Question

which is an example of a chemical change? a baking a cake b. freezing water c. crushing a can d. breaking an egg 16. which example best describes a physical change? a iron rusting b. charcoal burning c. an ice cube melting d. a marshmallow burning 17. a piece of wood is sawed into several small pieces. this is an example of what kind of change? a physical b. chemical c. electrical d. mechanical 18. stanley left an ice cube on his kitchen counter. an hour later, stanley observed that the ice cube melted. which statement best describes this change? a ice melting is a physical change because a new substance is created. b. ice melting is a chemical change because a new substance is created. c. ice melting is a chemical change because it may be reversed. d. ice melting is a physical change because it may be reversed.

Explanation:

1. For the first question, baking a cake involves chemical reactions like the reaction of baking - powder with other ingredients to produce carbon - dioxide gas, changing the chemical composition. Freezing water, crushing a can, and breaking an egg are physical changes as the substances' chemical identities remain the same.
2. For the second question, iron rusting, charcoal burning, and a marshmallow burning are chemical changes as new substances are formed. Ice - cube melting is a physical change as only the state of water changes from solid to liquid without a change in chemical composition.
3. For the third question, sawing wood into small pieces only changes the shape and size of the wood, not its chemical composition, so it is a physical change.
4. For the fourth question, ice melting is a physical change because it can be reversed (by refreezing) and no new substance is created.

Answer:

1. A. baking a cake
2. C. an ice cube melting
3. A. physical
4. D. Ice melting is a physical change because it may be reversed.