Samacheer Kalvi solutions for Science - Term 2 [English] Class 7 TN Board chapter 3 - Changes Around Us [Latest edition]

When a woolen yarn is knitted to get a sweater, the change can be classified as ____________.

______ of the following are endothermic changes.

The chemical change is ______.

______ is an example of a periodic change.

______ is not a chemical change.

Filling up a balloon with hot air is a _______ change.

Stretching gold coin into a ring is a ______ change.

Opening a gas cylinder knob converts _____ fuel into ______fuel. This is an example of _____ change.

Spoiling of food is a ______ change.

Respiration is a ______ change.

True or False. If false, give the correct answer.

Cutting of cloth is an example of a periodic change.

True or False. If false, give the correct answer.

Taking a glass of water and freezing it by placing it in the freezer is a chemical change.

True or False. If false, give the correct answer.

A bean plant collecting sunlight and turning it into bean seeds is an example of physical and non-periodic change.

True or False. If false, give the correct answer.

If the chemical properties of a substance remain unchanged and the appearance or shape of a substance changes it is called a periodic change.

True or False. If false, give the correct answer.

Tarnishing of silver is an example of endothermic change.

Match the following

Classify the following changes as physical and chemical changes

A rough piece of wood is sanded and polished resulting in change in texture, Rusting of a iron nail, Painting the grill, Bending a paper clip, Pounding silver into thin plate, Rolling the chappathi dough into thin wire, Occurrence of day and night, eruption of volcano, burning of matchstick, dosa from the batter, blinking of eyelids, occurrence of a thunderstorm, rotation of the earth, formation of eclipses.

Physical Change: Boiling::Chemical Change: ______.

Wood to sawdust:______:: Wood to Ash: Chemical change

Forest fire: ______ change::Change in period in a school: periodic change

State two examples of periodic changes.

Mention any two exothermic reactions.

Cold milk is heated and it becomes hot. Which type of change it is?

What type of change is artificial ripening of fruit?

What type of change is colouring of a paper?

Growing of nails is a periodic change. Why?

What type of energy changes is associated when ice melts?

Distinguish physical and chemical changes.

How can a change occur in a substance?

Can you suggest a method to collect water from sea water?

Is solar eclipse a periodic change? Give your reason.

What is the difference between dissolution of sugar and burning of sugar ?

Explain the following statement: Digestion is a chemical change.

How the iron blade is fixed into a wooden handle in tools used to dig the soil?

Higher order Thinking question

Peeled and unpeeled banana does not look the same. Does that mean peeling banana is a chemical change?

Higher order Thinking question

A very hot glass on putting in cold water cracks. What does this change indicate?

Higher order Thinking question

Boiling of water is a physical change; but boiling of egg is a chemical change. Why?

Assertion: The explosion of fire cracker is a physical change.

Reason: A physical change is a reversible change.

Assertion: The process of conversion of liquid water to its vapours by heating the liquid is called boiling.

Reason: The process of conversion of water vapours to liquid by cooling the vapours is called condensation.

Assertion: Burning of wood log to charcoal is a physical change.

Reason: The products formed of burning a piece of wood can be easily converted back to wood log.

Assertion: The formation of iron oxide from iron is a chemical change.

Reason: For the rust to form from iron, it must be exposed to air and water.

Assertion: A drop of petrol when touched with finger gives a chill feeling.

Reason: The above phenomenon is an endothermic one.

Picture based question

Observe the picture and list down the changes that are accompanied in the picture.

1. ______.
2. ______.
3. ______.

Observe the picture containing a kettle and note that it has salt water in it and answer the following questions:

1. What is name of the process that is done to the kettle? 
2. What will happen to the content of the kettle?
3. What kind of change is occurring on the cold surface of the metal plate? 
4. What can you say about the quality of water that is obtained in the beaker?