1. Chapter 3: Matter— Properties and Change
Table of Contents
Chapter 3: Matter—
Properties and Change
Laws of definite and multiple proportions

2. Elements in a specific compound always combine the same way.
Matter—Properties and Change: Additional Concepts
Law of definite proportions: regardless of the amount, a compound is always composed of the same elements in the same proportion by mass.
TRANSLATION:
Elements in a specific compound always combine the same way.
Mass (compound) = Mass (element 1 + element 2 +…)
ex) If 2 g hydrogen reacts with 16 g oxygen, what mass H2O would be produced?
2 g H + 16 g O = 20 g H2O

3. Mass of a compound 134.50 g aspirin 5.72 g copper
A sample of aspirin is made up of 6.03 g of hydrogen, g of carbon, and g of oxygen. What is the overall mass of the aspirin?
A 2.89 g sample of sulfur reacts with an unknown amount of copper to form 8.61 g of a black compound. What is the mass of the copper?
g aspirin
5.72 g copper

4. Law of Definite Proportions
Matter—Properties and Change: Additional Concepts
Law of Definite Proportions
Percent by mass: The ratio of the mass of each element to the total mass of the compound
Percent composition: The percent by mass for each individual element in a compound

5. Examples 39.34% sodium, 60.66% chlorine
A g sample of table salt is made up of g of sodium and g of chlorine. What is the percent by mass of each element in table salt?
2) g of sodium reacts with g of sulfur and g oxygen. What is the percentage composition of the compound?
39.34% sodium, 60.66% chlorine
32.37% sodium, 22.57% sulfur, 45.06% oxygen

6. Practice Percent by Mass
A g sample of aspirin is made up of 6.03 g of hydrogen, g of carbon, and g of oxygen. What is the percent by mass of each element in aspirin?
A 2.89-g sample of sulfur reacts with 5.72 g of copper to form a black compound. What is the percentage composition of the compound?
4.48% hydrogen, 60% carbon, 35.52% oxygen
33.6% sulfur, 66.4% copper

7. Law of Multiple Proportions
Matter—Properties and Change: Additional Concepts
Law of Multiple Proportions
Law of multiple proportions: when different compounds are formed by a combination of the same elements, they combine in different ratios.
Ratios compare the relative amounts of any items or substances.
EXAMPLE:
water (H2O) & hydrogen peroxide (H2O2)
H:O 2: :2