Match the following: A B C 1. Melting Change of state from liquid to solid Ticking of clock 2. Condensation Change of state from liquid to gas Formation of ice cube 3. Evaporation Change of state from solid to liquid Collecting flowers 4. Freezing Change of state from gas to liquid Ice cube to water 5. Periodic change Occurs at irregular time intervals Water to steam 6. Non-periodic change Occurs at regular time intervals Steam to water drops

1. Melting Change of state from solid to liquid Ice cube to water Melting is the process of conversion of a solid into its liquid state. For example, ice cube melts to form water. It is a reversible physical change. 2. Condensation Change of state form gas to liquid Steam to water drops Condensation is the process of conversion of a gaseous state into its liquid state. For example, conversion of steam to water. It is a reversible physical change. 3. Evaporation Change of state from liquid to gas Water to steam Evaporation is the process of conversion of a liquid into its vapours. That is, the conversion of water to steam. It is also a reversible physical change. 4. Freezing Change of state from liquid to solid Formation of ice cube Freezing is the process of a liquid into solid by cooling. For example, formation of ice cubes from water involves freezing. 5. Periodic change Occurs at regular time intervals Ticking of clock Periodic changes are the changes which repeats over a regular interval of time. Ticking of clock, change of seasons, etc. are a few examples of periodic changes. 6. Non-periodic change Occurs at irregular time intervals Collecting flowers Non-periodic changes does not occur at regular intervals of time. Collecting flowers and formation of earthquake are non-periodic changes. A B C 1. Melting Change of state from solid to liquid Ice cube to water 2. Condensation Change of state from gas to liquid Steam to water drops 3. Evaporation Change of state from liquid to gas Water to steam 4. Freezing Change of state from liquid to solid Formation of ice cube 5. Periodic change Occurs at regular time intervals Ticking of clock 6. Non-periodic change Occurs at irregular time intervals Collecting flowers

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7th Tamil Nadu Board

IMPORTANT

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Tarnishing of silver is an example of endothermic change.

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Important Questions on Changes Around Us

HARD

7th Tamil Nadu Board

IMPORTANT

Tamil Nadu Board Class 7 Science Term 2>Chapter 3 - Changes Around Us>Evaluation>Q IV

Match the following:

A	B	C
1. Melting	Change of state from liquid to solid	Ticking of clock
2. Condensation	Change of state from liquid to gas	Formation of ice cube
3. Evaporation	Change of state from solid to liquid	Collecting flowers
4. Freezing	Change of state from gas to liquid	Ice cube to water
5. Periodic change	Occurs at irregular time intervals	Water to steam
6. Non-periodic change	Occurs at regular time intervals	Steam to water drops

HARD

7th Tamil Nadu Board

IMPORTANT

Tamil Nadu Board Class 7 Science Term 2>Chapter 3 - Changes Around Us>Evaluation>Q V

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 an 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.