Science MCQs

Combustion is a chemical reaction (often with oxygen) that releases energy in the form of heat and light.

A chemical change involves the formation of new substances with different chemical compositions while a physical change does not.

Chlorine is used for its bleaching action (a chemical property). The other uses are based on physical properties like conductivity or strength.

Fractional distillation separates components of crude oil by exploiting their different physical property: boiling points.

The formation of zinc chloride a new substance with properties different from zinc or acid confirms it is a chemical change.

Proper storage in a dry environment (e.g. using silica gel or calcium chloride packets) prevents moisture thus preventing rust.

Sulphur dioxide (SO2) reacts with atmospheric water to form sulphuric acid a major component of acid rain.

Chemical equations often include state symbols: (s) (l) (g) (aq) to show the physical form of the substances.

Making an alloy involves melting metals together to form a new substance with different properties (e.g. steel from iron and carbon) which is a chemical change.

Flammability the ability to catch fire and burn easily is the key chemical property for a substance to be used as a fuel.