Some Magic

Conservation of Mass

One of the most basic things in chemistry. So according to this law, you will end up with the same amount as you started with.

Conservation? If I mix 5 grams of sand and 10 grams of salt, I will end up with 15 grams of sand and salt, right? At the beginning I have 15 grams, separated, and in the end I have 15 grams, mixed together. It's as simple as that.
Mass? Means that this applies to things measured in 'grams'. Kilograms, hectograms, decagrams, grams, decigrams, centigrams and milligrams are examples of these. (Yes, there are a lot more prefixes for this. Look them up on your own.)

Take caution though, the mass part is very important! If I mix 100 ml of water with 100 ml of alcohol, I only end up with 180 ml, NOT 200 ml. Why, you ask? To put it simply, when you put cookies into a jar, there's going to be spaces between the cookies and the jar, right? Though the jar is full of cookies, it is not actually full - you can still stuff in some rice cereals in the spaces. And if you put in 5 cookies, each weighs 6 grams and 15 rice cereals, 2 grams each, then you have 60 grams before and after putting those into the jar. So though if you look from the top of the jar nothing's changed, actually you've slipped in something to fill up the spaces.

If that's confusing, remember, chemistry is unseen by our eyes because everything's really really small. But that's the basic.

Back to the conservation of mass, this fancy term just means 'when you have that much, you only have that much'.
Remember, this works for grams grams grams grams.