Fired Up! Energy Changes

1. Fired Up!Energy Changes • Describe some of the changes you observed during today’s demos • What common features did you notice? • Is energy associated with these reactions? Explain.

2. Energy is a measure of how much you can move or change something. • Give examples of how you use the word energy in your daily life. • In your experience, how is energy related to change and motion? • How would you define energy? • Is energy a substance?

3. What reactions are sources of heat? • Changes in __________________________________. • Reactions of elements and compounds with _________ (or oxygen containing compounds like KClO3 typically produce products that are ____________________ the reactants. • Fire, or combustion, is a type of reaction that __________ _________________ in the form of flames, heat, and light. • Energy is a measure of the_________involved in moving or changing something.

4. Forms of Energy ____________________ ________ ______ _____ ________________ ________ ________ ______ ______ _______

5. Classify the Energy into Potential Kinetic

6. How a monkey uses energy conversion to leap from tree to tree

7. Power plant furnace (thermal energy) Generator turbine (mechanical energy) Electrical lines (electrical energy) Energy conversion steps in hair dryer operation Fossil fuel (potential energy) Hair dryer (mechanical, thermal, sound energy)

8. Not So Hot: Exothermic and Endothermic Chem Catalyst • Name at least 3 ways you can warm yourself on a cold day. • What do you think is the source of the heat in a hand warmer? • Why does rubbing your hands together make you warmer? • A toe warmer will work for up to 6 hours if it is in your shoe, but it won’t last as long out of your shoe. Explain.

9. Not So HotObserve energy changes that occur during a chemical reaction • Follow these instructions • Measure initial temperature • Conduct reaction • Measure highest/lowest temperature reached • Calculate change in temperature = T = Tfinal - Tinitial • Station 1. HCl(aq) + NaHCO3(aq) [mix 50:50] • Station 2. CaCl2 (s) + H2O(l) [start with ½ test tube water, add scoop of CaCl2(s)] • Station 3. NH4Cl(s) + H2O(l)[start with ½ test tube water, add scoop of CaCl2(s)]

10. Not So Hot • What did you observe at the three stations? • What did the thermometer tell you in each case?

11. Check-In You have water at 25C. You dissolve ammonium acetate, NH4C2H3O2, in the water and find that the temperature decreases to 15 C. • Is heat transferring from the solution to the surroundings, or from the surroundings to the solution? • Is the process exothermic or endothermic? Unit V • Investigation I

12. ChemCatalyst • Imagine you are sitting near a campfire. You feel warm. Explain how you think the warmth gets from the burning wood to your body. • The fire goes out. The next morning, you find ashes that are the same temperature as the air. Explain why the ashes are no longer hot. • Why do you think the campfire eventually burns out? Unit V • Investigation I

13. Wrap-Up • Heat is a ______________________________ ___________________________________(not a noun!) • The direction of energy transfer is ____________ at ________________ to an object at ______ temperature. • There is no such thing as “____________.” Cold is the experience of ___________________________ from your body. • _____________ is transferred when _________________ molecules ______________________ moving molecules. • Thermal equilibrium: ____________________________ _______________________________________________ _______________________________________________

14. Check-In • Imagine a thermometer is placed in a beaker of water and the temperature is noted. An ice cube is dropped into the water and after ten minutes the temperature is noted again. • What will you observe? • What is the direction of heat transfer?

15. Heat vs. Temperature Which will melt more of a snowman, a cup of coffee at 90oC, or a bathtub of water at 20oC? Explain.

16. Three Main Ways Heat is Transferred Conduction __________________________________________ _____________________________________________________ Convection ___________________________________________ _____________________________________________________ Radiation: ___________________________________________ _____________________________________________________

17. System vs. Surroundings Surroundings = thermometer, flask, and the rest of the universe. System System: _______________________________________________ _______________________________________________________ Surroundings: __________________________________________ _______________________________________________________

18. Exothermic and Endothermic • Heat: _____________________________________ ____________________________________________ • Exothermic process: ________________________ __________________________________________ • Endothermic process: _______________________ ____________________________________________

19. FRHs heat MREs quickly, without fire

20. GI’s MRE

21. MREs have changed over the years • 1980s MRE • BBQ Pork rib • Beef ravioli • Cheese & vegetable omelet • Chicken breast filet • Chicken fajita • Chicken with salsa • Hamburger patty • Beef stew • Chili with macaroni 1980s MRE • Pork Patty • Ham and chicken loaf • Beef slices in BBQ sauce • Beef and Mushroom • Beef stew • Frankfurters with beans • Turkey diced with gravy • Chicken a la King • Meatballs & BBQ sauce Some of the early MRE entrées were not very palatable, earning them the nicknames "Mr. E" (mystery),[3] "Meals Rejected by Everyone",[4] "Meals, Rarely Edible",[5] "Meals Rejected by the Enemy", "Meals Refusing to Excrete", and even "Meals Rejected by Ethiopians"[6] in reference to a country that was gripped by famine at the time. Some meals got their own nicknames. For example, the frankfurters, which came sealed in pouches of four, were referred to as "the four fingers of death."

22. FRH exothermic reaction: Mg + H2O  Mg(OH)2 + H2 + energy Vapors released by activated heater contain hydrogen, a flammable gas. Do not place an open flame in the vapor. WARNING: Government test: ignite MRE vapors with a match

23. Cargo fire during shipment of MREs in March 2001 FAA report: “Limiting Oxygen Concentration Required to Inert Jet Fuel Vapors Existing at Reduced Fuel Tank Pressures—Final Phase,” FAA Report DOT/FAA/AR-04/8, August 2004.

24. Endothermic reactions absorb energy from the surroundings NH4Cl(s) + H2O  NH4Cl(aq)

25. A water in a copper pot is placed on a burner. The pot soon becomes too hot to touch, but the water is only lukewarm. Why? 1 g Cu at 26°C Copper has a ___specific heat capacity – it only takes a little energy to heat it: +0.09 calories heat + 1.00 calories heat 1 g Cu at 25°C Water has a_____specific heat capacity – it takes a lot of energy to heat it: 1 g H2O at 26oC 1 g H2O at 25oC The specific heat capacity ____________________________________ ___________________________________________________________

26. The high specific heat of H2O protects firewalkers Unit V • Investigation I

27. Imagine that you heat water over a campfire. How can you tell that energy is transferred to the water? How could you measure the amount of energy transferred to the water? How could you measure the amount of energy one stick transfers to the water when it burns? Calorimetry

28. What units do we use to measure energy?What units measure the energy contained in these items? • Energy content is measured in units of calories or joules Unit V • Investigation I

29. Measuring Energy Changes • 1 calorie = amount of energy (heat) required to raise the temperature of 1 g water by 1°C • 1 calorie = 4.184 J (joules); J is SI unit • 1 food Calorie = 1000 calories = 1 kcal • How much energy (heat) in joules is required to raise the temperature of 7.40 g water from 29.0 °C to 46.0 °C? Unit V • Investigation I

30. q = m C T • q = thermal energy (heat) absorbed/released • m = mass that heats up • T = change in temperature, in °C • C= specific heat capacity= energy needed to raise 1.0 g of a substance by 1°C Cwater = 1.0 cal/g°C Caluminum = 0.2 cal/g°C • Which takes less energy to heat, water or Al? Unit V • Investigation I

31. heat gained or lost mass in grams change in temp, °C specific heat Calculations with Specific Heat Capacity(aka Specific Heat) = Q = (m) (T) (s) Conservation of Energy: heat gained = heat lost What is the final temp when 21.5 g iron at 100.0°C is dropped into an insulated container with 132 g water at 20.0°C? (The heat capacity of iron is 0.449 J/g°C) Unit V • Investigation I

32. Combustion of Cheetos: C24H50O25+ 24 O2 24 CO2 + 25 H2O + energy We will quantify the energy released as heat by measuring the increase in temperature of 100 mL of water Unit V • Investigation I

33. A bomb calorimeter measures the energy released in a reaction

34. Why do Florida citrus growers spray water on their trees to prevent frost damage? Why does hot apple pie filling burn your mouth, but the crust doesn’t? Unit V • Investigation I

35. 1 2 3 4 5 6 What happens when your body “burns” food? maintenance Total potential energy ruler growth body heat CO2 + 2H2O

36. Kaboom ! Explosions are exothermic! 4 C3H5N3O9 6N2 + 12CO2 + 10H2O + O2 + energy Many chemical explosives (e.g. ammonium nitrate, TNT, nitroglycerin) contain nitro groups (NO2) which decompose to give more stable products

37. Energy is stored in chemical bonds: the shuttle uses H2 as its fuel 2H2 + O2 2H2O + energy Ostrich egg:

38. 1 2 3 4 5 6 othermic reaction: products contain less stored (potential) energy than reactants Ex 2H2 + O2 difference in energy its as heat/light ex Total potential energy ruler 2H2O

39. 1 2 3 4 5 6 Combustion of hydrocarbons is exothermic because the products store less energy than the reactants CH4 + 2O2 Total potential energy ruler difference in energy expelled as heat+light CO2 + 2H2O

40. Combustion of methane is exothermic because Step 2 (bond formation) releases more energy than Step 1 (bond breaking) requires.

41. Combustion of fossil fuels for energy • What are fossil fuels and where did they come from? • Fossil fuels include coal, petroleum, natural gas • Probably from living matter dating back 500 million years • No detectable fossil fuel being produced now, so these are non-renewable resources • Combustion of coal and petroleum products produces air pollutants and heavy metal containing ash • CO2 contributes to global warming • NOx and SOx are air pollutants • Particulates from diesel may contribute to asthma and cancer • What are fossil fuels made of? • Fossil fuels are mostly hydrocarbons • What are the harmful effects of burning fossil fuels?