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

TEMP

Freezing/melting point = 0°C

Boiling pt = 100°C

SOLI

D

LIQU

ID

GAS

100°C

0°CMelting

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.