TOPIC : Evolution AIM : Explain the theory of Natural Selection.
TOPIC: Heat AIM: How do substances change from one phase to another?
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Transcript of TOPIC: Heat AIM: How do substances change from one phase to another?
TOPIC: HeatAIM: 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)
Phasechange
•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
Example: Iodine crystals gas (slightly above room temp)
Crystals
Gas
Freezing
LS
Melting SL
Evaporation LG
Condensation GL
Add heat Energy absorbed by molecules
Remove heat Energy released by molecules
PHASE CHANGES
SOLID LIQUID GAS
Freezingpoint
• Temp at which a liquid freezes (LS)
• FP of water = 0°C
Meltingpoint
• Temp at which a substance melts (SL)
• MP of water = 0°C
•Freezing Pt = Melting Pt
Boilingpoint
• Temp at which a substance evaporates (LG)
• 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).
Tempof asubstanceduring
phasechange
• Stays the same until all of the substance has changed
• Why? • 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.
Time
T
E
M
P
Freezing/melting point = 0°C
Boiling pt =
100°C
SO
LID
LIQ
UID
GAS
100°C
0°C
Melting
Freezing
Evaporation
Condensation
PHASE CHANGE GRAPH FOR WATER
= phase changes
What is amixture?
• 2 or more substances put together
• No new substances• (not chemically
combined) • Ex: salt water, salad…
• Can be separated• (Boiling, magnets, Filtering…)
What is asolution?
• Type of mixture• 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
Whataffects therate ofdissolving?
• 1. Heat• (more heat dissolves faster)
• 2. Surface area• (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 doestempaffectsolubility?
• Temperature increases solubility
Solubility curves, like the one shown here, tell us what mass of solute will dissolve in 100g of water.