Question

1. identify whether each is a physical or chemical change: a. ice melting b. wood burning c. salt dissolving d. iron rusting

Explanation:

Part a: Ice melting

A physical change is a change in which no new substance is formed, and the substance only changes its state or appearance. Ice melting is the process of solid water (ice) turning into liquid water. The chemical composition of water remains \(H_2O\) throughout this process, so no new substance is formed. This is a physical change.

A chemical change involves the formation of new substances. When wood burns, it reacts with oxygen in the air. The wood (which is mainly composed of cellulose, lignin, etc.) is converted into new substances like carbon dioxide, water vapor, and ash. Since new substances are formed, this is a chemical change.

When salt (sodium chloride, \(NaCl\)) dissolves in water, it breaks into \(Na^+\) and \(Cl^-\) ions, but the chemical identity of the salt (the ions are still \(Na^+\) and \(Cl^-\)) remains the same. No new chemical substance is created; it is just a change in the physical state of the salt (from solid to dissolved ions in a solution). So, this is a physical change.

Answer:

a. Ice melting: Physical change

Part b: Wood burning