RBSE Class 6 Science Important Questions Chapter 6 Changes Around Us

Rajasthan Board  RBSE Class 6 Science Important Questions Chapter 6 Changes Around Us Important Questions and Answers.

RBSE Class 6 Science Chapter 6 Important Questions Changes Around Us

Multiple Choice Questions

Question 1. 
Which of the following change cannot be reversed?
(a) Hardening of cement
(b) Freezing of ice cream
(c) Opening a door
(d) Melting of chocolate
Answer:
(a) Hardening of cement

 

Question 2. 
An iron ring is heated. Which of the following statement about it is incorrect? 
(a) The ring expands.
(b) The ring almost becomes smaller on cooling. 
(c) The change, in this case, is reversible.
(d) The ring doesn’t change its shape and the change cannot be reversed.
Answer:
(d) The ring doesn’t change its shape and the change cannot be reversed.

Question 3. 
Salt can be separated from its solution (salt dissolved in water), because:
(a) mixing of salt in water is a change that can be reversed by heating and melting of salt.
(b) mixing of salt in water is a change that cannot be reversed.
(c) mixing of salt in water is a permanent change.
(d) The mixing of salt in water is a change that can be reversed by evaporation.
Answer: 
(d) The mixing of salt in water is a change that can be reversed by evaporation.
 
Question 4. 
Growth of plant is a:
(a) non-periodic change
(b) temporary change
(c) permanent change
(d) periodic change
Answer:
(c) permanent change

Question 5. 
Which of the following can be considered as fast change?
(a) Growth of child
(b) Germination of seed
(c) Bursting of crackers
(d) Cooking of food
Answer:
(c) Bursting of crackers

Question 6. 
When air is filled! into a balloon, the shape and size of the balloon change due to:
(a) heat
(b) pressure
(c) physical change
(d) both (b) and (c)
Answer: 
(d) both (b) and (c)

Fill in the Blanks

Question 1. 
On pouring cold water, the metal rim ................ and fits into the wooden wheel.
Answer:
contracts

Question 2. 
Generally on heating metal ................ 
Answer:
expands

Question 3. 
Paper, petrol LPG, CNG, etc. are ................ substances.
Answer:
inflammable

Question 4. 
A change in which new substance is formed is called  ................ 
Answer:
chemical changes

Question 5. 
Water charges into ice on cooling is an example of ................ 
Answer: 
physical change

State whether True or False

Question 1. 
The evaporation of water is a reversible change.
Answer:
True

Question 2. 
Many changes are taking place around us on their own.
Answer:
True

Question 3. 
The burning of the candle is an irreversible change.
Answer:
True

Question 4. 
Burst ing of cracker is a fast change.
Answer: 
True

Question 5. 
Baking of dough into bread is a reversible change.
Answer: 
False

 

Match the columns

Column I	Column II
1. Diluted orange juice.	(a) blacksmith
2. Force, temperature, mixing	(b) slow change
3. Stretching a rubber band	(C) chemical changes
4. Gardening tools	(d) physical changes
5. Decaying of dead plants	(e) irreversible change
6. Changes in which physical properties like shape, size and state change without formation of new substance	(f) reversible change
7. Burning of fuel	(g) miring
8. Curdling of milk	(h) causes change
9. Bursting of a car tyre	(i) pressure

Answer:

Column I	Column II
1. Diluted orange juice.	(g) miring
2. Force, temperature, mixing	(h) causes change
3. Stretching a rubber band	(f) reversible change
4. Gardening tools	(a) blacksmith
5. Decaying of dead plants	(b) slow change
6. Changes in which physical properties like shape, size and state change without formation of new substance	(d) physical changes
7. Burning of fuel	(C) chemical changes
8. Curdling of milk	(e) irreversible change
9. Bursting of a car tyre	(i) pressure

Very Short Answer Type Questions 

Question 1. 
Give some day-to-day examples of reversible changes.
Answer: 
Some day-to-day examples of reversible changes are:

• drying of wet clothes.
• freezing water to make ice.

Question 2. 
Give two examples of irreversible changes occurring in food products. 
Answer: 
Examples of irreversible changes occurring in food products are:

• Milk to cheese, 
• Cooking of food. 

Question 3.
Deforestation is the cutting down of trees in a forest. Is it irreversible or reversible change?
Answer: 
It is a reversible change if the cut trees are planted again. However, if they are not planted again, it is a one-way process, hence, irreversible.

Question 4. 
Does the size of the paper change sifter make an aeroplane by folding it, or, by cutting it?
Answer: 
Folding the paper into an aeroplane does not change its actual size. But, cutting out an aeroplane from it, reduces its size.

Question 5.
What happens when sugar is heated? What form of change is it?
Answer:
When sugar is heated it melts and if heated for longer then a black sticky substance is formed. This is a chemical change.

Question 6. 
Explain, which type of change is associated with an iron rim fitted over a wooden wheel?
Answer: 
Iron expands on heating and contracts on cooling. Hence, a physical change is associated with this activity.

Short Answer Type Questions 

Question 1. 
Does the shape of an eraser change in any way after erasing?
Answer: 
Yes, the more we rub, the smaller it becomes. Hence, the shape of the eraser changes and it depends on which edge of the eraser is used more often.

Question 2. 
List down some changes occurring in our body.
Answer: 
Some changes occurring in our body include:
(a) our nails grow,
(b) milk teeth fall, and are replaced by permanent teeth,
(c) our hair grows white as we grow old, and) our height increases,
(e) our weight increases.

 

Question 3. 
What is a change?
Answer: 
A change is an event that may cause an object to undergo a different look, composition, colour, position, size or shape due to some factor (external or internal). Change may be permanent or temporary. 

Question 4. 
Classify the following into slow and fast changes: 
(a) Spinning of top
(b) Formation of day and night
(c) Formation of curd from milk
(d) Change of seaso n
(e) Making paneer from milk by adding lemon juice 
(f) Burning of paper 
(g) Weathering of rocks
(h) Melting of wax 
(i) Cooking of food
(j) Burning of wax
(k) Melting of ice cream
Answer:
(a) Fast change 
(b) Slow change 
(c) Slow change  
(d) Slow change
(e) Fast change 
(f) Fast change 
(g) Slow change 
(h) Fast change 
(i) Slow change 
(j) Fast change 
(k) Fast change. 

Question 5. 
What is a ‘ physical change? Explain with the help of an example. 
Answer: 
The change in which only the physical properties of substances1, are changed and no new substance is Formed is called a physical change. These are generally reversible changes. For example - Boiling changes water to, steam and cooling changes it back to liquid form of water.

Question 6. 
What is a chemical change? Explain with example.
Answer: 
Those changes in which the original substance is changed and new’ substances with new chemical properties are formed are called chemical changes.
For example - the burning of incense stick to produce ash and smoke. 

Long Answer Type Questions 

Question 1. 
What do you mean by reversible changes? Give examples.
Answer: 
Those changes which cam be reversed to obtain the original form by removing the cause of change are called reversible changes. These changes are generally physical in nature and do not involve any change in chemical composition. Examples include: 

1. Melting of ice 
2. Folding of paper
3. Evaporation of water.

Question 2. 
What are irreversible changes?
Answer: 
Those changes, which i cannot be reverted or converted back to its original form are called irreversible changes. Such changes generally involve a change in chemical composition of the substance. Examples include burning of candles, germination of seeds, bursting a balloon, rusting of iron.

Question 3. 
A blacksmith heats the metal rim to fix it on a cartwheel. Explain.
Answer: 
A blacksmith heats the metal rim because metals have a property to expand on heating. The rim is generally made slightly smaller than the wheel over which it has to fit. On heating, the rim expands and fits onto the wheel. Then on pouring cold water, the rim contracts and fits tightly onto the wheel.

Question 4. 
How do slow and fast changes differ? Give examples.
Answer: 
The changes which take place in a long period of time are called slow changes whereas the changes which take place in a short period of time are called fast changes. Examples include:
(a) rusting of iron, formation of day and night, ripening of fruits, growing of trees are slow changes,
(b) burning of paper, stretching of rubber bands, blowing off balloons, bursting of crackers are fast changes. 

 

Question 5. 
Differentiate between physical changes and chemical changes. 
Answer: 
Differences between Physical Changes and Chemical Changes

Physical Changes	Chemical Changes
1. Composition of substance remains same. No new substances are formed.	Composition of substance changes. New substance is formed.
2. Change in shape, size or. physical state occurs. Chemical properties of substance remain same.	New substances have new shape, physical states, different physical and chemical properties.
3. Physical changes are reversible.	Chemical changes are irreversible.
4. For example - Melting of ice, expansion of iron on heating.	For example - Burning of wood, rusting of iron.