IGCSE Chemistry – Unit 2 (25 Detailed MCQs by Subtopic)

Which of the following states of matter has particles arranged in a fixed pattern and only able to vibrate?

• Liquid

• Gas

• Solid

• Plasma

Answer explanation

The correct answer is 'Solid' because solids have particles arranged in a fixed pattern, allowing them to only vibrate in place, unlike liquids, gases, and plasmas where particles move more freely.

What change occurs when a solid turns directly into a gas?

• Condensation

• Sublimation

• Freezing

• Melting

Answer explanation

Sublimation is the process where a solid changes directly into a gas without passing through the liquid state, such as dry ice turning into carbon dioxide gas. This distinguishes it from condensation, freezing, and melting.

Which of the following has a definite volume but no definite shape?

• Gas

• Liquid

• Plasma

• Solid

Answer explanation

A liquid has a definite volume, meaning it occupies a specific amount of space, but it takes the shape of its container, thus having no definite shape. In contrast, gases and plasmas have neither definite volume nor shape, and solids have both.

According to particle theory, how are gas particles arranged?

• Closely packed in regular pattern

• Random and widely spaced

• Tightly packed and vibrating

• Fixed in a rigid shape

Answer explanation

According to particle theory, gas particles are arranged randomly and widely spaced, allowing them to move freely and fill their container. This distinguishes them from solids and liquids, where particles are more closely packed.

What happens to particles in a substance when it is heated?

• They contract

• They move more slowly

• They stop moving

Answer explanation

When a substance is heated, its particles gain energy and move more rapidly, not more slowly. This increased movement causes the substance to expand, not contract or stop moving.

What happens to the temperature of a substance during melting?

• It increases rapidly

• It stays the same

• It decreases

• It fluctuates

Answer explanation

During melting, a substance absorbs heat, but its temperature remains constant until the phase change is complete. This is why the correct answer is 'It stays the same'.

Which change of state involves the loss of energy from particles?

• Boiling

• Melting

• Condensing

• Evaporating

Answer explanation

Condensing is the change of state where gas turns into liquid, involving the loss of energy from particles. In this process, particles lose energy and move closer together, forming a liquid.

Which example best illustrates diffusion in gases?

• Ice melting

• Perfume scent spreading

• Boiling water

• Sugar dissolving

Answer explanation

The best example of diffusion in gases is the spreading of a perfume scent. This occurs as perfume molecules move from an area of high concentration to areas of lower concentration, illustrating the process of diffusion.

Why does diffusion occur faster in gases than in liquids?

• Gas particles are heavier

• Gas particles are closer

• Gas particles move faster and are further apart

• Gases are colder

Answer explanation

Diffusion occurs faster in gases because gas particles move faster and are further apart compared to liquids. This increased speed and distance between particles allow for quicker mixing and movement.

Which subatomic particle is found in the nucleus and has no charge?

• Proton

• Neutron

• Electron

Answer explanation

The neutron is a subatomic particle located in the nucleus of an atom and is electrically neutral, meaning it has no charge. In contrast, protons have a positive charge and electrons have a negative charge.