1. Chemistry
Unit 2:
Matter and its changes

2. Chemistry is… Combustion reaction:
…the study of the composition, structure, and properties of matter and the changes it undergoes
Combustion reaction:
C2H5OH O2  2 CO2 + 3 H2O + Energy
Reactants  Products

3. Matter Introductory Definitions
matter: anything having mass and volume
mass:
the amount of matter in an object
volume:
the space an object occupies
units: L, dm3, mL, cm3
properties:
describe the matter
what it looks like, smells like; its mass, temp., etc.
how it behaves

4. Properties of Matter Extensive properties
depend on the amount of matter that is present.
Extensive properties
Volume Length Height
Mass
Energy Content (think Calories!)
do not depend on the amount of matter present.
Intensive properties
Melting point
Color
Odor
Conductivity
Malleable
Ductile
Boiling point
Density

5. PHYSICAL PROPERTIES
characteristics that can be observed without changing the identity of the substance.
Examples:
mass
volume
color
shape
texture
density

6. CHEMICAL PROPERTIES
describe the tendency of a substance to undergo chemical change(s), or transform into new substances
Examples:
flammability
reactivity

7. Change in material (taste; bacterial growth)
Property:
Chemical (reason):
Physical (reason):
Luster
Surface of metal becomes dull when exposed to air
N2 reacts with high temperature of a car engine and makes nitrogen oxides
Milk turns sour when left out of fridge too long
Diamonds are hard enough to use as drill bits
No change in material
Metal reacts
with oxygen
New substance formed
Change in material (taste; bacterial growth)
No change in material

8. Physical Change
A change in a substance that does not involve a change in the identity of the substance.
Example:
Phase Changes
(liquid to gas)
Evaporation allows the solvent to be removed from the solute by boiling.

9. Chemical Change
A change in which one or more substances are converted into different substances.
Heat and light are often evidence of a chemical change.

10. Chemical Change Chemical Change on the atomic levelNa Cl
Na+
Cl-
So, which of these would be a chemical change?
- Grape juice after it has been left in the car for a few days during a hot summer.
- Logs burning in a fireplace.
- Toasting a bagel in the morning for breakfast.

11. Evidence of Chemical Change
Key to a chemical reaction is the formation of a new substance
*Evidence of new substance (s):
gas is produced
new taste, smell, or sound is produced
light and/or electricity is produced
color changes
temperature changes
Precipitate forms
a solid that forms from a solution during a chemical reaction.
These evidences do
not always work

13. Evaporation is a physical change

14. Breaking is a physical change.

15. Boiling is a change of state, and therefore a physical change!

16. Rusting is a Chemical Change

17. Burning is a Chemical Change

18. Phase Differences
Solid – definite volume and shape; particles packed in fixed positions.
Liquid – definite volume but indefinite shape; particles close together but not in fixed positions
Gas – neither definite volume nor definite shape; particles are at great distances from one another
Plasma – high temperature, ionized phase of matter as found on the sun.

19. Some Properties of Solids, Liquids, and Gases
Property Solid Liquid Gas
Shape Has definite shape Takes the shape of Takes the shape
the container of its container
Volume Has a definite volume Has a definite volume Fills the volume of
the container
Arrangement of Fixed, very close Random, close Random, far apart
Particles
Interactions between Very strong Strong Essentially none
particles

20. Energy Changes Accompanying Phase Changes
Gas
Vaporization
Condensation
Sublimation
Deposition
Energy of system
Liquid
Melting
Freezing
Solid
Brown, LeMay, Bursten, Chemistry 2000, page 405

21. Classification of Matter
Elements
Draw this chart!, leave space to define the terms
Pure Substances
Compounds
Matter
Homogeneous
Mixtures
Heterogeneous

22. sodium chloride (NaCl)
Classifying Matter
(Pure) Substances
…have a fixed composition
…have fixed properties
ELEMENTS
COMPOUNDS
e.g.,
Fe, N2, S8, U
e.g.,
H2O, NaCl, HNO3
sulfur (S8)
sodium chloride (NaCl)
Pure substances have a chemical formula.

23. retain their individual properties.
Mixtures
two or more substances mixed together
…have varying composition
…have varying properties
The substances are NOT chemically bonded,
and they…
retain their individual properties.
Tea, orange
juice, oceans,
and air are
mixtures.

24. Two Types of Mixtures
homogeneous: (or solution)
particles are microscopic; sample has same
composition and properties throughout;
evenly mixed
Kool Aid
salt water
e.g.,
alloy: a homogeneous mixture of metals
bronze (Cu + Sn)
pewter (Pb + Sn)
brass (Cu + Zn)
e.g.,

25. Two Types of Mixtures (cont.)
heterogeneous:
different composition and properties in the
same sample; unevenly mixed
raisin bran
tossed salad
e.g.,
suspension: settles over time
snowy-bulb gifts
paint
e.g.,

26. EXAMPLES
What type of matter are each of the following… ?

27. SAND

28. SAND
Heterogeneous mixture

29. Salt (NaCl)

30. Salt (NaCl)
COMPOUND

31. Air

32. Air Homogeneous mixture of:
Nitrogen, N %
Oxygen, O %
Argon, Ar 0.93%
Carbon dioxide, CO %
Neon, Ne %
Helium, He %
Methane, CH %
Krypton, Kr %
Nitrogen(I) oxide, N2O %
Hydrogen, H %
Xenon, Xe %
Ozone, O %
Homogeneous mixture of:
Many gases make up mixture, but it looks like it is all one gas.

33. Gold

34. Gold
ELEMENT: Au

35. Bronze

36. Bronze
Homogeneous mixture of copper and tin (alloy: mixture of metals)

37. Salad Dressing

38. Salad Dressing: Heterogeneous

39. Separation of a Mixture
The constituents of the mixture retain their identity and may be separated by physical means.

40. …involves physical means, or physical changes
Separating Mixtures
…involves physical means, or physical changes
1. sorting:
by color,
shape,
texture,
etc.
Mixture of
solid and
liquid
Filtrate (liquid
component
of the mixture)
Filter paper
traps solid
Funnel
2. filter:
particle size
is different

41. Separating Mixtures (cont.)
3. magnet:
one substance must
contain iron
4. chromatography:
some substances dissolve
more easily than others

42. Separating Mixtures (cont.)
5. density:
“sink vs. float”
perhaps use a centrifuge
blood after high-
speed centrifuging
decant: to pour
off the liquid

43. Separating Mixtures (cont.)
6. distillation:
different boiling points
heat source
thermometer
water in
(cooler)
water out
(warmer)
more-volatile
substance
mixture
condenser
substance, now
condensed
(i.e., the one
with the lower
boiling point)

44. Spin sample very rapidly: denser materials go to bottom (outside)
7. Centrifugation
Spin sample very rapidly: denser materials go to bottom (outside)
Separate blood into serum and plasma
Serum (clear)
Plasma (contains red blood cells ‘RBCs’)
Check for anemia (lack of iron)
AFTER
Before
Blood
Serum
RBC’s
A B C

45. are needed to separate mixtures; substances are NOT bonded.
No chemical reactions
are needed to separate mixtures;
substances are NOT bonded.
dental amalgam