Transcript CHAPTER 2 PROPERTIES OF MATTER

CHAPTER 2
PROPERTIE
S OF
MATTER
Chemists 6:45
PURE SUBSTANCES
• Matter w/ same composition
throughout
– Table salt or sugar
• Every pinch tastes equally salty/sweet
• 2 categories:
– Elements
– compounds
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
EXAMPLES OF
ELEMENTS
•At room temp (20°C, or
68°F), most solids, some
gases, 2 liquids
SYMBOLS FOR ELEMENTS
• 1813 - 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)
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
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
HETEROGENEOUS
MIXTURES
•parts of mixture noticeably
different from one another
– Sand, trail mix, Lucky Charms, Italian
salad dressing
Contents of Two Cans of Mixed Nuts
Type of Nut
Mass in
Mass in
Brand A
Brand B
Peanut
152.39 g
191.96 g
Almond
47.02 g
31.18 g
Brazil Nut
57.88 g
19.60 g
1. How are the two brands of mixed nuts alike? How are
Cashew
46.20 g
73.78 g
they different?
2.Hazelnut
What is the percent by
mass of
nut? g
19.90
g each type of16.90
3. Do the contents of each can meet the FDA regulations?
Pecan
21.40 g
16.90 g
Explain.
4. 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?
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
SUSPENSIONS, AND
COLLOIDS
•3 major classifications of
mixtures:
•Based on size of largest
particles:
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
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
COLLOIDS
• Intermediate size particles –
larger than solution, smaller
than suspension
• Large enough to scatter light,
too
small
to
settle
out
/
filtered
Matter Concept map
– Milk, shaving cream, smoke, fog
PHYSICAL
PROPERTIES
SECTION 2.2
VISCOSITY
•resistance to flow
•High viscosity  slow flow
•
high visc: – honey, lava, motor oil
•
low visc: – water, vinegar, olive oil
•
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
MALLEABILITY
•Material’s ability to be hammered
w/o shattering
• Most metals malleable
•
ex. gold, lead, iron
HARDNESS
•Material’s resistance to be
scratched
•Harder substances
•“scratch” softer ones
•Grinding wheels high $ b/c
•Contains diamond chips
MELTING & BOILING POINTS
•Melting pt – solid to liquid
•Boiling pt – liquid to gas
•These characteristics can be used
Melting and
boiling points of
Some
to separate
substances
out
of
Substances
mixtures
Substance
Melting point
Boiling
Hydrogen
Nitrogen
Ammonia
-259.3°C
-210.0°C
-77.7°C
point
-252.9°C
-195.8°C
-33.3°C
On
p.47
DENSITY
•Tests purity of substances
•Mass - volume ratio
•Methanol is fuel burned in some
racing motorcycles.
•Must be 99.65% pure
USING PROPERTIES TO SEPARATE
MIXTURES
•FILTRATION
•Separating materials based on
size of particles
• brewing coffee
• iced tea
•
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
RECOGNIZING PHYSICAL
CHANGES
•Physical change – some
properties of a material change,
but substance remains same
•Ex. Melting ice cream, cut hair,
crumple paper
CHEMICAL
PROPERTIES
SECTION 2.3
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
FLAMMABILITY
•Burning in presence of OXYGEN
•Burning substances used as fuel
•
Gasoline
•
coal
•
wood
•Sometimes not desirable
•
Children’s sleepwear – low
flammability
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
RECOGNIZING CHEMICAL
CHANGES
•Look for:
•
gas produced
•
heat produced
•
**change in color
•
precipitate (solid) formed
•**Color change alone can also be
physical change
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
PHYSICAL V.S. CHEMICAL
CHANGE
•When matter undergoes
chemical change, comp of
matter changes
•When matter undergoes physical
change, comp remains same