Topic 14: Particle Model

Question 1

14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - solids

Answer 1

• Particles are arranged in rows (in a regular arrangement).
• Particles vibrate about fixed point.
• There are forces of attraction between particles but don’t have enough energy to overcome the forces of attraction.

Question 2

14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - liquids

Answer 2

• Particles are randomly arranged.
• Particles can move around each other.
• Particles have more energy than solids and can therefore overcome the forces of attraction.
• Do not have enough energy to sufficiently overcome attractive forces completely.
• No fixed shape but take the shape of the container.

Question 3

14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - gases

Answer 3

• Particles arranged randomly and far apart.
• Sufficient energy to overcome forces of attraction completely.
• Particles are moving quickly in all directions.

Question 4

14.2 Recall and use the equation: density (kilogram per cubic metre, kg/m3) = mass (kilogram, kg) ÷ volume (cubic metre, m3)

Answer 4

density = mass ÷ volume

Question 5

14.3 Core Practical: Investigate the densities of solid and liquids - finding volume of irreg object in m^3

Answer 5

1. Place measuring cylinder under spout of can and fill displacement can to brim with water.
2. Place object in the water.
3. Measure water collected in measuring cylinder.
4. Volume of water displaced = volume of object
5. Convert from ml to m^3 (/1,000,000)

Question 6

14.3 Core Practical: Investigate the densities of solids - method

Answer 6

1. Measure mass of object using the scale.
2. Calculate the volume of the object if regular OR do practical to find out vol of irreg object
3. Calculate density by using equation: density (kg/m^3) = mass (kg) / volume (m^3)

Question 7

14.4 Explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules

Answer 7

Most substances are the most dense when they are in solid form and the least dense when they are in a gaseous form.

This is due to the arrangement of the molecules; with solids’ molecules being closer together and gases being far apart.

Question 8

14.5 Describe how physical changes of state differ from some chemical changes.

Answer 8

When substances melt, freeze, evaporate, boil, condense or sublimate, mass is conserved.

These physical changes differ from some chemical changes because the material recovers its original properties if the change is reversed.

Question 9

14.6 Explain how heating a system will change the energy stored within the system and raise its temperature or produce changes of state

Answer 9

Heating a system will cause the energy stored within the system will change and raise its temperature as heating a system causes thermal energy to be stored. The more energy being stored means the speed of the vibrating particles increases.

If enough energy is being stored, the particles vibrate fast enough in order to break the molecular forces between particles, causing changes in state.

Question 10

Temperature

Answer 10

Temperature is a measure of the movement of particles.

Question 11

14.7 Define the term specific heat capacity

Answer 11

Specific heat capacity is the amount of energy it takes to increase the temperature of 1°C of the substance of 1 kilogram.

Question 12

14.7 Define the term specific latent heat

Answer 12

Specific latent heat is the amount of energy it takes to make 1 kilogram of a substance change state.

Question 13

14.7 explain the differences between specific heat capacity and specific latent heat

Answer 13

• Specific heat capacity measures the change in temperature, whereas specific latent heat is the change in state.
• Specific heat causes temperature change where in latent heat there’s no temperature change involved.
• Latent heat is the amount of energy in joules and specific heat is the quantity of heat measured in degrees Celsius.

Question 14

14.8 Use the equation: change in thermal energy (joule, J) = mass (kilogram, kg) × specific heat capacity (joule per kilogram degree Celsius, J/kg °C) × change in temperature (degree Celsius, °C)

Answer 14

change in thermal energy = mass x specific heat capacity x change in temperature

Question 15

14.9 State SI units for the equation: thermal energy for a change of state = mass × specific latent heat

Answer 15

thermal energy for a change of state (Joules, J)= mass (kilogram, kg) x specific latent heat (joule per kilogram, J/kg)

Question 16

14.10 Explain ways of reducing unwanted energy transfer through thermal insulation

Answer 16

To reduce the amount of energy that is transferred to the surroundings by heating, the object needs to be surrounded with insulating materials such as:
- wool
- foam
- bubble wrap

It prevents any more thermal energy from being transferred.

Question 17

14.11 Core Practical: Investigate the properties of water by determining the specific heat capacity of water and obtaining a temperature-time graph for melting ice - equipment

Answer 17

400 ml beaker
Thermometer
Immersion heater
Voltmeter
Ammeter
Power supply
Digital balance
Stopwatch
Crushed ice
(roughly 200 grams)
Bunsen burner or
hotplate

Question 18

14.11 Core Practical: Investigate the properties of water by determining the specific heat capacity of water and obtaining a temperature-time graph for melting ice - method

Answer 18

1. Place the beaker on the digital balance and press ‘tare’
2. Add approximately 250 ml of water and record the mass of the water
3. Place the immersion heater and thermometer in the water
4. Connect up the circuit as shown in the diagram, with the ammeter in series with the power supply and immersion heater, and the voltmeter in parallel with immersion heater
5. Record the initial temperature of the water at time 0 s
6. Turn on the power supply, set at approximately 10 V, and start the stopwatch
   Record the voltage and current
7. Continue to record the temperature, voltage and current every 60 seconds for 10 minutes

Question 19

14.12 Explain the pressure of a gas in terms of the motion of its particles

Answer 19

The pressure of a gas is due to the forces on the walls of a container causing by moving particles hitting the walls.

The faster the particles are moving, the more collisions there will be and more force exerted.

Question 20

14.13 Explain the effect of changing the temperature of a gas on the velocity of its particles and hence on the pressure produced by a fixed mass of gas at constant volume (qualitative only)

Answer 20

For a fixed mass of gas at a constant volume, increasing the temperature of the gas increases the velocity of the particles so increases the pressure of the gas.

Question 21

14.14 Describe the term absolute zero, −273 °C, in terms of the lack of movement of particles

Answer 21

The temperature at which the pressure of a gas drops to zero, and the particles would not be moving.

-273°C or 0K

Question 22

14.15 Convert between the kelvin and Celsius scales

Answer 22

Kelvin to Celsius = subtract 273

Celsius to Kelvin = add 273

Question 23

14.16P Explain that gases can be compressed or expanded by pressure changes

Answer 23

If you increase the pressure of a gas, it can be compressed.

If you decrease the pressure of a gas, it can be expanded.

Question 24

14.17P Explain that the pressure of a gas produces a net force at right angles to any surface

Answer 24

The effect of gas particles hitting a surface causes a net (overall) force on the surface. The force acts at right angles to the surface; this is gas pressure.

Question 25

14.18P Explain the effect of changing the volume of a gas on the rate at which its particles collide with the walls of its container and hence on the pressure produced by a fixed mass of gas at constant temperature

Answer 25

Decreasing the volume of a fixed mass of gas at constant temperature on the rate at which its particles collide with walls increasing the pressure produced.

And increasing the volume, decreasing the pressure produced.

Question 26

14.19P Use the equation: P1 ×V1 = P2 ×V2 to calculate pressure or volume for gases of fixed mass at
constant temperature

Answer 26

P^1 x V^1 = P^2 X V^2

Question 27

14.20P Explain why doing work on a gas can increase its temperature, including a bicycle pump

Answer 27

When you use a bicycle pump, the work done force is transferring energy to gas inside the pump.

With every pump, the speed of the particles increases, and this is detected as an increase in temperature.