Have you ever wondered when you are driving in the car what makes the car run, where does the energy come from, or if you are getting heat from a fire what is behind the burning of the fire? What fuels it? What type of energy is in a specific type of fuel and what happens to it so that the energy is released?
Lets have a look if we can answer all these questions.
There are many types of energy but we are going to look at stored energy -it is exactly what it says, it is energy that is stored to be used later on when it is burned.
Fuel is the specific thing that is giving the energy - like for instance the wood is the fuel for the fire to burn, the petrol or diesel is the fuel for the car to run.
But where does energy come from? The first thing you need to know is that energy cannot be destroyed, it will however be carried over from one thing to another.
All stored energy on earth starts with the sun. Look at the following picture
What has the sun got to do with the stored energy that the wood has that you want to use to make a fire?
- The sun (energy) shines on the tree
- The energy from the sun is used by the tree to photosynthesise (make its own food) which is stored in the form of sugars which is energy that the plant can use later. The energy is everywhere in the plant
- The tree gets chopped down for wood (the energy is still in the wood)
- You now burn the wood and the energy is set free in the form of heat
Coal that can be used for heating and to make the water in the boilers boil to make steam to generate electricity, comes from plants that died millions of years ago and because of the pressure from earth was turned in to coal. The energy from the plant did not dissapear, it was trapped in the coal and will be released once it is burned.
- Watch the video and then try to explain this whole process in your own words
- Enrichment: Find your own video that explains how electricity is generated by using coal
Other examples of products with stored energy is the wax of a candle and paraffin and gas - these are all fuels with stored energy that will be released in the form of light energy or heat energy ones it burns.
- For fun you can make your own candles - be careful not to burn and ask an adult's help https://planningwithkids.com/2012/07/31/how-to-make-your-own-candles/
Why do we need food
In the same way as what the car needs fuel to run or the fire needs the wood as fuel to burn, our bodies need energy to burn so that you will be able to do your daily tasks.
If you eat food, the energy will go from the food into your body and your body will be able to run and jump and play because it will use the energy from the food.
- Where did the food get the energy? (look at the picture of the wood again if you cannot remember)
If you buy food from the shop, it will tell you on the side of the packet what is the energy levels (in kJ- kilojoules) in that specific food.
If we burn more energy than what we take in, we will loose weigh, but if we take in more energy than what our bodies use, we will gain weight.
An average man needs about 10 000kJ per day and children and adults who are not active needs less. The more active you are, the more energy you can take in, because your body will use/burn it all.
We have spoken about burning fuel in cars, fires and our body. In order for something to combust (set on fire) you will need 3 things
- a heat source
- fuel and
Think about a fire - you have the lighter or match as the heat source (the thing giving the heat), the wood as the fuel and the oxygen in the air around us - if one of these are absent, it will not burn.
Watch the experiment to see what happens if oxygen is not present when something is burning
People can make fire to keep themselves warm or to cook or braai food. It is very important that we stay safe whenever we are making a fire.
- do not play with lighters and matches
- if there is ever a fire in your house, get outside as quickly as you can
- know the number of your fire department
- have a plan what you will do if a fire breaks out in your house - who takes what, where must you go etc.
- Activity - design your own escape plan and all the duties for everybody in your house if a fire breaks out
- When you understand all the work you can have some fun on the site http://www.firesafekids.org/