1. Law of conservation of mass, definite proportions, and multiple proportions

2. Changes in Matter Conservation of Mass
SECTION3.2
Changes in Matter
Conservation of Mass
The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction, it is conserved.
The mass of the reactants equals the mass of the products.
massreactants = massproducts

3. SECTION3.2
Section Check
When one substances turns into another, what kind of change has taken place?
A. chemical reaction
B. physical reaction
C. extensive reaction
D. nuclear reaction

4. The law of conservation of mass states that:
SECTION3.2
Section Check
The law of conservation of mass states that:
A. Matter can be created and destroyed.
B. Matter can be created but not destroyed.
C. The products of a reaction always have a greater mass than the reactants.
D. The products of a reaction must have the same mass as the reactants.

5. Elements and Compounds
SECTION3.4
Elements and Compounds
Law of Definite Proportions
The law of definite proportions states that a compound is always composed of the same elements in the same proportion by mass, no matter how large or small the sample.
Ex. Water is always composed of 2 Hydrogen to 1 Oxygen

6. Elements and Compounds
SECTION3.4
Elements and Compounds
Law of Definite Proportions (cont.)
The relative amounts are expressed as percent by mass, the ratio of the mass of each element to the total mass of the compound expressed as a percentage.

7. Elements and Compounds
SECTION3.4
Elements and Compounds
Law of Definite Proportions (cont.)
This table demonstrates that the percentages of elements in sucrose remain the same despite differences in sample amount.

8. Elements and Compounds
SECTION3.4
Elements and Compounds
Law of Multiple Proportions
The law of multiple proportions states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in whole number ratios.
Ex. Peroxide, H2O2, and water, H2O.
Different compounds formed from the same elements.
Hydrogen mass the same in both compounds but oxygen mass is a 2:1 ratio in peroxide to water.

9. Matter—Properties and Changes
CHAPTER3
Matter—Properties and Changes
Chapter Assessment
28.0 grams of nitrogen gas reacts completely with 6.0 grams of hydrogen to form 34.0 grams of ammonia. What does this demonstrate?
A. the law of conservation of energy
B. sublimation
C. distillation
D. the law of conservation of mass