states of matter

Solid

A state of matter with a fixed shape and volume, particles arranged in a regular pattern.

Liquid

A state of matter that takes the shape of its container, has a fixed volume, and particles that are close but can move past each other.

Gas

A state of matter with no fixed shape or volume, where particles are far apart and move randomly.

Melting

The process of changing from a solid to a liquid at a specific temperature.

Freezing

The process of changing from a liquid to a solid at a specific temperature.

Boiling

The process where a liquid changes to gas throughout the liquid at a fixed temperature.

Evaporation

The process where a liquid changes to gas only at the surface at any temperature.

Condensation

The process where gas changes to liquid.

Sublimation

The process where a solid changes directly to gas.

Kinetic energy

The energy of particles in motion; increases with temperature.

Heating curve

A graph that shows how temperature changes as energy is added to a substance.

Cooling curve

A graph that shows how temperature changes as energy is removed from a substance.

Gas Pressure

The force exerted by gas particles when they collide with the walls of a container.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration.

Concentration gradient

The difference in concentration of a substance between two areas.

Relative Molecular Mass (RMM)

The mass of a molecule compared to the mass of a carbon-12 atom.

Particle Motion in Solids

Particles vibrate in fixed positions.

Particle Motion in Liquids

Particles move past each other while remaining close.

Particle Motion in Gases

Particles move randomly, rapidly, in all directions.

Forces in Solids

Strong forces holding particles in fixed positions.

Forces in Liquids

Weaker forces allowing particles to move closer.

Forces in Gases

Very weak forces resulting in far apart particles.

First Plateau in Heating Curve

Temperature remains constant as energy is used to break intermolecular forces during melting.

Second Plateau in Heating Curve

Temperature remains constant as energy is used to break intermolecular forces during boiling.

First Plateau in Cooling Curve

Temperature remains constant as energy is released when gas condenses into liquid.

Second Plateau in Cooling Curve

Temperature remains constant as energy is released when liquid freezes into solid.

Effect of Temperature Increase on Gas

Particles gain kinetic energy, move faster, and collide with walls more frequently.

Effect of Increased Pressure on Gas

Particles are forced closer together, resulting in decreased volume.

Diffusion Rate

The speed at which particles spread out, influenced by molecular weight.

Newtonian Fluid

A fluid that behaves according to Newton's law of viscosity.

Graham's Law of Effusion

States that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.

Ammonia (NH₃)

A lighter gas that diffuses faster due to lower relative molecular mass.

Hydrogen Chloride (HCl)

A heavier gas that diffuses slower due to higher relative molecular mass.

Particle Diagram of Solids

Particles drawn in neat, touching rows to show fixed positions.

Particle Diagram of Liquids

Particles drawn randomly but still close and touching.

Particle Diagram of Gases

Few particles drawn far apart with arrows indicating random movement.

Fixed Volume

A characteristic of solids and liquids, but not gases.

Compressibility

The ability of a substance to decrease in volume under pressure, which is significant in gases.

Temperature Change

The alteration in temperature as energy is added or removed from a substance.

Kinetic Particle Theory

The theory that explains the behavior of particles in different states of matter.

Net Movement of Particles

Movement of particles resulting from random motion leading to diffusion.

Energy Transfer in Phase Changes

The energy is used to break or form intermolecular forces, not change temperature.

Differences between Boiling and Evaporation

Boiling occurs throughout at fixed temperature; evaporation occurs only at the surface at any temperature.

Temperature Constant during Phase Change

Because energy is used to change the state rather than temperature.

Practical Implications of Diffusion

Understanding diffusion can explain processes like mixing and chemical reactions.

Are boiling and evaporation endothermic or exothermic processes?

Both boiling and evaporation are endothermic processes

Which phase changes involve the conversion of liquid into gas?

Boiling and evaporation

How does the distance between molecules change during boiling and evaporation?

Molecules move further apart from each other

What happens to the kinetic energy of particles during boiling and evaporation?

The kinetic energy increases, so the particles move faster

What happens to intermolecular bonds during boiling and evaporation?

Intermolecular bonds break

What is condensation?

Condensation is the process of gas being converted into liquid

Is condensation an endothermic or exothermic process?

Condensation is an exothermic reaction

At what specific temperature does condensation occur for a pure substance?

Condensation happens at the boiling point

How does particle kinetic energy change during condensation as temperature decreases?

The kinetic energy of particles will decrease, making them move more slowly

What happens to the bonds between particles during condensation?

Bonds form between particles.

What is melting?

Melting is the process in which a solid converts to a liquid.

At what specific temperature does melting occur?

Melting happens at the melting point

How do molecules behave during melting regarding their distance from each other?

Molecules move further apart from each other

What happens to the kinetic energy of particles during melting?

The kinetic energy increases, so the particles move faster

What happens to the bonds between particles during melting?

Bonds break

Is melting an endothermic or exothermic process?

Melting is an endothermic process

What is freezing?

Freezing is the process in which a liquid converts to a solid

At what specific temperature does freezing occur?

Freezing happens at the freezing point

Is freezing an endothermic or exothermic process?

Freezing is an exothermic process

How do particle kinetic energy and bonds change during freezing as temperature decreases?

As temperature decreases, the kinetic energy of particles will decrease, making them move more slowly, and bonds form

Explain why gases can be compressed but liquids cannot

Gas particles are far apart with large spaces between them, so they can be compressed.
Liquid particles are close together with almost no spaces, so they cannot be compressed.

Explain, in terms of particles, why the temperature remains constant during boiling even though heat is being supplied

The energy supplied is used to break the intermolecular forces between the particles (1), not to increase their kinetic energy (1), so the temperature does not rise (1)

Explain why the rate of diffusion is higher in gases than in liquids. [2 marks]

In gases, the particles have more kinetic energy (1) and are much further apart with negligible forces between them, allowing for faster movement (1)

A gas is compressed into a smaller volume. Describe what happens to the pressure of the gas. Explain your answer in terms of particles. [3 marks]

The pressure increases (1). The particles are forced closer together into a smaller space (1), so they collide with the container walls more frequently (1)