Question

1. use what you have learned about chemical and physical changes to identify the type of change that occurs in each of the following. circle the correct answer.

a. digestion of food within the digestive system: physical or chemical change?
b. the yellowing of the pages of an old book: physical or chemical change?
c. the evaporation of perfume from an open bottle: physical or chemical change?
d. the cutting of a piece of paper: physical or chemical change?
e. silver tarnishing: physical or chemical change?
f. instant ice tea mix dissolving in water: physical or chemical change?
g. condensing air (turning air from a gas to a liquid): physical or chemical change?

1. which type of change can be more easily reversed: chemical or physical? please explain in detail with an example of each.

Explanation:

Step1: Define physical and chemical change

Physical change: No new - substance formed, only change in state, shape, etc. Chemical change: New substances are formed.

Step2: Analyze digestion of food

Food is broken down by enzymes into new substances during digestion. So it is a chemical change.

Step3: Analyze yellowing of old - book pages

Oxidation and other chemical reactions cause the yellowing, forming new substances. So it is a chemical change.

Step4: Analyze evaporation of perfume

Perfume changes from liquid to gas, but no new substances are formed. It is a physical change.

Step5: Analyze cutting of paper

Only the shape of the paper changes, no new substances are formed. It is a physical change.

Step6: Analyze silver tarnishing

Silver reacts with sulfur - containing substances in the air to form silver sulfide (new substance). It is a chemical change.

Step7: Analyze instant ice - tea dissolving in water

The tea particles disperse in water, but no new substances are formed. It is a physical change.

Step8: Analyze condensing air

Air changes from gas to liquid, no new substances are formed. It is a physical change.

Step9: Analyze reversibility

Physical changes are generally more easily reversed. For example, melting ice (physical change) can be reversed by freezing the water back into ice. In a chemical change like burning wood, the wood turns into ash, carbon dioxide, etc., and it is very difficult to reverse this process to get the original wood back.

Answer:

a. Chemical change
b. Chemical change
c. Physical change
d. Physical change
e. Chemical change
f. Physical change
g. Physical change

1. Physical change can be more easily reversed. Example of physical change: Melting ice can be reversed by freezing. Example of chemical change: Burning wood is difficult to reverse to get the original wood.