C1 Particles and their behaviour

What is the change of state from liquid to gas that occurs when bubbles form throughout the liquid?

• Condensation

• Evaporation

• Freezing

• Boiling

Answer explanation

The change of state from liquid to gas that occurs when bubbles form throughout the liquid is called boiling. This process happens when the liquid reaches its boiling point, allowing vaporization to occur throughout the liquid.

At what temperature does a substance boil?

• Melting point

• Boiling point

• Freezing point

• Sublimation point

Answer explanation

A substance boils at its boiling point, which is the temperature at which it changes from liquid to gas. The other options refer to different phase changes: melting point (solid to liquid), freezing point (liquid to solid), and sublimation point (solid to gas).

What is the process by which a substance changes from one state to another?

• Diffusion

• Sublimation

• Conservation

• Change of state

Answer explanation

The process by which a substance changes from one state to another is called 'change of state'. This encompasses transitions like melting, freezing, and boiling, distinguishing it from other processes like diffusion or sublimation.

What is the change of state from gas to liquid called?

• Boiling

• Melting

• Freezing

• Condensing

Answer explanation

The change of state from gas to liquid is called condensing. This process occurs when gas particles lose energy and come together to form a liquid, distinguishing it from boiling, melting, and freezing.

What is conserved in chemical reactions and physical changes?

• Volume

• Density

• Mass

• Temperature

Answer explanation

In chemical reactions and physical changes, mass is conserved. This means that the total mass of reactants equals the total mass of products, regardless of the changes occurring in the substances.

What is the mass per unit volume of a substance?

• Weight

• Density

• Mass

• Volume

Answer explanation

The mass per unit volume of a substance is defined as its density. Density quantifies how much mass is contained in a given volume, making it the correct choice among the options provided.

What is the movement of liquid or gas particles from a region of high concentration to a region of low concentration called?

• Evaporation

• Sublimation

• Diffusion

• Condensation

Answer explanation

The movement of liquid or gas particles from a region of high concentration to a region of low concentration is called diffusion. This process occurs naturally as particles spread out to achieve equilibrium.

What is the change of state from liquid to gas that occurs at the surface of a liquid?

• Freezing

• Evaporation

• Condensing

• Boiling

Answer explanation

The change of state from liquid to gas at the surface of a liquid is called evaporation. This process occurs at any temperature and allows molecules at the surface to escape into the air, unlike boiling, which occurs throughout the liquid.

What is the change of state from liquid to solid?

• Boiling

• Melting

• Sublimation

• Freezing

Answer explanation

The change of state from liquid to solid is called freezing. During this process, a liquid loses energy and its particles come together to form a solid structure.

In which state can a substance flow and be compressed?

• Solid

• Liquid

• Plasma

• Gas

Answer explanation

A gas can flow freely and be compressed, as its particles are far apart and move independently. In contrast, solids maintain a fixed shape, and liquids flow but are not easily compressed.