Particle Model

Question 1

6.3.1.1
Density equations (+ units)

Answer 1

Density = mass / volume 
P = m / v

Density = kg/m^3
= g/cm^3

Mass = kg
= g

Volume = m^3
= cm^3

Question 2

6.3.1.1

Explain the difference In density between the states of matter

Answer 2

Density increases and the distance between the particles decrease

Solids = closely packed together in a regular arrangement, fixed position (very dense)

Liquids = particles are close to each other but can move around, in a regular arrangement (quite dense)

Gases = not close together, random arrangement (not dense)

Question 3

6.3.1.1
Req practical 17
How do I measure the density of an irregular object?

Answer 3

To find mass use a measuring scale
To find volume use a displacement can and fill to the top, wait for the water to stop flowing out through the tube. Place a 25cm^3 measuring cylinder below the tube. Place irregular object in the displacement can. Collect all the water that flows out through the displacement can tube.

To find density use the mass / volume formula

Question 4

6.3.1.1
Req practical 17
How do I find the density of a regular object

Answer 4

To find mass use a measuring scale
To find volume find the area of one side of the object then multiply by the length

To find density use the mass / volume formula

Question 5

6.3.1.1
Req practical 17
What is uncertainty?

Answer 5

The uncertainty of a measurement is a number that indicates the confidence in a given answer, the larger the uncertainty the further the quoted value may be from the true value.

Question 6

6.3.1.1
Req practical 17
How do I calculate absolute uncertainty?

Answer 6

Absolute uncertainty = range of measurement / 2

Question 7

6.3.1.1
Req practical 17
How do I calculate percentage uncertainty?

Answer 7

% uncertainty = absolute uncertainty / average (mean) of the measurements x 100

Question 8

6.3.1.1
Req practical 17
Advantages of using %uncertainty over absolute uncertainty?

Answer 8

% uncertainty makes it easier to compare to other objects/ answers

Question 9

6.3.2

What is internal energy?

Answer 9

Energy stored inside a system by the particles (atoms and molecules) that’s make up a system, this is called internal energy.
Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

Question 10

6.3.2

How does heating change the internal energy within a system?

Answer 10

Heating changes the energy stored within the system by increasing the energy of the particles that make up the system, this either:

raises the temperature of the system
OR
produces a state change

Question 11

6.3.2.2

What is specific heat capacity

Answer 11

The amount of energy required to increase the temperature of 1 kg of the substance by one degrees Celsius

Question 12

6.3.2.2
Specific heat capacity formula (+units)
(Given in exam)

Answer 12

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

Change in thermal energy = joules (J)
Mass = Kg
Specific heat capacity = J/kg °C
Temperature change e= °C

Question 13

6.3.2.2

Finding the specific heat capacity for vegetable oil

Answer 13

Measure mass of oil used.
Record the temperature of the oil every 60 seconds whilst heating.
Record the voltage and current (that should be the same for the whole expt)
Table with time, temperature and energy.

Equation:
E = i x V x t ( heating time)
Energy = current x voltage x time

Question 14

6.3.2.2

Finding the specific heat capacity for vegetable oil / aluminium block graph

Answer 14

Temperature on Y Axis
Energy on X Axis

The graph is flat to start with then increases steadily

Question 15

6.3.2.2

Finding the specific heat capacity for a block of aluminium

Answer 15

We use a power supply to heat a block of aluminium.

This apparatus can be connected to the power supply by either:
A joulemeter
A voltmeter and ammeter (and stop clock) [ E=IVt ]

To find the specific heat capacity of aluminium we must:
Measure the mass of Al to be heated.
Measure the initial temperature of the Al.
Turn on the heater and a stop clock.
Record the temperature of the Al at 60s intervals. Also record the energy input from the heater at these times.
Plot a graph

Question 16

6.3.2.2
Specific heat capacity graphs:
Using the graph how do I find “C”

Answer 16

C (specific heat capacity) = 1 / mass x gradient

Question 17

6.3.2

What is temperature?

Answer 17

A measure of the average internal energy of a substance

Question 18

4.3.1.2

What changes as the temperature changes

Answer 18

The kinetic energy

Question 19

4.3.1.2

What changes as the state changes

Answer 19

The potential energy

Question 20

4.3.1.2

What’s the conservation of mass

Answer 20

That no atoms are lost or made during the reaction so the total mass of the product at the start = total mass of product at the end

Question 21

4.3.2.3

What is the specific latent heat

Answer 21

The specific latent heat of a substance is the amount of energy required to change the state of 1kilogram of the substance with no change In temperature

The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.

Question 22

4.3.2.3

What is the latent heat of fusion

Answer 22

The energy required to change 1kg of a substance from a solid to a liquid with no change in temperature

Question 23

4.3.2.3

What is the latent heat of vaporisation

Answer 23

The energy required to change 1kg of a substance from a liquid to a gas with no change in temperature

Question 24

4.3.2.3
Latent heat formula (+units)
(Given)

Answer 24

Energy for a state change = mass x specific latent heat

E = m x L

Energy for a state change = Joules (J)
Mass = kg
Specific latent heat = (J/kg)

Question 25

4.3.2.3

Latent heat and ice experiment

Answer 25

To measure the latest heat of fusion of energy used to melt the ice that was being tested:
The heaters attached to a joulemeter to see the energy input can be read directly from the screen.
To measure the mass we must consider the proportion of the melted ice that’s due to the heater, and subtract The proportion due to the temperature of the room.

Experiment set up:
A heater is connected to a Joule meter which is connected to a power supply. That heater is placed in the funnel with the ice in it which is in a Beaker. There is also another funnel which contains ice that’s also in a beaker.

We use this as the control so we can see how much ice has been melted from the heater and how much from the room.

Question 26

4.3.3.1

What type of motion do gases move in

Answer 26

They move in a random motion to fill the room / container they’re put in

Question 27

4.3.3.1

How is the motion of the molecules in a gas related to it’s temperature

Answer 27

At lower temperatures the particles have lower kinetic energy so there are fewer collisions per second and these collisions are lower energy collisions causing there to be low pressure

Higher temperatures the particles have a higher amount of kinetic energy so there are more collisions per second and these collisions have a higher amount of energy causing there to be high pressure

Question 28

4.3.3.2

What happens to the pressure of a gas when the volume increases

Answer 28

The pressure decreases

The pressure of a gas is inversely proportional to the volume

Question 29

4.3.3.2
Gas pressure equation
(Given)

Answer 29

Constant = p x V
Constant = pressure (Pa) x volume (m^3)

EQUATION IS ONLY TRUE IF THE TEMPERATURE IS KEPT CONSTANT

Question 30

4.3.3.2

Boyles law

Answer 30

P1 x V1 = P2 x V2

Question 31

4.3.3.2

At what angle is the net force from the particles acting on a wall / container

Answer 31

Right angle (90°)
The pressure produces a net drive at right angles to the wall of the gas / container

Question 32

4.3.3.3
Describe the effect of doing work on an enclosed gas
(Bike pump example)

Answer 32

The gas particles colliding with the walls of the container apply a force at right angles to the walls of the container, this causes gas pressure.

If we compress the gas by applying force to the piston we have now carried out work (transfer of energy by force) on the gas. Because we have applied a force to the gas we’ve transferred energy to the gas particles.
This increases the internal energy of the gas (kinetic + potential energy).
Because we’ve increased the kinetic energy of the gas particles we’ve increased the temperature of the gas.