particle model of matter

Question 1

Describe the features of the particle model for a solid.

Answer 1

solid

• strong forces of attraction between particles
• fixed, regular pattern of particles
• particles vibrate in fixed positions

Question 2

Describe the features of the particle model for a liquid.

Answer 2

liquid

• weaker forces of attraction between particles
• particles are close to each other, but in an irregular pattern so they have enough room so slide over each other
• particles move in random directions at low speeds

Question 3

Describe the features of the particle model for a gas.

Answer 3

gas

• near to no forces of attraction between particles
• particles have the most energy (kinetic)
• particles are free to move in random directions at high speeds; constant random motion

Question 4

What is density?

Answer 4

Density is the mass of an object that occupies 1m^3. The more particles in a given volume, the higher the density.

Question 5

How do you calculate density?

Answer 5

density (kg/m^3) = mass (kg) / volume (m^3)

Question 6

What is internal energy?

Answer 6

Internal energy is the total energy stored in a system by the particles. It is the sum of kinetic energy and potential energy.

Question 7

What is potential energy? (in terms of particles)

Answer 7

Potential energy is the strength of the intermolecular forces, or how far apart the particles are.

Question 8

What happens to the mass of an object during changes of state?

Answer 8

During changes of state, the mass is conserved; there are only physical changes, no chemical changes.

Question 9

What is it called when a solid immediately changes state to a gas?

Answer 9

When a solid changes state directly to a gas, it is called sublimation.

Question 10

How does heating an object affect the internal energy?

Answer 10

Heating an object increases the internal energy. The kinetic energy is increased during heating and potential energy is increased during changes of state.

Question 11

What happens to the particles and temperature when melting occurs?

Answer 11

melting

• solid to liquid
• potential energy increases (as it is a change of state)
• kinetic energy stays the same
• internal energy increases
• temperature of substance stays the same

Question 12

What happens to the particles and temperature when a liquid is heated?

Answer 12

heating liquid

• not a change of state
• potential energy stays the same
• kinetic energy increases
• internal energy increases
• temperature of substance increases

Question 13

What happens to the particles and temperature when a liquid is boiled?

Answer 13

boiling liquid

• liquid to gas
• potential energy increases (as it is a change of state)
• kinetic energy stays the same
• internal energy increases
• temperature of substance stays the same

Question 14

What happens to the particles and temperature when a gas is cooled?

Answer 14

cooled gas

• not a change of state
• potential energy stays the same
• kinetic energy decreases
• internal energy decreases
• temperature of substance decreases

Question 15

What happens to the particles and temperature when condensation occurs?

Answer 15

condensation

• gas to liquid
• potential energy decreases (as it is a change of state)
• kinetic energy stays the same
• internal energy decreases
• temperature of substance stays the same

Question 16

What happens to the particles and temperature when a liquid is cooled?

Answer 16

cooled liquid

• not a change of state
• potential energy stays the same
• kinetic energy decreases
• internal energy decreases
• temperature of substance decreases

Question 17

What happens to the particles and temperature when freezing occurs?

Answer 17

freezing

• liquid to solid
• potential energy decreases (as it is a change of state)
• kinetic energy stays the same
• internal energy decreases
• temperature of substance stays the same

Question 18

What is specific latent heat? Give the units.

Answer 18

Specific latent heat is the energy required to change the state of 1kg of a substance without raising the temperature. It is given in J/kg.

Question 19

What is specific latent heat of fusion?

Answer 19

Specific latent heat of fusion is the energy required to change the state of 1kg of a solid to a liquid without raising the temperature. It is given in J/kg.

Question 20

What is specific latent heat of vaporisation?

Answer 20

Specific latent heat of vaporisation is the energy required to change the state of 1kg of a liquid to a gas without raising the temperature. It is given in J/kg.

Question 21

How does temperature relate to the particle motion in gases?

Answer 21

As the temperature increases, the particles have more energy transferred to their kinetic stores, so there is an increase in speed in a constant, random motion.

Question 22

What is the pressure of a gas due to?

Answer 22

The pressure of a gas is due to the particles colliding with the walls of the container and each other.

Question 23

How can the pressure of a gas be increased?

Answer 23

The pressure of a gas can be increased by increasing the number of collisions (so decrease the volume of the container) or by increasing the energy of collisions (so increase the temperature).

Question 24

Give the equation that links the pressure in gases and volume.

Answer 24

pressure (Pa) x volume (m^3) = a constant number (if the temperature is constant)

Question 25

In which direction is the pressure in gases exerted?

Answer 25

Particle collisions in gases cause a force at right angles to the walls of the container.

Question 26

What effect does doing work on a gas have? Why?

Answer 26

Doing work on a gas increases the internal energy as the force that you exert is transferred to the particles stores, increasing the temperature as well.