Class 9 Science : Practice Questions and Answers

Carbon dioxide traps heat in the atmosphere and contributes to the greenhouse effect.

J.J. Thomson proposed the plum pudding model of the atom.

James Chadwick discovered the neutron in 1932.

Protons and neutrons are located in the nucleus of an atom.

The mass of an electron is about 1/1836 of the mass of a proton.

Atomic number is equal to the number of protons in an atom.

Hydrogen atoms share electrons to form a covalent bond.

Carbon has an atomic number of 6.

An atom is the smallest unit of an element that retains its properties.

In compounds, elements are chemically bonded in fixed proportions.

Sugar dissolved in water forms a homogeneous mixture because it is uniformly distributed.

A pure substance contains only one type of particle and cannot be separated by physical methods.

Water exists as ice, liquid water, and steam under different conditions.

Reactivity with oxygen is a chemical property because it describes how a substance undergoes chemical change.

Heating increases the kinetic energy of particles, causing them to move faster.

Plants use sunlight to perform photosynthesis.

A chemical reaction forms new substances with different properties.

Metals are generally good conductors of heat and electricity.

Sublimation is the direct conversion of a solid into a gas without passing through the liquid state.

Dissolving salt in water is a physical change because no new substance is formed.