1. Conservation of Mass
SNC2D

2. It’s the Law
A scientific law is a general statement that summarizes an observed pattern in nature.

3. It’s the Law
A scientific law is a general statement that summarizes an observed pattern in nature.
E.g. the Law of Gravity

4. Conservation of Mass Law of Conservation of Mass:
In a chemical reaction, the total mass of the _______ is always ______ the total mass of the ________.

5. Conservation of Mass Law of Conservation of Mass:
In a chemical reaction, the total mass of the reactants is always _______ the total mass of the _________.

6. Conservation of Mass Law of Conservation of Mass:
In a chemical reaction, the total mass of the reactants is always _______ the total mass of the products.

7. Conservation of Mass Law of Conservation of Mass:
In a chemical reaction, the total mass of the reactants is always equal to the total mass of the products.

8. Conservation of Mass
i.e. compounds can be made or broken apart in a chemical reaction, but atoms are not created or destroyed, only rearranged.

9. Example
When magnesium is burned,

10. Example When magnesium is burned,
magnesium + oxygen gas magnesium oxide

11. Example When magnesium is burned,
magnesium + oxygen gas magnesium oxide
The mass of the magnesium and oxygen gas (gas has mass!) is equal to the mass of the magnesium oxide ash.

12. A Leading Question
But if we write out the formulas for the burning of magnesium:

13. A Leading Question
But if we write out the formulas for the burning of magnesium:
Mg + O MgO

14. A Leading Question
But if we write out the formulas for the burning of magnesium:
Mg + O MgO
If atoms can’t be created or destroyed
what happened to the second oxygen in O2???