1. Laws

2. Law of Conservation of Mass Lavoisier concluded that when a chemical reaction occurs, mass is neither created nor destroyed but only changed. Lavoisier’s conclusion became known as the law of conservation of mass. Law of Conservation of Mass Clip

3. Law of Conservation of Mass In this law – mass is neither created nor destroyed – it is conserved Basically that means what you start with has to equal what you end with Mass reactants = Mass products

4. Example Lets say that you have 10.00 g of mercury (II) oxide. It is placed into a flask and heated until it is converted into liquid mercury and oxygen gas. If I get 9.26 g of liquid mercury, how much oxygen gas was created?

5. Example First you need to write the reaction in word form –Mercury (II) oxide  mercury + oxygen Now place the amounts under the reaction –Mercury (II) oxide  mercury + oxygen –(10.00 g) = (9.26 g) + x Solve for x –X = 0.74 g of oxygen gas

6. Try this one… A reaction between sodium hydroxide and hydrogen chloride gas produces sodium chloride and water. A reaction of 22.85 g of sodium hydroxide with 20.82 g of hydrogen chloride gives off 10.29 g of water. What mass of sodium chloride is formed in the reaction? 33.38 g sodium chloride

7. Law of Definite Proportions The elements that composed the compounds were always in a certain proportion by mass. This principle is now referred to as the law of definite proportions. Another way to say this is…water is always water is always water…

8. The mass of the compound is equal to the sum of the masses of the elements that make up the compound. The ratio of the mass of each element to the total mass of the compound is a percentage called the percent by mass. Law of Definite Proportions

9. Example A compound is analyzed in the lab an found to contain 8.44 g C, 1.3 g H, and 10.26 g O. What is the % composition of each element in the compound? First we must find the total mass % = Part x 100 Whole

10. Example C = 8.44 g H = 1.30 g O = 10.26 g Total = 20.00g Now find the % of each / 20.00 g X 100 = 42.2% C 6.50% H 51.30% O We find that this compound is sucrose

11. Another Example Now let’s say that Mr. Romano finds a mystery white powder in the cafeteria. He asks us to analyze the substance and tell him what it is. We find that there is 211.0 g of C, 32.5 g H, and 256.5 g O. What is the % composition of the compound?

12. Another Example C = 211.0 g H = 32.5 g O = 256.5 g Total = 500.00g / 500.00 g X 100 = 42.2% C 6.50% H 51.30% O What is the mystery white powder??? SUCROSE

13. 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 a ratio of small whole numbers. Ratios compare the relative amounts of any items or substances. Law of Multiple Proportions

14. The two distinct compounds water (H 2 O) and hydrogen peroxide (H 2 O 2 ) illustrate the law of multiple proportions. Both water & hydrogen peroxide are made up of hydrogen and oxygen, the difference is in their proportions. When we compare the mass of oxygen in hydrogen peroxide to the mass of oxygen in water, we get the ratio 2:1. Law of Multiple Proportions

15. Dalton’s Atomic Theory Dalton proposed his atomic theory of matter in 1803. Although his theory has been modified slightly to accommodate new discoveries, Dalton’s theory was so insightful that it has remained essentially intact up to the present time.

16. 1.All matter is made up of atoms. 2.Atoms are indestructible and cannot be divided into smaller particles. (Atoms are indivisible.) 3.All atoms of one element are exactly alike, but are different from atoms of other elements. Dalton’s Atomic Theory