I'd love to test you on fuels! Since we don't have a table in front of us right now, let's start with question 1: think about wood, coal, and candle wax — before any of these can start burning, what do they all need to get them going?
Have a think and tell me what you notice they have in common.
17 Sept, 10:33
Is the answer heat and light or energy
17 Sept, 10:34
Good thinking, you're looking in the right place — that table! Now let's check your own question first: looking at wood, coal, and candle wax under "INPUT", what word or idea keeps appearing before any of them can burn? Not what they release, but what they all need to start.
17 Sept, 10:34
Can you explain what the answer is
17 Sept, 10:36
I hear you, but let's find it together rather than me just telling you — you're really close!
Think about lighting a candle. What do you actually do to make it start burning? You use a match, right? What does a match give the wax?
17 Sept, 10:36
Energy
17 Sept, 10:36
Yes! Exactly — energy, in the form of heat. To get any fuel burning, you first need to add some heat energy to start the reaction (this is sometimes called the "ignition" step).
Now here's the interesting bit: once wood, coal or wax start burning, what do you notice they then give off? Think about sitting near a campfire — what do you feel and see coming from it?
17 Sept, 10:36
Heat
17 Sept, 10:38
Good — heat is one! Look closely though, a fire gives you two things you can sense. You feel the heat... but what do you also see coming from the flames?
17 Sept, 10:38
Heat and light
17 Sept, 10:39
Exactly right! So fuels burning need heat energy to start (the input), and once they're burning they release heat and light energy (the output). That's the basic idea behind combustion.
Ready for question 2? Think about the fuels you listed — wood, coal, candle wax. Can you sort them into two groups: ones that come from living things that died long ago (fossil fuels) versus ones that come from plants we can grow again (renewable)? Which group do you think wood belongs to, and why?
17 Sept, 10:39
Can you explain the answer
17 Sept, 10:40
I won't give you the answer straight, but let's build it up with a simple example. Think about coal — where does coal come from? You may have heard it takes millions of years to form, deep underground from old dead plants and forests.
Now think about wood — if you chop down a tree today, how long does it take to grow a new one back? Days, months, or years?
17 Sept, 10:40
Years
17 Sept, 10:41
Exactly — years, not millions of years! That's an important clue. Think about how long it takes to grow a new tree compared to how long it takes coal to form from ancient plants underground.
If something can be replaced fairly quickly (like in years), what group would that put it in — renewable or non-renewable? And if something takes millions of years to form, like coal, what group would that be?