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TOPIC: Heat AIM: How do substances change from one phase to another?

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Presentation on theme: "TOPIC: Heat AIM: How do substances change from one phase to another?"— Presentation transcript:

1 TOPIC: Heat AIM: How do substances change from one phase to another?

2 States (phases) of matter 1. SOLID Molecules packed closely together Vibrate in place

3 Definite volume & shape

4 2. LIQUID Molecules farther apart & move around

5 Definite volume No definite shape

6 3. GAS Molecules very far apart & move around very fast A lot of empty space (smaller density)

7 No definite shape or volume

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11 4. PLASMA High energy molecules Sun, stars, lightening, fluorescent & neon lights

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13 Can you find the different phases of matter in this picture?

14 2 types of changes 1. Physical change Phase change Does not produce a new substance (change in appearance)

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16 Examples: freezing, melting, evaporation, tearing, crushing

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18 2. Chemical Change Produces a NEW substance Examples: burning, rusting

19 Paper  ash, smoke, heat

20 Iron + oxygen  iron oxide (rust)

21 Raw egg  cooked egg Cake batter  Cake

22 + Sodium Chlorine NaCl = Sodium Chloride (salt)

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24 Phase change Physical change Requires heat energy

25 Phase Changes

26 Freezing Liquid  Solid Heat removed

27 Melting Solid  Liquid Heat added

28 Evaporation Liquid  Gas Heat added Vaporization

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30 Condensation Gas  Liquid Heat removed

31 Opposite of evaporation

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35 Sublimation Solid  Gas Heat added Example: Dry ice (solid CO 2  gas)

36 Solid Gas

37 Example: Iodine crystals  gas (slightly above room temp) Crystals Gas

38 Freezing L  S Melting S  L Evaporation L  G Condensation G  L Add heat  Energy absorbed by molecules Remove heat  Energy released by molecules PHASE CHANGES SOLIDLIQUID GAS

39 Freezing point Temp at which a liquid freezes (L  S) FP of water = 0°C

40 Melting point Temp at which a substance melts (S  L) MP of water = 0°C

41 Freezing Pt = Melting Pt

42 Boiling point Temp at which a substance evaporates (L  G) BP of water = 100°C

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44 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).

45 Temp of a substance during phase change Stays the same until all of the substance has changed Why? Bc the energy is needed to change the substance, not the temperature

46 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.

47 Time TEMPTEMP Freezing/melting point = 0°C Boiling pt = 100°C SOLID LIQUID GAS 100°C 0°C Melting Freezing Evaporation Condensation PHASE CHANGE GRAPH FOR WATER = phase changes

48 What is a mixture? 2 or more substances put together No new substances (not chemically combined) Ex: salt water, salad…

49 Can be separated (Boiling, magnets, Filtering…)

50 What is a solution? Type of mixture 1 substance dissolved in another

51 2 parts: 1. Solute = what gets dissolved 2. Solvent = what does the dissolving

52 Example: Hot chocolate Solvent = Water Solute = Chocolate

53 SolubleAble to dissolve Ex: sugar is soluble in water

54 What affects the rate of dissolving? 1. Heat (more heat  dissolves faster) 2. Surface area (more surface area/smaller pieces  dissolves faster) 3. Stirring

55 SolubilityMax amount of substance that will dissolve in a certain amount of liquid

56 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.

57 Greatest solubility

58 How does temp affect solubility? Temperature increases solubility

59 Solubility curves, like the one shown here, tell us what mass of solute will dissolve in 100g of water.


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