1. CHAPTER 2 PROPERTIES OF MATTER
Chemists 6:45

2. PURE SUBSTANCES Matter w/ same composition throughout 2 categories:
Table salt or sugar
Every pinch tastes equally salty/sweet
2 categories:
Elements
compounds

3. ELEMENTS substance that cannot be broken down into simpler substances.
fixed comp b/c it has only 1 type of atom
Cutting copper wire into smaller and smaller pieces until you end up with copper atoms
No 2 elements contain same type atom

4. EXAMPLES OF ELEMENTS
At room temp (20°C, or 68°F), most solids, some gases, 2 liquids

5. SYMBOLS FOR ELEMENTS
Jöns Berzelius (Swedish chemist) suggested symbols
1 or 2 letters with 1st letter always CAPITALIZED
If 2 letters, 2nd letter not cap
Some Latin name of elements
Gold is Au (aurum)
Lead is Pb (plumbum)

6. COMPOUNDS Substance made of 2 or more simpler substances
Can be broken down into simpler substances (elements or other cmpds)
Always joined in fixed proportion
H20 – 1 drop or 1 gallon, always 2 parts hydrogen for every 1 part oxygen
Silicon dioxide (clear crystals in sand)
1 pt silicon : 2 pts oxygen
(di- means 2)

7. MIXTURES Similar to cmpds b/c multiple substances
Different b/c properties can vary b/c composition NOT fixed
salsa – each bite has different amt of onion, pepper, etc
Pizza – each slice has diff amt toppings

8. HETEROGENEOUS MIXTURES
parts of mixture noticeably different from one another
Sand, trail mix, Lucky Charms, Italian salad dressing

9. Contents of Two Cans of Mixed Nuts
Type of Nut
Mass in Brand A
Mass in Brand B
Peanut g g
Almond
47.02 g
31.18 g
Brazil Nut
57.88 g
19.60 g
Cashew
46.20 g
73.78 g
Hazelnut
19.90 g
16.90 g
Pecan
21.40 g
How are the two brands of mixed nuts alike? How are they different?
What is the percent by mass of each type of nut?
Do the contents of each can meet the FDA regulations? Explain.
On the Brand A label, the nuts are listed in this order: peanuts, Brazil nuts, almonds, cashews, pecans, and hazelnuts. What do you think determines the order?

10. HOMOGENEOUS MIXTURES Substances evenly distributed
difficult to distinguish one substance from another
Appears to contain only one substance
Stainless steel (iron, chromium, and nickel), Kool-Aid, and pool water

11. SOLUTIONS, SUSPENSIONS, AND COLLOIDS
3 major classifications of mixtures:
Based on size of largest particles:

12. SOLUTIONS small particles dissolved creating a homogeneous mixture
Windshield washer fluid, sweetened tea, Kool-Aid
Particles too small to settle out, be trapped by filter, or scatter light

13. SUSPENSIONS Heterogeneous mixture separates into layers over time
Italian salad dressing, dirt particles in the air, quicksand
Large particles can be trapped by filter and scatter light making suspensions cloudy

14. COLLOIDS
Intermediate size particles – larger than solution, smaller than suspension
Large enough to scatter light, too small to settle out / filtered
Milk, shaving cream, smoke, fog
Matter Concept map 14

15. PHYSICAL PROPERTIES SECTION 2.2

16. VISCOSITY resistance to flow High viscosity  slow flow
high visc: – honey, lava, motor oil
low visc: – water, vinegar, olive oil

17. CONDUCTIVITY
measure of material’s ability to allow flow of heat / electricity
Metals  high conductivity – called conductors
Wood, rubber, and styrofoam low conductivity – poor conductors

18. MALLEABILITY Material’s ability to be hammered w/o shattering
Most metals malleable
ex. gold, lead, iron

19. HARDNESS Material’s resistance to be scratched Harder substances
“scratch” softer ones
Grinding wheels high $ b/c
Contains diamond chips

20. MELTING & BOILING POINTS
Melting pt – solid to liquid
Boiling pt – liquid to gas
These characteristics can be used to separate substances out of mixtures
Melting and boiling points of Some Substances
Substance
Melting point
Boiling point
Hydrogen
-259.3°C
-252.9°C
Nitrogen
-210.0°C
-195.8°C
Ammonia
-77.7°C
-33.3°C
Octane (in gasoline)
-56.8°C
125.6°C
Water
0.0°C
100.0°C
Acetic acid (in vinegar)
16.6°C
117.9°C
Table salt
800.7°C
1465°C
Gold
1064.2°C
2856°C
On p.47

21. DENSITY Tests purity of substances Mass - volume ratio
Methanol is fuel burned in some racing motorcycles.
Must be 99.65% pure

22. USING PROPERTIES TO SEPARATE MIXTURES
FILTRATION
Separating materials based on size of particles
brewing coffee
iced tea

23. DISTILLATION
When solution can’t be filtered, distillation used
Distillation provides fresh water for submarines
Fresh H2O and sea H2O separated b/c differences in boiling pts

24. RECOGNIZING PHYSICAL CHANGES
Physical change – some properties of a material change, but substance remains same
Ex. Melting ice cream, cut hair, crumple paper

25. CHEMICAL PROPERTIES SECTION 2.3

26. OBSERVING CHEMICAL PROPERTIES
Candle burns causes hydrogen and carbon from paraffin to turn into carbon dioxide (new substance that was not originally present)
Chemical properties observed only when substances are changing into different substances

27. FLAMMABILITY Burning in presence of OXYGEN
Burning substances used as fuel
Gasoline
coal
wood
Sometimes not desirable
Children’s sleepwear – low flammability
Difficult to ignite
Burns slowly

28. REACTIVITY
When oxygen from air reacts with iron from car & water from air…..rust forms completely new substance………
Oxygen + water + iron = iron oxide (rust)
Nitrogen is less reactive – N gas used in submarine tanks to replace reactive O gas

29. RECOGNIZING CHEMICAL CHANGES
Look for:
gas produced
heat produced
**change in color
precipitate (solid) formed
**Color change alone can also be physical change

30. IS A CHANGE CHEMICAL OR PHYSICAL?
Color change as physical change…despite color change, iron is still iron
Gas produced as physical change/…water boiling changes phases (liquid to gas) but still H2O

31. PHYSICAL V.S. CHEMICAL CHANGE
When matter undergoes chemical change, comp of matter changes
When matter undergoes physical change, comp remains same