface & the air above it.
    The heat evaporates the water from the streams, rivers & the sea.
  2. Water [mainly in the form of water vapour] is also added to the atmosphere by —
    (a) Respiration by living organisims Glucose + Oxygen → carbon dioxide + water + energy
    (b) Burning of fossil fuels —
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 2
  3. Formation of clouds — The water vapour along with the warm air rises upwards, where at higher altitudes it condenses into small droplets of water forming clouds.

Back To The Earth’S Surface – As Rain Water

  1. Formation of rain — The clouds float in the atmosphere & when the size of the water droplets increases they fall down on the earth as rain water.
  2. Rain water falls into streams — The rain water is absorbed by the soil collects underground & flows into streams.
  3. Stream water enters rivers & seas — The stream water finds its outlets into rivers & later enters into the seas & oceans.
  4. River & sea water evaporates forming clouds and thus continuing the water cycle.

Question 7.
Give a reason why water is considered a universal solvent.
Answer:
Water is a polar covalent compound. When it comes in contact with any substance it breaks the electrostatic forces holding the molecules of that substance. Thus, the molecules break loose from the substance and hence dissolve in water. Thus, water is called a universal solvent and an alkali is not.

Question 8.
Define the term –

(a) solute
(b) solvent
(c) solution with reference to addition of sodium chloride to water.

Answer:

(a) Solute — The substance which dissolves or disappears in the solvent i.e. liquid to form a solution is called a solute. e.g. sodium chloride.
(b) Solvent — The liquid or medium of dissolution which allows the solute to dissolve in it, so as to form a solution is called a solvent, e.g. water.
(c) Solution — A homogenous mixture of a solute in a solvent is called a solution.

Question 9.
Draw a neat labelled diagram of addition of copper sulphate to water. Label the solute, solvent and solution in the same.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 3

Question 10.
From the following substances given below state which will form a solution in the same.

(a) sodium carbonate
(b) calcium carbonate
(c) charcoal powder
(d) sodium sulphate
(e) table salt
(f) powdered particles of lead from a lead pencil
(g) iron powder
(h) copper filings
(i) sand particles
(j) honey

Answer:

(a) sodium carbonate
(d) sodium sulphate
(e) table salt
(j) honey

Question 11.
Name two gases each

(a) which are soluble in water
(b) which are insoluble in water.

Answer:

(a) The gases which are soluble in water are Carbon dioxide and chlorine
(b) The gases which are not soluble in water are Nitrogen, hydrogen

Question 12.
If ‘X’ g. of potassium nitrate is added to 100 g. of water at 60°C and the salt dissolves completely then —

(a) is ‘X’ g. the solubility of potassium nitrate at 60°C.
(b) is the solution formed – saturated or unsaturated
(c) if on addition ‘X’ + ‘Y’ g. of potassium nitrate to the same amount of water at the same temperature and the solute now just remains behind after stirring then –
(d) is the solution now – saturated or unsaturated
(e) is ‘X’ + ‘Y’ g. the solubility of potassium nitrate.

Answer:
Add ‘X’ g. of solute i.e. potassium nitrate to 100 g. of water 60°C.

  1. Stir the solute i.e. potassium nitrate in water thoroughly.
  2. ‘X’ g. of the solute completely dissolves in water.
  3. Add more solute and again stir thoroughly.
  4. The solute continues to dissolves.
  5. Water i.e. the solvent can dissolve more of the solute at the given temperature.
  6. The solution is therefore is said to be unsaturated.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 4

Add more solute to water till on adding an amount ‘X + Y’ g. of the solute i.e. potassium nitrate to 100 g. of water at 60°C.

  1. The solute just remains behind after stirring.
  2. The solution is now saturated.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 5

A saturated solution cannot dissolve more of the solute at a given temperature.

Question 13.
State whether the following statements are true or false. If false write the correct statement.

(a) Solubility of most solids – decrease with increase in temperature.
Answer:
False.
Correct — Solubility of most solids – increase in temperature.

(b) Distilled water is potable water.
Answer:
False.
Correct — Drinking water is potable water.

(c) The process to remove germs in water is also called sterilization.
Answer:
True.

Question 14.
Differentiate between chemical pollution and thermal pollution.
Answer:
(a) Chemical pollution — A large number of industrial chemicals which include chemicals from paint, textile & dyestuff industry & various acids & salt solutions enter into water when discharged as industrial wastes.

  • Chemical pollutants include — Metallic salt solutions of mercury & lead which cause heavy devastation of marine & plant life.
  • Agricultural wastes include — Poisonous pesticides namely fungicides & insecticides which may also enter underground water through the soil.

(b) Thermal pollution — Certain industries such as the iron & steel industry & numerous chemical plants use large amounts of water for varied functions.

  • The discharged waste water after going through technical processes – is rendered hot & on entering streams of natural water – enhance growth of harmful biological organisms.

Question 15.
State some important steps to avoid pollution of water.
Answer:
Steps to avoid pollution of water are :

(a) Harmful wastes such as oils & chemicals should not enter into the water.
(b) Proper toilets & sewage systems should be used to prevent human excreta, containing disease causing organisms to enter into the water.
(c) Washing of clothes & bathing should be avoided near water sources.
(d) Planting of trees near water sources including river banks also minimizes pollution.
(e) To minimize thermal pollution the water should be cooled before being discharged as a waste.
(f) Man should be made aware through various awareness programmes & media about the harmful effects of water pollution & ways to control it.

Question 16.
State what is meant by the term ‘conservation of water’. State a few water saving methods, which may be used in the home to conserve water.
Answer:
Conservation of water is the means of preventing wastage of water so that clean water can be obtained by preventing pollution of water and by protecting the sources of water.
Need for conservation — Inspite of large quantities of water on the earth’s surface only a small percentage is potable water fit for human consumption and household purposes.
The need for water is ever increasing and hence all sources of water need to be conserved.
The various methods to conserve the water are :

  1. Well should be covered and washing and cleaning should be prevented near a well.
  2. Water saving devices must be used in homes

(a) such as closing running taps and using smaller cisterns in toilets.
(b) checking all leakages in household pipes.
(c) turning off the water tap while brushing teeth and while washing hands.
(d) using less electricity, since power plants also consume substantial amount of water.

Question 17.
Give a reason why :

(a) Conservation of water is essential in spite of the fact that three fourth of the earth’s surface is covered by water.
(b) Polluted water causes disease.
(c) Drip irrigation helps in conservation of water.

Answer:

(a) Because only a small percentage is potable water fit for human consumption and household purposes.
(b) Polluted water acts as a carrier for germs which causes various diseases.
(c) Drip irrigation in agriculture utilizes supply of water in small quantities.

Objective Type Questions

Q.1. Complete the statements by filling in the blanks with the correct word/s.

Question 1.
____is the purest form of water. It may dissolve gases like ____ forming weak acids, (sea water/ lake water/rain water ; chlorine/ammonia/carbon dioxide)
Answer:
Rain water is the purest form of water. It may dissolve gases like carbon dioxide forming weak acids.

Question 2.
Water generates ____ in hydroelectric power stations and ____ in boilers for industrial applications, (carbon dioxide/steam/heat/electricity)
Answer:
Water generates electricity in hydroelectric power stations and steam in boilers for industrial applications.

Question 3.
Water is added to the atmosphere by ____ and ____ (burning of fossil fuels/condensation of vapour/ respiration by living organisms/photosynthesis)
Answer:
Water is added to the atmosphere by burning of fossil fuels and respiration by living organisms.

Question 4.
If potassium nitrate is added to water in a beaker to give a homogeneous mixture, then potassium nitrate is referred to as the ____ water as the ____ and the homogeneous mixture as the ____ (solution/ solute/solvent/saturated solution).
Answer:
If potassium nitrate is added to water in a beaker to give a homogeneous mixture, then potassium nitrate is referred to as the solute, water as the solvent and the homogeneous mixture as the solution.

Question 5.
Water fit for human consumption and drinking purposes is called ____ (distilled water/potable water/rain harvested water).
Answer:
Water fit for human consumption and drinking purposes is called potable water. 

Q.2. State whether the following statements are true or false. If false, write the correct statement.

1. Sea water contains salts of calcium and magnesium.
Ans. True.

2. Water finds application as a means of transporting goods.
Ans. True.

3. On boiling water exists in the liquid state.
Ans. False.
Correct — On boiling water exists in the gaseous state.

4. Respiration uses up water from the atmosphere.
Ans. False.
Correct — Respiration add up water to the atmosphere.

5. Well water exists below the impervious rocky layers of earth.
Ans. False.
Correct — Well water exists above the impervious rocky layers of earth.

6. Sodium carbonate and sodium sulphate do not form an aqueous solution.
Ans. False.
Correct — Sodium carbonate and sodium sulphate form an aqueous solution.

7. If ‘X’ g. of solute is added to 100 g. of water at t°C and the solution formed is a saturated solution, then ‘X’ g. is the solubility of the solute.
Ans. True.

8. Purification of water is carried out to remove – dissolved gases e.g. carbon dioxide and dissolved minerals like magnesium salts.
Ans. True.

9. Water from rivers and lakes is – potable water.
Ans. False.
Correct — Water from rivers and lakes is impure water.

10. Chemical pollutants include metallic salt solution of mercury and lead.
Ans. True.

Q.3. Match the statements in List 1,1-10 with their correct answer in List II, A to J.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 6
New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 7
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 8
New Simplified Chemistry Class 6 ICSE Solutions Chapter 4 Water 9

Q.4. Explain the meaning of the following terms :

  1. Rain water harvesting
  2. Drip irrigation in agriculture
  3. Saturated solution
  4. Conservation of water
  5. Gaseous state of water in air

Answer:

  1. Rain water harvesting which is a means of utilizing rain water instead of allowing it to be wasted to be conducted by building tanks or pits in low lying areas and collecting roof top rain water through pipes into tanks.
  2. Drip irrigation in agriculture utilizes supply of water in small quantities.
  3. A saturated solution cannot dissolve more of the solute at a given temperature.
  4. Conservation of water is the means of preventing wastage of water so that clean water can be obtained by preventing pollution of water and by protecting the sources of water.
    Polluted water acts as a carrier for germs which causes various diseases.
  5. Gaseous state of water in air : Gaseous State as water vapour in air the amount depending on climatic conditions.

Q.5. Name the following :

Question 1.
A chemical used during chlorination of water.
Answer:
Chlorine.

Question 2.
An agricultural pollutant in water.
Answer:
Insecticides.

Question 3.
A solid, ‘natural form of water’.
Answer:
Snow.

Question 4.
The natural process by which circulation of water takes place from earth’s surface to atmosphere and back to earth’s surface.
Answer:
Water cycle.

Question 5.
The liquid or medium of dissolution which allows the solute to dissolve in it.
Answer:
Water (solvent).

New Simplified Chemistry Class 6 ICSE Solutions – Matter

New Simplified Chemistry Class 6 ICSE Solutions – Matter

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Exercise

Question 1.
Explain the term ‘matter’. One kind of matter can be distinguished from another by its physical properties and chemical properties. State the main physical properties of matter.
Answer:
Matter is the basic substance of which all materials are made of

  • Physical Properties — They are those properties which include state, colour, odour, density etc.
  • Chemical Properties — They are properties which include reactions of different materials with different chemical.

Physical Properties of Matter are :

  1. Colour : All matter an be distinguished by their varied – colours.
  2. Odour : Matter shows variation in odour or smell.
  3. Solubility : Matter may vary in solubulity in water or other solvents.
  4. Melting & Boiling Points : Substances variation in their melting and boiling points.

Question 2.
The three main states of matter are solids, liquids and gases. Compare the three states with reference to the following characteristics of matter –

(a) volume
(b) shape
(c) compressibility
(d) diffusion.

Answer:

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 1

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 2

Question 3.
Matter in any state is composed of particles. Compare the three states of matter i.e. solids, liquids and gases with reference to :

(a) intermolecular space
(b) intermolecular force of attraction
(c) movement of particles

Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 3

Question 4.
Describe simple experiments to prove that – solids

(a) occupy space
(b) have mass
(c) have a definite volume

Answer:
(a) occupy space : solid-occupies space –
‘A’-A measuring cylinder is filled with water to a particular mark- ‘A’.
‘B’-A piece of wooden block- is immersed inside the measuring cylinder. The water level rises up.
‘C’- On removal of the block- the water level in the measuring cylinder falls down back to the mark – ‘A’
Conclusion : The block pushes the water out and occupies its space, hence all solids occupy space.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 4
(b) Have mass : A solid has mass
A : A simple scale – is taken, as shown below
B : A solid is placed – on one side of the scale, causes the scale tilts towards one side.
Conclusion : The scale tilts due to the mass of the solid, hence all solids have mass.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 5
(c) Have a definite volume : A solid placed in any container filled with water displace the same amount of water.
Conclusion : Solid displace water and retain their own volume, hence all solids have a definite volume.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 6

Question 5.
Describe simple experiments to prove that – liquids

(a) have mass
(b) have a definite volume
(c) have no definite shape

Answer:
(a) have mass — a liquid occupies mass
Experiment : A liquid placed on one side of the scale, causes the scale to tilt towards one side.
Conclusion : The scale tilts due to the mass of the liquid, hence all liquids have mass.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 7
(b) have a definite volume —
Experiment : A liquid in a measuring cylinder can be poured into any container. The volume of liquid in the container, is the same as that in the measuring cylinder.
Observation : The volume of liquid in the container, is the same as that in the measuring cylinder. Hence, all liquids have a definite volume.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 8
(c) have no definite shape —
Experiment : A liquid poured into any container takes up the shape of each container.
Conclusion : All liquids have no definite shape

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 9

Question 6.
Describe simple experiments to prove that – gases

(a) occupy space
(b) have mass
(c) have no definite volume or shape

Answer:
(a) occupy space —
Experiment :

  • ‘A’ – A glass beaker or bowl is half filled with water.
  • ‘B’ – An empty glass tumbler [which of course contains air] is inverted an lowered inside it.
  • ‘C’ – On tilting the tumbler, air is displaced and bubbles are seen coming out.

Conclusion : Air or gases occupy space.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 10

(b) Have mass —
Experiment :

  • An inflated balloon placed on one side of the scale causes it to tilt towards one side.

Conclusion : The scale tilts due to the mass of the gas, hence all gases have mass.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 11

(c) Have no definite volume or shape —
Experiment :

  • A gas takes up the volume of any enclosed space filling it up completely.

Conclusion : Gases take up any volume and hence all gases have no definite volume.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 12

Question 7.
Explain the term ‘Interconversionof matter’. With reference to ice, water and water vapour show diagrammatically the change of state of matter from solid to liquid to gaseous and back to original state.
Answer:
INTERCONVERSION OF MATTER :
“Change of ,state of matter from one state to another state and back to its original state is called inter – conversion of matter.”
The diagram showing the Change of State of Matter :

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 13

(a) Ice To Water (Melting) : Conversion of a solid into a liquid on heating e.g. ice to water.
(b) Water To Water Vapour (Vaporisation) : Conversion of a – liquid into vapours (or gas) on heating e.g. water to water vapour.
(c) Water Vapour To Water (Liquefaction Or Condensation) : Conversion of VAPOUR (or gas) into a LIQUID on cooling e.g. water vapour to water.
(d) Water To Ice (Solidification Or Freezing) : Conversion of a LIQUID into a SOLID e.g. water to ice.

Question 8.
Explain the terms

(a) melting
(b) vaporization
(c) condensation
(d) freezing
(e) melting point
(f) boiling point.

Answer:
Matter can change from solid to liquid to gaseous state and back to solid state. This is called change of state of matter.

(a) Melting — The process of conversion of a solid into liquid on heating.
e.g. Ice to water. k
(b) Vaporization — The process of conversion of a liquid into vapour on heating.
e.g. Water to water vapour.
(c) Condensation — The process of conversion of vapour into a liquid.
e.g. Water vapour to water.
(d) Freezing — The process of conversion of a liquid into a solid.
e.g. Water to ice.
(e) Melting point — The constant temperature at which a solid melts into a liquid.
M.P. of ice – 0°C.
(f) Boiling point — The constant temperature at which a liquid starts boiling.
B.P. of water – 100°C.

Question 9.
State what would you observe if

(a) sugar is added to pebbles take in a plastic beaker
(b) sand is added to glass balls in a beaker. What would you conclude from this imaginative demonstration.

Answer:

  • Experiment : Add sugar to pebbles taken in a plastic beaker or sand to glass balls in a beaker.
  • Observation : The sugar or the sand goes into the space between the pebbles & the glass balls respectively.
  • Conclusion : An imaginative demonstration to show that intermolecular spaces between particles are occupied easily.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 14

Question 10.
With the help of a simple diagram how would you show that – solids expand on heating.
Answer:
Solids expand on heating can be shown by two different experiments. The experiments are :

  • Experiment A : An iron bar is taken and its length measured accurately.
    The iron bar is then slowly heated for a certain period of time & measured accurately [with a vernier calipers or otherwise]
  • Observation : It is observed that the iron bar has Increased in length on heating.
  • Experiment B : A simple ball & ring apparatus is taken, which consists of a metal ball which can just pass through the circular metal ring.
    The metal ball is then heated for a certain period of time.
  • Observation : After heating, the metal ball does not pass through the ring, since on heating it has expanded in size and hence cannot pass through the ring.
  • Conclusion : All solids expand on heating.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 15

Question 11.
Give reasons for the following :

(a) Solids have a definite shape and are highly rigid while gases have to definite shape and are least rigid.
(b) Sugar can be distinguished from talcum powder using water.
(c) Water on freezing turns into ice.
(d) A bottle of perfume on opening evolves an odour which can be sensed over a long distance.

Answer:

(a) Solids have very closely packed atoms with minimum spaces between them while gases have atoms which are for apart with maximum spaces between them. Solids have a definite shape and are highly rigid while gases have no definite shape and are least rigid.
(b) Sugar is soluble in water whereas talcum powder is not.
(c) Every pure substance has a fired melting point or boiling point.
(d) A bottle of perfume on opening evolves an odour because gases diffuse very easily and odour spreads over a large distance.

Question 12.
Complete the statements given below by selecting the correct word/s.

(a) Solids and liquids have a definite ____ but gases do not. [mass, shape, volume]
Answer:
Solids and liquids have a definite volume but gases do not.

(b) The space between atoms in is maximum while in ____ is minimum.[solids, liquids, gases]
Answer:
The space between atoms in gases is maximum while in solids is minimum.

(c) Conversation of a vapour into a liquid is called ____ [vaporization, condensation, freezing]
Answer:
Conversation of a vapour into a liquid is called condensation.

(d) ____ is an example of a crystalline substance. [wax, sugar, tea]
Answer:
Wax, sugar is an example of a crystalline substance.

Question 13.
State which of the following statements are false. If false write the correct statement.

(a) Solids are highly compressible and rigid.
Answer:
True.

(b) Atoms/molecules in gases move only about their own positions.
Answer:
False.
Atoms/molecules in gases move every where.

(c) The conversion of water to ice is called freezing.
Answer:
True.

Objective Type Questions

Q.1. Fill in the blanks with the correct word/s from the bracket.

  1. From the three states of matter, solids expand the least.
  2. Brownian movement is maximum in gases.
  3. Cohesive forces are negligible in gases.
  4. Matter can change from one state to another by change in temperature or pressure.
  5. The space between atoms [molecules] of solids is minimum.
  6. Intermingling of molecules is called diffusion.
  7. Ice on absorption of heat converts to ‘X’ a process called melting. ‘X’ changes to water vapour on heating. Water vapour changes back to ‘X’ on condensation. The constant temperature at which ice changes into ‘X’ is called its fusion point.

Q.2. State which of the following are physical properties of a substance.

Question 1.
Chlorine gas has a – strong irritating odour.
Answer:
Physical.

Question 2.
Sodium nitrate is soluble in water, but calcium carbonate is not.
Answer:
Physical.

Question 3.
Magnesium reacts with dilute hydrochloric acid, liberating hydrogen gas.
Answer:
Chemical.

Question 4.
Manganese dioxide, a catalyst which alters the rate of a chemical reaction is black in colour.
Answer:
Chemical.

Question 5.
The melting point of ice is 0°C.
Answer:
Physical.

Question 6.
Lead chloride reacts with barium sulphate to give a white precipitate of lead sulphate.
Answer:
Chemical.

Question 7.
Water acidified with dilute sulphuric acid is a good conductor of electricity.
Answer:
Physical.

Question 8.
Naphthalene on heating directly turns into vapour.
Answer:
Chemistry.

Question 9.
Hydrogen sulphide gas has a strong rotten egg odour.
Answer:
Physical.

Question 10.
Sulphur is a yellow amorphous powder insoluble in water.
Answer:
Physical.

Q.3. Match the characteristics of the three states of matter in List I with their correct answer from List II.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 16
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 17

Q.4. Match the arrangement of atoms in the three states of matter in List I with the correct state in List II.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 18
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 19

Q.5. State the correct term from A, B, C, D, E or F in List II which represents the change of state of matter or its relevant property from List I.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 20
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 3 Matter 21

New Simplified Chemistry Class 6 ICSE Solutions – Elements, Compounds & Mixtures

New Simplified Chemistry Class 6 ICSE Solutions – Elements, Compounds & Mixtures

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Exercise
Elements and Compounds

Question 1.
Classify substances into pure and impure substances in the form of a chart or tabulation.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 1

Question 2.
Differentiate between the terms – elements, compounds & mixtures.
Answer:
Element is a pure substance.

  1. It is the basic unit of matter and cannot be broken down into two or more simpler substances by any means.
  2. It is mainly classified into metals, non-metals, metalloids and noble gases.

Compound is a pure substance.

  1. It is formed by combination of two or more elements.
  2. The elements are combined together in a fixed ratio.
  3. It can be broken down into its elements by chemical means.

Mixture is an impure substance.

  1. It is formed by combination of two or more elements, compounds or both.
  2. The substances are mechanically mixed together in any ratio.

Question 3.
The important physical properties of substances are colour, odour, nature, density & solubility in water. Name –
(a) two coloured gases (with their colours)
(b) a gas with a pungent, choking odour which is lighter than air
(c) a poisonous gas almost as heavy as air.
Answer:
(a)

  1. Chlorine – greenish yellow
  2. Nitrogen dioxide – reddish brown.

(b) Ammonia.
(c) Carbon monoxide

Question 4.
Complete the statement – an element is a pure substance made up of (identical/different) atoms.
Answer:
An element is a pure substance made up of identical atoms.

Question 5.
Draw a labelled diagram of an atom including its nucleus, orbits & their contents.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 2

Question 6.
Elements are classified into – Metals – Non-metals – Metalloids – Noble gases. State which of A, B, C, D is a –

  1. Metallic element
  2. Non-metallic element
  3. Metalloid
  4. Noble gas.

A : Is non-malleable, non-ductile & a poor conductor of electricity____
B : Has lustre, is malleable and ductile & a good conductor of heat ____
C : Is unreactive and inert and present in traces in air____
D : Shows properties of both metals and non-metals____
Answer:
A : Is non-malleable, non-ductile & a poor conductor of electricity Non-metallic element
B : Has lustre, is malleable and ductile & a good conductor of heat Metallic element
C : Is unreactive and inert and present in traces in air Noble gas.
D : Shows properties of both metals and non-metals Metalloid

Question 7.
An atom of an element is denoted by a ‘symbol’. Explain the meaning of the term “symbol” State a reason for representing the following elements by their symbols.

(a) Hydrogen by ‘H’
(b) Helium by ‘He’
(c) Copper by ‘Cu’

Answer:
Symbols : The short form or abbreviated name of the element (or radicals)
The reason for representing the following elements by their symbols are as follow :

(a) Hydrogen by ‘H’ – First letter of the name of element
(b) Helium by He – First two letters of the name of Noble gases.
(c) Copper by ‘Cu’ – Deriving symbols from their Latin names

Question 8.
Match the metallic elements – with their correct symbols Metallic elements (a) Potassium (b) Sodium (c) Calcium (d) Magnesium (e) Zinc
(f) Aluminium (g) Iron (h) Lead (i) Copper (j) Mercury (k) Silver (l) Platinum (m) Gold
Symbols : (1) Ca ; (2) Zn ; (3) Pb ; (4) Hg ; (5) Cu ; (6) Au ; (7) K ; (8) Fe ; (9) Al ; (10) Na ; (11) Mg ; (12) Pt ; (13) Ag
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 3

Question 9.
Match the non-metallic elements – with their correct symbols
Non-metallic elements :
(a) Carbon (b) Chlorine (c) Oxygen (d) Phosphorus (e) Hydrogen (f) Nitrogen (g) Iodine (h) Bromine (i) Fluorine (j) Silicon (k) Sulphur
Symbols : (1) O (2) 1 (3) Si (4) C (5) Cl (6) P (7) F (8) H (9) S (10) Br (11) N
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 4

Question 10.
Match the noble gases – with their correct symbols Noble gases : (a) Helium (b) Neon (c) Argon (d) Krypton (e) Xenon (f) Radon
Symbols : (1) Ar (2) Xe (3) Rn (4) He (5) Kr (6) Ne
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 5

Question 11.
Give a reason why elements are tabulated in a table called the ‘Periodic table’.
Answer:
For arranging all the elements in a systematic and simple manner. The arrangement of elements was done in the form of a table called Periodic Table in which elements are arranged in increasing order of their atomic numbers. Elements in the Periodic Table are arranged in Horizontal rows called Periods and vertical columns called Groups. Metallic elements are placed on the left non-metallic on the right and noble gases on the extreme right of the Periodic table.

Question 12.
Give the names and symbols of the first twenty elements of the periodic table. Differentiate them into metals, non-metals, metalloids and noble gases.
Answer:

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 6

Question 13.
Explain the term – molecules. Give three examples of atoms of the same element forming a molecule. State the atomicity of the same.
Answer:
Atoms of the same element or different elements combine to form a molecule.
Atoms of the same element forming a molecule

  1. Oxygen
  2. Nitrogen
  3. Hydrogen

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 7

Atomicity is the number of atoms present in one molecule of the element.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 8

Question 14.
Give one example of
(a) a triatomic molecule
(b) a polyatomic molecule.
Answer:
(a) a triatomic molecule

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 9
(b) a polyatomic molecule.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 10

Question 15.
Explain the term compounds. Give the example of a compound containing

(a) hydrogen and oxygen
(b)carbon and oxygen
(c) nitrogen and oxygen
(d) calcium and oxygen.

Answer:
A compound is a pure substance made up of two or more different elements combined chemically in a fixed proportion.
Example of Atoms of different elements forming a compound

(a) 2 Atom of H and 1 atom of O = H2O
(b) Carbon dioxide, 1 atom of carbon and 2 atom of O = CO2
(c) Nitrogen dioxide, 1 atom of nitrogen 2 atom of O = NO2
(d) Calcium oxide, 1 atom of calcium 1 atom of O = CaO

Question 16.
State two characteristics of water which prove that it is a – compound.
Answer:
Characteristics of compounds

  1. Elements in a compound are present in a definite proportion.
    Example 2 atoms of hydrogen combine with 1 atom of oxygen to give 1 molecule of water (compound)
    H2 + O = H2O (water)
  2. Compounds have a definite set of properties example :
    The properties of the compound water are different from the properties of the elements hydrogen and oxygen in water.

Question 17.
Explain the terms ‘chemical formula\ State what a chemical formula denotes.
Answer:

  • Chemical formula is a representation of a substance either element or compound by means of symbols.
  • Chemical formula denotes the number of atoms of each element present in a compound.

Question 18.
Give the symbols and the number of atoms of each element present in

(a) sodium chloride
(b) water
(c) carbon dioxide
(d) zinc chloride.

Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 11

Question 19.
For writing a chemical formula – ‘symbols’ and combining capacity of an element with hydrogen i.e. ‘valency’ should be known. Explain the term – combining capacity of an element i.e. valency.
Answer:
The combining power of an element especially as measured by the number of hydrogen atoms can combine or displace with the element.

Question 20.
State what are radicals. Give the names of the radicals –

(a) NO3
(b) OH
(c) SO4
(d) CO3

Answer:
A radical is an atom or group of atom of same or different elements that behaves in the manner of positive or negative ions.

(a) NO3 – nitrate
(b) OH – hydroxide
(c) SO4 – sulphate
(d) CO3 – carbonate

Question 21.
Match the symbols of metallic elements – with their correct combining power or capacity.

(a) K
(b) Zn
(c) Al
(d) Na
(e) Ca

Combining power or capacity – A : 3 ; B : 2 ; C : 1. (positive valencies)
Answer:

(a) K — Valency-1 (C)
(b) Zn — Valency-2 (B)
(c) Al — Valency-3 (A)
(d) Na— Valency-1 (C)
(e) Ca — Valency-2 (B)

Question 22.
Match the symbols of non-metallic elements with their correct combining power or capacity.

(a) O
(b) S
(c) Cl

Combining power or capacity A : 3; B : 2; C : 1. (negative valencies)
Answer:

(a) O — Valency-2 (B)
(b) S — Valency-2 (B)
(c) Cl — Valency-1 (C)

Question 23.
Match the symbols of – radicals – with their correct combining power or capacity, (valency).

(a) OH
(b) SO4
(c) NO3
(d) CO3

Combining power or capacity – A : 3; B : 2; C : 1. (negative valencies)
Answer:

(a) OH— Valency- 1 (C)
(b) SO4 — Valency- 2 (B)
(c) NO3— Valency- 1 (C)
(d) CO3 — Valency- 2 (B)

Question 24.
Write the formula of the compound formed – given “symbols and combining power or capacity (valency) of each element in the compound.

(a) K1+ Cl1-
(b) Na1+ Cl1-
(c) Ca2+ NO31-

Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 12

Question 25.
Match the formulas of the following – gases – with their correct names :
Gases : (a) H2, (b) N2, (c) O2, (d) Cl2, (e) HCl, (f) NH3, (g) CO, (h) CO2, (i) SO2, (j) NO, (k) NO2
Names :
(1) Ammonia, (2) Nitrogen dioxide, (3) Oxygen, (4) Hydrogen, (5) Nitrogen, (6) Chlorine, (7) Carbon monoxide, (8) Sulphur dioxide, (9) Nitrogen monoxide, (10) Carbon dioxide, (11) Hydrogen chloride
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 13
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 14

Question 26.
Match the formulas of the following – acids – with their correct names
Acids : (a) HCl, (b) HNO3, (c) H2SO4, (d) H2CO3
Names : (1) Carbonic acid, (2) Sulphuric acid, (3) Hydrochloric acid, (4) Nitric acid
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 15

Question 27.
Match the formulas of the following – bases – with their correct names.
Bases : (a) NaOH, (b) KOH, (c) Ca(OH)2, (d) Zn(OH)2
Names : (1) Potassium hydroxide, (2) Zinc hydroxide, (3) Aluminium hydroxide, (4) Calcium hydroxide, (5) Sodium hydroxide
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 16

Question 28.
Complete the statements with the correct words.

(a) Acid’s – are chemicals which are ____ in taste and derived from plants and ____
Answer:
Acids – are chemicals which are sour in taste and derived from plants and minerals.

(b) Bases – are chemicals which are hydroxide (or oxides) of ____ eg. sodium hydroxide.
Answer:
Bases – are chemicals which are hydroxide (or oxides) of metals eg. sodium hydroxide.

(c) Salts- are chemicals formed on reaction of a base with an ____ giving salt and water.
Answer:
Salts- are chemicals formed on reaction of a base with an acid giving salt and water.

Question 29.
In the chemical word equation – Zinc + Sulphuric acid → Zinc sulphate + Hydrogen

(a) State the reactants and products of the above reaction. What does the arrow indicate.
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 17

(b) The molecular equation is :
Zn + H2SO4 → ZnSO4 + H2[g]. State what [g] represents.
Answer:
[g] represents gas.

Objective Type Questions

Q.1. Complete the statements given below by filling in the blank with the correct word/s.

  1. An element is a pure substance which cannot be broken down by physical or chemical methods.
  2. The basic unit of an element is an atom.
  3. Atom contains nucleus, with positively charged protons.
  4. Element silver has the symbol derived from its Latin name ‘argentum’.
  5. From the elements – He, Br, Pt and O ; the element which is metallic is Pt, an inert element is He, forms a triatomic molecule is O, is liquid at room temperature is Br.
  6. From the elements nitrogen, chlorine, bromine, the element present in the atmosphere is nitrogen.

Q.2. Match the statements in List I – 1 to 10 with their correct answers in List II – A to J.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 18
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 19
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 20

Q.3. Select the correct answer from the choice in brackets.

Question 1.
The symbol of – mercury [Mg / Hg / Ag]
Answer:
Hg

Question 2.
The type of element-phosphorus [metallic/non-metallic/noble gas]
Answer:
non-metallic

Question 3.
The type of molecule- bromine [monoatomic/diatomic/triatomic]
Answer:
diatomic

Question 4.
A compound [nitrogen/ozone/zinc chloride]
Answer:
zinc chloride

Question 5.
The unreactive non-metallic element [chlorine / argon / sulphur]
Answer:
argon

Question 6.
The negatively charged particles in an atom [protons/neutrons/electrons]
Answer:
electrons

Question 7.
The element which is malleable [sulphur / carbon / iron]
Answer:
iron

Question 8.
An impure substance [element / mixture / compound]
Answer:
mixture

Question 9.
An element which is a poor conductor of heat [copper / carbon / aluminium]
Answer:
carbon

Question 10.
A group of atoms of elements [ion / radical / combining power]
Answer:
radical

Q.4. Match the compounds in List I – 1 to 20 with their correct formulas from in List II – A to T.
1. Hydrochloric acid, 2. Potassium hydroxide, 3. Sulphuric acid, 4. Zinc hydroxide, 5. Sodium chloride, 6. Nitric acid, 7. Calcium hydroxide, 8. Carbonic acid, 9. Sodium hydroxide, 10. Copper sulphate, 11. Potassium chloride, 12. Calcium carbonate, 13. Magnesium suiphide, 14. Zinc sulphate, 15. Aluminium hydroxide, 16. Sodium carbonate, 17. Calcium sulphide, 18. Magncsium oxide, 19. Zinc oxide, 20. Ammonium chloride.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 21
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 22
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 23

Exercise
Mixtures

Question 1.
Explain the term mixtures. Give an example of mixtures of –

(a) two elements
(b) two compounds
(c) elements and compounds.

Answer:
Mixture : A mixture is an impure substance made up of two or more elements or compounds mechanically mixed together in any proportion.
Examples :
(a) Of two elements
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 24
(b) Of two compounds
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 25
(c) Of elements and compounds
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 26

Question 2.
Differentiate between homogeneous and heterogeneous mixtures with suitable examples.
Answer:
The main characteristics of mixture (Iron + Sulphur) are :

Homogeneous mixtures :

  1. There constituents are uniformly mixed.
  2. The properties and composition are same throughout the mixture.
  3. Examples :
    (a) alcohol and water
    (b) salt and water
    (c) sugar and water

Heterogeneous mixtures :

  1. There constituents are not uniformly mixed.
  2. The properties and composition vary throughout the mixture.
  3. Examples :
    (a) oil and water
    (b) sand and water
    (c) chalk and water

Question 3.
With reference to the mixture of iron and sulphur, state the main characteristics of mixture.
Answer:
The main characteristics of mixture (Iron + Sulphur) are :

  1. The mixture of iron and sulphur may contain iron and sulphur in varying proportions.
  2. The original properties of each element are retained in the mixture of iron and sulphur.
  3. Mixture of the two elements iron and sulphur can be separated by i.e. a physical method, i.e. by using a magnet since iron is attracted to the magnet.

Question 4.
Tabulate a comparative chart – to differentiate between elements, compounds and mixtures. Differentiate them with reference to

(a) the term
(b) existence
(c) properties
(d) separation of components.

Answer:
(a) Term —

  • Elements – Pure substance made up of one kind of atoms only. e.g. Iron [Fe], Sulphur [S]
  • Compounds – Pure substance made up of two or more different elements, e.g. Iron sulphide [FeS]
  • Mixtures – Impure substance made up of two or more elements or compounds, e.g. Iron and sulphur mixture.

(b) Existence—

  • Elements – Elements i.e. atoms are present on their own. e.g. Iron and sulphur exist on their own as elements iron and sulphur.
  • Compounds – Components in a compound present in a definite proportion.
    e.g. Iron and sulphur are chemically combined in a fixed ratio in iron sulphide.
  • Mixtures – Components in a mixture present in any proportion.
    e.g. Iron and sulphur are mixed in any ratio in the mixture of iron and sulphur.

(c) Properties —

  • Elements – Elements have a definite set of properties.
    Elements classified into metal and non-metals each with its own properties.
  • Compounds – Compounds have a definite set of properties. Elements of a compound do not retain their original properties.
  • Mixtures – Mixture not have a definite set of properties.
    Components of a mixture do retain their original properties.

(d) Separation of compound —

  • Elements – Elements occur on their own or as compounds and can be separated by chemical and physical methods.
    Example : Iron, copper.
  • Compounds – Elements in a compound are chemically combined and can be separated by chemical methods only.
    Example : Iron Sulphide, copper oxide.
  • Mixtures – Components in a mixture can be separated by , physical methods only.
    Example : Iron + sulphur

Question 5.
State the principle involved in separation of solid-solid mixtures by –

(a) sieving
(b) magnetic separation
(c) sublimation.

Answer:
(a) Sieving

  • Principle — Based on the difference in size of the solid particles.
  • Examples — Mixture of Rice powder and soil, mixture of different sized particles of diamond and of sand.

(b) Magnetic separation

  • Principle — One component of the mixture is a magnetic substance.
  • Example — Mixture of iron ore and sand, Mixture of cobalt and lead.

(c) Sublimation

  • Principle — One of the components sublimes on heating.
  • Example — Mixture of iodine and salt, Mixture of ammounium chloride and sand.

Question 6.
State the principle involved in separation of solid-liquid mixtures by –

(a) sedimentation and decantation
(b) filtration
(c) evaporation

Answer:
(a) Sedimentation and decantation —

  • Principle — The solid component is insoluble and heavier than the liquid component.
  • Example — Mixture of sand and water

(b) Filtration —

  • Principle — Seperation of insoluble solid component by “ passing through a porous material like filter paper.
  • Example — Mixture of chalk and water, Mixture of Agcl and Water.

(c) Evaporation —

  • Principle — Seperation of the mixture by evaporating the liquid component. The solid should be soluble in the liquid and should not sublime.

Question 7.
Explain the term ‘sieving’. State the structure of a sieve and explain the separation of different sized particles by sieving.
Answer:
Sieving is a method of separation, which is used for separating substances of different sizes that cannot be separated in hand picking.
Principle — Based on the difference in size of the solid particles.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 27

  • Technique of Separation — The large sized par icles are separated from the small or finer particles by passing the mixture through a sieve.
    The sieve has a wooden frame, with a metal mesh at its base.
    The mixture is added from the top of the sieve, when the larger particles stay above and the finer particles collect below it on shaking the sieve.
  • Examples — Separation of rice powder from soil, seperation of different sized particles of diamond and of sand.

Question 8.
State what is meant by ‘magnetic separation of two mixtures’. Explain how iron particles can be separated from sulphur particles.
Answer:
Magnetism is ideal for separating mixtures of two solids with one part having magnetic properties. Some metals like iron, nickel and cobalt have magnetic properties whiles gold, silver and aluminum do not. Magnetic elements are attracted to a magnet.

  • Principle — Based on the difference in magnetic and non-magnetic nature of particles.
    New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 28
  • Technique of Separation — The magnetic particles such as iron are separated from the non-magnetic particles such as sulphur – by utilizing the magnetic properties of iron. The iron gets attracted to the magnet and seperates from the non-magnetic substance.

Question 9.
Give a reason why sublimable and non-sublimable substances can be separated easily, but two sublimable substance cannot.
Answer:
While seperating the mixture sublimable and non- sublimable substances, sublimable substance turns directly into vapour on heating whereas non-sublimable solid remains behind. Since, if we try to seperate the mixture of two sublimable substances, then both the sublimable substances turns into vapour on heating and vapour on cooling give back the pure same solid.

Question 10.
Explain the technique for separating – insoluble solid particles in a solid-liquid mixture.
Answer:
The insoluble solid particles in a solid-liquid mixture can be seperated by filtration.
Technique of Seperation — A filter paper is made into a cone & placed in a funnel. The solid particles remain behind on the filter paper while the liquid collects below.

Question 11.
Differentiate between the terms sedimentation and decantation with a suitable experimental technique.
Answer:
Sedimentation and decantation are two very different terms. Sedimentation is defined as the process of settling down of the heavier components present in a mixture.
For example : When the mixture of sand in water is allowed to stand undisturbed for some time, it is observed that sand settles at the bottom.
Decantation is defined as the process of separating the Liquid portion of a mixture when the heavier component settles at the bottom as sediments.
In other words, it is the process of transferring a liquid from one container to another without disturbing the sediments that are present at its bottom.
For example : When a mixture of sand and water is allowed to stand, sand settles at the bottom of a container since it is heavier. Water is present in the upper portion of the container. This can be separated from sand settled at the bottom simply by pouring in a different container without using any other separating device. This is known as decantation.

Question 12.
Explain how a solid component is separated in a soluble solid-liquid mixture.
Answer:
A Solid component is separated in a soluble solid-liquid mixture by evaporation.
Principle — Seperation of the mixture by evaporating the liquid component. The solid should be soluble in the liquid and should not sublime.
Technique of Separation : The soluble solid can be seperated from its liquid component by allowing the liquid component to evaporate either on its own or by heating. During evaporation, the liquid component is lost to the atmosphere & the solid remains behind.
Example : Evaporation of a common salt solution or sea water leaves behind common salt.
Common salt remains behind whereas water lost to the atmoshphere.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 29

Question 13.
Draw a neat labelled diagram for separation of the following mixtures.

(a) Coarse sand from fine sand
(b) A magnetic particle from a non-magnetic particle
(c) Naphthalene from sodium chloride
(d) Chalk and water using a filter paper
(e) Sand and water without using a filter paper
(f) Common salt from a solution of common salt and water

Answer:
(a) Coarse sand from fine sand
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 30
Separation of particles of sand, Coarse sand stays above and fine sand below.
(b) A magnetic particle from a non-magnetic particle
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 31
(c) Naphthalene from sodium chloride
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 32
(d) Chalk and water using a filter paper
Filtration of chalk particles in water.
Filtered out solid chalk particles.
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 33
(e) Sand and water without using a filter paper
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 34
(f) Common salt from a solution of common salt and water
New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 35
Common salt remains behind.

Question 14.
State the technique involved in separating the following:

(a) Iodine crystals and potassium chloride
(b) Iron and chalk powder
(c) Potassium chloride from an aqueous solution of potassium chloride.
(d) Rice powder from soil particles
(e) Iron filings from pieces of copper wire
(f) Large diamonds from very small diamonds

Answer:

(a) Sublimation
(b) Magnetic separation
(c) Evaporation
(d) Seiving
(e) Magnetic separation
(f) Seiving

Objective Type Questions

Q.1. Match the statements in List I with the correct answer in List II.

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 36

Answer:

New Simplified Chemistry Class 6 ICSE Solutions Chapter 2 Elements, Compounds & Mixtures 37

Q.2. State whether the following statements are true or false. If false write – the correct statement.

1. Components in a mixture are present in a definite proportion.
Ans. False.
Correct — Components in a mixture are present in a varying proportion.

2. Mixture have no definite set of properties.
Ans. True.

3. Components in a mixture can be separated by physical and chemical methods.
Ans. False.
Correct — Components in a mixture can be separated by physical methods.

4. Sodium chloride and water is an example of a mixture of elements and compounds.
Ans. False.
Correct — Sodium chloride and water is an example of a mixture of compounds.

5. Heterogeneous mixtures have different composition and properties throughout the mixture.
Ans. True.

Q.3. Name the following :

Question 1.
A black non-metallic component of the mixture gunpowder.
Answer:
Carbon.

Question 2.
A physical method of separating iron from an iron- sulphur mixture.
Answer:
Magnetic separation.

Question 3.
The component of the soluble solid-liquid mixture, which is lost to the atmosphere on heating.
Answer:
Liquid component i.e. water.

Question 4.
The component of a naphthalene-sodium chloride mixture, which remains in the evaporating dish when heated together, covered with a funnel.
Answer:
Sodium chloride.

Question 5.
A mixture of two immiscible liquids.
Answer:
Kerosene oil and water.

Q.4. Give reasons for the following :

Question 1.
Naphthalene and camphor cannot be separated by sublimation.
Answer:
Because both of these are sublimable solids and they sublimes on heating.

Question 2.
Sodium chloride cannot be separated out from its aqueous solution by filtration.
Answer:
Filtration is a method that is used to separate insoluble solids from liquids, since both salt dissolve in water.

Question 3.
Two varieties of wheat flour cannot be separated by sieving.
Answer:
Since in sieving we can separate larger particle but in this case both particles are finer in nature.

Question 4.
Sulphur and charcoal powder cannot be separated by magnetic separation.
Answer:
Because both are non-magnetic particles.

Question 5.
Both components of a soluble solid-liquid mixture cannot be recovered by evaporation.
Answer:
Because liquid is lost/evaporated in atmosphere.

New Simplified Chemistry Class 6 ICSE Solutions – Introduction to Chemistry

New Simplified Chemistry Class 6 ICSE Solutions – Introduction to Chemistry

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Exercise

Question 1.
State what is Science and give the basic bifurcation of Science with reasons.
Answer:
Science is the subject which includes the study of various experiments performed by a scientist with all observations recorded and inferences concluded.
Bifurcation : Science is bifurcated into three main branches— Physics, Chemistry and Biology which make study of each branch simple and more focussed.

Question 2.
Give the basic difference between Inorganic Chemistry and Organic Chemistry.
Answer:
(a) Inorganic chemistry includes study of innumerable elements and compounds
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 1
(b) Organic chemistry includes study of specific carbon compounds built up mainly of carbon and hydrogen.

  • Compounds include hydrocarbons e.g., Methane
  • Acids include-acetic acid

Question 3.
State the functions of the following basic glass apparatus.

(a) Glass test tube
(b) Hard glass boiling tube
(c) Beaker
(d) Round bottom flask
(e) Retort

Answer:

(a) Glass test tube : It is used for heating chemicals and studying reactions in chemicals solution.
(b) Hard glass, boiling tube : It is resistant to chemicals and used for special purposes. It is made of pyrex.
(c) Beaker : It is used for holding pouring and mixing solutions.
(d) Round bottom flask : In preparation of gases, where heating is required. Since the flask is round bottomed, heat is uniformly distributed throughout on heating.
(e) Retort : For carrying out distillation experiments which include distillation of acids.

Question 4.
State why a round bottom flask is preferred to a flat bottom flask – during preparation of gases in the laboratory.
Answer:
Round bottom flask is preferred to flat bottom flask because in round bottom flask heat is uniformly distributed throughout on heating.

Question 5.
State the function of –

(a) The wooden handle at the end of the test tube holder.
(b) The asbestos fixed at the centre of the wire gauze.
(c) The clamp mounted on the rod of a retort stand.
(d) The air regulator in a Bunsen burner.
(e) The tap at the base of a burette.

Answer:

(a) The wooden handle at the end of test tube being a poor conductor of heat, makes holding the test tube holder easy.
(b) The asbestos fixed at the centre of the wire gauze initiates even distribution of heat to the bottom of the apparatus. It also prevents glass apparatus from cracking.
(c) The clamp mounted on the rod of a retort stand helps in holding the apparatus and adjusting its level upwards or downwards.
(d) The air regulator has holes and is used for regulating the flame.
(e) The tap at the base of the burette helps in removing the measured liquid drop wise.

Question 6.
State the method used for collecting the following gases –

(a) Oxygen – a gas slightly soluble in water.
(b) Ammonia – a gas highly soluble in water and lighter than air.
(c) Sulphur dioxide – a gas highly soluble in water and heavier than air.

Answer:

(a) The method used for collecting oxygen gas is downward displacement of water.
In this method, the gas jar is filled with water and inverted over the beehive shelf, so that the water is displaced downwards and oxygen is collected upwards.
(b) The method used for collecting ammonia gas is downward displacement of air.
This method is used for gases like ammonia which is soluble in water and lighter than air.
(c) The method used for collecting SO2 is upward displacement of air.
This method is used for gases like SO2 which is soluble in water and heavier than air.

Question 7.
Explain in brief the importance of Chemistry in agriculture and production of various products.
Answer:
Importance of Chemistry : In agriculture end products and as follow :
1. AGRICULTURE
(a) Fertilizers – A substance to improve fertility and supply of nutrients to plant and is essential for growth.
Example :

  1. Ammonium nitrate – widely used as a fertilizer.
  2. Urea – an important source of nitrogen [non-explosive and solid in nature]
  3. Phosphatic fertilizer – super phosphates.

About 90% of fertilizers are in the solid form. Liquid fertilizers comprise – aqueous solutions of amnionia or ammonium nitrate.

(b) Pesticides

  1. Chemicals added to the soil, to kill pests. They include – Herbicides; insecticides; termiticides etc.
  2. Pesticides protect the plants from – weeds, fungi and insects.
  3. About 30% of crops are destroyed by agricultural pests.

(a) Herbicides – Kill or inhibit growth of – unwanted plants.
(b) Insecticides – Destroy insects, which harm or destroy plants.

Pesticides may come in contact with other living organisms and disrupt the balance of the eco-system.

2. PRODUCTS

Knowledge of Chemistry has initiated production of – different products

  1. Food – Refined oils, butter, cheese, etc. are obtained through chemical reactions.
  2. Construction – Mortar, cement, glass, etc. are various chemical compounds.
  3. Clothing – Natural fabrics such as silk are made through chemical reactions.
  4. Household – Cooking gas which is liquefied petroleum gas or LPG, food preservatives, specific utensils and electronic items, all involve use of Chemistry.
  5. Daily usage – Paints, dyes, perfumes, paper, ink etc. involve chemical reactions.
  6. Industrial – Metals & alloys [mixture of metals] which find application in innumerable machines and metallic structures like automobiles, involve Chemistry.
  7. Petrolium – Petrol, kerosene & diesel oil are products – obtained from petroleum

Question 8.
‘Alchemists are older words for Chemists’. Discuss the statement in brief.
Answer:
Alchemy and alchemists are older words for Chemistry and chemists where – alchemists transformed or created substances through a seemingly – magical process.
An alchemists Nicolas flamel claimed to transform metals into gold.

Question 9.
In the medieval ages – philosopher’s stone was connected with all transformations. Explain.
Answer:
In the medievel ages to the 17th Century the so-called philosopher’s stone – held priority and alchemists were successful to a certain extent, in the development of processes, which helped later chemists to extract metals and develop – path-breaking avenues in Chemistry. The scientific process involving modern chemistry started poving paths and chemistry regains its rightful position. The Scientific Process involving Modern Chemistry started paving paths & chemistry regains its rightful position.

Question 10.
State the contributions of

(a) Dimitri Mendeleev
(b) Antoine Lavoisier
(c) John Dalton – towards the development of Chemistry.

Answer:
(a) Dimitri Mendeleev : He formulated the – Periodic Table of elements.

  1. He systematically arranged the dozens of known element by atomic weights and could even predict the properties of the still unknown elements.
  2. He devised the Periodic Table. He was best known for his discovery of the – Periodic Law.

(b) Antoine Lavoisier :

  1. He recognised and named oxygen in 1778 & later – hydrogen in 1783.
  2. He also wrote the first extensive list of elements and helped to reform chemical nomenclature.
  3. In 1774, he turned his attention to the phenomenon of combustion with his famous experiment, in which he heated pure mercury in a swan necked retort, leading to the discovery of oxygen.

(c) John Dalton :

  1. He compiled his theory in 1803 known as Dalton’s atomic theory.
  2. The main postulates of Dalton’s atomic theory are that “Matter consists of particles called atoms, which are indivisible and cannot be created or destroyed.”
  3. The theory was later contradicted in certain aspects by the Modem atomic theory.

Question 11.
Differentiate between the terms – food preservatives and food processing with appropriate examples.
Answer:
Food preservatives – are substances or chemicals – added to food or beverages to

  1. Prevent decomposition by bacteria or microbes.
  2. Reduce risk of food borne infections.
  3. Preserve nutritional quality of food.

Preservatives :

  1. Benzoic acid
  2. Nitrates
  3. Sulphur compounds

Food items :

  1. Jams, pickles, carbonated drinks.
  2. Meat products
  3. Beverages, wines etc.

Question 12.
Explain the term ‘cosmetics’ & ‘talc’. Name a few main ingredients in cosmetics the role they play.
Answer:
Cosmetics are mixtures of chemical compounds from natural sources or from synthetic sources.
Cosmetics – enhance or alter the appearance or fragrance of an individual. Some sources of compounds used in cosmetics include – modified natural oils and fats, processed minerals e.g. – zinc oxide, iron oxide and talc.
Talc :

  1. Talcum powder is made from talc – a mineral made up of – hydrated magnesium silicate, (contains elements – magnesium silicon, oxygen).
  2. In its natural form – talc contains asbestos – which is removed from consumer products.
  3. Talc – absorbs moisture, cuts down on friction, keeps skin dry and prevents rashes.

Question 13.
Differentiate between – natural fibres & synthetic fibres. State what is – Terylene. State some of its characteristic properties which make it suitable for commercial use.
Answer:
Natural fibres – such as cotton and wool which were directly converted into clothing material.
Synthetic fibres – such as terylene, nylon and rayon are used in expensive clothing ; carpets etc.
Terylene – It is a synthetic polyester fibre or fabric formed generally, by – addition of polyester to natural fibre – cotton. The combination makes the fabric, easy to clean and crease resistant.,

Properties – It is a strong fabric –

(a) elastic in nature, resistant to friction,
(b) suffers little loss in strength,
(c) crease resistant,
(d) easily washable and dries quickly.

Uses –

(a) in fashion garment fabrics
(b) in nonwoven carpets, rain coats, sails
(c) in making of nets, ropes, hoses etc.

Question 14.
Explain how medicines are a boon to mankind. State the positive & negative effects of medicines like aspirin and paracetamol.
Answer:
Medicines are natural or synthetic substances which when taken in a living body, affects its functioning, and treats or prevents a disease.
Aspirin
Positive effect :

  1. It is a medicine to treat pain, fever and inflammation.
  2. Aspirin given shortly after a heart attack, may decrease risk of death.
  3. As long term use it may reduce, blood clots in people who are at a high risk.

Negative effect :

  1. It is generally not recommended in children with infections.
  2. Its side effects may include upset stomach, stomach ulcers etc.

Paracetamol :

  1. It is a medicine to treat mild to moderate pain and fever.
  2. It may also be used in low back pain, headaches and for dental use.

Negative effect :

  1. It maybe sold in combination with cold medications.
  2. It is safe at recommended doses, but too high a dose may result in liver problems.

Question 15.
Give a comparitive difference between – soaps and detergents. Give a reason why detergents have an advantage over soap.
Answer:
Soaps are substances used with water, for cleaning and washing and are made from a compound of vegetable oils or animal fats along, with sodium or potassium hydroxide and generally have perfumes or colourants, added to it.
Whereas
Detergents are synthetic water soluble cleaning agents that unlike soap (which are prepared from vegetable oils or fats) are prepared from petroleum products along with sodium or potassium hydroxide.
Detergents have an advantage over ordinary soap

  1. Hard water is one which does not lather with soap, while soft water lathers easily.
  2. Ordinary soap when rubbed in hard water is wasted and lather forms only after all the insoluble salts in hard water are removed as scum.
  3. Synthetic detergents do not form scum and lather even in hard water.

Question 16.
State what are – ‘stain removals’. Name three important stain removers & give their prime functions.
Answer:
Stain removals It is the process of removing a mark or a stain left by one substance on a specific surface fabric. Most stains are removed by dissolving with a solvent.
Examples of stain removers
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 2

Objective Type Questions

Q.1. Select the correct name from the choice A, B or C in each case.

Question 1.
The branch of Science which deals with the different forms of energy e.g. light and sound.
A : Chemistry
B : Physics
C : Biology
Answer:
B : Physics

Question 2.
The branch of Chemistry which includes study of specific carbon compounds – built up of mainly carbon and hydrogen.
A : Inorganic Chemistry
B : Physical Chemistry
C : Organic Chemistry
Answer:
C : Organic Chemistry

Question 3.
The scientist who formulated the Periodic Table.
A : John Dalton
B : Daniel Rutherford
C : Demitri Mendeleev
Answer:
C : Demitri Mendeleev

Question 4.
Predecessors to the modern Chemist who created the Philosoper’s stone’.
A : Botanists
B : Alchemists
C : Physicists
Answer:
B : Alchemists

Question 5.
A synthetic fibre used in clothing.
A : Cotton
B : Jute
C : Terylene
Answer:
C : Terylene

Question 6.
A medicine to treat pain, fever & inflammation.
A : Anaesthetic
B : Aspirin
C : Antacid
Answer:
B : Aspirin

Question 7.
A water soluble cleaning agent – not inactivated by hard water.
A : Soap
B : Detergent
C : Cleanser
Answer:
B : Detergent

Question 8.
A substance which absorbs moisture and keeps the skin dry and free from rashes.
A : Talc
B : Preservative
C : Emulsifier
Answer:
A : Talc

Question 9.
A chemical used as a preservative for jams, pickles etc.
A : Titanium dioxide
B : Rayon
C : Benzoic acid
Answer:
C : Benzoic acid

Question 10.
A substance which dissolves grease & oil and is preferred as a – drain cleaner.
A : Glycerine
B : Sodium hydroxide
C : Hydrogen peroxide
Answer:
B : Sodium hydroxide

Q.2. Match the apparatus A to J shown below with their correct names 1 to 10 given below :
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 3
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 4
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 5
Answer:
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 6

Q.3. Select the correct apparatus from A, B or C for each of the functions of the apparatus given.

Question 1.
For gas preparations where heating is required.

(A) Flat bottom flask
(B) Retort
(C) Round bottom flask

Answer:
(C) Round bottom flask

Question 2.
For holding washed test tubes.

(A) Test tube holder
(B) Test tube stand
(C) Retort stand

Answer:
(B) Test tube stand

Question 3.
A glass apparatus resistant to chemicals, made of pyrex and used for heating specific liquids.

(A) Beaker
(B) Retort
(C) Boiling Tube

Answer:
(C) Boiling Tube

Question 4.
A metallic apparatus which supports the wire gauze.

(A) A Tripod stand
(B) Retort stand
(C) Test tube stand

Answer:
(A) A Tripod stand

Question 5.
A long glass apparatus closed at one end used for collecting gases.

(A) Measuring cylinder
(B) Gas jar
(C) Beehive shelf

Answer:
(B) Gas jar

Question 6.
A glass apparatus which measures liquid by sucking the liquid at one end upto the marked level and later pouring it out.

(A) Burette
(B) Measuring cylinder
(C) Pipette

Answer:
(C) Pipette

Question 7.
A long glass tube with a broad inlet at the top, which allows entry of the reactants into the round bottom flask, during laboratory preparations of gases.

(A) Thistle funnel
(B) Delivery tube
(C) Funnel.

Answer:
(A) Thistle funnel

Question 8.
A clay vessel kept in a trough of water during collection of a gas by downward displacement of water.

(A) Retort
(B) Beehive shelf
(C) Burette

Answer:
(B) Beehive shelf

Question 9.
A modern apparatus with an air regulator, used for heating purposes.

(A) Spirit lamp
(B) Bunsen burner
(C) Electric stove

Answer:
(B) Bunsen burner

Question 10.
A rectangular mesh with an asbestos at its centre, kept for initiating even distribution of heat to the bottom of the apparatus.

(A) Tripod stand
(B) Wire gauze
(C) Retort stand

Answer:
(B) Wire gauze

Q4. Give reasons for the following :

Question 1.
Alchemy was considered a pseudoscience.
Answer:
Towards the end of the 17th Century the scientific processes involving modem Chemistry started paving paths and Alchemy today is considered a pseudoscience and Chemistry regains its rightful position as a serious scientific field.

Question 2.
Preservatives are added to food or beverages.
Answer:
Preservatives are added to food or beverages because of following reasons :

  1. Prevent decomposition by bacteria or microbes.
  2. Reduce risk of food borne infections.
  3. Preserve nutritional quality of food.

Question 3.
Titanium dioxide is an important ingredient in cosmetics.
Answer:
It is a natural pigment powder which provides a base for mineral makeup. It provides mild sun protection and as a pigment gives a white colouration to coloured ingredients.

Question 4.
Aspirin is one of the most widely used medication – globally.
Answer:
Aspirin is one of the most widely used medication – globally because of following reasons :

  1. It is a medicine to treat pain, fever & inflammation.
  2. Aspirin given shortly after a heart attack, may decrease risk of death.
  3. As long term use it may reduce, blood clots in people who are at a high risk.

Question 5.
Ordinary soap is wasted in hard water.
Answer:
Ordinary soap is wasted in hard water because hard water is one which does not lather with soap.

Question 6.
A philosopher’s stone is not exactly a stone.
Answer:
Philosopher’s stone in a legendary substance, capable of turning inexpensive metals like lead or mercury into – gold.and silver.
(It was not literally a stone, but a powder or potion).

Question 7.
Food processing is an important procedure for obtaining marketable food products.
Answer:
Food processing – involves physical or phemical processes, to transform or change the raw ingredients in food into easy usable forms of food available in markets. Raw materials – in food to Marketable food products
New Simplified Chemistry Class 6 ICSE Solutions Chapter 1 Introduction to Chemistry 7

Question 8.
Cosmetics may contain preservatives, as one of their ingredients.
Answer:
They extend the shelf life of a cosmetic and may prevent growth of microorganisms.

Question 9.
Polyester is added to natural fibre cotton, to give terylene.
Answer:
Polyester is added to natural fibre cotton, to give terylene because this combination makes the fabric easy to clean and crease resistant.

Question 10.
All medicines must be taken under proper doctors supervision and in the correct dose.
Answer:
All medicines must be taken under proper doctors supervision and in the correct dose because some medicine has side effect as aspirin not taken in proper dose may cause stomach ulcers similarly paracetamol if taken in high dose may cause liver problems.