Science MCQs

The color change in zinc oxide is temporary and reversible upon cooling indicating a physical change.

Melting wax is physical but the wick burning and producing soot/CO2 is chemical.

CO₂ and methane are greenhouse gases that trap heat in the atmosphere leading to global warming.

Tarnishing is the corrosion of metals like silver and copper when they react with gases like hydrogen sulphide or oxygen.

Rusting is a chemical property because it describes how iron reacts with oxygen and water to form a new substance (iron oxide).

The solute is the substance that is dissolved (salt). The solvent is the substance that does the dissolving (water).

Melting point is the specific temperature at which a solid begins to melt.

Water (H2O) is broken down into hydrogen gas (H2) and oxygen gas (O2) which are completely new substances.

Galvanizing involves coating iron or steel with a layer of zinc to prevent rusting.

Oxygen is a reactant that combines with the fuel during combustion to produce new products like CO2 and H2O.