P3: Particle model of matter

Question 1

Describe the arrangement and movement of particles in solids.

Answer 1

1) Strong forces of attraction hold particles together in a fixed, regular arrangement.
2) Particles vibrate about a fixed point.
3) Solids are more dense than liquids and gases of the same substance.

Question 2

Describe the arrangement and movement of particles in liquids.

Answer 2

1) Forces of attraction are weaker than in solids.
2) Particles are close together but in an irregular arrangement.
3) Particles are loosely packed; they move around each other randomly at low speeds.
4) Liquids are less dense than solids of the same substance.

Question 3

Describe the arrangement and movement of particles in gases.

Answer 3

1) Weak forces of attraction between particles means particles are widely spaced.
2) Particles have more KE than solids and liquids; their average KE is related to their temperature.
3) Particles are in constant random motion (random speeds and directions).
4) Gases have low densities.

Question 4

What is the formula for density?

Answer 4

Density = mass / volume

ρ = m / V

^{remember that volume is V, not v, which is velocity.}

Question 5

1g/cm³ = ___kg/m³

Answer 5

1000 kg/m³

Question 6

1000kg/m³ = ___g/cm³

Answer 6

1g/cm³

Question 7

How would you find the volume of an irregular object?

Answer 7

• Submerge the object in a eureka can filled with water.
• Position a measuring cylinder next to the can so that the volume of water displaced by the object is transferred to the cylinder.
• Record the volume of water in the cylinder, in ml, and convert this into cm³; this gives you the object’s volume.

Question 8

How would you find the density of an irregular object?

Answer 8

• Measure the object’s mass, using weighing scales.
• Submerge the object in a eureka can filled with water.
• Position a measuring cylinder next to the can so that the volume of water displaced by the object is transferred to the cylinder.
• Record the volume of water in the cylinder, in ml, and convert this into cm³; this gives you the object’s volume.
• Find the object’s density using density = mass/volume.

Question 9

How would you find the density of a liquid?

Answer 9

• Place a measuring cylinder on a weighing scale and zero the balance.
• Add a set volume of liquid (1ml = 1cm³) to the cylinder and measure the mass on the scales.
• Find the density using density = mass/volume.
• You could improve the accuracy by taking repeat readings and calculating an average.

Question 10

What is the word for when a solid becomes a gas?

Answer 10

Sublimation

Question 11

What is the word for when a gas becomes a solid?

Answer 11

Deposition

Question 12

The internal energy of a substance is stored in what two ways?

Answer 12

1. Kinetic energy stored in particles.
2. Potential energy stored in their bonds.

Question 13

If energy is supplied to a substance, what determines how much hotter it will get?

Answer 13

1. Mass
2. Specific heat capacity/what it’s made of
3. Energy supplied

Question 14

What is specific heat capacity?

Answer 14

The amount of energy required to raise the temperature of 1kg of a substance by 1ºC.

Question 15

The formula for specific heat capacity is given (ΔE = mcΔθ). What is its symbol and unit?

Answer 15

Symbol: c

Unit: J / kg°C

Question 16

What is specific latent heat?

Answer 16

The energy required to change the state of a substance, or the energy released when a substance changes state.

Question 17

Specific latent heat, solid ⇌ liquid, = ___

Specific latent heat, liquid ⇌ gas, = ___

Answer 17

1. SLH of fusion
2. SLH of vaporisation

Question 18

What is the formula for specific latent heat?

Answer 18

E = mL

Question 19

What is the unit and symbol for specific latent heat?

Answer 19

1. Unit = J/kg
2. Symbol = L

Question 20

Why is the kinetic energy of particles in gases given as an average?

Answer 20

Because particles move at varying speeds. (This is due to collisions.)

Question 21

What causes pressure in containers filled with gases?

Answer 21

Particles move at high speeds so they collide with, and exert a force on, the walls of the container.

Question 22

In a sealed container filled with gas, the outward ___ is the total ___ exerted by all of the gas particles on a ___ ___ of the container walls.

Answer 22

In a sealed container filled with gas, the outward pressure is the total force exerted by all of the gas particles on a unit area of the container walls.

Question 23

The pressure of a gas causes a net outward force at ___ ___ to the surface of its container.

Answer 23

The pressure of a gas causes a net outward force at right angles to the surface of its container.

Question 24

1. For a gas of a fixed mass at a fixed temperature, what is the relationship between the pressure and the volume of the container?
2. What is the formula that shows this?

Answer 24

1. Pressure and volume are inversely proportional.
2. pV = constant

Question 25

What is the unit and symbol for pressure?

Answer 25

1. Unit = pascals (Pa)
2. Symbol = p

Question 26

The pressure of a gas causes a net outward force at right angles to the surface of its container. What other force does the container experience?

Answer 26

There is also a force on the outside of the container, due to the pressure of the gas around it.

Question 27

If a container easily changes size, what will happen when it experiences a change in pressure?

Answer 27

It will expand or compress, according to the resultant force of the pressures inside and outside it.

Question 28

Describe and explain what happens when a helium baloon is released into the air.

Answer 28

1. Helium is less dense than air, so the balloon rises.
2. Atmospheric pressure decreases with height, so the pressure outside of the balloon decreases as it rises.
3. The force on the surface of the balloon, coming from the gas on the inside pushing out, is now greater than that from the outside.
4. This means that the resultant force on the balloon’s surface is one that pushes out, so the balloon expands.
5. This happens until the internal pressure drops to reach equilibrium with the atmospheric pressure.
6. This repeats in a cycle until the balloon pops.

Question 29

Explain why a bicycle tyre feels warmer after being inflated with a pump.

Answer 29

1. Gas inside the pump applies pressure to the plunger of the pump, exerting a force on it.
2. Work has to be done against this force to push down the plunger.
3. This transfers energy to the kinetic energy stores of the gas particles, increasing the gas’ temperature.
4. When gas particles collide with the surface of the tyre, they transfer some of their kinetic energy to the tyre, warming the tyre up.

Question 30

Describe what happens to the internal energy of a liquid when it is heated and explain why.

Answer 30

1. When the liquid is heated, the internal energy store of the substance increases.
2. This is because energy is transferred by heating to the kinetic and potential energy stores of the particles.