Question

1. you forgot to dry the bread knife when you washed it and reddish brown spots appeared on it.
2. you blow dry your wet hair.
3. in baking biscuits and other quick breads, the baking powder reacts to release carbon dioxide bubbles. the carbon dioxide bubbles cause the dough to rise.
4. you take out your best silver spoons and notice that they are very dull and have some black spots.
5. a straight piece of wire is coiled to form a spring.
6. food color is dropped into water to give it color.
7. chewing food to break it down into smaller particles represents a ________ change, but the changing of starch into sugars by enzymes in the digestive system represents a ________ change.
8. in a fireworks show, the fireworks explode giving off heat and light.

part c: true (t) or false (f)

1. f changing the size and shapes of pieces of wood w
2. f in a physical change, the makeup of matter is chan
3. t evaporation occurs when liquid water changes into
4. t evaporation is a physical change.
5. f burning wood is a physical change.
6. f combining h

Explanation:

1. Rust on the bread - knife is a chemical change (iron reacts with oxygen and water to form iron oxide).
2. Blow - drying wet hair is a physical change (water changes from liquid to gas state).
3. Baking powder reaction in baking is a chemical change (produces carbon dioxide gas through a chemical reaction).
4. Tarnishing of silver spoons is a chemical change (silver reacts with sulfur - containing compounds in air to form silver sulfide).
5. Coiling a wire to form a spring is a physical change (only the shape of the wire changes).
6. Adding food color to water is a physical change (the color spreads through the water without a chemical reaction).
7. Chewing food is a physical change (breaking into smaller pieces), while the conversion of starch to sugars by enzymes is a chemical change.
8. Fireworks explosion is a chemical change (produces heat, light, and new substances).

For Part C:

• Changing the size and shape of wood is a physical change, so the statement about it being false in the context of physical change is incorrect (should be T).
• Evaporation is a physical change where liquid water changes to gas, so the related statements are correct as marked (T).
• Burning wood is a chemical change, so the statement marking it as a physical change is false (F).

Answer:

1. Chemical change
2. Physical change
3. Chemical change
4. Chemical change
5. Physical change
6. Physical change
7. Physical; Chemical
8. Chemical change

Part C:

1. T
2. T
3. T
4. T
5. F
6. F
7. T