Chemistry IGCSE Midcourse Exam

Which of the following is a distinguishing property of solids?

• They are compressible
• They have fixed shapes
• They can flow freely
• They can expand to fill a container

Answer explanation

Solids have fixed shapes because their particles are closely packed and vibrate in place. (C1.1.1)

How are particles arranged in a gas?

• Closely packed and vibrating
• Widely spaced and moving randomly
• In a regular lattice
• Compressed in a smaller volume

Answer explanation

Gas particles are widely spaced and move randomly, allowing them to fill any container. (C1.1.2)

Which process involves the change of a liquid to a gas at the surface below boiling point?

• Boiling
• Condensation
• Evaporation
• Freezing

Answer explanation

Evaporation occurs when a liquid changes to gas at the surface, below boiling point. (C1.1.3)

What happens to the volume of a gas when temperature increases, assuming pressure is constant?

• It decreases
• It stays the same
• It increases
• It fluctuates randomly

Answer explanation

When temperature increases, gas particles move faster, increasing the volume. (C1.1.4)

Why does heating a solid cause it to melt in terms of kinetic particle theory?

• Particles become stationary
• Particles break apart
• Particles gain energy and vibrate more
• Particles lose energy and form bonds

Answer explanation

Heat increases the kinetic energy of particles, causing them to overcome attractive forces. (C1.1.5)

What is diffusion best described as?

• Particles condensing
• Movement of particles from low to high concentration
• Movement of particles from high to low concentration
• Movement of particles between substances

Answer explanation

Diffusion is the movement of particles from a high to a low concentration. (C1.2.1)

How does the relative molecular mass of a gas affect its rate of diffusion?

• Increases the rate of diffusion
• Decreases the rate of diffusion
• Has no effect
• Only affects liquid diffusion

Answer explanation

Higher molecular mass decreases the rate of diffusion as heavier particles move slower. (C1.2.2)

Which apparatus is best used to measure the volume of a liquid?

• Burette
• Measuring cylinder
• Volumetric pipette
• Gas syringe

Answer explanation

A measuring cylinder is suitable for measuring the volume of a liquid. (C12.1.1)

What is the definition of a saturated solution?

• A solution with one solute
• A solution with maximum solute
• A solvent with maximum solute
• A mixture with dissolved gases

Answer explanation

A saturated solution contains the maximum amount of solute at a given temperature. (C12.1.2)

What is the purpose of an indicator in titration?

• To calculate concentration
• To neutralize the solution
• To indicate pH levels
• To signal the endpoint

Answer explanation

Indicators change color to signal the endpoint of a titration. (C12.2.2)