1. Chapter 2 Properties of Matter
Chemistry 1

3. Pure Substances 2.1
Matter that always has exactly the same composition
Every sample the same b/c substance has a fixed, uniform composition
2 categories
Element – Ex: Iron, Copper, Carbon
Compound – Ex: Water, Sugar, Table Salt

4. Elements 2.1
Substance that can’t be broken down into a simpler substance
Only contains 1 type of atom
Atom – smallest particle of an element
Room temp (68oF) = most elements are solid
Elements:
1 or 2 letters (1st capitalized, 2nd lowercase)
Based on Latin names

5. Compounds 2.1
Substance made of 2 or more elements in a fixed proportion
Can be broken down into simpler substances
Compound properties different than elements’ properties that make up compound

6. Mixtures 2.1 Properties can vary b/c composition is not fixed
Tend to retain properties of individual substance
HETEROGENEOUS MIXTURE
“different kind”
Parts are noticeable different
Ex: mixed nuts
HOMOGENEOUS MIXTURE
Substances are so evenly distributed that it is difficult to distinguish one substance from another
Ex: stainless steel = iron + chromium + nickel

8. Solution – homogenous mixture
Liquids do not separate into layers over time
If poured thru a filter, substances are not trapped
Can see thru b/c light passes without being scattered in all directions
Very Small particles
Suspensions – heterogeneous mixture
“shake well before use”
Separate into layers
Trapped by a filter
Can scatter light in all directions = cloudy
Large particles
Colloid
Contains intermediate particles
Do not separate into layers
Cannot use a filter to separate
Scattering of light
Examples: milk and fog

9. Physical Properties 2.2

10. Physical Properties 2.2
Characteristic of a material that can be observed or measured without changing composition
Viscosity, conductivity, malleability, hardness, melting point, boiling point, density
Viscosity
its resistance to flow
The higher the viscosity, the slower the substance flows
Usually decreases when heated
Conductivity
Ability for heat flow
High conductivity = good conductor  metals
If good conductor of heat, normally good conductor of electricity

11. Melting/Boiling Point
Malleability
Ability of a solid to be hammered without shattering
Most metals are malleable
Solids that shatter = brittle
Hardness
See what materials scratch the other
Diamond = hardness known material
What do you use to sharpen a knife?
Melting/Boiling Point
Melting Point – Substance changes from a solid to a liquid
Water = 0oC
Boiling Point – Substance boils
Water = 100oC

12. Density Can be used to test purity d = m/v
Test purity of methanol (fuel)
d = m/v

13. Using Physical Properties 2.2
Identifying Material
Decide which properties to test
Run tests on sample of unknown
Compare with previous data reported
Choose Materials
Wouldn’t want a shoelace from wood (must be flexible and durable)

14. Using Properties to Separate Mixtures 2.2
Filtration – process that separates materials based on the size of their particles
Small particles can pass thru a strainer
Ex: brewing coffee
Distillation – process that separates the substance in a solution based on their boiling points
Ex: fresh water for a submarine
Subs can only hold water for about 10 day  convert seawater to fresh water

16. Recognizing Physical Changes 2.2
Occurs when some of the properties of a material change but the substance remains the same
Ex: phase changes
Cutting
Crumpling
Some can be reversed, some can not

17. Chemical Properties 2.3

18. Observing Chemical Properties 2.3
Ability to produce a change in the composition of matter
Can only be observed when sample is changing to a different substance
Ex: Candles Burning
Candle = made of paraffin = made of C & H
When candle burns, C combines with air to from Carbon Dioxide and H combines with the air to form water.

19. Chemical Properties 2.3 Flammability Reactivity
Materials ability to burn in the presence of oxygen
Ex: paper and gasoline
Reactivity
How readily a substance combines chemically with other substance
Ex: N – extremely low reactivity
Ex: O – highly reactive element (rust)

20. Recognizing Chemical Changes 2.3
Substance reacts and forms one or more new substances
Change in Color
Jewelry darkens
Matches turn black
Roofs
Rust
Production of Gas
Mix vinegar with baking soda = bubbles of carbon dioxide
Baking powder + acid in a cake recipe = bubbles of carbon dioxide
Formation of a Precipitate
Formation of any solid that separates from a liquid mixture
Curdling of milk

21. Is a Change Chemical or Physical?
Can not be POSITIVE a chemical change has occurred when you see bubbles, color change, or precipitate
Ex: water boiling = physical change
Iron heated = gray  red = physical change
Ask: are different substances present after the change?
Chemical Change = Composition of matter changes
Physical Change = Composition of matter is the same