1. Matter – Properties and Changes
Chapter 3

2. Organizing & Describing Matter
Substances – matter that has a uniform and unchanging composition (pure substance)
NaCl
H2O
Salt Water is not a pure substance – depending on where you take your sample it may have a different composition

3. Physical Properties of Matter
A physical property is a characteristic that can be observed or measured without changing the sample’s composition
Shape Taste
Color Hardness
Weight Melting Point
Density Boiling Point
Odor
Pure substances will have uniform physical properties regardless of where the sample comes from – some (not all) of these properties can be used as identifying characteristics

4. Physical Properties of Matter
Extensive Properties
Properties dependent upon the amount of the substance present
Length, volume & mass are dependent upon the sample observed
Intensive Properties
Properties that are independent of the amount of the substance present
Density does not change – it is the same for all samples of a pure substance
Can be used to identify samples of pure substances

5. Chemical Properties of Matter
Chemical properties are based on the ability of a substance to combine with or change into one or more other substances
May involve adding thermal or electrical energy
May involve combining substances
Example: iron forms rust when combined with air
The inability of a substance to change is a chemical property
Example: iron will not react with Nitrogen gas at room temperature

6. Observing Properties of Matter
Properties may change depending on the conditions in which you observe the sample
Physical & Chemical Properties depend on the temperature and pressure
Water is liquid at room temperature, gas above 100 oC, and solid below 0oC
When atmospheric pressure increases, the boiling point of water becomes higher (hotter)
When atmospheric pressure decreases (as with increasing elevation) the boiling point becomes lower (cooler)
We use the statement at standard temperature and pressure (o Kelvin and 1 atm)

7. States of Matter Solid – definite shape and volume
Liquid – definite (or constant) volume & takes the shape of its container (no definite shape); flows
Gas – flows to conform to the shape of its container; fills the entire volume of its container
Solid
Liquid
Gas

8. Mixtures
A mixture is a combination of two or more pure substances in which each pure substance maintains its individual chemical properties
Anything mixed with water (ie salt water) is a mixture
Aqueous solution

9. Types of Mixtures Homogeneous Heterogeneous
Constant composition throughout
Always has a single phase
Salt water
SOLUTIONS
Heterogeneous
Does not blend smoothly throughout
Parts remain distinct
Sand & water

10. Types of Solution Examples

11. Changes in Matter
Physical Changes
Changes that alter the substance without changing its composition
Examples
∆ in State of matter (changes depend on temperature and pressure)
Bend
Tear
Grind
Crumple
Split
Crush
Chemical Changes
Process that involves one or more substances changing into new substances
New substances are formed with new compositions and different properties than the reactants
Starting substances are called reactants
Ending substances are called products
Examples – rust, explode, oxidize, corrode, tarnish, ferment, burn, rot

12. Indicators of Chemical Changes
Formation of a gas (bubbles)
Formation of a solid (precipitate)
Generally, color changes
Energy given off (heat, light, sound)
Change in Odor

13. Massreactants = Massproducts
Conservation of Mass
Mass is neither created nor destroyed during a chemical reaction – it is conserved
Massreactants = Massproducts

14. Elements
Pure substances that cannot be separated into simpler substances by physical or chemical means
91 elements occur naturally on Earth
Unique Chemical Name & Symbol (made of one, two or three letters & first letter is always capitalized
Organized into the Periodic Table

15. Compounds
Combination of two or more different elements that are combined chemically
Water, table salt, sugar, aspirin
Can be broken down into simpler substances by chemical means
Typically involves energy

16. Law of Definite Proportions
Elements that combine to form compounds in definite proportions
Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass
Percent by mass = mass of the element x 100
mass of compound

17. Law of Multiple Proportions
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

18. Understanding Matter