TOPIC: Heat
AIM: How do
substances change from
one phase to another?
States •
(phases) •
of
matter •
1. SOLID
Molecules packed
closely together
Vibrate in place
• Definite volume & shape
• 2. LIQUID
• Molecules farther apart &
move around
• Definite volume
• No definite shape
• 3. GAS
• Molecules very far apart &
move around very fast
• A lot of empty space (smaller
density)
• No definite shape or volume
• 4. PLASMA
• High energy molecules
• Sun, stars, lightening,
fluorescent & neon lights
Can you find the different phases of
matter in this picture?
2 types
of
changes
• 1. Physical change
• Phase change
• Does not produce
a new substance
• (change in
appearance)
• Examples: freezing, melting,
evaporation, tearing, crushing
• 2. Chemical Change
• Produces a NEW substance
• Examples: burning, rusting
Paper  ash, smoke, heat
Iron + oxygen  iron oxide (rust)
Raw egg  cooked egg
Cake batter  Cake
Sodium
+
Chlorine
NaCl = Sodium Chloride
(salt)
Phase
change
• Physical change
• Requires heat
energy
Phase Changes
Freezing
• Liquid  Solid
• Heat removed
Melting
• Solid  Liquid
• Heat added
Evaporation • Liquid  Gas
• Heat added
• Vaporization
Condensation • Gas
 Liquid
• Heat removed
•Opposite of
evaporation
Sublimation • Solid  Gas
• Heat added
• Example: Dry ice
(solid CO2  gas)
Solid
Gas
Gas
Crystals
Example:
Iodine
crystals 
gas (slightly
above room
temp)
PHASE CHANGES
Add heat  Energy absorbed by molecules
Melting
SL
SOLID
Evaporation
LG
LIQUID
Freezing
LS
GAS
Condensation
GL
Remove heat Energy released by molecules
Freezing • Temp at which a liquid
freezes
(LS)
point
• FP of water = 0°C
Melting • Temp at which a
substance melts (SL)
point
• MP of water = 0°C
• Freezing Pt = Melting Pt
Boiling • Temp at which a
point substance evaporates
(LG)
• BP of water = 100°C
Evaporation occurs at the surface of a liquid
(left). When a liquid boils, gas bubbles form
throughout the liquid and then rise out of the
liquid (right).
Temp
• Stays the same until
of a
all of the substance
substance
has changed
during phase• Why?
change
• Bc the energy is
needed to change the
substance, not the
temperature
When water reaches its boiling point, it
stays at 100°C until it all changes to
steam. Them temperature of the steam
can then rise above 100°C.
PHASE CHANGE GRAPH FOR WATER
Condensation
Boiling pt =
100°C
Evaporation 100°C
T
E
M
P
Freezing
0°C
Melting
Freezing/melting
point = 0°C
= phase
changes
Time
What is a • 2 or more substances
put
together
mixture?
• No new substances
• (not chemically
combined)
• Ex: salt water, salad…
• Can be separated
• (Boiling, magnets, Filtering…)
What is a • Type of mixture
solution? • 1 substance dissolved
in another
• 2 parts:
• 1. Solute = what gets dissolved
• 2. Solvent = what does the
dissolving
• Example: Hot chocolate
• Solvent = Water
• Solute = Chocolate
Soluble • Able to dissolve
• Ex: sugar is soluble in
water
What
• 1. Heat
affects • (more heat 
dissolves faster)
the
• 2. Surface area
rate of
dissolving? • (more surface
area/smaller pieces
 dissolves faster)
• 3. Stirring
Solubility • Max amount of
substance that will
dissolve in a certain
amount of liquid
At 20°C, 38
grams of salt
will dissolve in
100 grams of
water.
If more salt is
added, it will
not dissolve. It
will sink to the
bottom.
Greatest solubility
How does • Temperature
temp
increases solubility
affect
solubility?
Solubility curves, like the one shown here, tell
us what mass of solute will dissolve in 100g of
water.