Year 7 Potential Energy

“Energy cannot be created nor destroyed;
Energy can only be transferred or changed from one form to another”
(First law of Thermodynamics*)

“Energy needs to come from somewhere for anything to happen;
Once the energy is ‘used’ it doesn’t disappear, instead it transforms into something else;
The most common energy ‘loss’ is heat, which we are unable to use again effectively”
(Mr Danic’s attempt to simply complex stuff)

Where does energy come from?

Many objects around you have stored energy within them, which we call potential energy. This energy has the potential to do work or generate heat when it is used.

We will cover 3 main sources of Potential energy in this topic, listed below with examples. It is important to understand that every time energy is transformed or converted from one form to another, that some energy is typically lost.

Chemical Potential energy

  • Food energy burned within you and converted into chemical energy for your cells
  • Chemical energy in your cells transformed into kinetic energy
  • Petrol / Diesel burned within a car for movement kinetic energy
  • Battery chemical energy to power your devices light and sound energy

Gravitational Potential energy

  • Gravitational potential energy is transformed into kinetic energy when you drop a ball from your hand.
  • Rolling a ball down a hill or ramp transforms Gravitational potential energy into kinetic energy, however it happens slower than being dropped.

Elastic Potential energy

  • Stretching a metal spring stores kinetic energy to be released when needed.
  • Cars can use this energy to absorb excess kinetic energy when you go over a bump to make a safer and smoother drive.

What are some examples of potential energy that you can think of happening now in the classroom?

Note: from this point on Potential Energy will be shown as PE.

Below are some examples of items with PE. List them as either Gravitational PE, Chemical PE or Elastic PE and explain how that energy can be released/used.

  • Slice of cake
  • A compressed spring
  • A can of energy drink
  • An empty water bottle sitting high on a table
  • A teaspoon of sugar
  • A cardboard box
  • A 12-volt battery
  • A roofer at the top of a ladder
  • A banana
  • A squashed football

e.g. Eat an apple for breakfast and have energy to walk to school
Chemical PE –> Kinetic energy

Mini Prac / Demo

You and a partner take a paddle pop stick and wooden skewer. Guesstimate which one weighs more and therefore has more Chemical PE.
Hypothesise which stick do you think will burn quicker and why?
Put on your safety glasses and put your theory to the test.
Light a Bunsen burner and hold you sticks horizontally over the flame at the same distance. You can use tongs or a retort stand to hold them in place safely. (Note: the metal will also get hot towards the end so DON’T touch it!)
As the sticks burn keep moving them towards the flame until they are both transformed into CO2 gas and water vapour. All the PE is gone and now you will have less to clean up too! (Note: you might get some blackened leftovers, just put them into the bin please.)

Results, answer the follow questions: (verbally if good, book if misbehaved!)
Which one burnt the quickest?
Did you hypothesise correctly?
Was this a fair test? Why/why not?
How could this experiment be improved?

Thermodynamics focuses on the physical interactions and relationships of energy e.g. heat, sound, light, mechanical, electrical, chemical
Transformed is when it changes from one form to another form
Converted is when it stays in the same form, however is transferred into a new thing.

If you’re struggling with any of the concepts still or just want a visual representation, watch the video below.

Home page
Year 7 Energy intro