Question

1. use the word equation below to explain how a chemical change differs from a physical change.

iron + sulfur $xrightarrow{\text{heat}}$ iron sulfide
*60. classify each of the following as a physical or chemical change. for any chemical change, list at least one clue to support your answer.
a. a copper wire is bent.
b. charcoal burns in a grill.
c. bread dough rises when yeast is added.
d. sugar dissolves in water.

Explanation:

Question 59

A physical change doesn't form new substances, just changes appearance/state. The word equation \( \text{iron} + \text{sulfur} \xrightarrow{\text{heat}} \text{iron sulfide} \) shows iron and sulfur (reactants) form iron sulfide (new substance, product) with heat. This is a chemical change (new substance, energy change - heat used). Physical changes don't have new substances, so the key difference is chemical changes form new substances (like iron sulfide here), physical don't.

Bending a copper wire changes its shape, not its chemical identity (still copper). No new substance forms.

Burning charcoal (carbon) reacts with \( \text{O}_2 \) to form \( \text{CO}_2 \) (and heat/light). New substance (\( \text{CO}_2 \)) forms, plus clues like heat, light, gas production (burning is combustion, a chemical reaction).

Answer:

In the word equation \( \text{iron} + \text{sulfur} \xrightarrow{\text{heat}} \text{iron sulfide} \), a chemical change occurs because new substance (iron sulfide) forms from iron and sulfur. A physical change would not form a new substance (only change state/appearance, no new compound). So chemical change produces new substances (like iron sulfide), physical change does not.

Question 60

Part (a)