Chap 3

Physical Properties of Matter Characteristics observed or measured without changing the identify of a substance. Shape, physical state, odor, boiling and freezing points, density, and color of that substance.

Physical Changes A physical change occurs in a substance if there is A change in the state. A change in the physical shape. No change in the identity and composition of the substance. Examples of physical changes: Paper torn into little pieces (change of size) Copper hammered into thin sheets (change of shape) Water poured into a glass (change of shape )

Chemical Properties Chemical properties describe the ability of a substance To interact with other substances. To change into a new substance. Example: Iron has the ability to form rust when exposed to oxygen.

Chemical Changes In a chemical change, a new substance forms that has A new composition New chemical properties New physical properties

4 Ways to Separate a Mixture 1. Filtration 2. Distillation 3. Crystallization 4. Chromatography

Evidence of a Chemical Reaction 1. Change in color 2. Production of Gas or odor 3. Formation of Heat 4. Formation of Precipitate

Conservation of Mass Mass reactants = Mass products 2 HgO  2 Hg + O 2 216g200g + 16g

Sample Problem From a laboratory process designed to separate water into hydrogen and oxygen gas, a student collected 10.0g hydrogen and 79.4g oxygen. How much water was originally involved in the process?

Sample Problem A student carefully placed 15.6g sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7g of sodium chloride. How many grams of chlorine gas reacted? How many grams of sodium reacted?

Sample Problem A 28.0g sample of nitrogen gas combines completely with 6.0g of hydrogen gas to form ammonia. What is the mass of the ammonia formed?

Sample Problem A substance breaks down into its component elements when heated. If 68.0g of the substance is present before it is heated, what is the combined mass of the component elements after heating?

Sample Problem 12.4 grams of nitrogen are combined with 32.5g of oxygen. What mass of nitrogen oxide is formed?

Sample Problem If 122.7g of lithium fluoride are broken down into lithium and fluorine gas. The amount of lithium produced is 78.4g. How much fluorine gas was produced?

Law of Definite Proportions A compound is always composed of the same elements in the same proportions by mass Water H 2 O H 1.0g x 2 O 16.0g

Percent by Mass % Mass = Mass Element X 100 Mass Compound The percent by mass of each element in a compound remains constant even if the amount changes.

Analysis of Sucrose ElementAnalysis by MassPercent by Mass Carbon8.44g42% Hydrogen1.30g6.50% Oxygen10.26g51.30% Total20.00g100% Analysis of a 20.oo g quantity of sucrose

Analysis of Sucrose 500g ElementAnalysis by MassPercent by Mass Carbon211.0 g42% Hydrogen32.5 g6.50% Oxygen256.5 g51.30% Total500 g100%