Chemical Properties

1
Chemical Properties Physical and Chemical
Changes
2
Physical changes are those changes that do not
result in the production of a new substance.  If
you melt a block of ice, you still have H2O at
the end of the change.   
3
If you break a bottle, you still have glass. 
Painting your nails will not stop them from being
fingernails.  Some common examples of physical
changes are melting, freezing, condensing,
breaking, crushing, cutting, and bending.
4

• When a change of state occurs,
• molecules or atoms may move
• faster or slower, may spread out
• or clump together, but they do not
• change.
• i.e. An H2O molecule is still an H2O molecule!

5
Some, but not all physical changes can be
reversed. You could refreeze the water into ice,
but you cannot put your hair back together if you
dont like your haircut!
6
Special types of physical changes where any
object changes state, such as when water freezes
or evaporates, are sometimes called change of
state operations.
7
The distinction between physical and chemical
change.
8
Sample Problem 1.5
Calculating Density from Mass and Length
PROBLEM
Lithium (Li) is a soft, gray solid that has the
lowest density of any metal. If a slab of Li
weighs 1.49 x 103 mg and has sides that measure
20.9 mm by 11.1 mm by 11.9 mm, what is the
density of Li in g/cm3 ?
9
(No Transcript)
10
CHEMICAL PROPERTIES
Chemical properties can ONLY be observed AS the
substances are changing into different
substances.
11
Chemical changes, or chemical reactions, are
changes that result in the production of a new
substance. 
12
FLAMMABILITY A materials ability to BURN in
the presence of OXYGEN A chemical property
13
REACTIVITYHow readily (easily) a substance
combines chemically with other substances. A
chemical property
14
Some Characteristic Properties of Copper
Table 1.1
Physical Properties
Chemical Properties
slowly forms a basic blue-green sulfate in moist
air
reddish brown, metallic luster
easily shaped into sheets (malleable) and
wires (ductile)
reacts with nitric acid and sulfuric acid
good conductor of heat and electricity
density 8.95 g/cm3
slowly form a deep-blue solution in aqueous
ammonia
melting point 10830C
boiling point 25700C
15
When you burn a log in a fireplace, you are
carrying out a chemical reaction that releases
carbon.  When you light your Bunsen burner in
lab, you are carrying out a chemical reaction
that produces water and carbon dioxide. 
16
Common examples of chemical changes that you may
be somewhat familiar with are digestion,
respiration, photosynthesis, burning, and
decomposition. 
17
Physical or Chemical Change?

• Painting Wood
• PHYSICAL

18
Physical or Chemical Change?

• Burning Paper
• CHEMICAL

19
Physical or Chemical Change?

• Digestion of food
• CHEMICAL

20
Physical or Chemical Change?

• Sugar dissolving in water
• PHYSICAL

21
Physical or Chemical Change?

• Iron turning red when heated
• PHYSICAL

22
Physical or Chemical Change?

• Evaporation
• PHYSICAL

23
Physical or Chemical Change?

• A pond freezing in winter
• PHYSICAL

24
Physical or Chemical Change?

• Melting ice
• PHYSICAL

25
Physical or Chemical Change?

• Cutting wire
• PHYSICAL

26
Physical or Chemical Change?

• Painting fingernails
• PHYSICAL

27
Physical or Chemical Change?

• Cutting fabric
• PHYSICAL

28
Physical or Chemical Change?

• Baking muffins
• CHEMICAL

29
Physical or Chemical Change?

• Shattering glass
• PHYSICAL

30
Physical or Chemical Change?

• Decomposition of old leaves
• CHEMICAL

31
Physical or Chemical Change?

• Wrinkling a shirt
• PHYSICAL

32
Physical or Chemical Change?

• An old nail rusting
• CHEMICAL

33
(No Transcript)
34
Substance Physical State
Density (g/cm3)
At room temperature(200C) and normal atmospheric
pressure(1atm).
35
Physical versus Chemical Properties

• Unit II - Part 1
• The study of matter

36
Reviewing MATTER

• Matter anything that has mass and takes up
  space
• Mass the amount of matter in something
• Volume the amount of space something occupies
• Which of the following is matter?
• A car?
• A box?
• You?

37
What is a property?

• Property a characteristic of a substance that
  can be observed

38
Physical Property
Physical property a property that can be
observed without changing the identity of the
substance.

• Examples
• luster
• malleability the ability to be hammered into a
  thin sheet
• ductility the ability to be stretched into a
  wire

• melting point
• boiling point
• density
• solubility
• specific heat

39

• In a physical change no new substances
• are formed
• Physical changes include changes of
• state.
• liquid to solid Solidifying or Freezing
• solid to liquid Melting
• liquid to gas Evaporation or Boiling
• gas to liquid Condensation
• gas to solid or solid to gas Sublimation

40
Special Physical Properties

• Melting point the temperature at which a
  substance changes from a solid to a liquid at a
  given pressure
• water 0oC
• Boiling point the temperature at which a
  substance changes from a liquid to a gas at a
  given pressure
• water 100oC

41
Chemical Properties

• Chemical property a property that can only be
  observed by changing the identity of the
  substance

• Examples
• flammability
• ability to rust
• reactivity with vinegar

42
Density

• Density is the amount of mass per unit of volume.
• Density can be used to identify a substance.
• The density of water is 1.0g/mL

43
Density Calculations

• Calculations
• D m/V g/mL g/cm3
• Ex A cube has a mass of 2.8 g and occupies a
  volume of 3.67 ml. Would this object float or
  sink in water?
• Mass 2.8 g Volume 3.67 mL
• D 2.8g/3.67 mL 0.76 g/mL
• This object would float in water because its
  density is less than water (1.0 g/mL).

44
More Density Calculations

• Ex A liquid has a mass of 25.6 g and a volume
  of 31.6 mL. Use the table below to identify the
  substance.

M25.6 g V31.6 mL D 25.6 g/31.6 mL
D 0.81 g/mL The substance is ethanol.
45
Rules for Rounding Off Numbers
1. If the digit removed is more than 5, the
preceding number increases by 1. 5.379 rounds to
5.38 if three significant figures are retained
and to 5.4 if two significant figures are
retained.
2. If the digit removed is less than 5, the
preceding number is unchanged. 0.2413 rounds to
0.241 if three significant figures are retained
and to 0.24 if two significant figures are
retained.
3.If the digit removed is 5, the preceding number
increases by 1 if it is odd and remains unchanged
if it is even. 17.75 rounds to 17.8, but 17.65
rounds to 17.6. If the 5 is followed only by
zeros, rule 3 is followed if the 5 is followed
by nonzeros, rule 1 is followed 17.6500 rounds
to 17.6, but 17.6513 rounds to 17.7
4. Be sure to carry two or more additional
significant figures through a multistep
calculation and round off only the final answer.
46
Clues that a Chemical Change has occurred.

• Color change
• Heat or light given off
• Odor given off
• Gas released
• Solid forming in a liquid