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The universe is made up of: The system – the thing that you are studying The surroundings- everything else 2

 Quantity of energy needed to raise 1 gram of a substance 1° C; unit is J/g°C; symbol is “c”  Every pure substance has a unique chemical composition, and therefore a unique specific heat.  Substances with a low specific heat make good thermal conductors.  Substances with a high specific heat make good thermal insulators. 3

INSULATORS  High specific heat CONDUCTORS  Low specific heat 4

 A physical property because it can be observed without changing the chemical composition of the substance  An intensive property because it is independent of sample size.  Because it is an intensive property, it can be used to identify an unknown substance. 5

TO INCREASE THE TEMPERATURE OF 1 GRAM OF WATER BY 1 °C, THE WATER MUST ABSORB 4.18 J OF ENERGY 6

TO INCREASE THE TEMPERATURE OF 1 GRAM OF ICE BY 1 °C, THE ICE MUST ABSORB 2.03 J OF ENERGY 7

TO INCREASE THE TEMPERATURE OF 1 GRAM OF STEAM BY 1 °C, THE STEAM MUST ABSORB 2.01 J OF ENERGY 8

 FORMULA: q= m x c x ΔT  q= heat (J)  c = specific heat (J/g°C)  m = mass (g)  ΔT = change in temp., T f - T i (°C)  Use this equation when ONLY the temp changes (on the diagonal lines), not the phase 9

 Take the absolute value of q.  Describe whether or not that energy is being absorbed by the system (endothermic) or released to the surroundings (exothermic).  When you get to AP Chem, you will learn that negative and positive values can be assigned to q to indicate endothermic(+) or exothermic (-). 10

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Calculate the amount of heat, in Joules, needed to warm 250 g of water from 25°C to 95°C. 12

How much heat is lost when 50.0 grams of solid Al is cooled from 130°C to 62°C? The specific heat of Al is J/g°C 13

1 calorie (cal) = 4.18 Joules 1 kilocalorie = 1 Calorie = 1000 calories 14

Use dimensional analysis to convert 550 Joules into calories. 15

 550 Joules 1 calorie____ = 132 Joules 4.18 Joules 16

 A granola bar has 126 Calories. Use dimensional analysis to convert this into a) calories and b) Joules 17

 Change in internal energy of a substance  Amount of heat absorbed or released during a phase change is ΔH 18

 heat (or enthalpy) of fusion (ΔH f )  also called “latent energy of fusion”  amount of energy needed to melt 1 gram of a substance at its melting point (solid  liquid)  Δ H f copper = 205 J/g  Δ H f water = 334 J/g  Formula: q = m ΔH f  q= heat (J)  ΔH f = heat of fusion (J/g)  m = mass (g) 19

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 Calculate the amount of heat, in Joules, needed to melt 70.0g of copper at its melting point. 21

 heat (or enthalpy) of vaporization (ΔH v )  also called “latent heat of vaporization”  the amount of energy needed to vaporize 1 gram of a substance at its boiling point; liquid  gas  ΔH v water = 2260 J/g  Formula: q = m ΔH v  q= heat (J)  ΔH v = heat of vaporization (J/g)  m = mass (g) 22

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 Calculate the heat required, in Joules, to change 250g of water at 100°C to steam at 100°C. 24

Calculate the amount of heat needed to change 20g of ice at -10.0°C to water at 80.0°C. 25

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 An instrument used to measure the amount of heat transferred during physical or chemical changes. 29

 Can be used to determine the identity of a sample based on temperature changes and mass of sample. Unknown metal block gas.html Mass of block: 226g Initial Temp: 100°C Mass of water: 60g Initial Temp: 30°C Final Temp: 50°C 30

Calculate the specific heat of the unknown metal. Unknown metal block gas.html Mass of block: 226g Initial Temp: 100°C Mass of water: 60g Initial Temp: 30°C Final Temp: 50°C 31

The heat (Q) lost by the block is gained by water -Q block = Q water C water = 4.18 J/g°C (226g)(C)(50°C-100°C)= (60g)(4.18 J/g°C)(50°C-30°C) C = J/g°C 32

For our unknown metal C = J/g°C What is its identity? ml 33

 A 50 gram piece of metal at 175 o C is dropped into 100 g of water at 25 o C. The final temperature of the system is 52 o C. What is the specific heat of the unknown metal? (Draw a diagram FIRST.) 34

 t/en/periodical/simulations.html 35