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

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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

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INSULATORS High specific heat CONDUCTORS Low specific heat 4

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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

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

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

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

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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

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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

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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 0.897 J/g°C 13

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

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Use dimensional analysis to convert 550 Joules into calories. 15

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550 Joules 1 calorie____ = 132 Joules 4.18 Joules 16

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

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

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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

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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

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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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http://www.dnatube.com/video/11327/Principles-Of-Thermal-Equilibrium 28

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

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Can be used to determine the identity of a sample based on temperature changes and mass of sample. Unknown metal block http://durangotexas.blogspot.com/2010/06/crowley-texas-school-bunsen-burner- gas.html Mass of block: 226g Initial Temp: 100°C Mass of water: 60g Initial Temp: 30°C Final Temp: 50°C 30

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Calculate the specific heat of the unknown metal. Unknown metal block http://durangotexas.blogspot.com/2010/06/crowley-texas-school-bunsen-burner- gas.html Mass of block: 226g Initial Temp: 100°C Mass of water: 60g Initial Temp: 30°C Final Temp: 50°C 31

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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 = 0.444 J/g°C 32

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For our unknown metal C = 0.444 J/g°C What is its identity? http://www.webassign.net/sample/ncsugenchem202labv1/lab_4/manual.ht ml 33

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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

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https://www.teachchemistry.org/content/aac t/en/periodical/simulations.html 35

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