1. UNIT 3 ENERGY AND STATES 1

2. The State of Matter of a substance depends on several things Attraction between particles called IMF or Inter- Molecular Forces Solids have very high IMF Gases have no attraction between molecules Liquids have IMF a bit lower than solids Energy of the particles Space between particles 2

3. PHASE CHANGES Energy added Melting: Solid to Liquid Vaporizing: Liquid to Gas Sublimation: Solid to Gas Energy removed Freezing: Liquid to Solid Condensing: Gas to Liquid Deposition: Gas to Solid 3

4. Solid Melting Liquid Gas Vaporizing Temperature Time HEATING CURVE 4

5. COOLING CURVE Solid Temperature Freezing Liquid Gas Condensing Time 5

6. 6 Energy - capacity for doing work  weightless, odorless, tasteless All chemical reactions and changes in state involve either: a)release of energy, or b)absorption of energy

7. The Law of Conservation of Energy states that in any chemical or physical process, energy is neither created nor destroyed.  All the energy is accounted for as E th, E ph or E ch. 7

8. E th flowing into a system from it’s surroundings:  Q has a positive value  system gains heat (gets warmer) as the surroundings cool down Endothermic Reactions 8

9. Exothermic reactions Heat flowing out of a system into it’s surroundings:  Q has a negative value  system loses heat (gets cooler) as the surroundings heat up 9

10. 1)A calorie is defined as the quantity of heat needed to raise the temperature of 1 g of pure water 1 o C.  1 Calorie = 1 kilocalorie = 1000 cal. 2)The Joule, the SI unit of heat and energy  4.184 J = 1 cal 10 UNITS

11. Heat Capacity - the amount of heat needed to increase the temperature of an object exactly 1 o C Depends on both the object’s mass and its chemical composition Specific Heat Capacity (abbreviated “C”) - the amount of heat it takes to raise the temperature of 1 gram of the substance by 1 o C 11

12. 12 The higher a material’s specific heat the LONGER it take to heat up and the LONGER it takes to cool down. ex. metals have low specific heat they heat up and cool down quickly.

13. Q = mc∆T Q = mH v Q = mc∆T Q = mH f Q = mc∆T HOW TO SOLVE HEAT CAPACITY PROBLEMS: 13

14. MEANING OF FORMULA SYMBOLS Q = heat or energy unit calories or kilocalories or joules or kilojoules (1 cal = 4.18 joules) m = mass in grams c = specific heat – the amount of energy or heat needed to raise 1 gram of something 1°C, it is different for each substance and phase of matter. J/g°C or cal/g°C ∆T = Change in temperature (Temp final – Temp initial ) H f = Heat of fusion or melting. The amount of heat or energy needed to melt or freeze something. Energy needed for a phase change. H v = Heat of vaporization or condensation. The amount of heat or energy needed to vaporize or condense something. Energy needed for a phase change. 14

15. Energy Constants For water c solid = 2.1 J/g°C or 0.5 cal/g°C 1 kcal = 1000 cal c liquid = 4.18 J/g°C or 1 cal/g°C 1 kJ = 1000 J c vapor = 1.8 J/g°C or 0.44 cal/g°C H f = 334 J/g or 80 cal/g Hv = 2260J/g or 540 cal/g 15