Double Science Award
Note that the following is taught in year 9 however you will need it in this topic.
a) Units
a) Units
4.1: use the following units: kilogram (kg), joule (J), metre (m), metre/second (m/s), metre/second² (m/s²), newton (N), second (s), watt (W)
kilogram (kg): used to measure mass
joule (J): used to measure energy
metre (m): used to measure length or distance
metre/second (m/s): used to measure speed
metre/second² (m/s²): used to measure acceleration
newton (N): used to measure mass 10N=1kg (on earth)
second (s): used to measure time
watt (W): used to measure power
b) Energy Transfer
4.2: describe energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)
Energy converts between the different types of energy.
For example:
The chemical energy in food is converted into thermal and kinetic energy.
The electrical energy in a circuit is converted into thermal and light energy if there is a light bulb.
The gravitational potential energy when at the top of a mountain is transferred into kinetic energy as an object such as a ball rolls down the mountain.
The elastic potential energy is transferred to kinetic energy in for example an elastic band.
4.3: understand that energy is conserved
Energy can never be created or destroyed, it can only be converted.
4.4: recall and use the relationship:
second (s): used to measure time
watt (W): used to measure power
b) Energy Transfer
4.2: describe energy transfers involving the following forms of energy: thermal (heat), light, electrical, sound, kinetic, chemical, nuclear and potential (elastic and gravitational)
Energy converts between the different types of energy.
For example:
The chemical energy in food is converted into thermal and kinetic energy.
The electrical energy in a circuit is converted into thermal and light energy if there is a light bulb.
The gravitational potential energy when at the top of a mountain is transferred into kinetic energy as an object such as a ball rolls down the mountain.
The elastic potential energy is transferred to kinetic energy in for example an elastic band.
4.3: understand that energy is conserved
Energy can never be created or destroyed, it can only be converted.
4.4: recall and use the relationship:
efficiency = useful energy output / total energy output
Let's try it: If 20 out of 25 joules are useful then the efficiency would be:
20J/25J
=0.8
Remember to convert it into a percentage you can do this by multiplying it by 100 and don't forget the percentage sign! So the efficiency is 80%.
Remember the efficiency is of a device is always less than 100%
4.5: describe a variety of everyday and scientific devices and situations, explaining the fate of input energy in terms of the above relationship, including their representation by Sankey diagrams
A Sankey diagram is used to show how the proportions of what the energy is converted into.
For example: Here is a Sankey diagram for a typical filament light bulb.
(credits to BBC Bitesize)
As you can see it obviously isn't a very efficient light bulb as most of the energy is being transferred into heat energy rather than light energy.
We can calculate the efficiency of the light bulb by using the equation on 4.4.
In this case, the useful energy output is light energy (10J) and the total energy output is the same amount as the electrical energy (100J). So let's substitute that into the equation:
efficiency = useful energy output / total energy output
= 10J / 100J
= 0.1
Now convert this into percentage and you get 10%, so this shows that only 10% of the energy output is useful.
Here is an energy-saving light bulb
(credits to BBC Bitesize)
As you can see this light bulb is much more efficient as there is more electrical energy being converted to light energy rather than heat energy. Let's make sure by calculating the percentage of useful energy:
efficiency = useful energy output / total energy output
= 75J / 100J
= 0.75
If you convert that into percentage by multiplying by 100 then you get 75%. The percentage of the useful energy output for the energy-saving light bulb is higher than the filament light bulb which is only 10%.
4.6: recall that energy transfer may place by conduction, convection and radiation
Conduction is the transfer of heat when particles collide and transfer the heat energy from one particle to another. It can happen in solids, liquids and gases.
Convection is when particles with heat energy rise to the top which then leads to the colder being drawn to the bottom, this creates a convection current. Convection can only happen in liquids and gases because there is not enough space for particles in a solid to move freely.
Radiation is the the transfer of energy through electromagnetic radiation (infrared waves). It doesn't need an medium and so can even happen in a vacuum. An example of radiation is from the sun, in space there is nothing so the heat and light from the sun comes to earth as radiation as it does not require a medium. Depending on the colour of the surface, an object that is shiny or light (as in colour light) the surface then reflects more rather than absorbing and emitting it. If an object is dull (not shiny) or dark coloured then the surface would absorb and emit more.
4.7: describe the role of convection in everyday phenomena
Although we can necessarily see it, convection and the effects of convection happen around us all the time. For example the wind that we feel when you go outside.
First off let's start with wind and convection currents. The sun heats the air and causes the air to rise, when heated, the air is less dense this therefore makes the air rise and the colder air that is denser to sink to the ground. This creates the wind that you may feel when you go outside.
c) Work and Power
4.9: recall and use the relationship between work, force and distance moved in the direction of the force:
As we can see from the calculation above work done is measured in joules. Therefore work done is the same as energy transferred.
Convection is when particles with heat energy rise to the top which then leads to the colder being drawn to the bottom, this creates a convection current. Convection can only happen in liquids and gases because there is not enough space for particles in a solid to move freely.
Radiation is the the transfer of energy through electromagnetic radiation (infrared waves). It doesn't need an medium and so can even happen in a vacuum. An example of radiation is from the sun, in space there is nothing so the heat and light from the sun comes to earth as radiation as it does not require a medium. Depending on the colour of the surface, an object that is shiny or light (as in colour light) the surface then reflects more rather than absorbing and emitting it. If an object is dull (not shiny) or dark coloured then the surface would absorb and emit more.
4.7: describe the role of convection in everyday phenomena
Although we can necessarily see it, convection and the effects of convection happen around us all the time. For example the wind that we feel when you go outside.
First off let's start with wind and convection currents. The sun heats the air and causes the air to rise, when heated, the air is less dense this therefore makes the air rise and the colder air that is denser to sink to the ground. This creates the wind that you may feel when you go outside.
(credits to kids.britannica.com)
From the diagram, you can see that during the day, the land heats faster than the water, this makes the air on land heat up and rise to the top, this makes the displaced cooler air on sea sink and move to inland, this creates a cool sea breeze. At night, the water is warmer than land, therefore the air over the water heats up and rises, displacing the cooler and denser air on land, this creates a cool land breeze.
4.8: describe how insulation is used to reduce energy transfers from buildings and the human body
Insulation for buildings include: wall, floor and roof insulation. Whilst for the human body clothes are used as insulation.
All the different types of insulation used for buildings and humans contain many small holes which contain air. As you may already know, air is a bad conductor of heat as the molecules in the air are spaced out thus making it hard to conduct the heat.
Insulation for buildings include: wall, floor and roof insulation. Whilst for the human body clothes are used as insulation.
All the different types of insulation used for buildings and humans contain many small holes which contain air. As you may already know, air is a bad conductor of heat as the molecules in the air are spaced out thus making it hard to conduct the heat.
c) Work and Power
4.9: recall and use the relationship between work, force and distance moved in the direction of the force:
work done= force x distance moved
W = F x d
Let's try it: If a bike travels 2km and it's driving force is 700N. The work done would be calculated like this
work done= force x distance moved
= 700N x 2km
=700N x 2000m
=1400000J
=1400000J
4.10: understand that work done is equal to energy transferred
As we can see from the calculation above work done is measured in joules. Therefore work done is the same as energy transferred.
Note that the following is taught in year 10 NOT in year 9.
4.11: recall and use the relationship:
4.11: recall and use the relationship:
gravitational potential energy = mass x g x height
GPE = m x g x h
Let's try it: If an airplane with a mass of 600kg takes off and climbs to a height of 1000m and we know that g on Earth is 10ms². The gravitational potential energy gained by the airplane would be calculated like this:
gravitational potential energy = mass x g x height
= 600kg x 10ms² x 1000m
= 6,000,000 J
4.12: recall and use the relationship:
kinetic energy = 1/2 x mass x speed²
KE = 1/2 x m v²
Let's try it: If a car with a mass of 600kg has a velocity of 28m/s. Then it's kinetic energy would be calculated like this:
kinetic energy = 1/2 x mass x speed²
= 1/2 x 600kg x 28m/s²
= 235,200 J
4.13: understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work
