Question

directions: tell whether the following changes are physical (p) or chemical (c) and whether they are reversible (r) or nonreversible (n).

______ 8. iron rusting

______ 9. salt dissolving

______ 10. water freezing

______ 11. wood burning

______ 12. pottery shattering

matter: properties and changes

Explanation:

Question 8: Iron rusting

Iron rusting involves a reaction between iron, oxygen, and water to form iron oxide (rust), which is a new substance. So it's a chemical change (C). Rusting is a slow, irreversible process as it's difficult to convert rust back to iron under normal conditions, so it's nonreversible (N).

Salt dissolving in water is a physical change (P) because the salt (sodium chloride) retains its chemical identity; it's just dispersed in water. This process is reversible (R) as we can recover the salt by evaporating the water.

Water freezing is a physical change (P) as it changes from liquid to solid (ice) without altering its chemical composition (still H₂O). It's reversible (R) because we can melt the ice back to water by increasing temperature.

Answer:

C, N

Question 9: Salt dissolving