CBSE Class 6 Science Changes Around Us Worksheet Set A

Learning Objectives
1. To understand changes around us.
2. To understand effect of causes of these changes on things around us.
3. To understand classification of different changes on the basis of their effect.
4. To understand characteristics of these changes.

Every day, we see different types of changes around us, like day turning into night, the season changing from winter to summer, melting of ice to water, cooking of food, rusting of iron, growth of our body and so on.
There are number of changes taking place around us. Some of these changes can be noticed immediately, some changes can be noticed after some time and there are some changes that cannot be noticed.
Every change has a cause, for example, day and night alternate because of the rotation of the earth around the sun. Changes in weather is due to the heat of the sun. These causes can bring about changes in:

Shape and size : There is a change in shape and size of a balloon when air is blown into it.
Making of various toys or geometrical figures (such as rectangle, square etc.) using a paper sheet bring about a change in the sheet of paper. The ball of dough takes the shape of a chapati when it is properly rolled.

State: Ice melts on heating,melting of butter and ice cream etc.

Position: Sun changes its position from east to west due to rotation of the earth around it, position of a football changes on kicking it.

Colour: On heating an iron piece it becomes red hot, colour change of silver ornament, etc.

CLASSIFICATION OF CHANGES

1. Based on Speed
Slow changes : A change that occurs very slowly and takes a very long time for completion is called a slow change.
For example
1. Growth of a child into an adult and then into an old men takes years to occur.
2. Curdling of milk takes few hours to occur.
3. Germination of seed to form a plant takes 2-4 days.
4. Ripening of fruits is also a slow change.
5. Conversion of night into day occurs slowly.
6. Cooking food also takes some time.
7. One complete rotation of the earth around sun takes 24 hours.

Fast changes : A change that occurs spotaneously or occurs at a very fast speed is called a fast change. For example :
1. Burning of a paper.
2. Bursting of crackers.
3. Dropping an object from height.
4. Opening of a drawer.
5. Blinking of eyes.
6. Sneezing.
7. Burning of a match stick, etc. are examples of fast changes.

2. Based on Reversibility
Reversible changes : Some of the changes can be reversed to get back the original shape, size, etc. of the material, e.g. if we deflate the inflated balloon it takes its original shape and size. Such changes are called reversible changes.
A reversible change can take place in both the directions. For example, ice changes to water on heating and water changes to ice on cooling.
Melting of ice cream is a reversible change.

Some other examples of reversible changes:
1. All the steam that is made when water in a kettle boils, turn back into water by cooling it.
2. An electric bulb can be made to give light by passing electric current through it. The bulb returns to its original state and does not give light when the electric current is switched off.
3. A blacksmith changes a piece of iron into different tools. For that, a piece of iron is heated to red hot. This also softens it. It is then beaten into the desired shape. It is a reversible change.
4. When leaves of ‘touch me not’ plant is touched, they close and after some time open out again as before.
5. Evaporation and Condensation process are reverse of each other.
Evaporation is a change in which a liquid gets converted into vapour. Condensation is the process in which the vapour changes into a liquid when it is cooled.

Note : Most of the reversible changes are physical changes, since the individual properties of the matter are still present.

6. Melting and boiling are reversible processes.
Melting : This change in state occurs when a solid is heated to a particular temperature called the melting point of solid. In it the state of matter changes from solid to liquid.
Boiling : This brings about a change in state of a liquid. A liquid when heated to a particular temperature called boiling point changes to vapour (gaseous) state. In it the state of matter changes.

7. Our heart beat increases on doing vigorous physical exercise but it becomes normal after some time.
Irreversible changes : Some of the changes cannot be reversed back, e.g. if an inflated balloon is tightly closed at its mouth and then pricked, it burst and then it cannot regain its original shape and size. This type of change is called an irreversible change. Irreversible change can take place only in one direction.
For example, formation of omlette from egg is an irreversible process as omlette cannot be converted back into raw egg.

Some other examples of irreversible changes
1. Cake batter is made from eggs, flour, sugar and butter. Once the cake has been baked, we cannot get the ingredients back.
2. Rippening of fruits is an irreversible process as we cannot get unripe fruit from riped one.

Do You know : Artificial ripening of fruits and vegetable is an irreversible process. This method is used to accelerate the ripening of fruits and vegetables under controlled conditions. This forced change result in fruits and vegetables becoming tasteless and toxic.
3. Cooking of food is another example as we cannot get back the substances that we originally started with.
4. Blooming of flowers is an irreversible process as flowers cannot change back into buds.
5. When a paper is burnt, it changes to ash and smoke. From ash and smoke,we cannot get back paper.
Thus, the change is irreversible.
Based on reversibility changes can also be classified as temporary and permanent changes.

Temporary change : A change that can be easily reversed to get back the original substance is a temporary change e.g. any physical change such as evaporation, melting, etc.

Permanent change : A change that can not be easily reversed to get back the original substance is called a permanent change e.g. any chemical change.

3. Based on Time Interval
The cyclic repetition of changes after fixed interval of time decides whether a change is periodic or non-periodic.
Periodic changes : These changes occur in a periodic manner i.e., get repeated after a certain definite interval.
For example : change in position of a simple pendulum when it is vibrating. They are also called cyclic changes. Seasons repeat themselves each year hence are example of periodic changes.

Some other example of periodic changes
1. Day and night are periodic changes as they repeat after every twenty four hours.
2. Beating of heart is an example of periodic change.
3. Certain species of flowers open at sun rise and close at sun set.
4. Even changes in period in a school is an example of periodic change.
5. Change in phases of moon.

Non-periodic changes : These are the changes that may occur at any time and show no periodicity.
Example of non-periodic changes:
1. Freezing of water to form ice.
2. Natural disasters like cyclons, volcanic eruption, tsunami are nonperiodic changes.
3. Burning of fossil fuels.
4. Melting of glaciers.

4. Based on composition
Physical change: It is a temporary change and in it no new substance is formed. It can be reversed. It may be a change in shape, size, etc. It may be a change involving a change in state e.g. liquid water on evaporation changes to steam which when cooled again (condensation) changes to liquid water.

Characteristics of a physical change:
Any change in the physical properties of a substance will result in a physical change. To bring about a physical change some external force or energy has to be applied. The molecules of the substance remain same after and before the change. For example:
1. On kicking a football it changes its position but no new substance is formed. The molecule that make up football remains the same.
2. On tearing a paper it changes its shape and size but it remains paper. No new substance is formed.
3. If we crush sugar cubes into small particles, these small particles still remain sweet as there is no change in its molecules. Physical changes result in change in molecular arrangement of a substance which leads to change in state of the matter. For example, melting of ice.

Chemical change: It is a permanent change and it can not be reversed easily (i.e. it is irreversible change). In it a new substance is formed and the original substance can not be easily formed from the new substances.

Characteristics of chemical changes
In chemical changes the molecules of original substance undergo changes to form molecules of new substance. A chemical change occurs when there is chemical reaction between the substances. Original substance is called reactant and new substance formed is called product.
Chemical changes are always accompanied by some external indications such as production of heat or light, precipitation, change in colour or appearance, etc.

Some examples of chemical changes are:
1. Burning of paper gives smoke and gases like water vapour and carbon dioxide. The ash left behind is different from paper in its properties
2. The decomposition process of dead organic and inorganic matter is an example of chemical change. The organic waste or dead animals undergo gradual degradation and they finally mix with the soil. The chemical reactions that assist the process result in producing sharp odor, which is an evidence of the chemical change.
3. One of the best example of day-to-day chemical change is the process of photosynthesis. This is a process by which plants synthesize food and release oxygen as the by-product.
4. The process of rusting is also an example of chemical change. When iron is exposed to water and oxygen, it gets coated with a brown layer, called rust.
5. The most common example of chemical change is cooking. When we boil egg, it becomes hard and taste very different. The molecules of egg changes to give new substance. Cooking of rice, vegetables, etc. are chemical changes.

Note : Cutting of wood is an physical change as in this no new substance is formed, molecules of the wood remain the same. While burning of wood results in the formation of certain gases and ash is formed that has different properties than wood, hence it is a chemical change.

5. Based on Energy
Energy initiates a change,when any change takes place energy is either evolved or absorbed.

Exothermic change : A change that is accompanied by release of heat energy is called an exothermic change e.g. burning of magnesium ribbon.

Some other examples of exothermic reactions:
1. During making of ice cubes heat is released.
2. Formation of snow in cloud is exothermic.
3. When water vapours condenses into liquid water energy is released.
Hence condensation is exothermic.
4. Flame of candle or burner is example of exothermic change.
5. During mixing of water and strong acid heat is released.
6. When a bomb explodes, large amount of heat is released so explosion of bomb is exothermic.
Do You Know : Respiration is also an example of exothermic change. During respiration glucose molecules breakdown and energy is released which can be utilized for our day to day actions. Similarly digestion of food is also exothermic change.

Endothermic changes : A change that is accompanied by absorption of heat energy is called an endothermic change e.g. change of state from solid to liquid.

Note : While energy is involved in all types of changes ,it is not always easy to see these changes happening. For example, we cannot see the energy involved in case of weather changes or drying of clothes.

Examples of endothermic changes
1. In evaporation process heat is absorbed by the water molecules at the surface of the water. Hence evaporation is endothermic.
2. Heat is absorbed during melting of ice.
3. Heat is adsorbed in baking bread and cooking food.
4. Photosynthesis is an endothermic process because it will not happen without an external source of energy, which in this case is sunlight.

EXPANSION AND CONTRACTION OF MATERIALS
Heating and cooling of materials can make them change. This change occurs in all materials, from water to metals to air. But the effect of heating is opposite to that of cooling.
Heating a substance can make it expand, but the degree of expansion differs in solids, liquids, and gases. Gases expand the most while solids expand the least.
For example, metals expand on heating. Railway track consist of two parallel metal rails joined together. Small gap is left between the rails as there is an expansion of the rails in hot weather.

Cooling of a substance result in contraction. Solids contract the least while gases contract the most. For example, a very hot glass cracks on putting it under cold water. This is because the outer surface of the glass when it comes in direct contact with the cold water contracts more compared to the inner surface of glass that is not in direct contact with cold water and hence takes time to cool down and contract.

Class-VI

L-6

Changes Around Us

1) Can you change the shape of paper by folding?

Ans. ...................................

2) Can all changes always be reversed?

Ans. ...................................

3) List five changes which can be reversed.

Ans. i) ......................................

ii) ......................................

iii) ......................................

iv) ......................................

v) ......................................

4) List five changes which cannot be reversed

Ans. i) ......................................

ii) ......................................

iii) ......................................

iv) ......................................

v) ......................................

5) Define Evaporation?

Ans. .............................................................................................................................

.............................................................................................................................

6) What is melting?

.............................................................................................................................

.............................................................................................................................

7) Write True of false against each statement ___

Students should free download the worksheets as per CBSE and CCE patters and get better marks in exams. Studiestoday.com panel of teachers recommend students to practice questions in the worksheets.

Multiple Choice Questions

Question. Which of the following is a reversible change?
(a) Change of raw egg to boiled egg.
(b) Change of stretched rubber band to its normal size.
(c) Change of bud to flower.
(d) None of these.
Answer : B

Question. Any change in which the original substance can be obtained by reversing conditions is known as a
(a) reversible change
(b) periodic change
(c) physical change
(d) Both (a) and (c)
Answer : D

Question. The melting of wax is an example of
(a) physical change
(b) chemical change
(c) reversible change
(d) Both (a) and (c)
Answer : D

Question. Burning of candle is a
(a) physical change
(b) chemical change
(c) periodic change
(d) Both (a) and (b)
Answer : D

Question. When a woolen yarn is knitted to get a sweater, the change can be classified as
(a) physical change
(b) chemical change
(c) exothermic change
(d) endothermic change
Answer : A

Question. The change of milk to curd, when we add a small quantity of curd to milk, can be classified as
(a) Fast change
(b) Slow change
(c) Periodic change
(d) None of these
Answer : B

Question. Which of the following are endothermic change?
(a) Condensation and melting
(b) Condensation and freezing
(c) Evaporation and melting
(d) Evaporation and freezing
Answer : C

Question. The change of bud to flower is a/an
(a) physical change
(b) reversible change
(c) irreversible change
(d) None of these
Answer : C

Question. Which of the following is a periodic change?
(a) Change of season
(b) Phases of moon
(c) Beating of human heart
(d) All of these
Answer : D

Question. A chemical change is one which occurs with
(a) the formation of new substances
(b) the evolution or absorption of energy
(c) Both the above
(d) None of these
Answer : C

Question. A change is called physical change because in it
(a) only change in physical properties takes place
(b) transfer of energy takes place
(c) can be easily reversed
(d) All of the above
Answer : A

Question. Select the one that is a chemical change.
(a) rusting of iron
(b) tearing of paper
(c) Both of these
(d) None of these
Answer : A

Question. Select a reversible change.
(a) milk to paneer
(b) growth of a tree
(c) cow-dung to biogas
(d) ice-cream to molten ice cream
Answer : D

Question. Which one is a periodic change?
(a) Earth-quake
(b) Formation of rainbow in sky
(c) Occurrence of tides in seas
(d) None of these
Answer : C

Question. Select the one that represents a periodic change.
(a) Occurrence of tides
(b) Opening of a morning glory flower
(c) Both the above
(d) None of these
Answer : C

Question. The change of a ball of dough to a rolled out roti is a
(a) physical change
(b) chemical change
(c) periodic change
(d) None of these
Answer : A

Question. An aeroplane was cut out from a rectangular sheet of paper. The change involved is a
(a) physical change
(b) temporary change
(c) irreversible change
(d) None of these
Answer : C

Question. Which type of change takes place when a rolled roti is baked on tawa ?
(a) physical change
(b) permanent change
(c) periodic change
(d) None of these
Answer : B

Question. What type of change is used for fixing a metal rim on a wooden wheel of a cart?
(a) physical change
(b) chemical change
(c) Both the above
(d) None of these
Answer : A

Question. Heating of wax in a pan is a
(a) reversible change
(b) irreversible change
(c) permanent change
(d) None of these
Answer : A

Question. The dissolution of salt in water is a
(a) reversible change
(b) irreversible change
(c) chemical change
(d) periodic change
Answer : A

Question. Select the one that is not a chemical change.
(a) dissolution of ammonia in water
(b) dissolution of carbon dioxide in water
(c) dissolution of oxygen in water
(d) None of these
Answer : C

Question. Which one is reversible change?
(a) melting of ice candy
(b) cooking of food
(c) ripening of mango
(d) None of these
Answer : A

Question. Cooking of an egg in boiling water containing salt is a
(a) permanent change
(b) temporary change
(c) irreversible change
(d) Both (a) and (c).
Answer : D

Question. Condensation is a physical change. Why?
(a) Vapour turns into liquid
(b) No heat is required
(c) It happens automatically
(d) No new substance is formed
Answer : D

Question. Which of the following is a natural change?
(a) Cutting hair
(b) Graying hair
(c) Oiling hair
(d) Colouring hair
Answer : B

Question. Choose the correct alternative to complete the given analogy. Physical change : Boiling : : Chemical change _____________
(a) Melting
(b) Burning
(c) Condensing
(d) Evaporating
Answer : B

Question. Which of the following is a reversible change?
(a) Ripening of the fruit
(b) Melting of ice
(c) Burning of paper
(d) Converting wood into saw dust
Answer : B

Question. What is difference between making of furniture from wood and burning of wood?
(a) First is irreversible and second is reversible change.
(b) First is physical and second is chemical change.
(c) First is fast and second is slow change.
(d) First is periodic and second is non-periodic change.
Answer : B

Question. A change that results in formation of new substances and can't be reversed easily is known as a
(a) physical change
(b) chemical change
(c) reversible change
(d) None of these
Answer : B

Question. A physical change is a
(a) temporary change
(b) change in which no new substance is formed
(c) reversible change
(d) All of the above are correct
Answer : D

Question. Evaporation is
(a) a physical change
(b) a temporary change
(c) a change in state of matter
(d) All of the above
Answer : D

Question. A periodic change is a change
(a) that get repeated many a times in our life
(b) that get repeated after a certain definite interval
(c) that never get repeated
(d) All of the above
Answer : B

Question. Exothermic change is
(a) accompanied by release of energy
(b) accompanied by absorption of energy
(c) a change in which heat energy is neither released nor absorbed
(d) All of the above
Answer : A

Question. What happens to the metals on heating?
(a) They expand
(b) They contract
(c) They remains unaffected
(d) None of these
Answer : A

Question. Which of the following is not a man-made change?
(a) Burning of fuels
(b) Change of day and night
(c) Drying of clothes
(d) Formation of curd from milk
Answer : B

Question. Which of the following is an example of chemical change?
(a) Filling up a balloon with hot air.
(b) Taking a glass of water and freezing it by placing it in the freezer.
(c) A plant collecting sunlight and turning it into food.
(d) None of these
Answer : C

Question. When a new substance is formed with different properties than the original substance it is called
(a) chemical change
(b) physical change
(c) freezing
(d) boiling
Answer : A

Question. If the chemical properties of a substance remains unchanged and the appearance or shape of a substance changes then it is called a
(a) chemical change
(b) physical change
(c) slow change
(d) periodic change
Answer : B

Question. Which is an example of a physical change?
(a) Metal rusting
(b) Silver tarnishing
(c) Water boiling
(d) Paper burning
Answer : C

Question. Which is an example of chemical change?
(a) Water freezes
(b) Wood is cut
(c) Bread is baked
(d) Wire is bent
Answer : C

Question. Find the odd one out.
(a) crushing
(b) pulling
(c) burning
(d) tearing
Answer : C

Question. Artificial ripening of fruit is a
(a) reversible change
(b) periodic change
(c) irreversible change
(d) fast change
Answer : C

Question. Which of the following is a chemical change to a piece of paper?
(a) Colouring
(b) Burning
(c) Folding
(d) Tearing
Answer : B

Question. Choose the correct alternative to complete the given analogy.
Change in period in a school: Periodic change : : _____________ : Non-periodic change
(a) Heart beating
(b) Formation of day and night
(c) Forest fire
(d) Change in phases of moon
Answer : C

Question. Find the odd one out.
(a) Cutting of nails
(b) Breaking of glass
(c) Formation of ash from paper
(d) Tearing of paper
Answer : C

Question. During which of the following changes a new substance is formed?
(a) Cooking
(b) Melting
(c) Freezing
(d) Crushing
Answer : A

Question. Physical changes are usually
(a) periodic changes
(b) a change in state of matter
(c) fast changes
(d) a change in composition
Answer : B

Changes Around Us

FILL IN THE BLANKS

1. The changes that can be reversed are called ______________ changes.

2. The changes that cannot be reversed are called ______________ changes.

3. On heating , the metals _________________

4. On cooling , the metals _________________

5. Burning of incense stick is an ___________________ change.

6  On heating metal rim _______________ and fits into the wooden wheel.

CHOOSE THE CORRECT ANSWER

1 Ripening of fruit is a ( reversible / irreversible ) change.

2 In ( reversible / irreversible ) change we cannot get back the original components.

TRUE OR FALSE

1. Growing of trees is an irreversible change. _________

2  Formation of curd from milk is a reversible change .___________

NAME THE FOLLOWING

1  Name any two reversible changes .

2  Name any two irreversible changes.

DISTINGUISH BETWEEN

Reversible and Irreversible changes

CLASSIFY THE FOLLOWING CHANGES INTO REVERSIBLE AND IRREVERSIBLE CHANGES

1 Crumpling of paper

2 Burning of paper

3 Sawing of wood

4 Cooking of food

5 Change of water into water vapour

6 Ironing of clothes

Changes Around Us

I. Fill in the blanks :

1. Knitting of woolen yarn is a ____________________ changes.

2. On cooling, the metal __________________.

3. Falling of leaves from a tree is an _________________ changes.

4. On heating, metal rim ________________ and fits into the wooden wheel.

5. Burning of incense stick is a _________________ change.

6. Reversible changes are ______________ in nature.

7. A change from liquid to solid state on cooling is called ______________.

II. Write True or False :

1. Making dough with water and wheat flour is an irreversible change.

2. Magnetisation of iron is an irreversible change.

3. On heating, the metal expands.

4. Irreversible changes are temporary in nature.

5. Disappearance of a substance in a liquid is known as dissolution.

III. Choose the correct answer :

1. Germination of seed is a reversible / irreversible ) change.

2. All metal expands on (cooling / heating ).

3. In (reversible / irreversible ) change, we cannot get back the original compound.

4. Lighting of candle is a (reversible / irreversible ) change.

IV. Classify the following changes into reversible and irreversible change :

1. Boiling of raw egg in water.

2. Crumpling of paper.

3. Burning of wax.

4. Souring of milk.

5. Change of water into water vapour.

6. Rusting of iron.

Multiple Choice Questions

Question. The burning of magnesium in air is accompanied by production of heat and light. This can be classified as
(a) physical and exothermic change
(b) chemical and exothermic change
(c) physical and endothermic change
(d) chemical and endothermic change
Answer : B

Question. To fix up the fractured bone a paste made of Plaster of Paris (POP) is used as a coating over the bandage on the fractured bone. After some time the plaster becomes hard and dry. This change in POP can be classified
(a) physical change
(b) permanent change
(c) change of state of mater
(d) None of these
Answer : B

Question. Consider the following changes and select the option that can be used to classify these.
(i) stretching of rubber band
(ii) cooking of food
(iii) heating of milk
(iv) stretching of spring
(v) burning of paper
(a) periodic and non-periodic change
(b) physical and chemical change
(c) expansion and contraction
(d) None of these
Answer : B

Question. A list of changes is given below. Identify their type and choose correct option.
(i) Boiling of egg.
(ii) Making curd from milk
(iii) Flowering of bud
(iv) Making flour from grain
(a) (i), (ii), (iii) and (iv) are irreversible changes
(b) (i) and (iv) are chemical changes
(c) (i), (ii), and (iv) are natural changes
(d) (ii), (iii) and (iv) are periodic changes
Answer : A

Question. In an experiment the following changes were observed. (i) It was accompanied by change in colour (ii) It was accompanied by a change in temperature (iii) It was accompanied by a change in energy. The change involved can be classified as a
(a) periodic change
(b) non-periodic change
(c) physical change
(d) chemical change
Answer : D

Question. The melting of gold is a physical change because
(a) melted gold is still gold but in different form
(b) no new substance is formed in it
(c) on cooling melted gold returns back to its original state
(d) All of the above
Answer : D

Question. Why is spoiling of food considered a chemical change?
(a) In it the food changes from one chemical substance to another.
(b) It is not possible to get original food from spoiled food.
(c) It is a permanent change.
(d) All of the above.
Answer : D

Question. Why is earthquake considered a non-periodic change?
(a) Its occurrence is possible at any time.
(b) It occurs rarely at some places.
(c) It occurs only in certain quake prone areas.
(d) None of these.
Answer : A

Question. Anaerobic bacteria digest animal waste and produce biogas (change-A). The biogas is then burnt as fuel (change-B). The following statements pertain to these changes. Choose the correct one.
(a) Process A is a chemical change.
(b) Process B is a chemical change.
(c) Both processes A and B are chemical changes.
(d) None of these processes is a chemical change.
Answer : C

Question. If few drops of petroleum are poured on your palm, you feel cool as the petrol evaporates. This change is
(a) slow change
(b) chemical reaction
(c) endothermic change
(d) periodic change
Answer : C

Question. Which of the following is an example of physical change?
(a) Mixing baking soda and vinegar together, and this causes bubbles and foam.
(b) A glass cup falls from the counter and shatters on the ground.
(c) Lighting a piece of paper on fire and the paper burns up and leaves ashes.
(d) Baking a birthday cake for your mother.
Answer : B

Question. Find the odd one out.
(a) respiration
(b) digestion
(c) photosynthesis
(d) freezing
Answer : C

Question. What new material is formed when a candle burns?
(a) Melted wax
(b) Water vapour
(c) Carbon dioxide
(d) Both (b) and (c)
Answer : D

Question. In which of the following cases heat energy is released?
(A) When ice melts
(B) When water freezes to ice
(C) When water vapour condenses into liquid water
(D) When water evaporate into water vapours
(a) (A), (B) and (C)
(b) (B), (C) and (D)
(c) (B) and (C)
(d) All of the above
Answer : C

Question. Ramesh wants to buy a clay pot. For which he went to a potter. Ramesh asked potter to make clay pot of his desired design, shape and size.
Will potter be able to do this? This is an example of which kind of change?
(a) Yes, physical change
(b) Yes, chemical change
(c) No, physical change
(d) No, chemical change
Answer : A

Question. Peeled and unpeeled banana doesn’t look same.
Does that means peeling banana is a chemical change?
(a) No, we just separated skin of banana and there is no change in its composition.
(b) Yes, through peeling a new product is formed.
(c) Yes, both chemical and physical change happen here.
(d) No, neither chemical nor physical change happen here.
Answer : A

Question. Do you think we break molecules when we turn chalk into chalk powder?
(a) Yes, chalk powder is formed by breaking chalk into small pieces.
(b) Yes, because formation of chalk powder is a chemical change.
(c) No, because no new substance is formed molecules of chalk and chalk powder are same.
(d) Yes, because chalk is bigger in size than particles of chalk powder.
Answer : C

Question. Which of the following are examples of chemical changes?
(A) Cutting of wood
(B) Burning of wood
(C) Baking of cake
(D) Growth in plants and animals
(a) (A) and (D)
(b) (B) and (C)
(c) (A), (B) and (C)
(d) (B), (C) and (D)
Answer : D

Question. Charcoal burning on the grill is an example of _________.
(a) physical change
(b) chemical change
(c) periodic change
(d) reversible change
Answer : B

Question. During burning of paper which of the following acts as a reactant?
(a) Flame
(b) Ash
(c) Paper
(d) None of these
Answer : C

Question. Find the odd one out.
(a) Permanent change
(b) Reversible
(c) Change in composition
(d) Formation of new substance
Answer : B

Question. A very hot glass on putting under cold water cracks. This change is due to ____________.
(a) expansion
(b) contraction
(c) formation of new substance
(d) None of these
Answer : B

Match the Column

DIRECTIONS : Match column-I with column-II and select the correct answer using the codes given below the column.

Question.
Column-I                                                   Column-II
A. Formation of day and night            (p) Chemical change
B. Ripening of a mango                      (q) Physical change
C. Dissolving of sugar in water           (r) Periodic change
D. Occurrence of rainbow                  (s) Non-periodic change
(a) A → (p), B →(r), C → (q), D → (s)
(b) A → (q), B →(r), C → (p), D → (r)
(c) A → (r), B →(q), C → (s), D → (p)
(d) A → (r), B →(p), C → (q), D → (s)
Answer : D

Question.
Column-I                                                                                Column-II
A. The process of photosynthesis               (p) This process involves reversible and irreversible process respectively.
B. Change in phases of moon                     (q) This process involves presence of sunlight.
C. Candle wax melts and burns at same     (r) This is the process which involves time physical and chemical changes respectively.
D. Cutting wood for furniture and                (s) This process occur after a fixed interval burning of wood of time.
(a) A → (s), B → (q), C → (p), D → (r)
(b) A → (q), B → (s), C → (p), D → (r)
(c) A → (p), B → (s), C → (q), D → (r)
(d) A → (s), B → (p), C → (q), D → (r)
Answer : B

Question.
Column-I                                              Column-II
A. Crushing of an ice cube                  (p) Periodic change
B. Making of curd                                (q) Slow change
C. Germination of seed into plant       (r) Physical change
D. Formation of day and night            (s) Chemical change
(a) A → (s), B → (r), C → (q), D → (p)
(b) A → (r), B → (s), C → (q), D → (p)
(c) A → (s), B → (r), C → (p), D → (q)
(d) A → (r), B → (p), C → (q), D → (s)
Answer : B

Passage Based Questions

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

Passage-1
Copper statues exposed to carbon dioxide and water in the air become coated with patina.
The patina is not copper, it is not carbon dioxide, and not water.
It is a new substance formed by the reaction of these chemicals with one another.

Question. The appearance of patina on copper statues when these are exposed to moist air is which type of change?
(a) Physical change
(b) Chemical change
(c) Periodic change
(d) Non-periodic change
Answer : B

Question. The change described above is a
(a) reversible change
(b) irreversible change
(c) expansion
(d) contraction
Answer : B

Question. The change of copper to patina as described above is a
(a) fast change
(b) slow change
(c) exothermic change
(d) endothermic change
Answer : B

FILL IN THE BLANKS

1. The changes that can be reversed are called ______________ changes.

2. The changes that cannot be reversed are called ______________ changes.

3. On heating , the metals _________________

4. On cooling , the metals _________________

5. Burning of incense stick is an ___________________ change.

6 On heating metal rim _______________ and fits into the wooden wheel.

CHOOSE THE CORRECT ANSWER

1 Ripening of fruit is a ( reversible / irreversible ) change.

2 In ( reversible / irreversible ) change we cannot get back the original components.

TRUE OR FALSE

1. Growing of trees is an irreversible change. _________

2 Formation of curd from milk is a reversible change .___________

NAME THE FOLLOWING

1 Name any two reversible changes .

2 Name any two irreversible changes.

DISTINGUISH BETWEEN

Reversible and Irreversible changes

CLASSIFY THE FOLLOWING CHANGES INTO REVERSIBLE AND IRREVERSIBLE CHANGES

1 Crumpling of paper

2 Burning of paper

3 Sawing of wood

4 Cooking of food

5 Change of water into water vapour

6 Ironing of clothes