is the branch of science that studies the transformation of energy from one form to another. Thermochemistry specifically studies.

Transcription

1 is the branh of siene that studies the transforation of energy fro one for to another. Theroheistry speifially studies. I. Energy and Its Fors A. Energy Defined B. Two Fors of Energy Energy ( ) Energy due to or Energy ( ) The energy of easured as OR Fors of Energy Potential Kineti Energy: Heat, Nutrients, and Enthalpy Page 1

2 The Law of Conservation of Energy states that II. Quantifying Theral Energy A. Heat is ; it is a way of between objets and their surroundings. B. TEMPERATURE Measure. The heat the substane has absorbed, the ore otion it has, and therefore, the the teperature. When substanes lose energy, teperature. Relative teperatures are easured by, whereas the absolute teperatures are easured by. Teperature is an property. C. FOUR UNITS FOR MEASURING HEAT The Metri Syste unit for heat is the (al). One (1) al =. The (Cal) or nutritional Calorie is atually a. So, a 60-Cal apple ontains al. The SI unit for heat is the (J). 1 al = One kilojoule (kj) = Energy: Heat, Nutrients, and Enthalpy Page 2

3 Conversion Pratie: Solve the following probles using diensional analysis (bridges). Convert alories to Calories. How any alories are in 99 Calories? How any joules are in kilojoules? Convert 884 joules to kilojoules. Convert 195 alories to joules. How any alories are in 5.44 joules? Convert 555 alories to kilojoules. How any kiloalories are in 1099 joules? How any alories are in 55.4 kilojoules? Convert 40.1 Calories to kilojoules. D. SPECIFIC HEAT 1. Defined as the. 3. The speifi heat of water is eual to or. This value is onsidered a speifi heat. Energy: Heat, Nutrients, and Enthalpy Page 3

4 Speifi Heat Capaity Table Values are at 25 C and 1 at unless otherwise stated. Substane J/g o C Liuid water (0 C to 100 C) Lithiu 3.56 Ethanol (ethyl alohol) 2.44 Ie ( 10 C to 0 o C) 2.03 Stea (100 o C) 2.01 Vegetable oil 2.00 Berylliu (solid) Sodiu 1.23 Air (50 C) Magnesiu (solid) Aluinu Conrete (solid) Glass (typial) Granite (solid) Potassiu 0.75 Sulphur 0.73 Caliu (solid) Iron/Steel Nikel Zin 0.39 Copper Brass Strontiu (solid) Sand Silver (solid) Tin Bariu (solid) Merury Lead (solid) Gold (solid) Energy: Heat, Nutrients, and Enthalpy Page 4

5 III. Heat Absorbed and Released A. is a proedure used to easure theral energy in a heial reation. B. A is an insulated devie used for easuring the aount of heat or during a heial or physial proess C. EQUATION FOR CALCULATING HEAT 1. = Variable Representation Unit The absorbed or released The The of the substane The 2. Proble-Solving Strategy Write the. Draw a. Assign to the variables. Solve for the variable. Energy: Heat, Nutrients, and Enthalpy Page 5

6 3. Exaple How uh heat is needed to raise the teperature of 10.0 g of water fro 10.0 C to 15.0 C? = TI TF T I = Initial teperature T F = Final teperature = T F T I Speifi Heat Pratie 1. The teperature of a 5.00 x 10 3 gra blok of onrete sidewalk inreased by 6.00 C. Calulate the aount of heat the onrete absorbed. The speifi heat of onrete is J/g C. = TI TF 2. The teperature of a saple of iron with a ass of 10.0 gras has hanged fro 50.4 C to 25.0 C with the release of 114 J of heat. What is iron s speifi heat? [Note: Rearrange the euation to solve for speifi heat by isolating the variable.] = TI TF Energy: Heat, Nutrients, and Enthalpy Page 6

7 Fro Another Angle ating a balaned diet is fundaental to good health. Energy that keeps your brain and body E funtioning oes fro the foods you eat. Your digestive syste and the ells in your body break down and gradually oxidize food to release energy that your ells an use and store. Taking in ore energy than your body expends results in an inrease of stored fuel and, onseuently, an inrease in body ass. How an you alulate your energy expenditure and plan your alori intake to aintain your body weight within a speifi range? IV. Nutrients and Calorietry A. Energy is during etabolis. B. Different nutrients are used as. 1. are nutrients that are burned as fuel. 1 gra arbohydrate = 2. Building nutrients inlude. 1 gra fat = 1 gra protein = 3. The energy unit for easuring energy in foods is the. C. Reall: The speifi heat of is eual to. D. ENERGY CALCULATION WITH FOODS 1. = Variable Representation Unit The absorbed or released The The of the substane The 2. Food alorietry probles often ask for the, whih is expressed in ( ). Calulate the. The ass for the heat euation is the ass of the. Convert, using the neessary. Set alulated over the ass in gras of the to deterine energy ontent of the food saple. Energy: Heat, Nutrients, and Enthalpy Page 7

8 Pratie with Foods 1. A sall piee of bread heats 150 L of water fro 25 o C to 65 o C. How any Calories are stored in the bread? [The density of H2O is 1g/L.] TI TF 2. What is the energy ontent of a 1.28 g saple of oateal that raises the teperature of 2500 g of water within a alorieter fro 25.0 C to 27.2 C? Express energy ontent in Cal/g. TI TF Energy ontent: 3. How uh energy in Calories is produed when 37 gras of sugar heat 63 gras of water fro 44 C to 63 C? Express the energy ontent of the sugar in Cal/g. TI TF Energy: Heat, Nutrients, and Enthalpy Page 8

9 D. NUTRITION LABELS ON FOODS Nutrition Fats Serving Size 1 Pakage (39g) Servings Per Container 12 Aount Per Serving Calories 200 Calories fro Fat 90 % Daily Values* Total Fat 10g 15% Saturated Fat 1.5g 8% Trans Fat 2g Cholesterol 0g 0% Sodiu 410g 17% Total Carbohydrate 23g 8% Dietary Fiber 1g 5% Sugars 4g Protein 4g Vitain A 0% Vitain C 0% Caliu 2% Iron 6% Nutrition Fats Serving Size 1 bar (28g) Servings Per Container 10 Aount Per Serving Calories 110 Calories fro Fat 20 % Daily Values* Total Fat 2g 3% Saturated Fat 0.5g 3% Trans Fat 0g Polyunsaturated Fat 0.5g Monounsaturated Fat 0.5g Cholesterol 0g 0% Sodiu 80g 3% Potassiu 65g 2% Total Carbohydrate 22g 7% Dietary Fiber 1g 4% Sugars 10g Protein 2g Reall 1 g arbohydrate provides Cal of energy 1 g fat provides Cal of energy 1 g protein provides Cal of energy Aording to the nutrition label to the left, one serving ontains 10 gras of total fat. How any Calories of energy will be provided by the total fat in one serving? 10 g fat = One serving ontains 23 gras of arbohydrates. How uh energy an be provided by the total arbohydrates in one serving? 23 g arb = Calulate the heat energy that an be provided by the gras of protein in one serving. 4 g protein = The nutrition label to the left is opied fro a box of hoolate hunk granola bars. Respond to the following uestions using this label inforation. Calulate the energy, in Calories, provided by one hoolate hunk granola bar. [Use gras provided by fat, arbohydrate, and protein only.] What perentage of the alulated Calories is provided by fat? What perentage of the alulated Calories is provided by arbohydrates? What perentage of the alulated Calories is provided by protein? Energy: Heat, Nutrients, and Enthalpy Page 9

10 Food Calorietry Pratie Follow the step-by-step proess outlined in this notes paket. SHOW ALL WORK. Use 1.00 al/g C as the speifi heat of water. 1. When burned, a heese ball will raise the teperature of 200 L of water fro 30 C to 95 C. Calulate the food Calories of the heese ball. [Calulate the energy released and then onvert al to Cal.] 2. A bag of Cheetos ontains 170 food Calories. If burned in a alorieter with 50 L of water at an initial teperature of 25 C, what will the final teperature of the water be? 3. A Rie Krispies treat ontains 200 food Calories. When burned in a alorieter, it raises the teperature of water fro 25 C to 40 C. What is the ass of the water? Energy: Heat, Nutrients, and Enthalpy Page 10

11 V. Heat Transfer A. In a alorieter, heat flows fro. The flow of heat stops ; energy is eual to energy. B. In other words,. C. Exaple A 125-gra saple of water is plaed in a alorieter with an initial teperature of 25.6 C. A 50.0-gra saple of an unknown etal is heated to C and is plaed in the water. The final teperature of the water and the etal is 29.3 C. Write the heat euation. Draw the data table. = Plae values fro proble into table. water = etal = Calulate for water and the etal and add to table. For whih substane water or etal is there enough inforation to use the heat euation? Solve for the unknown. One for water is known, use heat euation to solve for speifi heat,, of the etal. Calulate heat absorbed for water: Calulate speifi heat of etal: Energy: Heat, Nutrients, and Enthalpy Page 11

12 Heat Transfer Pratie Follow the step-by-step proess outlined in this notes paket. SHOW ALL WORK. 1. A 77.5 gra saple of an unknown etal is heated to 62.5 C and plaed into a alorieter ontaining 93 gras of water at 23.3 C. If the final teperature of the solid saple and the water is 26.2 C, what is the speifi heat of the solid? 2. A 27.9 gra saple of an unknown etal is heated to 75 C and plaed into a alorieter ontaining 45 gras of water at 14 C. If the final teperature of the syste (the solid saple and the water) is 26.5 C, what is the speifi heat of the solid? 3. A 50.6 gra saple of iron etal is heated and put into 104 gras of 19.7 C water in a alorieter. If the final teperature of the iron saple and the water is 24.3 C, what was the teperature of the iron saple when it was plaed in the water? Energy: Heat, Nutrients, and Enthalpy Page 12