Unit B 2.5

Question 1

What’s the most obvious evidence that an energy conversion has happened?

Answer 1

Motion

Question 2

What are 3 ways (other than motion) that shows evidence of a change in energy?

Answer 2

Change in shape
Change in position
Change in temperature

Question 3

How does a natural system’s energy conversion work?

Answer 3

1. Nuclear fusion of hydrogen in the sun releases solar energy to earth; earth either absorbs or reflects that energy
2. There’s chemical potential energy in the chlorophyll of plants and when the sunlight energy hits the chlorophyll, it starts to convert CO2 and water into glucose and oxygen (Photosynthesis)
3. The glucose has the chemical potential energy now and when animals eat these plants, cellular respiration happens in them and water and CO2 is released back

Question 4

What is ATP?

Answer 4

ATP stands for adenosine triphosphate and it’s a form of energy that’s released during cellular respiration.

ATP provides the energy animals need to carry out life functions and also produces heat

Question 5

How are fossil fuels made?

Answer 5

From dead animals and plants that were buried deep into the earth and has been through a lot of pressure, heat and other processes. So when we burn fossil fuels, this energy is released

Question 6

What are the 4 energy conversions of technologies you need to know?

Answer 6

• Hydroelectric power station
• Coal burning power station
• CANDU Nuclear power station
• Solar Cell

Question 7

How does a hydroelectric power station work?

Answer 7

1. The water reservoir (behind a dam)collects water higher than the generator so the water has Ep (grav)
2. That Ep(grav) of water is converted into Ek when released into the penstock
3. The rushing water moves the blades of turbines so Ek –> Ek
4. The turbine turns a coil of wire in a magnetic field creating electrical energy from the kinetic energy of the moving turbines

Question 8

How does a coal burning station work?

Answer 8

1. coal placed in a combustion chamber burns at high heat; so the chemical potential energy of the coal turns into heat energy (kinetic energy)
2. The heat energy heats up water into steam (kinetic & thermal energy)
3. Steam under pressure is injected into turbines turning it (thermal & kinetic energy of steam –> kinetic energy turning turbines)
4. Turbines use the kinetic energy to turn a coil of wire in a magnetic field {Ek –> E(elec)}

Ep Chemical-> Ek (Thermal) –> Ek –> E (elec)

Question 9

How does a nuclear power station work?

Answer 9

1. Uranium disintegrates during nuclear fission releasing radiation (Ep nuclear)
2. The radiation is used as heat to heat up water to steam; Ep Nuclear –> Ek (Thermal)
3. The steam under pressure is piped into turbines causing it to turn; Ep Nuclear –> Ek (Thermal) –> Ek
4. The kinetic energy of the turbines is used to move a coil of wire through a magnetic field

Ep Nuclear –> Ek (Thermal) –> Ek –> E (elec)

Question 10

How does a solar cell work?

Answer 10

Ep (solar) –> E(elec)

1. 2 layers of silicon with 1 layer of boron and phosphorus (electrons are bound in silicon crystals of the layers)
2. When solar energy hits, the electrons break out of the crystals and move; boron becomes positive and phosphorus negative ( acts like a battery)
3. Current is collected by electrical contact layers and can be stored or used directly

Question 11

How does a fuel cell work?

Answer 11

Converts the potential chemical energy (in a fuel) into electricity; a hydrogen fuel cell operates like a battery

It will produce electrical energy as long as it has fuel and doesn’t need to charge

The byproducts of a hydrogen fuel cell are water and heat