1. PRETEST: Try your Best ! Your mid-unit quiz will look very similar!

2. What is the difference between heat and temperature heat energy Heat energy moves from greater to lesser Q=cmT Temperature A measure of kinetic energy F, K, C

3. Does the temperature change during a reaction? HCl (aq) + NaOH (aq)  NaCl(aq) + H2O (l) Temperature of HCl = Temperature of NaOH = Temperature of NaCl(aq) + H2O (l)

4. Does a hot cup of water have more or less heat than a bucket of warm water?

5. Misconceptions Which has a higher temperature? 100.0 g of ethanol at 25C or 10.0 g of ethanol at 30.0C? Which can transfer more heat as it cools by 10C? 10.0 g of ethanol at 30C! 100.0 g of ethanol

6. Units and Variables Units to express energy calorieJouleCalorieKilocalorie Variables to Come! Q= heat C=specific heat M= mass T=temperature Hf=Heat of fusion Hc=Heat of combustion S= entropy G=gibb’s free energy

7. Specific heat Definition: the amount of heat required to raise the temperature of 1 gram of a substance by one degree Celsius. Water (l) 4.184 J/gC Aluminum 0.897 J/gC Gold (s) 0.129 J/gC Water has a very high specific heat. Although that means that it takes a lot of energy to raise the temperature of water, it also releases a lot of energy when cooling. What does this have to do with sweating?

8. Specific Heat Calculations Q= cmT Calculate how much heat is absorbed by a pond on a sunny day when the temperature changes 22C and the mass of water is 2.25 x 10 7 g Q= 4.184 J/gC x 2.25 x 10 7 g x 22C = 2.1 x 10 9 Joules

9. Specific heat lab Heat Flow-heat flows from warmer objects to cooler objects (much like diffusion moves molecules from high concentration to low concentration). Transferring of heat is accompanied by a change in temperature. (Final minus initial) ( T) (so T can be positive or negative) Specific heat capacity-(c) is the amount of heat required to raise the temperature of 1 gram of a substance, 1 degree Celsius. C of water = 4.184 J/gC Q= mcT Q= positive for endothermic reactions that ABSORB heat. Q= negative for exothermic reactions that RELEASE heat.

10. Q=cmT example A 25.0 g of sample of water is heated from 27.0 C to 53.0C. Calculate the amount of heat absorbed by the water. Q=cmT Q= unknown c-= 4.184 J/gC M= 25.0 g T= Final – initial (53.0 – 27.0) = 26 C Q= (25.0C) (4.184 J/gC)(26) Q=2720 J or 2.720 kJ (1000 J in a kJ)

11. Calorimeter A calorimeter is an insulated device that allows for accurate measure of heat transfer.

12. Calorimetry Exothermic reactions- cause the temperature of the calorimeter to increase (the reaction gives off energy to the thermometer). Endothermic reactions- cause the temperature of the calorimeter to decrease (the reaction absorbs energy from the thermometer). Polystyrene Cup Calorimeters 1.The sample releases heat into the water and the water temperature increases. 2.The sample absorbs energy from the water and the water temperature decreases. -qmetal = q water qmetal = -q water Q=m metal C (T) Q= m water C (T)

13. Endothermic reactions Absorb energy Reactant + Reactant + ENERGY  Products The temperature would decrease in a calorimeter. If you felt them with your hand, your hand would feel cold. Examples of an endothermic reactions: CO2 + H2O  C6H12O6 + O2 Citric acid + baking soda Examples of an endothermic process: Melting Boiling Evaporating cooking

14. Exothermic reactions Release energy Reactants + Reactants  Products + ENERGY The temperature in a calorimeter would increase. If you felt them with your hand, your hand would feel warm. Examples of exothermic reactions: Fe + O2 (handwarmers), fireworks, acid + water Examples of exothermic processes: Condensation, freezing,

15. Endothermic and Exothermic Lab Part I Citric acid + baking soda  Part II Magnesium + hydrochloric acid  Perform each reaction in a Styrofoam cup while monitoring the temperature. Conclusions of Part I? Conclusions of Part II? Drawings of Endothermic and Exothermic reactions?

16. Changes of state Changes of state song! Melting (s  l) Freezing (l  s) Boiling, evaporating (l  g) Condensation (g  l) ??What do you notice about the temperature change during the phase changes? Temperature Time

17. Melting and freezing Melting- Solid changes to liquid Endothermic process Absorbs energy No temperature change during melting Freezing- Liquid changes to a solid Exothermic process Releases energy No temperature change during freezing

18. Boiling, evaporating Boiling- Liquid changes to a gas all throughout the liquid Endothermic process No temperature change during boiling Evaporating Liquid changes to a gas at the surface of the liquid Endothermic process No temperature change during evaporation Vaporization includes boiling and evaporation

19. condensation Gas changes to a liquid Exothermic process No temperature change during condensation

20. Heat of fusion The heat required to melt one mole of a solid substance. Water= 6.01 kJ/mol Ethanol = 4.94 kJ/mol Methanol= 3.22 kJ/mol Ammonia = 5.66 kJ/mol Calculating total heat = Hf x mole

21. Heat of combustion The energy released when one mole of a substance burns. Hcomb Sucrose = -5644 kJ/mol Octane = -5471 kJ/mol Glucose = -2808 kJ/mol Carbon (graphite) = -394 kJ/mol

22. Heat of fusion of ice lab Purpose: Determine the heat of fusion of ice. Calculate percentage error Background: Hf= heat energy required to melt a mole of a substance. kJ/mol The substance absorbs energy from the surroundings.

23. Heat of combustion of paraffin wax Purpose: Calculate the molar heat of combustion of paraffin wax. Burning a candle releases energy. Calculate the energy released per mole. Energy released = negative!

24. review Temperature Heat Specific heat Units Endothermic Exothermic Changes of state (melting, freezing, boiling, condensation)

25. Heating Curves review

26. Phase diagram of water

27. Phase diagram of carbon dioxide

28. Ice Glaciers activity Time lapse video of glacier activity Glacier Calving video Glaciers cover about 10% of the Earth’s surface and contain 75% of the freshwater on Earth. Appears blue when dense. Snow in one area for at least a year turns into ice. When snowfall and evaporation are in equilibrium, the glacier is stationary, but when the equilibrium is disrupted, the glacier can move. TITANIC

29. Generating body heat How do we regulate our body temperature? Thermoregulation Shivering! Adjusting the size of the arterioles (small arteries) Insulation (keeps heat in-does not generate heat Fat (adipose tissue) Hair Clothing

30. hypothermia Normal body temperature is 98.6F, hypothermia occurs when the body temperature reaches below 95F. The body loses heat faster than it can generate it. Symptoms: shivering, dizziness, hunger, nausea, faster breathing, confusion, fatigue. Death by hypothermia

31. nutrition Food Calories are 1 kcal in chemistry

32. calorimetry You can burn calories with a calorimeter! Or with a calculator

33. Calorimetry lab Video explanation Calculation video

34. Review entire unit