It’s a valid question, if you’re under the age of 10, otherwise you should read on to get some education – quick smart.
It’s all connected to a well known (to most normal adults) chemical process that not only gives plants the ability to grow, but also gives us humans oxygen, so that we can breathe.
Before your question about why leaves are green are answered, it’s important to remember that – in the world of Science – everything exists for a reason.
The leaves of plants are not simply green because that’s the prettiest colour, the appear green because of the little bits and pieces that they are made from. You see, normal green plants can’t grow without the sunlight. They need the rays of the sun, like us humans need food and water, to galvanise the cells in their bodies into actions, so that they can grow taller and taller.
Sunlight comprises of loads of different light rays. You know rainbows, right? Well, when you see a rainbow, what you’re seeing is the light from the sun refracted into it’s constituent rays. Without the water (or something like a glass prism) there’s no way for us to see these rays. Plants, like this little green chap in the picture above, have found a way (over years of evolution) of channelling the energy from the sun through the photosynthetic pigments in the membranes of the sub-cellular organelles.
“What are all those long crazy words?” – I hear you say!
Well, if you were listening – you’d have heard he answer to the question that you were looking for in the first place!
The reason why grass is green is because of the ‘photosynthetic pigments in the membranes of the sub-cellular organelles’, these are otherwise known as ‘chloroplasts‘ and they’re what makes grass green.
Still confused? OK, then I’ll explain some more…
So the power of the sunlight smashes down into the chloroplasts (the thing that makes the leaves green, remember?), this rejigs the molecular anatomy of the plant, forcing atoms to shift around and a chemical process to take place. Here comes the real part!
Now if you don’t know Science that good yet (and maybe you struggle with words, just like I do from time to time) – I’ll try and explain this to you.
So the carbon dioxide exists in the air all around us. It’s the stuff that we breathe out, so it’s handy that the plant can use this as food for it’s chemical equation. The water is just plain old water that the plant gets from rain (or from a water can that we water it with). The arrow is the part where the sun comes in. It acts as the ‘catalyst’ – forcing the carbon dioxide and water to buddy up and get jiggy with it.