1. It’s the Law
Foothill Chemistry

2. Law of Conservation of Mass
Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.
Mass of Reactants = Mass of Products
Mass (HCl + NaOH) = Mass (NaCl + H2O)

3. Law of Definite Proportions
A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.
NaCl – Sodium Chloride
For this molecule to be called sodium chloride, it will always have one sodium atom and one chlorine atom. The ratio of these atoms will always be 1:1.
The mass for the molecule will be the sum of the masses of the elements it contains.
H2O – Water
For this molecule to be called water, it will always have two hydrogen atoms and one oxygen atom. The ratio of these atoms will always be 2:1, hydrogen to water.

4. Law of Multiple Proportions
If two or more different compounds are composed of the same elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.
OMG – What the heck does that mean?
CO – carbon monoxide
CO2 – carbon dioxide
In CO, the ratio of carbon to oxygen is 1:1
In CO2, the ratio of carbon to oxygen is 1:2
In both compounds, the mass of carbon is the same.
In both compounds, the mass of one oxygen atom is the same, but in CO2 there is twice as much of it. The ratio of the amount of oxygen in CO to the amount of oxygen in CO2 is 1:2 (two small whole numbers)

5. Law of Conservation of Matter
It states that in any given system that is closed to the transfer of matter (in and out), the amount of matter in the system stays constant.
A concise way of expressing this law is to say that the amount of matter in a system is conserved.
Matter is neither created nor destroyed.

6. Law of Conservation of Energy
The total energy of an isolated system remains constant—it is said to be conserved over time
Energy cannot be created or destroyed, but may be changed from one form to another.
Pot on a stove – Energy from the stove is transferred to the pot and its immediate environment, making both hotter.