Selina Class 6 ICSE Solutions

Selina Concise Physics Class 6 ICSE Solutions – Simple Machines

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Selina Concise Physics Class 6 ICSE Solutions – Simple Machines

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Physics. You can download the Selina Concise Physics ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Physics for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Physics Chapter 4 Simple Machines

  • Synposis
  • Work is said to be done when a force applied on a body moves it. If the body does not move on applying a force on it, no work is done by the force.
  • The capacity of doing work is called energy.
  • A machine is a device which helps us to do work more easily.
  • A machine enables us to apply a less effort for a load greater than the effort or to apply the effort at convenient point and in a desired direction.
  • Some machines are simple and some are complex.
  • The mechanical advantage of a machine is the ratio of the load to the effort, i.e., Mechanical advantage = Load / Effort
  • Smaller the effort required for a certain load, greater is the mechanical advantage of the machine.
  • The efficiency of a machine is the ratio of the useful work done on the load by the machine to the work put into the machine by the effort, i.e.
    Efficiency = Work output / Work input
  • The efficiency of an ideal machine is 1 (or 100 per cent).
  • The efficiency of an actual machine is less than 1 because some part of the work put into the machine is lost in overcoming the friction between the moving parts of the machine.
  • A lever is a simple machine which we most commonly use in our daily life. It is a rod which can turn about a fixed point called the fulcrum.
  • The mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm, i.e. Mechanical advantage of a lever = Effort arm / Load arm
    The levers are of three kinds :
    Class I levers which have fulcrum in between the load and the effort.
    Class II levers which have load in between fulcrum and the effort.
    Class III levers which have effort in between the fulcrum and the load.
  • The mechanical advantage of class I lever can be 1, more than 1 or less than 1.
  • The mechanical advantage of class II levers is always more than 1.
  • The mechanical advantage of class III levers is always less than 1.
  • A pulley is a simple machine which is used for raising a load up by applying the effort downwards.
  • The mechanical advantage of an ideal pulley is 1. In an actual pulley, due to friction, the mechanical advantage is less than 1 (i.e., the effort is more than the load).
  • The pulley allow us to apply the effort downwards which is a convenient direction.
  • The wheel and axle is a simple machine having a wheel and an axle. The linear motion of axle is obtained by rotating the wheel so as to reduce friction. Example: Steering wheel, screw drivers, water tap etc.
  • An inclined plane is a simple machine which is used to move a load up with a less effort. It is a sloping (or slanting) surface.
  • Less the slope of the inclined plane, less is the effort needed to push a load up.
  • The mechanical advantage of an inclined plane is greater than 1 (i. e. a less effort is required to push a heavy load up an inclined plane).
  • A wedge is a sharp edge formed by joining the two inclined planes together. Example: nail, knife, axe, plough etc.
  • A screw is a modified form of an inclined plane.
  • A screwjack is a simple machine having a combination of a screw and a lever. It is used to lift the heavy vehicles such as cars, trucks, buses etc.
  • Machines are used for our convenience. Therefore, we should take proper care of a machine by painting the machine parts to avoid rusting, lubricating its parts to reduce friction etc. This increases the life span of the machine.

Test yourself

A. Objective Questions

1. State whether the following statements are True or False.

(a) A boy does work while pushing a wall.
Answer. False

(b) A machine performs work by itself.
Answer. False

(c) In an ideal machine, work done on load is equal to the work done by effort.
Answer. True

(d) All levers are force multipliers.
Answer. False

(e) A pulley changes the direction of force.
Answer. True

(f) An inclined plane always has the mechanical advantage more than 1.
Answer. True

2. Fill in the blanks

(a) The useful work done by an actual machine is always less than the work done on the machine.
(b) In class II levers, the load is in between fulcrum and effort.
(c) The mechanical advantage of class III lever is always less than 1.
(d) A pulley is used to change the direction of effort.
(e) Mechanical advantage of an inclined plane is always greater than 1.

3. Match the following

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 1

Answer.

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 2
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 3

4. Select the correct alternatives

(a) For an ideal machine, the efficiency is

  1. greater than unity
  2. less than unity
  3. equal to unity
  4. depends on the value of load

(b) Mechanical advantage of a machine is defined as:

  1. Load X Effort
  2. Load / Effort
  3. Load + Effort
  4. Effort / Load

(c) The mechanical advantage of a lever is equal to:

  1. Load arm / Effort arm
  2. Effort arm / Load arm
  3. Load arm + Effort arm
  4. Load arn — Effort arm

(d) A pulley is used because it

  1. has the mechanical advantage greater than one
  2. has 100% efficiency
  3. helps to apply the force in a convenient direction
  4. requires more effort to raise a less load.

(e) Wheel is used with axle because

  1. sliding friction is less than the rolling friction
  2. rolling friction is less than the sliding friction
  3. they work as the inclined plane
  4. They help us to change the direction of force.

B. Short/Long Answer Questions

Question 1.
When is work said to be done by a force ?
Answer:
Work is said to be done when a force moves an obj ect through a distance in its own direction.

Question 2.
What is energy ?
Answer:
Energy: The ability or capacity to do work is called energy.

Question 3.
What do you understand by a machine ?
Answer:
Machine: A machine is a device that allows us to do work with less effort. Machines make our work easier to do. Machines have made our li ves comfortable and faster.

Question 4.
What is the principle on which a machine works ?
Answer:
Principle of a Machine: The work output of a machine is equal to the work input.

Question 5.
State two functions of a machine.
Answer:
Various functions that a machine can perform are:

  1. Changing the direction of applied force — Example: When a flag is hoisted with the help of a pulley.
  2. Changing the magnitude of applied force — Example: Bottle opener multiplies the applied force and much less effort is required to open the cap.
  3. Applying force at a convenient point — Example: In a pair of scissors, the input force is applied at the handle of the scissors which cuts the paper at the other end of the blade.
  4. Changing the speed of an object — Example: While riding a bicycle, force is applied on pedals which multiplies the speed.

Question 6.
Name six simple machines. Give an example of each machine.
Answer:
The Simple Machines and there examples are as follows:

  1. The lever: Examples are a crow bar, claw hammer, a pair of pilers etc.
  2. The Inclined plane: Examples are ramp, staircase, hilly roads etc.
  3. The wedge: Examples are knife, axe, plough, nail etc.
  4. Screw: Examples are A screw.
  5. The wheel and axle: Examples are steering wheel of a car, bicycle pedal etc.
  6. The pulley: Examples are a pulley used in raising a load.

Question 7.
Define the term ‘work input’ and ‘work output’ in relation to a machine.
Answer:
Work input is work done on a machine equal to the effort force times the distance through which the force is applied.
Work output is work that is done by a machine equals resistance force times the distance through which the force applied.
For an ideal machine, the work output is equal to the work input i. e. the efficiency.

Question 8.
Explain the term mechanical advantage of a machine.
Answer:
The mechanical advantage of a machine is the ratio of the load to the effort. In other words
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 4

Question 9.
Define the term efficiency of a machine.
Answer:
The ratio of the work done by the machine to the work done on the machine is called efficiency of a machine
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 5
(Work done by a machine is called the output energy and the work done on a machine is called the input energy.)

Question 10.
What is an ideal machine ?
Answer:
A machine is which no part of the work done on the machine is wasted, is called an ideal or perfect machine. Thus, for an ideal machine, the work output is equal to the work input, i.e., the efficiency of an ideal machine is 1 (or 100 per cent).

Question 11.
Can a machine have an efficiency of 100% ? Give a reason to support your answer.
Answer:
Efficiency of a machine is always less than 100% as output energy is always less than the input energy, because some energy is lost to overcome friction.

Question 12.
A machine is 75% efficient’. What do you understand by this statement ?
Answer:
If a machine is 75% efficient, it means that 75% of the work input to the machine is obtained as the useful work output. The remaining 25% of the work input has been lost in overcoming the friction.

Question 13.
What is a lever ?
Answer:
Lever: A lever is a simple rigid bar which is free to move around a point called fulcrum.

Question 14.
Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.
Answer:
The levers are of three kinds :
Class I levers which have fulcrum in between the load and the effort.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 6
Class II levers which have load in between the fulcrum and the effort.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 7
Class III levers which has effort in between the fulcrum and the Load
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 8

Question 15.
What do you mean by the mechanical advantage of a lever ?
Answer:
The mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm. This is also called the principle of a lever.

Question 16.
Which class of lever has the mechanical advantage always more than 1 ? Give an example.
Answer:
The mechanical advantage of class II levers is always more- than 1.
Example – Nut cracker, wheel barrow, bottle opener etc.

Question 17.
Which class of lever has the mechanical advantage always less than 1 ? Give an example.
Answer:
The mechanical advantage of class III levers is always less than 1.
Example: a pair of tongs, sugar tongs, knife, forceps etc.

Question 18.
Give one example of class I lever in each case where the mechanical advantage is

  1. more than 1
  2. equal to 1
  3. less than 1.

Answer:

  1. more than 1: Load arm of pliers
  2. equal to 1: See – saw
  3. less than 1: The load arm of a pair of scissors.

Question 19.
Name the class to which the following levers belong:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 9
Answer:
(a) A pair of scissors — Class I lever
(b) a lemon squeezer — Class II lever
(c) a nut cracker — Class II lever
(d) a pair of sugar tongs — Class III lever
(e) a beam balance — Class I lever
(f) an oar rowing a boat — Class I lever
(g) a wheel barrow — Class II lever
(h) a see saw — Class I lever
(i) a pair of pilers — Class I lever
(j) a crow bar — Class I lever

Question 20.
The diagram given below shows the three kinds of levers. Name the class of each lever and give one example of each class.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 10
Answer:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 11
Examples : The examples of class I levers are : a see saw, a pair of scissors, a pair of pilers, crow bar, common balance, spoon opening the lid of a tin can, handle of a hand pump.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 12
Examples : The examples of lever of class II are : nut cracker, wheel barrow, paper cutter, mango, lemon squeezer, bottle opener.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 13
Examples: The examples of levers of class III are : a pair of tongs, sugar tongs, knife, forceps,-forearm of a person holding a load, spade for lifting soil or coal.

Question 21.
Draw diagrams to illustrate the positions of fulcrum, load and effort, in each of the following:
(a) a see saw
(b) a beam balance
(c) a nut cracker
(d) a pair of forceps
Answer:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 14

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 15

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 16

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 17

Question 22.
How can you increase the mechanical advantage of a lever ?
Answer:
The mechanical advantage of a lever can be increased by increasing the effort arm or reducing the load arm.

Question 23.
How does the friction at the fulcrum affect the mechanical advantage of the lever ?
Answer:
Friction at the fulcrum reduces the mechanical advantage.

Question 24.
State three differences between the three classes of levers.
Answer:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 18

Question 25.
What is a pulley ?
Answer:
Pulley: It is a flat circular disc with a groove in its edge and a rope passing through the groove. It is capable of rotating around a fixed point passing through its central axis called axle.

Question 26.
What is the mechanical advantage of an ideal pulley ?
Answer:
In an ideal pulley, the effort applied is equal to the load to be lifted.
i.e. Effort = Load
Mechanical advantage = Load / Effort = 1

Question 27.
The mechanical advantage of an actual pulley is less than 1. Give a reason. What is the justification for using the pulley then ?
Answer:
In an actual pulley due to friction, the mechanical advantage is less than 1 (i.e. the effort is more than the load).
The reason for using the pulley when its mechanical advantage is equal to 1 or less than 1 is that the pulley allows us to apply the effort downwards i.e. in a convenient direction. To raise a load directly upwards is difficult. But with the help of a pulley, the effort can be applied in the downward direction to move the load upwards. One can hang on it to make use of his own weight also in order to apply the effort.

Question 28.
Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Answer:
To raise a load, the load is attached to one end of the string and the effort is applied at the other end by pulling it is downward direction . as shown in fig.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 19

Question 29.
What is an inclined plane? What is its use ? Give two examples where ¡t is used.
Answer:
An inclined plane is a rigid sloping surface over which heavy loads can be raised or lowered to a certain height or depth.
The mechanical advantage of an inclined plane is the ratio of the length of the plank to the vertical height of the load raised. Its value is greater than one. Therefore, an inclined plane acts as a force multiplier. Thus, it can be used to lift heavy loads.
Example : If a heavy box needs to be loaded on a lorry, it is far easier to push it over an inclined plane than to lift it up. Steeper the inclined plane, greater will be the effort required to push up the load.
Sloping ramps, flyovers, roads on hills and staircases are all examples of inclined planes.

Question 30.
What is a screw ? Give two examples.
Answer:
A screw is a simple machine which appears like an inclined plane wound around a rod with a pointed tip.
Examples : ajar lid, a drill.

Question 31.
What is wheel and axle ? Give two examples.
Answer:
The wheel and axle is a simple machine having a wheel and an axle. The linear motion of axle is obtained by rotating the wheel so as to reduce friction. Example: Steering wheel, screw drivers, water tap etc.

Question 32.
How does a wheel help in moving the axle ?
Answer:
Wheel-and-axle arrangement consists of two cylinders of different diameters joined together such that if one is made to rotate, the other also rotates. The axle is a cylindrical rod fixed to the centre of a circular disc-like object called the wheel.
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 20
This machine acts as a speed multiplier device.
In riding a bicycle, when we apply force on the wheel (by pedal), the fixed axle rotates with it easily. This force that turns the axle produces a much larger movement of the wheel.

Question 33.
What is a wedge ? Give two examples.
Answer:
A wedge is a double inclined plane such that the two sloping surfaces taper to form either a sharp edge or a pointed edge. Examples : A knife, an axe, a chisel.
In some special cases, the number of inclined planes used can be more than two as well. In such cases, the sloping surfaces generally taper to form either a very sharp or a pointed edge to split or pierce materials. Pins, nails and needles are examples of pointed wedges. The front end of a boat is shaped like a wedge so that it can easily cut across the flowing water.
The wedge works on a principle of an inclined plane.

Question 34.
Name the machine to which the following belong :

  1. Beam balance
  2. Lemon crusher
  3. Sugar tongs
  4. Ramp
  5. Door knob
  6. Needle

Answer:

  1. Beam balance — A lever (lever of class I)
  2. Lemon crusher — A lever (lever of class II)
  3. Sugar tongs — A lever (lever of class III)
  4. Ramp — An inclined plane
  5. Door knob — Wheel and axle
  6. Needle — Wedge

Question 35.
What care would you take to increase the life span of a machine which you use ?
Answer:
Taking care of machines: Some of the ways in which machines should be cared for are given below :

  1. Machines should be kept in a clean environment, which is free from dust and moisture.
  2. When not in use, machines should be kept covered to prevent collection of dust on them.
  3. Machines made of iron should be protected from rust by coating them with paint.
  4. The moving parts of a machine should be regularly oiled with a good-quality machine oil to reduce friction and wear and tear. The above care of machines increases their life.

Question 36.
Select the correct statement :
(a) A wheel barrow is a lever of class I.
(b) The efficiency of a machine is always 100%
(c) Friction in moving parts of a machine reduces its efficiency.
(d) No lever has the mechanical advantage greater than 1.
(e) It is easier to lift a load vertically up than to push it along an inclined plane.
(f) A screw is made by two inclined planes placed together.
Answer:
(c) Friction in moving parts of a machine reduces its efficiency.

C. Numericals

Question 1.
In a machine an effort of 10 kgf is applied to lift a load of 100 kgf. What is its mechanical advantage ?
Answer:
Given,
Load = loo kgf
Effort = 10 kgf
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 21

Question 2.
The mechanical advantage of a machine is 5. How much load it can exert for the effort of 2 kgf ?
Answer:
Given,
Mechanical advantage = 5
Effort 2 kgf
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 22

Question 3.
The mechanical advantage of a machine is 2. It is used to raise a load of 15 kgf. What effort is needed ?
Answer:
Given,
Mechanical advantage = 2
Load = 15 Kgf
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 23

Question 4.
A lever of length 100 cm has effort of 15 kgf at a distance of 40 cm from the fulcrum at one end. What load can be applied at its other end ?
Answer:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 24

Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 25

Question 5.
In a lever, fulcrum is at one end at a distance of 30 cm from the load and effort is at the other end at a distance of 90 cm from the load. Find :
(a) the length of load arm,
(b) the length of effort arm, and
(c) the mechanical advantage of the lever.
Answer:
Selina Concise Physics Class 6 ICSE Solutions Chapter 4 Simple Machines 26

Selina Concise Chemistry Class 6 ICSE Solutions – Matter

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Selina Concise Chemistry Class 6 ICSE Solutions – Matter

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Chemistry for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 6 Chemistry ICSE SolutionsPhysicsBiologyMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 6 Chemistry Chapter 3 Matter

POINTS TO REMEMBER

  1. Horse, mango tree, dog, animals, plants are living, while stone, pen, glass, water, book, table, air are non-living.
  2. All the above mentioned things living and non-living are matter.
  3. Energies like light, sound, heat are not matter, as these have no mass.
  4. Matter : “Anything that has mass and occupies space is called matter.” Matter (mass) remains same at all places.
  5. Molecules of matter are in motion.
  6. The things which are similar in one or more ways are grouped together and this practice is classification.
  7. There are inter-molecular gaps (spaces) and inter-molecular attraction (force of attraction) between molecules.
  8. Solids are rigid, have definite volume, retain their shape and are incompressible.
  9. Liquids can flow, have definite vol., have no definite shape. Have only one free surface.
  10. Gases Have no definite volume, no definite shape can flow are compressible.
  11. Inter-molecular force : Solids > Liquids > Gases.
  12. Inter-molecular volume : Solids < Liquids < Gases.

Activity 1

Question 1.
List five substances made using each of the following materials:
Answer:

  1. Wood : Chair
  2. Paper : Book
  3. Plastic : Bucket
  4. Metals : Copper wire
  5. Leather : Shoes
  6. Cloth : Shirt or bag

EXERCISE- I

Question 1.
Define matter.
Answer:
Anything that has mass and occupies space is called matter.

Question 2.
What are the two main types of matter? Give two examples for each type.
Answer:
The two main types of matter are :

  1. Living matter: The earth is home to all kinds of plants and animals. They can grow, move and reproduce on their own. Examples : Plant, lotus, animals, human etc.
  2. Non-living matter : Most of the matter in the universe is non-living. It means that it does not grow, move or reproduce on its own. It can be natural or man made.

(a) Natural matter: It occurs in nature and can be used to make more useful substances, e.g., wood, coal, silk, water, stone, cotton, jute, cereals, fruits, etc.
(b) Man-made matter : It is produce artificially from natural matter, e.g., plastics, soaps, detergents, medicines, glass, nylon, steel, ceramic, etc.

Question 3.
Differentiate between living and non-living matter.
Answer:
Living matter:

  1. The earth is home to all kinds of plants and animals. They can grow, move and reproduce on their own.
  2. It is natural only.

Non-living matter:

  1. Most of the matter in the universe is non-living. It means that it does not grow, move or reproduce on its own.
  2. It can be natural or man made.

Question 4.
Select natural and man made matter from the following
list: Wood, plastic, silk, medicines, detergents, coal, water, ceramic, cotton, glass, nylon, fruits.

Answer:
Natural matter: Wood, silk, coal, water, fruits.
Man made matter: Plastic, medicines, detergents, ceramic, cotton, glass, nylon.

EXERCISE-II

Question 1.
Name the smallest particle from which matter is made up.
Answer:
The smallest particle from which matter is made up is atom.

Question 2.
What are molecules ?
Answer:
Molecules are the smallest unit of matter. They exhibit all the properties of that kind of matter and is capable of independent existence.

Question 3.
Give one difference between atoms and molecules.
Answer:
Atoms may or may not have independent existance. While molecules have independent existence.

Question 4.
Define:
(a) Intermodular force of attraction.
(b) Intermodular space.

Answer:
(a) The molecules of matter are always in motion and attract each other with a force, and this force is called intermodular force of attraction due to which they are held together.
(b) The molecules can move only when there are gaps or space between them, this space is called intermodular space.

Question 5.
Name the three states of matter and define them.
Answer:
The three states of matter are :

  1. Solid State
  2. Liquids
  3. Gases :

Solid State : The molecules are very close to each other hence intermodular spaces are small and intermodular force is strong.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 1
Hence solids have definite volume, rigid, retain definite shape and are incompressible.
Liquids : The molecules are less closely packed have more intermolecular spaces than solid, less stronger forces than solids.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 2
Hence liquids have definite volume but no definite shape. They take the shape of container in which they are put.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 3
Gases : The molecules in the gases are far apart with weakest force of attraction. Hence gases have neither definite volume nor definite shape but easily compressible.

Question 6.
What are fluids ? Give two examples
Answer:
Substances that can flow are called fluids. Both gases and liquids are fluids, e.g. gases (carbon dioxide, hydrogen), liquids (water, petrol and sulphuric acid).

Question 7.
Classify the following into solids, liquids and gases.
Oxygen, milk, common salt, wax, stone, L.P.G, carbon- dioxide, sugar, mercury, coal, blood, butter, copper, coconut oil, kerosene.
Answer:
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 4

Question 8.
Give reasons
(a) Liquids and gases flow but solids do not ?
(b) A gas Alls up the space available to it.
(c) The odour of scent spreads in a room.
(d) We can walk through air.
(e) Liquids have definite volume but no definite shape.
(f) When a teaspoon of sugar is added to half a glass of water and stirred, the water level in the glass remains unchanged.
(g) When an empty gas jar is inverted over a gas jar containing a coloured gas, the gas also spreads into the empty jar.
(h) A red ink drop added to small amount of water in a glass turns the water red in some time.

Answer:
(a) The molecules of liquids and gases are far apart i.e. have more gaps, intermolecular attraction force is very less as compared to solids, hence liquids and gases can flow but solids do not as gaps*in solid molecules is less and molecular force of attraction very strong.
(b) Intermolecular force of attraction is least and intermolecular spaces are very large, hence gases can fill up the space available to them.
(c) Scent fumes (molecules) being gases fill the spaces between air molecules and the molecules of air fill the spaces between scent molecules due to diffusion, fumes spread into a room.
OR
Due to inter-mixing of scent molecules and air molecules, scent fumes spread into the room.
(d) The molecules of air are far apart i.e. large gaps and we can walk through air easily.
(e) The molecules of liquid are loosely packed and intermolecular force of attraction is small but number of molecules in it remain the same. Hence liquids have definite volume but no definite shape.
(f) When a teaspoon of sugar is added to half a glass of water and stirred, the water level in the glass remains unchanged because the sugar particles are adjusted between the water molecules as inter-molecular gaps are more in liquids.
(g) This is because Gases can diffuse or flow in all directions.
(h) When we put a drop of red ink in a glass of water, its particles diffuse with particles of water slowly but continuously and the water turns red.

Question 9.
Define:
(a) cohesive force
(b) diffusion
(c) Brownian movement

Answer:
(a) Cohesive force : The force of attraction between particles of the same substance is called cohesive force.
(b) Diffusion: The phenomenon of intermixing of particles of one kind with another kind is called diffusion.
(c) Brownian movement: The zig-zag motion of particles suspended in a medium is called Brownian movement

Question 10.
Why is an egg kicked out of a bottle when air is blown inside the bottle?
Answer:
When we invert the bottle and blow air into the bottle throw the side opening. It creates high pressure inside the bottles and the egg is kicked out of the bottle.

EXERCISE-III

Question 1.
State the three effects of heat on matter.
Answer:
When a substance is heated, it can cause.

  1. Interconversion of states of matter.
  2. Thermal expansion of the substance.
  3. Chemical change.

Question 2.
(a) Define : interconversion of states of matter.
(b) What are the two conditions for the interconversion of states of matter ?

Answer:
(a) The process by which matter changes from one state to another and back to original state, without any change in its chemical composition.
(b) Two conditions are :

  1. Change in temperature
  2. By applying pressure

Question 3.
Define the following terms:
(a) Fusion
(b) Vaporisation
(c) Condensation
(d) Sublimation
(e) Diffusion
(f) Melting point
(g) Boiling point
(h) Liquefaction

Answer:
(a) Fusion : The heating process by which a solid changes into the liquid state is called fusion.
(b) Vaporisation : The heating process by which a liquid changes into its vapour state is called vaporisation.
(c) Condensation : The process by which a substance in gaseous state changes into its liquid state is called condensation.
(d) Sublimation: The change of solid on heating to vapours directly and vice-versa without passing through the liquid state is called sublimation.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 5
(e) Diffusion : The phenomenon of intermixing or spreading of gaseous molecules is called diffusion.
(f) Melting point: The fixed temperature at which a solid changes into a liquid at a given pressure is called its melting point. The temperature remains constant as long as the conversion is going on.
(g) Boiling point: The fixed temperature at which a liquid starts changing into gaseous state is called its boiling point. The temperature remains constant till the whole of the liquid changes into gaseous state.
(h) Liquefaction : Change of vapours on cooling to liquid is called liquefaction.

Question 4.
Differentiate between:
(a) Solidification and condensation
(b) Melting and boiling
(c) Gas and vapour
(d) Miscible and immiscible liquids.

Answer:
(a) Solidification : The process of changing liquid into a solid state by cooling is known as solidification.
Example : water → ice.
Condensation : The process of changing a gas or vapour state to a liquid state by cooling is known as condensation. Example : steam → water.
(b) Melting : The fixed temperature at which a solid changes into a liquid at a given pressure is called its melting point.
e.g. ice → water.
Boiling : The fixed temperature at which a liquid starts changing into gaseous state is called its boiling point.
e.g. water → steam.
(c) Vapourisation : The process by which a substance changes from a liquid state to vapour state is called vaporisation or evaporation.
e.g., Water changes into gaseous state on heating.
Gas : The substance which remain in the gaseous state under normal conditions of temperature and pressure are called gases.
e.g, Oxygen, hydrogen, nitrogen.
(d) Miscible: Liquids which mix with each other are called miscible liquids. Example : Water and alcohol.
Immiscible liquids : Liquids which do not mix with each other are called immiscible liquids. Example Water and oil.

Question 5.
Give reasons :
(a) How is interconversion of states of matter different from chemical reaction ?
(b) Why a solid does not flow, but a liquid flows ?
Answer:
(a) During interconversion of state of matter composition
of substance remains the same matter changes from one state to another and back to the original state, while chemical reaction involves re-arrangement of the molecular structure and composition changes.
(b) In solids there is a strong force of attraction between the molecules and the space between them is very negligible. The molecules are therefore, not free to move. They merely vibrate about their mean positions. But in the case of liquids, the molecules are not very closely packed. They do not attract each other as strongly as the molecules of solids. Thus, the intermolecular spaces are larger and the molecules are able to move about more freely. This makes a liquid flow.

Question 6.
How does a liquid changes into its gaseous state? Explain ?
Answer:
As a liquid is heated, its particles starts gaining energy and move more vigorously which increases the gaps between the particles and decreasing the force of attraction. Ultimately a liquid changes into gaseous state.

Question 7.
Water cycle is an example of interconversion of states of water. Explain.
Answer:
Water from oceans, rivers, lakes from leaves of trees (transpiration) changes into vapours when temperature increases or evaporates and enters the atomsphere as clouds when temperature falls the vapours change into water and some of it in the form of snow fall on mountains and earth in the form of water and hales and this continues. Thus water cycle is example of interconvertion of states of water.

Question 8.
What happens to a metal ball when it is heated? What does this show?
Answer:
When metal ball is heated, it expands. This can be proved by following experiment:
Take a metallic ring and ball. Try to pass the metal ball through the ring. The ball is able to pass through the ring. Now heat the metal ball for 5-6 minutes. The hot ball is not be able to pass through the ring.
This shows that a solid expands on heating. Now cool the ball, it again passes through the ring. This shows that a solid contacts on cooling.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 6

Question 9.
Why does a candle become smaller on burning with time?
Answer:
On heating, candle wax melts, then turns into vapour which reacts with air to produce two new substances, carbondioxide and water.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 7
Therefore a candle on burning becomes smaller and smaller and the part of wax which has undergone chemical change cannot be recovered.

OBJECTIVE TYPE QUESTIONS

Question 1.
Fill in the blanks :

(a) Water is a matter because it has mass and occupies space.
(b) Any matter which has a definite volume but no definite shape is called a liquid.
(c) Liquids and gases can flow.
(d) The molecules are at a greater distance in gases compared to liquids.
(e) Water boils at 100 °C.
(f) The physical state of a substance, which has neither fixed volume nor fixed shape is a gas.

Question 2.
Write whether the following statements are true or false.

(a) Only water can exist in three different states.
(b) If the container in which a gas is collected has an opening, the gas will flow out and spread itself indefinitely.
(c) Solids have the large inter-molecular space.
(d) There is no difference between evaporation and boiling.
(e) All solids, on heating, first change to the liquid and then to the gaseous state always.
(f) The intermolecular force of attraction is the weakest in gases.
(g) A gas has no free surface.

Answer:
(a) True
(b) True
(c) False
Correct: Solids have the very small (negligible) inter-molecular space.
(d) False
Correct : There is a difference between evaporation and boiling.
(e) False
Correct : Few solids, on heating, first change to the liquid and then to the gaseous state always.
(f) True
(g) True

Question 3.
For each of the following statements, say whether it describes a solid, a liquid or a gas.

(a) Particles move about very quickly but do not leave the surface : Liquid
(b) Particles are quite close together : Solid
(c) Particles are far apart and move in all directions : Gas

Question 4.
Match the following :
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 3 Matter 8

Question 5.
Name the phenomenon which causes the following changes:
(a) Formation of water vapour from water.
(b) Disappearance of camphor when exposed to air.
(c) Conversion of ice into water.
(d) Conversion of water into steam.

Answer:
(a) Formation of water vapour from water is vaporisation.
(b) Disappearance of camphor is sublimation.
(c) Conversion of ice into water is melting.
(d) Conversion of water into steam is boiling.

Question 6.
Give two examples for each of the following :
(a) Substances which sublime.
(b) Substances which do not change their states.
(c) Substances which are rigid and not compressible.

Answer:
(a) Naphthalene, camphor, dry ice.
(b) Oxygen, hydrogen, nitrogen
(c) Glass, stone, pen.

MULTIPLE CHOICE QUESTIONS

1. Which one is a kind of matter :
(a) light
(b) petroleum
(c) sound
(d) heat

2. the state of matter which has no definite shape or volume is called
(a) solid
(b) liquid
(c) gas
(d) water

3. There are large intermolecular gaps in
(a) water
(b) iron ball
(c) common salt ..
(d) air

4. All kinds of matter
(a) occupy space and have a definite mass
(b) have mass and a definite shape
(c) can change their states
(d) have a definite volume

5. A kind of matter which can sublime is
(a) water
(b) plastic
(c) milk
(d) iodine

6. A substance which can change its state
(a) wood
(b) oxygen
(c) paper
(d) cloth

7. The process by which a solid changes into a liquid is called
(a) freezing
(b) melting
(c) condensation
(d) evaporation

PROJECT

Question 1.
Fill the following chart showing twelve solids, twelve liquids, four gases and eight materials.
Answer:
Solids : (1) Mobile. (2) Pen. (3) Pair of shoes. (4) A T.V. set (5) Chair. (6) Telephone. (7) Remote control. (8) Wood. (9) Ornaments. (10) Scissors. (11) Eraser. (12) Mirror.
Liquids : (1) Ink. (2) Water. (3) Lemon juice. (4) Cough syrup. (5) Mouth wash. (6) Petrol. (7) Kerosene oil. (8) Spirit. (9) Thinner. (10) Mercury. (11) Milk. (12) Copper sulphate solution.
Gases : (1) Hydrogen. (2) Oxygen. (3) Sulphur dioxide. (4) Chlorine gas.
Materials : (1) Paper. (2) Wood. (3) Iron nails. (4) Cement. (5) Tiles. (6) Plaster of paris. (6) Sand. (7) Iron rods. (8) Bricks.

Question 2.
Think and try to find a way to demonstrate water cycle in class.
Answer:
Do it yourself.

Question 3.
To identify materials of common use 
Procedure – Just move around in your house – in the drawing room, sitting room, bedroom, kitchen, bathroom etc.
Identify the things and All in the blanks in the table given below:

  • Study room
  •  Drawing room
  •  Kitchen
  •  bathroom
  • another place
S.No. PlaceName of the thingMaterial used for making the thing
  1. Study room
  2. Drawing room
  3. Kitchen
  4. bathroom
  5. Any other place

Answer:

S.No. PlaceName of the thingMaterial used for making the thing
1. Study roomTable, chair, books pens, pencils, table lamp, computer, fanWood, plastic, paper, glass, bakelite, connecting wires made of metal and plastics
2. Drawing roomSofa, table, chairs, fan, curtains, windows etc.Wood, cloth, coir, paint, plastics, aluminium, glass etc.
3. KitchenTaps, wash basin, cupboards, utencils, heating vessels strainer, containers aqua pure etc.Steel, aluminium, glass, china clay, iron, plastic, copper, stainless steel, brass etc.
4. BathroomTaps, tubs, mugs, tooth brush, tooth paste, soap, pail etc.Iron, brass, stainless steel, plastics etc.
5. Any other placeScooter, car, road, rooms, trucks, shops.Iron, rubber, coaltar, bricks, wood, plastics, clothes.

 

Selina Concise Chemistry Class 6 ICSE Solutions – Water

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Selina Concise Chemistry Class 6 ICSE Solutions – Water

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

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Selina Concise ICSE Solutions for Class 6 Chemistry Chapter  7  Water

POINTS TO REMEMBER

  1. Water cannot be replanished and without water we cannot live.
  2. 4 / 5 th of earth’s surface is covered with water and 1% of this available water is in the form of rivers, lakes, ponds and under ground water. It is utilized for agriculture and living beings consumption.
  3. In the atmosphere water is present in the form of vapour, mist, clouds etc.
    Selina Concise Chemistry Class 6 ICSE Solutions Chapter 7 Water 1
  4. Distillation : The process of removal of the dissolved salts from sea/ocean water.
  5. Purest form of water is rain water as it is formed by evaporation and condensation.
  6. Sea water is unfit for agriculture as plants do not tolerate saline water.
  7. Change of water from water bodies (lakes, rivers and oceans) into vapours in air and condensing of vapours and fall in the form of snow, water is called water cycle and water cycle plays an important role in
    (i) restoring the lost water from earth’s surface
    (ii) in controlling the climatic conditions.
  8. Water vapour is one of the invisible gases which makes up the air we breathe.
  9. Drinking water may contain some minerals and salts but it must be free from suspended impurities, harmful bacteria and germs.
  10. Sometimes water from a source look clear but may contain germs which cause water borne diseases like typhoid, cholera, jaundice, dysentry, gastroenteritis etc.
  11. Water can be made fit for drinking by
    (i) boiling,
    (ii) sterilisation
    (iii) exposing to air and sunlight
    (iv) by chemical treatment like chlorination or ozonisation.
  12. Water is universal solvent i.e. water can dissolve nearly in every substance.
  13. Distilled water is the purest form of water but not good for drinking purposes. It is good for medicinal purposes, laboratories and batteries.
  14. Both stirring and heating help in dissolving the substance in water.
  15. “The amount of solute that dissolves in a given quantity of solvent at a given temperature is called solubility of the solute.”
  16. Air dissolved in water helps aquatic animals and plants to survive.
  17. Eutrophication : “The deficiency of oxygen in the water may cause death of aquatic animals. This loss of dissolved oxygen from water in water bodies is called eutrophication.”

EXERCISE-I

Question 1.
Name:

(a) Three major sources of natural water
(b) Four sources of surface water.
(c) Two underground sources of water.

Answer:

(a) Three major sources of natural water :

  1. Surface water (sea water)
  2. Above surface water (rain)
  3. Underground water (springs)

(b) Four sources of surface water sources :

  1. Ocean water
  2. River water
  3. Lake water
  4. Glaciers

(c) Two sources of underground water :

  1. Well water
  2. Spring water

Question 2.
Answer the following questions in short:

(a) In which form is water present in the atmosphere ?
(b) Which source of water contains the highest concentration of salt in it ?
(c) Why is rain water considered the purest form of natural water?
(d) What possible impurities does rain water contain ?
(e) What is water table ?
(f) Why is spring water pure enough for drinking but unsuitable for laboratory use ?
(g) Why the taste of spring water differs at different places ?

Answer:

(a) Water is present in the form of water vapours in the atmosphere.
(b) Sea water contains highest concentration of salt.
(c) Rain water is the purest form of water as it is distilled water i.e. water from surface of earth has evaporated and then vapours condense in the atmosphere.
(d) The impurities present in rain water are dust and dissolved gases like oxygen, nitrogen and carbon dioxide and these gases are not poisonous, rain water is safe for drinking.
(e) Level of ground water is called water table.
(f) Spring water is free from suspended impurities and germs (harmful bacteria) as water has been filtered through different layers of soil and is fit for drinking. Spring water contains dissolved impurities which are due to the nature of soil surrounding the spring and cannot be used for laboratory purposes, where distilled water free from impurities is needed.
(g) Spring water contains unsolved impurities which have entered the water from surrounding soil and soil impurities (salts) differ from place to place. Hence taste of water differs from place to place.

Question 3.
List three major impurities present in river water.
Answer:
Three major impurities present in river water :

  1. Suspended impurities like clay and sand particles.
  2. Harmful bacteria.
  3. Mineral salts.

Question 4.
Give the percentage of water in the following :

(a) Rice and wheat grains
(b) Eggs
(c) Tomatoes
(d) Bread
(e) Water melon

Answer:
Percentage of water in :

(a) Rice — 3 % to 4% Wheat grain — 3% to 4%
(b) Eggs —75%
(c) Tomatoes — 95%
(d) Bread —25%
(e) Water melon — 97%

Question 5.
What are the three states of water ?
Answer:
Three states of water are :

  1. Ice (solid)
  2. Liquid (water)
  3. Gaseous (steam)

Question 6.
Why are ice, liquid water and steam considered to have the same chemical substance ?
Answer:
Ice, liquid water and steam have same composition i.e. 2 parts hydrogen and one part oxygen by volume and same formula H2O, can be easily transformed from one state to other by heating or cooling.

Question 7.
How is a cloud formed ?
Answer:
Water from the surface of earth, lakes, seas, rivers, formed by plants (transpiration) etc. evaporates and rises high up in the atmosphere and condense into water droplets and collect to form cloud.

Question 8.
What is water cycle ? What is its importance ?
Answer:
Water cycle : The change of water from one form to another in nature which results in continuous circulation of water from earth’s surface to the atmosphere and from the atmosphere back to the earth’s surface is called water cycle.
Importance of water cycle:

  1. It assures a continuous supply of water to us.
  2. In controlling the climatic conditions all over the world.

Question 9.
How are the following formed ?

(a) fog
(b) mist
(c) dew
(d) frost

Answer:

(a) Fog : When water vapours change into tiny droplets of water near the ground, fog is formed.
(b) Mist: When tiny droplets of water remain suspended in air it is called mist.
(c) Dew : When the water vapour condenses on cold objects like grass, leaves and flowers in winter in the form of tiny droplets of water called dew.
(d) Frost: When the dew freezes it is called frost.

EXERCISE-II

Question 1.
Name:

(a) Two chemicals used to destroy germs present in water.
(b) Two diseases which spread through impure water.
(C) A chemical used for loading.
(d) Two substances which add taste to water.
(e) Two household methods to get safe drinking water.

Answer:
(a) Two chemicals used to kill germs in water are:

  1. Chlorine.
  2. Potassium permanganate.
  3. terilizing water with ozone.

(b) Two diseases are cholera, dysentry.
(c) Chemical used for loading is potash alum.
(d) Minerals and carbon dioxide gas adds taste to water.
(e) Methods to get safe drinking water:

  1. Adding chlorine tablets.
  2. By adding potassium permanganate crystals.

Question 2.
Answer in brief:

(a) Why is river water unfit for drinking?
(b) Why is tap water a mixture?
(c) What is mineral water?
(d) What is the purpose of adding bleaching powder to water supplied to the town?
(e) How is chemically pure water obtained in the laboratory?
(f) how is water in swimming pool kept free a germs?

Answer:

(a) River water contains mineral salts, suspended impurities like clay, sand particles, organic matter and bacteria and is not fit for drinking.
(b) Tap water contains, minerals, air, chlorine and other dissolved impurities that varies from place to place, therefore it is a mixture.
(c) Mineral water is pure water fit for drinking. It is collected from natural source and contains air, minerals and salts free from suspended impuiities, harmful bacteria and germs.
(d) Adding bleaching powder to water, kills germs and harmful bacteria and viruses present in water.
(e) Chemically pure water for laboratories is obtained-by distillation. Distilled water does not contain any salt or mineral
(f) Water in swimming pool kept free from infections and germs by chlorination i.e. treating water with chlorine gas.

Question 3.
Define:

(a) Sterilisation
(b) Sedimentation
(c) Loading
(d) Aeration

Answer:

(a) Sterilisation : The process of removal of microorganisms including bacterial spores from water to avoid water borne diseases is known as sterilisation.
(b) Sedimentation : The setting of suspended solid matter at the bottom of a liquid is called sedimentation.
(c) Loading : The process of adding a chemical to an impure liquid in order to increase the speed of sedimentation of suspended particles is called loading.
(d) Aeration : To kill harmful micro-organisms present in filtered water, air underpressure is blown into the filtered water. This process is called aeration.

Question 4.
What is potable water ? List four characteristics of potable water.
Answer:
Potable water : Water fit for drinking purposes is called potable water.
Four characters of drinking water :

  1. It should be transparent.
  2. Should have no colour, no odour.
  3. Should be free from harmful bacteria and germs.
  4. It should contain same salts and minerals needed by the body CO2 to add to taste.

Question 5.
Why is water important for plants and animals ?
Answer:
Importance of water for plants:

  1. Plants need water to prepare their food, for germination and growth to produce fruits, flowers etc.
  2. For conduction of food prepared by plants to other-parts of plant i.e., for translocation.
  3. Large number of plants live in water; water provides nutrients and oxygen for their survival.
    Crops need water for their growth. Water in the form of rain, washes the dust and smoke deposited on leaves by vehicles and helps the stomata in exchanging gases.

Importance of water for animals:

  1. Lot of water is lost by the body of animals by sweating, in the form of urine and evaporation while doing various activities, so to make up for the lost water animals consume a lot of water in the form of drinking.
  2. Water keeps the animals fresh and is natural medicine for their many ailments.
  3. Water is good solvent and helps in the process of digestion, blood circulation, excretion etc. in the body of organisms.
  4. Water is essential for the cleanliness of animals and their surroundings.

Question 6.
What are the three methods of removing germs from natural water. Explain.
Answer:
Three methods to remove germs :

  1. By boiling : Boiling kills germs present in water.
  2. Adding potassium permaganate: By adding potassium permaganate in the well the germs can be killed.
  3. Chlorination : After filtration water is passed through chlorination tank here chlorine kills the germs.

Question 7.
Name the steps involved in the purification of drinking water supplied in cities and towns.
Answer:
The water source for our towns and cities are river, lakes or underground water which contains suspended and dissolved impurities.
To remove these impurities steps involved are :

  1. Loading and sedimentation : to settle the suspended impurities to form a sediment for this purpose potash alum is added.
  2. Filtration : The water still contains lighter suspended impurities which are removed by filtration through sand and gravel. In cities ground water is drawn from tube well or submurcible pumps which have filters fitted in them. This clear water still contains germs.
  3. Chlorination : To kill germs water is passed into chlorination tank where it is treated with chlorine to kill germs.
    Water is now potable i.e. safer for drinking and supplied to homes.

Question 8.
What is the taste of distilled water ? Why is it not potable?
Answer:
Taste of water is tasteless i.e. flat. It is because distilled water does not contain any salt or mineral required for our body. So it is not potable water.

Question 9.
Give reasons :

(a) Ice floats on water.
(b) Marine life is able to survive in colder regions.
(c) Water droplets can be seen outside a chilled water bottle.

Answer:

(a) Water has maximum density at 4°C. Ice is lighter than water therefore it floats on water.
(b) This anomalous property of water enables aquatic plants and animals to survive in colder regions of world because even when the water of ponds, lakes, river freezes it freezes on the top but remains a liquid below ice layer.
(c) Sometimes we see water droplets on the outer surface of the glass containing ice-cold water, this is because the water vapour presents in’air, on coming in contact with the cold glass of water, loses energy and gets converted into liquid state, which we see as water droplets.

EXERCISE-III

Question 1.
Why is water called a universal solvent ?
Answer:
As water can dissolve in most of the substances, solids, liquid and gaseous. Therefore it is called universal solvent.

Question 2.
Define:

(a) Solute
(b) Solvent
(c) Solution
(d) Saturated solutions
(e) Unsaturated solutions

Answer:

(a) Solute : A solute is a substance that dissolves in a medium which can be water or any other substance. Solute is in smaller quantity in a solution.
(b) Solvent : A solvent is a medium in which a solute dissolves. It is in large quantity in a solution. Water is the most common solvent. The other solvents are alcohol, carbon tetrachloride etc.
(c) Solution : A solution is a homogeneous uniform mixture formed by a solute and a solvent.
(d) Saturated solution : When a solution cannot dissolve any more of solute at a given temperature, it is called saturated solution.
(e) Unsaturated solution : A solution that can take up more of the solute at a given temperature, is said to be an unsaturated solution.

Question 3.
State two factors by which solubility of a solute in a solvent can be increased.
Answer:
Two factors are :

  1. Stirring.
  2. Increase in temperature.

Question 4.
Why do aquatic animals die in boiled water ?
Answer:
Boiled water is deprived of oxygen i.e. there is no oxygen. For want of oxygen animals die in boiled water.

Question 5.
State three differences between water and air.
Answer:
Differences between water and air :
Water :

  1. Water is liquid and can exist in three states i.e. solid-ice, liquid-water, gas – vapours.
  2. Is a compound.
  3. H2O is its formula.

Air :

  1. Air is gaseous and can exist in liquid state when cooled under pressure.
  2. Is a mixture.
  3. Has no formula.

EXERCISE -IV

Question 1.
State four ways by which water can be conserved.
Answer:
Four ways to conserve water:

  1. Do not allow water to drip from defective taps.
  2. More dams should be built.
  3. More plantation should be done as plants help in bringing rain.
  4. Wastage of water should be avoided.
  5. Close the tap when you are brushing your teeth. Rather use a mug. Close the tap when you are washing clothes, open the tap only when you need it. Reduce, Reuse and recycle should be our mantra

Question 2.
Explain harvesting of water.
Answer:
When it rains heavily water runs into streets, drains and wasted we can not make use of it. Our purpose is to catch this rain water, store it for future use when we actually need it. For this harvesting of rain water should be done. Rain water is collected from the roofs and verandas of the buildings with the help of pipes and carried to tanks for storage and is used at the time of need when it is not raining.

Question 3.
What are the three main causes of water pollution ?
Answer:
Three main causes of water pollution :

  1. Addition of waste products from homes.
  2. Addition of waste products from agriculture.
  3. Addition of waste from industries.
  4. Addition of sewage in water bodies.

Question 4.
State the main steps to be taken to prevent water pollution.
Answer:
Steps to be taken to prevent water pollution :

  1. Trees and plants be planted along the banks of rivers and canals.
  2. Bathing and cleaning of animals near or in water sources be not allowed.
  3. Use of pesticides, insecticides, fungicides and fertilisers should be reduced.
  4. The polluted water from industries should be treated first and then discharged into water bodies.
  5. Use biodegradable detergents.
  6. Water containing sewage should be passed through sewage treatment plants first and then this water should be used for irrigation.
  7. Wells should be covered properly and washing and cleaning of clothes, utensils and animals should not be done near the well to keep them clean.

Question 5.
What are the causes of floods and drought?
Answer:
Problems cause by floods :

  1. A rise in the level of water in dams, rivers, lakes etc.
  2. Heavy rainfall also causes floods.
  3. Floods cause extensive damage to crops, property, animal and human life.
  4. Crop-fields, villages and”many low-lying areas get submerged under flood water.
  5. Rains/floods also affect smaller animals living in the soil.

Problems cause by drought :

  1. Crops may die, fodder may become scarce.
  2. Living organisms of the soil die.
  3. Animals may die, plants and trees will not survive.
  4. Soil becomes dry, water level in rivers, lakes, dams etc. may fall. The ground water-level falls.
  5. Drought displaces people from a large number of villages and towns.

Question 6.
State some of the ways in which you as an individual can conserve water.
Answer:
The ways in which we can conserve water are as follows :

  1. Use a bucket for taking it.
  2. Make sure, water does not overflow from overhead tanks of your house.
  3. Close the tap when you are brushing your teeth.
  4. Wash fruits, vegetable in a bowl of water, rather than under a running tap. Water used for washing vegetables may be used to water plants in the garden.

OBJECTIVE TYPE QUESTIONS

1. Fill in the blanks

(a) Water is a universal; solvent.
(b) Rainwater is the purest form of natural water.
(c) Sand and dust are suspended impurities in water.
(d) Sea water has high concentration of salt (impurity).
(e) Water covers nearly 4 / 5 th of the surface of the earth.
(f) Evaporation of rain water leaves NO residue.
(g) Potash alum is the chemical added to water to remove the tiny suspended particles.
(h) A solution is a uniform mixture of a solute and a solvent.
(i) Ice, water and steam have different physical states but are chemically identical.
(j) Boiling kills most of the germs in water.
(k) The elements present in the molecules of water are hydrogen and oxygen.

2. Write True or False for the following statements

(a) Water is an element.
Answer. False
Correct: Water is aL compound.

(b) Tap water does not contain dissolved impurities.
Answer. False
Correct: Tap water contain dissolved impurities.

(c) Alum is commonly used for removing suspended impurities.
Answer. False
Correct : Alum is commonly used for settling down of suspended impurities.

(d) Distillation is a good method for purifying water for town supply.
Answer. False
Correct : Distillation is a good method-for purifying water for medicinal purpose.

MULTIPLE CHOICE QUESTIONS

Tick (√) the correct alternative from the choice given for the following statements:

1. Water content in human body is

  1. 70%
  2. 75%
  3. 80%
  4. 90%

2. The purest form of natural water is

  1. seawater
  2. river water
  3. rainwater
  4. lake water

3. When the water vapour changes into tiny droplets of water near the ground, it is called

  1. mist
  2. dew
  3. fog
  4. frost

4. Water is a

  1. compound
  2. element
  3. mixture
  4. none of the above

5. Common salt is obtained from sea water by

  1. distillation
  2. crystallisation
  3. evaporation
  4. sublimation

6. Jaundice affects

  1. heart
  2. lungs
  3. liver
  4. kidney

7. Chlorination of water is done

  1. to kill the germs
  2. to remove the suspended impurities
  3. to remove the dissolved impurities
  4. none of the above

Selina Concise Chemistry Class 6 ICSE Solutions – Introduction To Chemistry

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Selina Concise Chemistry Class 6 ICSE Solutions – Introduction To Chemistry

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Chemistry Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Chemistry Chapter 1 Introduction To Chemistry

Points To Remember

  1. Science : “Science is the systematic effort by human being to study, understand and utilise nature for meaningful purposes. This understanding is slowly developed by careful observations and experiments.”
  2. Chemistry: “The branch of science that deals with the study of the composition, physical and chemical properties of various forms of matter is called chemistry.”
  3. Fertilisers : “Are the chemicals which provide nutrients to crops and increase their yield.” e.g. Urea, calcium nitrate, sodium nitrate, potash, ammonium sulphate etc.
  4. Pesticides : “Are the chemicals used to kill pests which affect the production of crops and fruits.” e.g. Aldrin, malathion, parathion etc.
  5. Insecticides are the chemical used to kill insects, e.g. D.D.T. and B.H.C.
  6. Fungicides are substances which protect the crops from fungi, e.g. Bordeaux mixture and sulphur act as fungicides.
  7. Hormones are group of chemicals secreted in our body to control various activities.
  8. Enzymes are the chemicals secreted by our body and react with food water and oxygen as raw material in mouth and intestines.
  9. Role of Chemistry : Without chemistry our life would have been dull, it has helped us in every field of life. The production of better and faster crops to meet the needs of such a huge population is possible only because of chemicals produced by chemistry, i.e. Pesticides, fungicides, insecticides preservatives help us to preserve food in a better state and of good taste for a long time.
    In Industry : paints, drugs, fibres, soap, toothpaste, dyes plastics even fuels, atomic energy, petrol, diesel, kerosene, wax, paraffin rubber, acids, alkalies metals alloys are the gift of chemistry.
    Medicines: Penicillin, Tetracycline, pain killers and various other antibiotics are used to kill germs and cure diseases. Building and Daily Life: Building materials, items of daily use like, ink, pen, glass, sugar, common salt, paper.
  10. Preservatives are the chemicals which maintain the taste for longer time and do not let the food degrade to produce obnoxious (unpleasant smell), e.g. sugar, common salt, sodium benzoate and sodium meta-bisulphate.

Exercise

Question 1.
Give two examples for each of the following substances :
(a) food preservatives
(b) fuel
(c) fungicides
(d) medicines
(e) building materials
(f) chemical war weapons

Answer:
Two examples of :
(a) Food preservatives :

  1. Sodium Benzoate
  2. Sodium metabisulphate
  3. Sugar
  4. Common salt

(b) Fuel:

  1. L.P.G.
  2. Petrol
  3. Coal

(c) Fungicides :

  1. Sulphur
  2. Bordeaux mixture

(d) Medicines :

  1. Penicillin
  2. Painkillers
  3. Antibiotics

(e) Building materials :

  1. Cement
  2. Steel
  3. Glass

(f) Chemical war weapons :

  1. TNT
  2. RDX

Question 2.
Give short answers :
(a) What is science ?
(b) What is chemistry ?
(c) What is a fuel ? 
(d) How is chemistry helpful in improving the health of human beings ?
(e) What is alchemy?
(f) What kind of experiments did Alchemists do?
(g) What is ‘Philosopher’s stone’ ?
(h) What is the main difference between alchemy and chemistry?
(i) Name the chemicals which help in increasing food production.
(j) Name six such products, which we use daily.
(k) How is the knowledge of chemistry important to mankind ?

Answer:
(a) SCIENCE is the systematic effort by human beings to control nature through experiments and observation for their own use.
OR
SCIENCE is the systematic ongoing effort by human beings to study understand and utilise nature for meaningful purposes. This understanding is slowly developed by careful observations and experiment.
(b) Chemistry : “The branch of science that deals with the study of the composition and the physical and chemical properties of various forms of matter is called Chemistry.”
(c) Fuels : The substances which on burning produce heat energy are called fuels.
(d) Chemistry is very helpful in improving the health of human beings by providing Antibiotics, Pain killers, Pencilin, Tetracycline etc. It has provided us with Vitamins, Enzymes, Minerals and Anesthesia (chloroform, formalene etc.)
(e) The word “Alchemy” has its origin in a Greek word ‘Khemeia’ means “art of transmuting metals”. It was partly based on experimentations and partly on spiritual discipline.
(f) ‘Alchemists’ considered to be early chemists. They used all general techniques of chemistry in healing humans. Their contribution proved valuable to the society and in the advancement of civilization.
They had contributed to an incredible number of future uses of chemicals, metals, ink, paints, cosmetic, medicines, porcelain, etc.
(g) The goal of alchemy was to find a mythical and magical substance called “philosopher’s stone” not a literal stone but wax, liquid or powder with magical power, which on heating with a base, iron and copper metals would turn into gold, the purest form of matter which would bring wealth, health and immortality.
(h) Alchemy was both scientific and spiritual. Alchemists never separated them. It also lacked a common language for its concepts and processes i.e. there was no standardized scientific practice.
Chemistry was completely separated from ancient traditional alchemy. Still modern chemistry in general owes a great deal to alchemy. Alloys are formed by mixing metals with other metals and substances.
(i) Chemicals which help in increasing food production are fertilisers like urea, sodium nitrate, potash, ammonium phosphate, calcium nitrate etc. Pesticides like aldrin, malathion which are used to kill pests. Insecticides like D.D.T., B.H.C. fungicides like sulphur, bordeaux mixture etc.
(j) Six products of daily use are soap, paints, pen, tooth-paste, cooking oil, potable water.
(k) Importance of chemistry to mankind chemistry plays an important role to provide us with things of daily use like toothpaste, soap, detergents, paints, clothes,
medicines, fertilisers, pesticides, plastics, in preparing fuels, consumer products like glass, paper, pencils, pens, in substances used in defence like gunpowder, T.N.T. etc.

Question 3.
What is the contribution of chemistry in the following fields ?
(a) Industry
(b) Clothings
(c) Cosmetics
(d) National Defence
(e) Medicines

Answer:
Contribution of chemistry in the field of :
(a) Industry : To improve efficiency and production of metals, paints, paper, plastics, alloys, textile, pharmaceuticals, electroplating, cosmetics, synthetic fibres etc.
(b) Clothings: Chemistry is widely used in textile industry which manufactures clothing for us. Clothes guard our body from external environment.
Formation of clothing begins with the knowledge of conversion of fibres into fabrics. Fibres can be natural or synthetic. Earlier only natural fibres were known to man such as cotton, jute, silk, wool, etc. which were used to produce dress materials, sarees, bags, sweaters, shawls, etc. With more development, synthetic fibres were also made such as nylon, terylene etc. These fibres are strong, wrinkle resistant and dry quickly. They are used to make towels, bed sheets, bags, curtains, carpets, blankets, dress materials, etc.
(c) Cosmetics: The use of talcum powder, skincare creams, lipsticks, eyes and facial make up, deodorants, lotions, perfumes, bathing oil, body butter, baby products, etc. It is possible to convert various ingredients into usable cosmetics due to knowledge of chemistry.
(d) National Defence : Substances like gunpowder, T.N.T. (trinitrotoluene), phosgene, chemical weapons, laughing gas, etc., are all products of chemistry which contribute to the national defence.
(e) Medicines : Extensive researches by chemists have led to the discovery of number of medicinal drugs. These drugs help in fighting diseases and have thus increased the life span of human beings.
Examples : Aspirin, paracetamol, antibiotics like penicillin, tetracyline, antiseptics and various other medicines used to kill germs and cure diseases and their symptoms.

Question 4.
Who is known as Father of chemistry? Why?
Answer:
Robert William Boyle is known as ‘Father of Modern Chemistry’. He was an Anglo Irish scientist born in Ireland. He was the first to perform experiments under controlled conditions and publish his researches with elaborate details of procedure, apparatus and observations. Robert Boyle put chemistry on a firm scientific footing transforming it from alchemy into one based on measurements. He defined elements, compounds and mixtures.

Question 5.
Name the scientists who discovered the following.
(a) Atoms
(b) Oxygen
(c) Safety lamp
(d) Elements
Answer:
The scientists who discovered
(a) Atoms : John Dalton was a British chemist and physicist. He proved that matter consists of small indivisble called ‘atoms’. For this he proposed the atomic theory which was later on called “Dalton’s atomic theory”.
(b) Oxygen : Joseph Priestly.
(c) Safety lamp : Sir Humphry Davy.
(d) Elements : Antoiene Lavoisier was a French nobleman. He revolutionized chemistry. Lavoisier named the elements carbon, hydrogen and oxygen and discovered the role of oxygen in combustion and respiration for which he is most noted. He established that water is a compound and helped to continue the transformation of chemistry from a qualitative science to a quantitative one.

Objective Type Questions

Question 1.
Fill in the blanks :
(a) Chemistry deals with the study of matter and the changes it undergoes.
(b) Fertilizers help to increase the production of food.
(c) Food items like jams and pickles are protected by using preservatives (salt and sugar).
(d) L.P.G. is used for fuel.
(e) Inert gases were discovered by William Ramsay.

Question 2.
Match the following words in column A with those in column B:
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 1 Introduction To Chemistry 1

Question 3.
Write “True” or “False” against each of the following statements.

(a) Chemistry plays an important role in national economy: True
(b) Antibiotics are used as preservatives : False
(c) D.D.T. is an important fertiliser: False
(d) Gunpowder is an pesticide : False
(e) Enzymes secreted by our body are chemicals : True

Question 4.
Choose the correct alternative from the choices given below for the following statements :
(a) Trinitrotoluene is used as

  1. a preservative
  2. a fertiliser
  3. a fuel
  4. an explosive

(b) Which one of the following is a pesticide ?

  1. benzoic acid
  2. aldrin
  3. sugar
  4. gunpowder

(c) Mortar is used as a

  1. plastic material Urea is an
  2. a building material
  3. an insecticide
  4. as medicine

(d) Used is an important

  1. fuel
  2. preservative
  3. fertiliser
  4. food item

(e) The chemicals prescribed by a doctor in treatment of infectious diseases are called

  1. antigens
  2. lotions
  3. antibiotics
  4. creams

Question 5.
Match the following scientists in column A with their discoveries or contributions in column B.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 1 Introduction To Chemistry 2

 

Selina Concise Chemistry Class 6 ICSE Solutions – Common Laboratory Apparatus and Equipments

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Selina Concise Chemistry Class 6 ICSE Solutions – Common Laboratory Apparatus and Equipments

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Chemistry for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Chemistry Chapter 2 Common Laboratory

Points To Remember

  1. Chemistry is an experimental science.
  2. A chemical laboratory is a place to perform experiments and to observe chemical processes.
  3. Knowledge of chemistry is based on experiment and observation.
  4. A chemical laboratory is a place to perform chemical experiments.
  5. Various kinds of apparatus and equipments are required to perform experiments.
  6. Necessary precautions should be taken while performing experiments.
  7. Maintain silence and discipline in the laboratory and concentrate on your experiment.

Exercise

Question 1.
Mention one use of each of the following equipments
(a) Spirit lamp
(b) Test tube
(c) Conical flask
(d) Evaporating dish
(e) Wire gauze
(f) Beaker
(g) Mortar and pestle
(h) Measuring cylinder
(i) Glass tube
(j) Gas jar
(k) Reagent bottle.

Answer:
(a) Spirit lamp is used to heat up substances.
(b) Test tube is used to conduct tests with small quantities of chemicals for heating and boiling purposes.
(c) Conical flask to hold sufficient quantities of substance in the form of solution.
(d) Evaporating dish is used for evaporating liquids.
(e) Wire gauze is used to keep glass apparatus (flask, beaker) on while heating is in progress. It is also used for uniform distribution of heat.
(f) Beaker is used for keeping of solutions.
(g) Morter and pestle is used to grind and crush solid substances into a pov
(h) Measuring cylinder is used to measure the volume of (mainly) liquid substances.
(i) Glass tube is used to transfer fluids or gases from one vessel to another.
(j) Gas jar is used for collecting gases and holding them in captivity vaccum.
(k) Reagent bottle is used for storing chemicals.

Question 2.
From what materials are the following made up of ?
(a) Test tube rack
(b) Test tube holder
(c) Measuring cylinder
(d) Wire gauze
(e) Mortar and pestle

Answer:
(a) Test tube rack is made up of wood or plastic.
(b) Test tube holder is made up of a iron clamp at front and wood or plastic handle at other end.
(c) Measuring cylinder is made of glass.
(d) Wire gauze is made of meshed iron wire and a thin asbestos sheet that is fixed at its centre.
(e) Morter and pestle is made of porcelain.

Question 3.
List any five precautions taken care of while performing an experiment in a chemistry laboratory.
Answer:
Five precautions to be taken in laboratory are :

  1. Do not touch or taste any unknown substance.
  2. Use only small quantity of chemical to carry out experiment.
  3. Do not work alone in the laboratory.
  4. Do not throw hot concentrated acids into the sink directly.
  5. Always wear an apron in the laboratory to protect your clothes.
  6. While heating keep the mouth of test tube away from your eyes and face.
  7. The apparatus to be used in an experiment should be arranged neatly before beginning an experiment.
  8. Do not throw broken glass apparatus or used filter paper in the sink. Throw them in a dustbin.

Question 4.
Answer the following questions in brief:
(a) Why is chemistry known as an experimental science?
(b) Why are most apparatus made of glass ?

Answer:
(a) Chemistry is known as experimental science as an experiment is performed under controlled conditions in an activity and we observe a natural or an artificially created phenomenon.
(b) Most of the laboratory apparatus is made of glass because :

  1. glass is easy to clean.
  2. Glass is transparent material and we can see through it clearly.
  3. It does not react with most of the chemicals used in experiments.
  4. Glass withstands high temperatures.
  5. Pyrex glass or borosil glass is a special type of glass which hardly expands on heating. Such glasses do not break even at high temperatures.

Question 5.
Label the marked equipment s in the diagram given below.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 2 Common Laboratory Apparatus and Equipments 1
Answer:

  1. Glass tube (delivery tube)
  2. Flask (round bottomed)
  3. Wire gauze
  4. Burner
  5. Tripod (stand)
  6. Gas jar
  7. Water trough
  8. Water

Selina Concise Chemistry Class 6 ICSE Solutions Chapter 2 Common Laboratory Apparatus and Equipments 2

Objective Type Questions

Question 1.
Fill in the blanks :

(a) Experiment and observation are the two important basics of chemistry.
(b) A porcelain dish is used for evaporation.
(c) A test tube holder is used to hold the test tube while-it is heated.
(d) Mortar and pestle is used for grinding and crushing solid substances into a powder.
(e) Glass apparatus is made of Pyrex or borosil glass.

Question 2.
Match the words in Column A with their respective functions in Column B.
Selina Concise Chemistry Class 6 ICSE Solutions Chapter 2 Common Laboratory Apparatus and Equipments 3
Question 3.
Choose the correct alternative from the options given for each of the following statements.

(a) The evaporating dish is made of

  1. porcelain
  2. glass
  3. metal
  4. plastic

(b) The spirit lamp is made of

  1. glass
  2. brass
  3. steel
  4. all of the above

(c) The apparatus to measure an accurate volume of liquid, is

  1. beaker
  2. conical flask
  3. measuring cylinder
  4. test tube

(d) To pass a gas from one vessel to another, you will use

  1. gas jar
  2. delivery tube
  3. glass rod
  4. test tube

(e) To prevent the escape of a gas from a gas jar, you will cover its mouth with

  1. watch glass
  2. crucible
  3. beaker
  4. round bottom flask

Question 4.
Write true or false against the following statements and correct the false ones.

(a) A glass funnel is used to pour off liquids.
(b) A test tube is used to test liquid chemicals.
(c) A mortar and pestle is used for evaporation.
(d) A glass rod is used to stir solutions.
(e) A round-bottom flask is used to store chemicals.

Answer:
(a) True
(b) False
Correct: A test tube is used to test chemicals and for heating and boiling purposes.
(c) False
Correct: Mortar and pestle is used to grind and crush solid substances into powder.
(d) True
(e) False
Correct: A REAGENT bottle is used to store chemicals.