1. Chemistry – Chapter 3, Section 1
St. Augustine Preparatory School
August 18 Lecture

2. Read pages 63 and 64. Particularly, you are focusing on being able to explain the following:
The law of conservation of mass
The law of definite proportions
The law of multiple proportions

3. Law of Conservation of Mass
Mass is neither created nor destroyed during ordinary chemical reactions or physical changes
Simply put, whatever the mass of the reactants is, will be the mass of the products
If you dissolve 6.2g of sodium chloride (NaCl) in25.2g of water (H2O), then the final mass of the solution should be 31.4g.

4. 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.
For example: Sodium chloride (NaCl) always gets 39.34% of its mass from sodium (Na) and 60.66% of its mass from chlorine (Cl).
If you have 15.00g of NaCl, you would have 5.901g of Na and 9.099g of Cl.

5. Law of Multiple Proportions
If two or more different compounds are composed of the same two 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
Comparing CO2 and CO
In CO2, 2.66g of O combine with 1.00g of C
In CO, 1.33g of O combine with 1.00g of C
2.66:1.33 = 2:1

7. Beginning Atomic Theory: John Dalton (1766-1844)
All matter is made up of very tiny particles called atoms
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass and other properties
Atoms cannot be subdivided, created, or destroyed
Atoms of different elements combine in simple whole-number ratios to form chemical compounds (NaCl, H2O, Fe2O3 – NEVER: H1.5O, Na2.5Cl2.5)
In chemical reactions, atoms are combined, separated, or rearranged

8. Lab Safety
What safety procedures do you think are required to be followed within the lab?

9. Lab Safety (a few of the many rules)
Follow all verbal and written directions
DO NOT randomly mix chemicals
If you spill or break something, let the teacher know immediately.
Ladies, if we are dealing with flame your hair must be tied back
Absolutely 0 tolerance for fooling around (Friday Detentions for this)
Do not taste or smell anything in the lab
Many rules come down to common sense and thinking before you act