Which is an example of a chemical change?

Which is an example of a chemical change?

• A. Burning a candle
• B. Ice melting
• C. Water boiling
• D. Paper tearing

Answer: (A)

Chemical changes involve forming new substances with different properties from the originals. A key sign is that bonds are broken and new ones are formed, often with noticeable energy changes, color or odor changes, gas production, or a precipitate. Burning a candle fits this because the wax reacts with oxygen in the air in a combustion reaction. The wax and oxygen rearrange their atoms to produce new substances—carbon dioxide and water vapor—while releasing heat and light. The material at the start is no longer the same after combustion, so a chemical change has occurred. In contrast, melting ice and boiling water are changes of state that keep the same substance (water), so they’re physical changes. Tearing paper changes its shape but not its chemical composition, another physical change.

Chemical changes involve forming new substances with different properties from the originals. A key sign is that bonds are broken and new ones are formed, often with noticeable energy changes, color or odor changes, gas production, or a precipitate.

Burning a candle fits this because the wax reacts with oxygen in the air in a combustion reaction. The wax and oxygen rearrange their atoms to produce new substances—carbon dioxide and water vapor—while releasing heat and light. The material at the start is no longer the same after combustion, so a chemical change has occurred.

In contrast, melting ice and boiling water are changes of state that keep the same substance (water), so they’re physical changes. Tearing paper changes its shape but not its chemical composition, another physical change.