CBSE Class 6 Science Changes Around Us Worksheet Set D

Passage-1
Ravi and Tina were working on a project based on ‘changes around us’, for which they were observing different changes occuring in their daily life. 
They went to kitchen where they saw there mother was cooking food on LPG stove. Ravi said that burning of LPG in LPG stove involves chemical change.
But Tina argued that both physical and chemical changes are involved this process.

Question. According to you what is the physical change involved as mentioned by Tina?
(a) Burning of LPG gas.
(b) Conversion of liquid form of LPG into gaseous form.
(c) Cooking of food.
(d) There is no physical change.
Answer : B

Question. Burning of LPG gas is which kind of change?
(a) Chemical change
(b) Physical change
(c) Periodic change
(d) Reversible change
Answer : A

Question. Which one of the following examples involves both chemical and physical changes?
(a) Cutting of wood
(b) Melting of ice
(c) Burning of a candle
(d) Burning of paper
Answer : C

Question. What is the term used to describe the phase change of a liquid to a gas?
(a) Boiling
(b) Condensation
(c) Melting
(d) None of the above
Answer : A

Question. What term is used to describe the phase change of a solid to a liquid?
(a) Freezing
(b) Melting
(c) Boiling
(d) None of the above
Answer : B

Question. What is the term used to describe the phase change as a liquid becomes a solid?
(a) Evaporation
(b) Condensation
(c) Freezing
(d) None of the above
Answer : C

Question. Which of the following represents 'A'?
(a) Solar eclipse
(b) Formation of rainbow
(c) Occurrence of season
(d) Both (a) and (c)
Answer : D

Question. Which of the following represents 'D'?
(a) Making tea
(b) Burning of sulphur
(c) Dissolving salt in water
(d) Burning of coal
Answer : C

Question. Which of the following represent 'C'?
(a) Solar eclipse
(b) Raining
(c) Formation of rainbow
(d) Growth of a plant
Answer : A

Passage-4
Mohan was boiling water in a pan for making tea.
His brother Ram came there and observed that during boiling of water some bubbles are formed.
He told his brother Mohan that boiling of water is a chemical change as gas is evolved in this process.
But Mohan argued that this is not a chemical change.

Question. Do you agree with Mohan? What kind of change is this?
(a) Yes, physical change
(b) No, chemical change
(c) No, irreversible change
(d) No, periodic change
Answer : A

Question. According to you what is the gas that is observed by Ram?
(a) Oxygen
(b) Water vapours
(c) Carbon dioxide
(b) No gas is formed
Answer : B

Question. What kind of change takes place after formation of tea?
(a) Physical change
(b) Chemical change
(c) Reversible change
(d) Both (a) and (c)
Answer : B

Assertion/ Reason Based Questions

DIRECTIONS : The questions in this segment consists of two statements, one labelled as “Assertion A” and the other labelled as “Reason R”. You are to examine these two statements carefully and decide if the Assertion A and Reason R are individually true and if so, whether the reason is a correct explanation of the assertion. Select your answers to these items using codes given below.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion (A) : Respiration is an exothermic process.
Reason (R) : In an exothermic process heat is evolved.
Answer : B

Question. Assertion (A) : The change of water from liquid to steam on heating is a physical change.
Reason (R) : Conversion of liquid into steam is called evaporation.
Answer : B

Question. Assertion (A) : Explosion of a bomb is an exothermic change.
Reason (R) : Large amount of heat energy is released during explosion of bomb.
Answer : A

Question. Assertion (A) : Small gap is left between the rails of a railway track.
Reason (R) : Cooling of substances result in contraction.
Answer : B

Statement Based Questions

DIRECTIONS : Read the following three statements carefully and choose the correct option.
(a) Statements (i) and (iii) are incorrect but (ii) is correct.
(b) Statements (i) and (ii) are incorrect but (iii) is correct.
(c) All three statements are correct.
(d) All three statements are incorrect.

Question. (i) A physical change is one in which the substance undergoing change is not destroyed and no new substance is formed.
(ii) Glowing of an electric bulb is a physical change.
(iii) When antacid tablet is dropped in water, it fizzes. This is a chemical change.
Answer : C

Question. (i) Turning off of a bulb is an irreversible change.
(ii) When the leaves of the ‘touch-me-not’ plant is touched, they close. This is an reversible change.
(iii) Ripening of fruits is a reversible change as we can get unriped fruit from riped one.
Answer : A

Figure Based Questions

Question. Carefully observe the figures A and B below and choose the correct option.

(a) Both 'A' and 'B' are periodic changes.
(b) Both 'A' and 'B' are non-periodic change.
(c) 'A' is periodic and 'B' is non-periodic change.
(d) 'B' is periodic and 'A' is non-periodic change.
Answer : B

Question. The picture given below represents a chemical process On the basis of given figure choose the correct option.

(a) Reactant → Bicarbonate of soda, Product → Vinegar
(b) Reactant → Vinegar, Product → Carbon dioxide
(c) Reactant → Vinegar, Product → Bicarbonate of soda and carbon dioxide
(d) Reactant → Vinegar, Bicarbonate of soda, Product → Carbon dioxide
Answer : D

Question. Look at the following figures and choose the correct option.

(a) (i), (ii) and (iii) represents exothermic change.
(b) (ii), (iv) and (v) represents endothermic change.
(c) (i), (iii) and (v) represents exothermic change.
(d) only (ii) and (iv) represents endothermic change.
Answer : B

Match the Column

DIRECTEIONS : Match Column-I with Column-II and select the correct answer using the code given below the columns.

Question.
Column-I                                              Column-II
A. Melting                        (p) Change of state from liquid to solid
B. Condensation             (q) Change of state from liquid to gas
C. Evaporation                (r) Change of state from solid to liquid
D. Freezing                     (s) Change of state from gas to liquid
(a) A → (p), B →(q), C→ (r), D → (s)
(b) A → (s), B →(r), C→ (q), D → (p)
(c) A → (r), B →(s), C→ (q), D → (p)
(d) A → (q), B →(p), C→ (s), D → (r)
Answer : C

Question.
Column-I                                                                                     Column-II
A. Burning of carbon in air to produce                      (p) Endothermic change carbon dioxide
B. Melting of wax                                                      (q) Exothermic change
C. A change accompanied by absorption of heat      (r) Physical change
D. A change accompanied by evolution of heat        (s) Chemical change
(a) A → (s), B →(q), C→ (p), D → (r)
(b) A → (s), B →(r), C→ (p), D → (q)
(c) A → (r), B →(s), C→ (q), D → (p)
(d) A → (r), B →(q), C→ (s), D → (p)
Answer : B

Question.
Column-I                                          Column-II
A. On heating iron rod                      (p) It melts
B. On cooling water vapour              (q) Expands
C. On heating candle wax                (r) Salt and Sugar
D. Dissolves easily in water             (s) It condenses
(a) A → (q); B → (s); C → (p); D → (r)
(b) A → (s), B →(r), C→ (p), D → (q)
(c) A → (r), B →(s), C→ (q), D → (p)
(d) A → (r), B →(q), C→ (s), D → (p)
Answer : A

Passage Based Questions

DIRECTIONS : Read the passage(s) given below and answer the questions that follow.

Passage-1
For changing milk into curd we add a small quantity of curd into milk.
The milk is stirred and is set aside for a few hours at a warm place.
In a few hours the milk changes into curd.

Question. The change of milk into curd is a
(a) physical change
(b) chemical change
(c) periodic change
(d) None of the above
Answer : B

Question. On the basis of energy, the change of milk into curd is a
(a) slow change
(b) fast change
(c) exothermic change
(d) endothermic change
Answer : A

Question. Chemical changes are generally
(a) reversible change
(b) irreversible change
(c) periodic change
(d) None of these
Answer : B

Passage -2
Sheetal once preparing evening tea. In the meanwhile telephone bell rangs and she rushed up to attend telephone call.
She got busy on phone and suddenly heard a sound from kitchen.
When she enter back into kitchen she saw that tea water was boiling with steam over it and cover of tea container is flew aside with water droplets over it.

Question. Why cover of tea kettle flew away?
(a) Not properly tight
(b) Tea is explosive in nature
(c) Pressure of steam
(d) None of these
Answer : C

Question. Water droplets on cover of tea container represents
(a) condensation
(b) evaporation
(c) melting
(d) freezing
Answer : A

Question. Steam over tea represents phenomena of
(a) condensation
(b) Boiling
(c) Fusion
(d) None of these
Answer : B

Assertion/ Reason Based Questions

DIRECTIONS : The questions in this segment consists of two statements, one labelled as “Assertion A” and the other labelled as “Reason R”. You are to examine these two statements carefully and decide if the Assertion A and Reason R are individually true and if so, whether the reason is a correct explanation of the assertion. Select your answers to these items using codes given below.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion (A) : The explosion of fire cracker is a physical change.
Reason (R) : A physical change is a reversible change.
Answer : D

Question. Assertion (A) : The process of conversion of liquid water to its vapours by heating the liquid is called boiling.
Reason (R) : The process of conversion of water vapours to liquid by cooling the vapours is called condensation.
Answer : B

Question. Assertion (A) : Burning of paper is a physical change.
Reason (R) : The products formed on burning of paper cannot be easily converted back to paper.
Answer : D

Question. Assertion (A) : The formation of rust is a chemical change.
Reason (R) : For the formation of rust iron must be exposed to air and water.
Answer : B

Statement Based Questions

DIRECTIONS : Read the following two statements carefully and choose the correct option.
(a) Statement (i) is correct while statement (ii) is incorrect.
(b) Statement (ii) is correct while statement (i) is incorrect.
(c) Both statements are correct.
(d) Both statements are incorrect.

Question. (i) Rusting of iron is a chemical change.
(ii) The change of liquid water to ice on cooling is a reversible change.
Answer : C

Question. (i) Change of liquid water to steam, on boiling, is an irreversible change.
(ii) Beating of human heart is a non-periodic change.
Answer : D

Figure Based Questions

Question. In the figure below the change occurring is a

(a) physical change
(b) chemical change
(c) periodic change
(d) None of these
Answer : B

Question. Carefully observe the figures below and choose the correct

(a) Both the changes show in 'A' and 'B' are irreversible.
(b) Both the changes 'A' and 'B' are reversible.
(c) 'A' is reversible but 'B' is irreversible.
(d) 'A' is irreversible but 'B' is reversible.
Answer : B

Question. Look at the picture given below. What kind of change is shown in the picture? Choose the correct option.

(a) Irreversible change, melted wax cannot be solidified again.
(b) Reversible change, melted wax can be solidified again.
(c) Periodic change, candle melts after an interval of an hour.
(d) Chemical change, melting of candle wax results in change in composition of candle.
Answer : B

DIRECTIONS : Look at the following diagram and answer the following questions.

Question. Which of the following represents ‘P’?
(a) Freezing of water into ice
(b) Burning of coal
(c) Cooking of food
(d) Bursting of cracker
Answer : A

Question. Which of the following represents ‘Q’ in the above diagram?
(a) Crushing of ice
(b) Cooking of food
(c) Explosion of a bomb
(d) Melting of ice
Answer : C

Question. Give any five examples of changes taking place in your daily life.
Answer : The examples of various changes are:
a) Germination of seeds
b) Growing of height
c) Inflating a balloon
d) Melting of ice
e) Burning of candle

Question. What are the various types of changes?
Answer : a) Slow & fast change
b) Reversible & irreversible change
c) Desirable & undesirable change
d) Physical & chemical change

Question. Diiferentiate between reversible & irreversible change. Also give examples.
Answer : Reversible change: Those changes which can be reversed to the original form by removing the cause of change are called reversible changes.
Example: melting of ice, stretching of rubber band, folding of paper etc.
Irreversible change: Those changes which cannot be reversed to the original form are called irreversible changes.
Example: burning of candle, formation of flower to bud, bursting a balloon etc.

Question. What are desirable & undesirable changes?
Answer : Desirable changes: Those changes which are desired to occur that is we want them to take place are known as desirable changes.
Example: ripening of fruits, germination of seeds etc.
Undesirable change: Those changes which we do not want to take place are called undesirable changes.
Example: rusting of iron, souring of milk, rottening of fruits etc.

Question. Classify the following as reversible or irreversible changes:
Answer : 
a) Growth of a plant                 Irreversible change
b) Cooking of food                   Irreversible change
c) Melting of wax                     reversible change
d) Dissolving salt in water       reversible change

Question. How do following changes differ from each other:
a) Burning of wax
b) Melting of wax
Answer : Burning of wax is an irreversible change whereas melting of wax is an example of a reversible change.
When we light a candle, then the wax present burns to produce various new substances like carbon dioxide, water vapour, smoke etc. which cannot be combined together to give back wax.
Also, solid wax on heating melts to form liquid wax which can be solidified again by cooling it.

Question. What are slow & fast changes? Give example.
Answer : Slow change: Those changes which take place in a long period of time are called slow changes.
Example: rusting of iron, germination of seeds etc.
Fast change: Those changes which take place in a short time are called fast changes.
Example: burning of paper, bursting a balloon.

Question. How is inflating a balloon different from bursting an inflated balloon?
Answer : Inflating a balloon is an example of a reversible change whereas bursting a balloon is irreversible change.
When we blow air into a balloon, its shape & size changes. But it regains its original form when the air is allowed to escape. On the other hand a bursted balloon cannot be changed back to the original form.

Question. Differentiate between physical & chemical change. Give 2 examples of each.
Answer : Physical Change
• Those changes in which no new substance is formed are called physical changes.
• Physical changes are usually reversible.
• Example: melting of wax, tearing of paper etc.
Chemical Change
• Those changes in which a new substance with new chemical properties is formed are known as chemical changes.
• Chemical changes are irreversible.
• Example: burning of paper, baking a chapatti etc.

Question. Explain how, a metal wheel is fixed around the wooden wheel of a cart.
Answer : The iron rim is fixed around the wooden wheel of a cart by the process of expansion on heating. The rim is made slightly smaller than the wooden wheel. On heating; the rim expands & fits onto the wheel.
After that cold water is poured over the rim, as a result, it contracts & fits tightly onto the wheel.

Question. Explain how, the iron blade of the digging objects like spade is fixed to a wooden handle.
Answer :  The iron is fixed by the process of expansion on heating.
The iron blade of tools has a ring in which the wooden handle is to be fixed. The ring is slightly smaller than the handle. To fix the handle, the ring is heated & it expands. Now, the handle easily fits on the ring. When the ring cools down then it contracts & fits tightly on the handle.

Question. When water is mixed with Plaster of Paris & allowed to dry, it sets into a hard mass. State whether the change is reversible or irreversible. Justify your answer.
Answer : The above change is an example of an irreversible change. This is because when water is added to Plaster of Paris then it sets as a hard mass & cannot be converted back into the original form.

Question. A bag of cement lying in the open gets wet due to rain. Can the change which takes place in cement on getting wet be reversed by drying?
Answer : No, this change cannot be reversed on drying as some changes occur in cement on getting wet due to which it gradually sets as a hard mass. Even if it is kept in bright sunshine, then also the change cannot be reversed.

Question. Milk can be changed into curd but curd cannot be changed back into milk. What is the general name of such changes?
Answer : Such changes are known as irreversible changes.

Question. How does a blacksmith change a piece of iron into different tools?
Answer : A blacksmith first heats a piece of iron till it becomes red hot. It then becomes soft & can be beaten into desired shape.

Question. You must have seen that construction workers heat a black material called coal tar for repairing a road. State whether the change which has occurred in coal tar on being heated is reversible or irreversible.
Answer : When coal tar is heated, it melts to form a thick dark liquid. The melting of coal tar is a reversible change as it solidifies again on cooling.

Question. Why is shaping of wet clay into clay pot a reversible change whereas baking a clay pot an irreversible change?
Answer : The shaping of wet clay into a clay pot, a reversible change as wet clay can be converted back into the original clay. Whereas a baked clay pot cannot be changed back into the original form, therefore it is an irreversible change.

Changes Around us

<1M>

1.Whenever a metal is first heated and then cooled, which of the following changes take place?
(A) First contracts and then expands.
(B) First expands and then contracts.
(C) Cannot determine.
(D) Both (a) & (b).

2.When water is boiled, it changes into vapours, the process is called ................ and these vapours deposit as water droplets on a cooler plate covering the vessel by the process of .................. .
(A) Condensation, Evaporation
(B) Freezing, melting
(C) Evaporation, condensation
(D) Melting, freezing

3.A mixture of salt in water can be separated by
(A) Evaporation
(B) Filtration
(C) Sedimentation
(D) Decantation

4.When sugar is dissolved in water it is a .................. change.
(A) Reversible
(B) Irreversible
(C) Chemical
(D) Periodic

5.When a candle is burnt, it becomes short in size. This change is
(A) Melting
(B) Evaporation
(C) Irreversible
(D) Reversible

6.When the original substances of an activity can be recovered, it is called
(A) Reversible change
(B) Irreversible change
(C) Periodic change
(D) Both (a) & (b)

7.Why cold water is poured over the hot metal rim which covers a wooden wheel?
(A) Because the rim contracts and fits over the wheel.
(B) Because cold water is good for the life of the wheel.
(C) Because the wooden wheel expands.
(D) However, cold water has no effect.

8.When a piece of paper is burnt, it is an example of.................... change.
(A) Physical
(B) Periodic
(C) Irreversible
(D) Reversible

9.Water changes into vapours due to
(A) Evaporation
(B) Condensation
(C) Sublimation
(D) Melting

10.On a hot summer day, ice-cream melts faster than in winters. This process of melting is
(A) Chemical change
(B) Reversible change
(C) Periodic change
(D) Irreversible

11.When water is left in a bowl in the sun it
(A) Boils
(B) Evaporates
(C) Cools
(D) Remains same

12.Match the following and choose the answer from the code given below
A.Metals on heating                     (i) Reversible change
B.Souring of milk                         (ii) Expand
C.Making clay toys                      (iii) contracts
D.Hot Metal Rim on cooling        (iv) Irreversible change

(A) (A)-(iv), (B)-(i), (C)-(ii), (D)-(iii)
(B) (A)-(ii), (B)-(i), (C)-(iv), (D)-(iii)
(C) (A)-(iii), (B)-(iv), (C)-(i), (D)-(ii)
(D) (A)-(ii), (B)-(iv), (C)-(i), (D)-(iii)

13.Melting of wax is a ................. change, while burning of candle is ..................... change.
(A) Irreversible, Reversible
(B) Reversible, Irreversible
(C) Physical, Reversible
(D) Chemical, Irreversible

14.The process of changing of water into vapours when heated is called
(A) Condensation
(B) Evaporation
(C) Melting
(D) Freezing

15.Select the reversible changes from the following and choose the answer from the options given below.
(i) Melting of wax.
(ii) Freezing of water.
(iii) Formation of curd from milk.
(iv) Expansion of metals on heating
(A) (i) & (ii)
(B) (i), (ii) & (iv)
(C) (iii) only
(D) All the above.

16.Which of the following is an irreversible change?
(A) Rottening of bread.
(B) wetting of cloth.
(C) Heating ofwater.
(D) Melting of ice.

17.Melting of ice is a-
(A) Periodic change.
(B) Reversible change.
(C) Slow change.
(D) Irreversible change.

18.The process by which a liquid changes into its vapours (gas) on heating is called-
(A) Melting.
(B) Freezing.
(C) Evaporation
(D) None of these.

19.Formation of paneer from milk is a/an -
(A) Physical change.
(B) Irreversible change.
(C) Reversible change.
(D) None of these.

20.Which of the following is not a man- made change?
(A) Formation of curd from milk.
(B) Burning of fuels.
(C) Drying of clothes.
(D) Change of seasons.

21.What happens when an iron piece is heated?
(A) It expands.
(B) It contracts.
(C) Both (A) and (B).
(D) Neither expands nor contracts.

22.When we add salt to hot water, the solubility is than in cold water.

23.To reverse the change of ice turning into water, it is required tothe water.

24.Souring of milk is a change.

25.A flower turning into a fruit cannot be a change, because It is irreversible.

26. What happens to the solubility of solid in any liquid when that solution is cooled ?

27.Why burning of candle is considered as an irreversible chemical change ?

<2M>

28.Suppose you have dropped your favorite toy and broken it.Can this change be reversed?

29.How does a blacksmith change a piece of iron into different tools?

30.Identify the following changes whether the change can be reversed or not-
(i) The cooking of food
(ii) The melting of wax
(iii) Souring of milk
(iv) Dissolving salt in water

31.What are the changes that occur in the incense stick when it is burnt?

32.Define condensation and evaporation .

33.To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?

34.You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?

<3M>

35.What are irreversible changes? Give two examples of changes, which cannot be reversed.

36.Give three examples of change that are taking place around us on their own. .

<5M>

37.What are the different ways of bringing about change? Give two examples for each.

38.Define expansion and contraction. Explain how the metal rim is fixed on a wooden wheel of a cart.

39.What are the two types of changes? Define them, with two examples each.

40.A drawing sheet changes when you draw a picture on it. Can you reverse this change ?

41.Give examples to explain the difference between changes that can or cannot be reversed.

42.A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed ?

43.A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed ?

44.Define the following :
(a) Evaporation
(b) Condensation
(c) Soluble Substance
(d) Insoluble substance.