Understanding and Explaining

1. Describe the energy transfers when...a. an object is projected upwards – kinetic energy from the moving object is transferred in to gravitational potential energy as it moves higher upb. a car braking – kinetic energy from the car transferred to thermal energy from the friction in the brakesc. water boiling in a kettle – electrical energy to thermal energy

2. Explain how changes could be made to a bike to reduce the unwanted transfer of heat through frictionThe moving parts of the bike (e.g. the chain) could be lubricated to reduced friction.

3. A kettle transfers 20J of electrical energy into 5J of thermal energy. Calculate the efficiency of the kettle.Efficiency = useful energy output = 5 = 0.25 or 25% total energy input 20

4. Show how to rearrange the efficiency equation for ‘useful energy output’. useful energy output = efficiency total energy output

5. Put these resources into the correct column:biofuel, nuclear, wind, hydroelectric, geothermal, tidal, coal, oil, natural gas, solar, waves

Renewable Non-renewablebiofuel nuclearwind coalhydroelectric oilgeothermal natural gastidalsolarwater waves

Physics Revision: Energy Loss and Efficiency

Key Knowledge

The law of conservation of energy states that energy can either be transferred usefully, stored, or dissipated.

Two ways that we can reduce energy being wasted:- lubrication (reducing friction)- insulation (reducing heat loss)

Definitions:Dissipated – wasted into the surroundings

Renewable resource – can be replenished while it is being usedNon-renewable – cannot be replenished while it is being used

The higher the thermal conductivity of a material the faster the rate ofenergy transfer by conduction.

Two factors that affect how quickly a building cools down- thickness of the walls- the thermal conductivity of the walls

Equations:Efficiency = useful energy output total energy input

Efficiency is always a % or a decimal.

Mastery Matrix Points Describe ways to reduce unwanted energy transfersLink energy loss to insulation and thermal conductivityUse and rearrange both equations for calculating efficiency

Physics Revision: Work, Power and Specific Heat Energy

Key Knowledge

Definitions

Work done – the energy transferred

Power – the rate of energy transfer

Equations (including units)

Work done (J) = force (N) x distance (m)

Power (W) = work done (J) time (s)

Mastery Matrix Points Define and calculate work doneDefine and calculate powerDescribe examples of applications of power in everyday life

Understanding and Explaining1. Calculate the work done by a 100N car when it travels 10m.work done = 100 x 10 = 1,000 J

2. Calculate the force needed to push a box 5m if you transfer 20J of energy to move it.force = work done = 20 4N distance 5

3. Calculate the distance travelled by a car of 200N if 1.5kJ of energy is transferred.distance = work done = 1,500 = 7.5m force 200

4. Calculate the power of the car in question 1 if it is moving for 80s.power = work done = 1000 =12.5W time 80

5. Two kettles bring the same amount of water to boil. Kettle A takes 1 minute and kettle B takes 3 minutes. Explain which is the most powerful kettle.Kettle A is more powerful because it transfers the same amount of energy is less time.

6. Convert the following:1 minute to seconds = 60s1 hour to seconds = 3600s1kW to W = 1000W

Physics: Density and Changes of StateKey KnowledgeEquation for density – Density (kh/m3)= mass (kg)/ volume (m3)

The particle model assumes all particles are small, solid spheres. It is used to explain density and states of matter.

What are the state changes?Melting: solid to liquid Freezing: liquid to solid Boiling: liquid to gasEvaporating: liquid to gas Condensing: gas to liquid Sublimating: solid to gas

Internal Energy – total kinetic energy and potential energy of all of the particles that make up a system

Heat can either - Raise the temperature of

the system OR

- Cause a change in state Equation for specific heat capacity:Change in thermal energy= mass x specific heat capacity x temperature change.

Equation for specific latent heat:Energy for a state change= mass x specific latent heatDefine ‘specific latent heat of vaporisation:

Change of state from liquid to a vapour (gas)

Define ‘specific latent heat of fusion:

Change of state from solid to liquid

Understanding and Explaining

1. Explain how to calculate the density of a) a regular shape

Density= mass / volume. 1)Use a top pan balance to measure the mass. 2) Use a ruler to measure volume (l x w x h). 3) Use the calculation to calculate density.

b) an irregular shape. 1) Use a top pan balance to measure mass2) Use a displacement can to measure the volume of displaced water when the object is

submerged into the can3) Use the equation density= mass / volume to calculate density.

2. Sketch and explain the shape of a heating curve and a cooling curve. Heating curveA- Solid B- Melting C- liquid D- Evaporating E-gas

During the state changes, the graph is flat as energy is being used to break bonds

Cooling curveDuring the state changes, the graph if flat as energy is being used to make bonds.