Test: Chemical Changes - Year 8 MCQ

The word equation for the formation of water is Hydrogen + Oxygen → Water.

Rusting of iron (option C) is a chemical change because it involves a chemical reaction between iron, oxygen, and water to form iron oxide (rust), which has different properties than iron itself. Melting ice (option A), dissolving sugar in water (option B), and cutting a piece of paper (option D) are physical changes where the substance retains its chemical identity

A change in state (solid to liquid) (option C) is a physical change because the substance remains chemically the same (ice melting to water, for example). Options A, B, and D are evidence of chemical changes: production of a gas (option A) indicates a chemical reaction, change in color (option B) can indicate a change in chemical composition, and formation of a precipitate (option D) suggests a chemical reaction has occurred.

A chemical change (option C) involves a chemical reaction where one or more substances are converted into different substances with different properties. Options A, B, and D describe characteristics of physical changes rather than chemical changes: option A describes reversibility (physical change), option B describes a change in state (physical change), and option D describes a change in appearance (physical change).