Sunlight into food
Underneath everything in this chapter is one change: energy arriving as light, leaving as food.
Chemical energy
Energy stored in the bonds between the atoms of a substance, which is released when those bonds are broken. It is not one of the six forms of energy you listed in grade 10, but it belongs with them — and it is the form the energy of sunlight is turned into here.
What the plant actually does
In photosynthesis, solar energy is converted by green plants into chemical energy. In doing so the plants produce food, and all living things on Earth depend on that food either directly or indirectly.
A leaf is an energy converter
Grade 10 spent a whole lesson on energy changing form — a swing trading height for speed, a dam storing water to make electricity. A leaf belongs on that list. Light goes in, glucose comes out, and the energy is not created or destroyed anywhere in between. What makes it remarkable is only that the store it fills can be eaten.
Nothing else can do it
Photosynthesis is a process that cannot be carried out artificially. We can build machines that turn sunlight into electricity, and we can make sugars in a laboratory from other sugars. Nobody can do what a leaf does — take light, water and air, and assemble food. This process carried out by green plants is therefore essential for maintaining life on Earth.
Every store of energy you use began here
The food in your body, the wood in a fire, the coal and the oil that ran the machines of the last two centuries — all of them are chemical energy that was once sunlight, put into that form by a leaf. Coal is a fossil of photosynthesis that happened three hundred million years ago.