Conservation of Matter

Law of Conservation of Matter (Mass)

Matter can be changed from one form to another, mixtures can be separated and pure substances can be decomposed, but the total amount of mass remains constant.

During a chemical reaction you do not add or subtract any mass. Instead the matter is rearranged.

Imagine that you had a bunch of Legos. Say you had a box made from 4 red Lego bricks and a tower made from 6 blue Lego bricks.

Let's say that you handed it to your little sister and she makes a tower with 4 red Lego bricks and 4 of the blue Lego bricks, and then makes a box with the last 2 blue Lego bricks.

There are still a total of 4 red Legos and 6 blue Legos, nothing has been taken away or added. The only difference is that they have been rearranged.

What IS Mass?

We use the word mass to talk about how much matter there is in something. (Matter is anything you can touch physically.) On Earth, we weigh things to figure out how much mass there is. The more matter there is, the more something will weigh. Often, the amount of mass something has is related to its size, but not always. A balloon blown up bigger than your head will still have less matter inside it than your head (for most people, anyhow) and therefore less mass.

The difference between mass and weight is that weight is determined by how much something is pulled by gravity. If we are comparing two different things to each other on Earth, they are pulled the same by gravity and so the one with more mass weighs more. But in space, where the pull of gravity is very small, something can have almost no weight. It still has matter in it, though, so it still has mass.