Download Chemical changes

PHYSICAL
Properties
- characteristics that can be observed or measured
without changing the composition
- Ex. Breaking a glass, dying your hair
- Color, density, odor, taste, melting, freezing &
boiling point, magnetism, solubility
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 don’t like your
haircut!
CHEMICAL
Properties
- ability of a substance to combine with or change into 1 or more
other substances
Ex. Combustible, reactivity, flammability, rusts,
Obla Di Obla Da – The Properties Song
http://www.youtube.com/watch?v=uJOGy0dgmUU
http://www.teachertube.com/viewVide
o.php?video_id=129193
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.
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.
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 don’t like your
haircut!
Special types of physical changes
where any object changes state,
such as when water freezes or
evaporates, are sometimes called
change of state operations.
CHEMICAL PROPERTIES
Chemical properties can ONLY
be observed AS the substances
are changing into different
substances.
Chemical changes, or chemical
reactions, are changes that
result in the production of
another substance.
FLAMMABILITY: A material’s ability to
BURN in the presence of OXYGEN
REACTIVITY:
How readily (easily) a substance
combines chemically with other
substances.
Which has higher reactivity? A 14 karat
gold ring or a cheap metal ring from the
vending machine at the grocery store?
What is your evidence?
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.
Common examples of chemical
changes that you may be
somewhat familiar with are;
digestion, respiration,
photosynthesis, burning, and
decomposition.
Physical or Chemical Change?
•Painting Wood
•PHYSICAL
Physical or Chemical Change?
•Burning Paper
•CHEMICAL
Physical or Chemical Change?
•Digestion of food
•CHEMICAL
Physical or Chemical Change?
•Sugar dissolving in
water
•PHYSICAL
Physical or Chemical Change?
•Iron turning red when
heated
•PHYSICAL
Physical or Chemical Change?
•Evaporation
•PHYSICAL
Physical or Chemical Change?
•A pond freezing in
winter
•PHYSICAL
Physical or Chemical Change?
•Melting ice
•PHYSICAL
Physical or Chemical Change?
•Cutting wire
•PHYSICAL
Physical or Chemical Change?
•Painting fingernails
•PHYSICAL
Physical or Chemical Change?
•Cutting fabric
•PHYSICAL
Physical or Chemical Change?
•Baking muffins
•CHEMICAL
Physical or Chemical Change?
•Shattering glass
•PHYSICAL
Physical or Chemical Change?
•Decomposition of old
leaves
•CHEMICAL
Physical or Chemical Change?
•Wrinkling a shirt
•PHYSICAL
Physical or Chemical Change?
•An old nail rusting
•CHEMICAL
Classify each statement as physical or chemical property/change.
1. Pure metals have a higher luster (are shiny and reflect light).
2. The surfaces of some metals become dull when exposed to air.
3. Nitrogen gas, a relatively nonreactive material at room
temperature, can form nitrogen oxides at the high temperatures
of an operating automobile engine.
4. Milk turns sour if left too long at room temperature.
5. Diamonds are hard enough to be used as a coating for drill bits.
6. Leavened bread dough increases in volume if it allowed to “rise”
before baking.
7. Generally, metals are better conductors of heat and electricity
than are nonmetals.
8. Unreactive argon gas, rather than air, is used to fill many light
bulbs to prevent the metal filament wire inside the bulb from
being destroyed through chemical reactions.
9. Metals are typically ductile (can be drawn into wires).
Classify each statement as physical or chemical property/change.
1. Pure metals have a higher luster (are shiny and reflect light). P
2. The surfaces of some metals become dull when exposed to air. C
3. Nitrogen gas, a relatively nonreactive material at room
temperature, can form nitrogen oxides at the high temperatures
of an operating automobile engine. C
4. Milk turns sour if left too long at room temperature. C
5. Diamonds are hard enough to be used as a coating for drill bits. P
6. Leavened bread dough increases in volume if it allowed to “rise”
before baking. C
7. Generally, metals are better conductors of heat and electricity
than are nonmetals. P
8. Unreactive argon gas, rather than air, is used to fill many light
bulbs to prevent the metal filament wire inside the bulb from
being destroyed through chemical reactions. C
9. Metals are typically ductile (can be drawn into wires). P
Real Life Problem: Designing the Penny
• COST of materials is an issue when manufacturing
coins and paper money.
– Early 1980’s copper became too expensive to be used as
primary metal in pennies
– Zinc replaced most of the copper in all post 1982
pennies
PROs - Zinc – about as hard; almost as dense, readily
available and less expensive than copper
CONs – more chemically reactive (zinc-plated steel pennies
created in 1943 corroded and looked considerably
different)
• Solved the penny issue in early 1980s
• Copper properties best fit for outside of the coin
and zinc properties best fit for inside of the coin
(increase coin’s durability and maintain familiar
appearance)
PHYSICAL
Changes
CHEMICAL
Changes
- changes that alter a
substance’s appearance
without changing its
composition
- chemical reactions
- process that involves 1 or
more substances changing into
new substances
- Ex. Cutting paper, breaking
crystals, melting/freezing ice,
boiling water
Ex. combusts, rusts, reacts
with oxygen, ferments, burns,
rots
http://www.teachertu
be.com/viewVideo.ph
p?video_id=214083
http://vital.cs.ohi
ou.edu/steamweb
site/downloads/C
hangeLab.swf
Online Quiz
What is Density?
If you take the same volume of different substances, then
they will weigh different amounts.
Wood
Water
Iron
1 cm3
1 cm3
1 cm3
0.50 g
1.00 g
8.00 g
IRON
Q) Which has the greatest mass and therefore the most dense?
Density is the Mass per unit Volume
http://www.youtube.com/watch?v=GMNpPgLT
8Fk
Density Equation:
g
Density =
g/mL or g/cm-3
M=DxV
V=M/D
mass
Volume
mL (for liquids)
or cm3 (for solids)
http://science360.gov/obj/video/f251
1bad-b43f-4dbd-84f9ace57941ac90/mass-volume-density
NHL Hockey Rinks
DENSITY OF A REGULAR SOLID
m = 240 g
2.0 cm
3.0 cm
 = m = 240 =10.0 g/cm3
V 24
4.0 cm
1. Find the Mass of
the solid on a
balance.
2. Measure the three
lengths and calculate
the Volume.
(ie V = l x w x h )
• Calculate the
Density.
DENSITY OF AN IRREGULAR SOLID
m = 360 g
80 ml
50 ml
1. Find the Mass of the solid on a
balance.
2. Fill the Measuring Cylinder
with Water to a known Volume.
3. Add the Object.
4. Work out the Volume of Water
that is displaced.
5. Calculate the Density.
Density = m = 360 =12.0 g/cm3
V 30
DENSITY OF AN IRREGULAR SOLID
• OR use a Eureka (overflow) Can to find the Volume.
1. Find the mass of the solid on a
balance.
m = 440 g
2. Add water until just
overflowing.
3. Place a Measuring Cylinder
under the spout.
4. Add the Object.
40.0 ml
5. Collect the Water and read
Density = m = 440 =11.0 g/cm3 off the Volume.
V 40
6. Calculate Density
DENSITY OF A LIQUID
1. Find the Mass of an empty
25.0 g
25.0 g
45.0
graduated cylinder.
2. Add a certain Volume of Liquid.
3. Find the Mass of the Measuring
Cylinder and Liquid
4. Calculate the Mass of Liquid.
– How?
• Mass of Liquid = Mass of Measuring
Cylinder and Liquid – Mass of empty
Measuring Cylinder
20.0 ml
• Calculate Density of Liquid.
45 – 25 = 20 g
Density = m = 20 =1.00 g/mL
V 20
Density Practice Problems
1. What is the density of a piece of wood that has a mass of
25.0 grams and a volume of 29.4 cm3?
Density = m
V
D = 25.0g
29.4cm3
D = 0.85g/cm3
2. A piece of wood that measures 3.0cm by 6.0cm by 4.0 cm
has a mass of 80.0 grams. What is the density of the wood?
Volume = l x w x h
Density = m
V
V = 3.0cm x 6.0cm x 4.0cm
V = 72.0cm3
m = 80.0g
D = 80.0g
72.0cm3
D = 0.85g/cm3
3. Would the piece of wood in #2 float in water?
Yes, the wood’s density is less than the density of water (1.0g/cm3)
4. An ice cube measuring 5.80cm by 5.80cm by 5.80cm
has a density of 0.917g/cm3. What is the mass?
Volume = l x w x h
Density = m
V
m=DxV
V = 5.8cm x 5.8cm x 5.8cm
V = 195.11cm3
D = 0.917g/cm3
m = 0.917g/cm3 x 195.11cm3
m = 178.92g
5. The density of aluminum is 2.7g/ml. If the mass of a
piece of aluminum is 244g, what is the volume of the
aluminum?
V = 244g
D=m
V
V=m
D
D = 2.7g/ml
m = 244g
2.7g/ml
V = 90.37ml
How to TEST for GASSES!
Oxygen (O2), Hydrogen (H2) & Carbon Dioxide (CO2) 
colorless and odorless (for the most part)….
SOOO how can you tell which gas is emitted after a chemical
reaction?????
http://www.youtube.com/watch?v=LiAvDpl5aJA