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Law of Conservation of Mass

Chemical Equations

Teika Clavell

on 14 September 2013

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Transcript of Law of Conservation of Mass

Law of Conservation
of Mass
Where did the matter go?
It's hard to think about not loosing matter. But check out this video.
Step 1: Know what you're working with.
Keep Calm
and solve
It's not as hard as it sounds. Just keep YOUR HEAD IN THE GAME!!
Step 2: Know the numbers.
Step 4: Determine if the Equation is Balanced.
Step 5: Know the rules.
The Law of Conservation
of Mass, developed by Antoine Lavoine, simply states that
matter is neither created nor destroyed during a chemical change.
In an open system, whatever gasses or vapors are caused by a chemical reaction are not contained. This makes the measurement of matter impossible.
How we show the Law of Conservation of Mass is not always tangible (touchable). Scientist know that it is a law so they are able to show it in a chemical formula. A
chemical formula is a group of chemical symbols and numbers that shows the number of atoms of each element in a molecule.
A chemical formula is only the first bit of information scientist need. It is the chemical equation that proves the Law of Conservation of Mass. A chemical equation is a description of a chemical reaction using chemical formulas, subscripts, and coefficients.
Did you notice in that the flask had a stopper at the top? This is called a
close system, or a system where matter cannot enter nor escape.
Step 3: Know the order.
A chemical equation is made up of many parts. One part is the reactants.
The reactants are the substances that are present at the beginning of a chemical reaction.
Another part is the products.
The products are the substances produced during a chemical reaction.
In a chemical equation, the numbers are what balance the equation. Because we know that mass cannot be created or destroyed, the number of atoms on the reactant side need to equal the number of atoms on the product side. There are two number types in chemical equations; subscripts and coefficients.
Subscripts are the numbers that tell us how many atoms of each element are in a molecule.


Coefficients are the numbers written before a chemical formula to show how many atoms or molecules of that substance are involved.
Whatever amount of atoms you have one the reactant side of the equation, must
yield, or equal,
the amount of atoms on the product side.
Notice that the number of atoms are equal
Not every chemical equation is equal.
Because the subscripts cannot be changed, we will need to add coefficients to fix this equation.
There are two rules to chemical equations. One, you cannot change the subscript or add subscripts. Two, when adding a coefficient, it is multiplied by the subscript for only that atom. Here is what I mean:
In order to get the Hydrogen atoms to be the same on either side of the yield sign, a coefficient will have to be added to the product side.
2 * ? = 4
(2 is the number of H atoms but we need 4 to be equal)
The 2 we added effects both the H and the O atoms. There are now 4 H atoms and 2 O atoms in the chemical formula.
4 O atoms
4 H atoms
Notice we are still not equal.
4 O atoms
4 H atoms
2 * ? = 4
Here we added a 2 to balance the equation.
4 O atoms
It's your turn......have a go.
2 H
2 H
1 O
2 O
4 H
2 O
4 H
Full transcript