2.1 Energy There are many forms of energy: solar, electrical, nuclear, mechanical…. but only two types: Kinetic Energy = energy due to movement Bullet Water flowing over a dam Steam Potential energy = energy due to position a compressed spring chemical bonds in gasoline, coal, or food Gravitational potential energy (due to mass and height) The total energy of an object (system) is the sum of its Ek and Ep Et = Ek + Ep The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.

All objects possess Thermal energy which is the potential and kinetic energies associated with the random motion of the atoms and molecules within an object that results in the system temperature. time Hot coffee Higher thermal energy Temperature is high Cold coffee Lower thermal energy Temperature is low The Change in temperature is due to a transfer of thermal energy from the coffee (system) to its surroundings (room). The transfer of thermal energy is called heat and symbolized q. Heat lost by the coffee = -q Heat gained by the room = +q Heat = energy in transit, from one system to another due to a temperature difference.

Temperature = a quantitative description of hotness or coldness Heat can be transferred from one substance to another. Temperature = a quantitative description of hotness or coldness To use temperature as a measure of hotness or coldness, we need to construct a temperature scale. This is what we call a thermometer.

To convert from one T scale to another: 1.8, 32 and 273 are defined numbers and therefore are exact numbers

Example -- Solving a Temperature Problem A person with hypothermia has a body temperature of 34.8 °C. What Is that temperature in °F? TF = 1.8 (TC) + 32 ° TF = (1.8) (34.8 °C) + 32 ° exact 3 sf = 62.6 ° + 32 ° 1 decimal pl. exact = 94.6 °F 1 decimal pl. 5

the amount of heat required to raise the T of 1g of water by 1 ˚C At the beginning, scientist started to measure heat in terms of its ability to raise the T of water. the amount of heat required to raise the T of 1g of water by 1 ˚C calorie In 1948, scientists decided that since heat (like work) is transferred energy, the SI unit of heat (the joule) should be the one to use for energy. In honor of 19th century English physicist Prescott Joule Symbol is capital J Pronounced “jewel” Energy Units joule The calorie is now defined to be 4.184 J, with no reference to the heating of water. 1 cal = 4.184 J (exactly) The “calorie” used in nutrition, sometimes called the Calorie (Cal), is really a kilocalorie. 1 Cal = 1 kcal = 1000 cal.

Practice 2.1 1. When 1.0 g of octane fuel burns in an automobile engine, 48 000 J are released. Convert this quantity of energy to the following units: calories b. kilojoules 2. In a type of cancer treatment called thermotherapy, temperatures as high as 113 ˚F are used to destroy cancer cells. What is that temperature in degrees Celsius? 3. A dermatologist may use cryogenic liquid nitrogen at –196 ˚C to remove skin lesions and some skin cancers. What is the temperature of the liquid nitrogen in K? 7

Practice 4. State the temperature, including the estimated digit, on each of the following Celsius thermometers: Chapter 2, Unnumbered Figure 1, Page 74

= Tf - Ti The amount of heat transferred, depends on 3 factors: The amount of substance: 10 g 100g 1000g It takes twice the amount of heat to boil 2 cups of water than 1 cup It take more heat to raise the T by 100 degrees than by 10 degrees The T change of the substance: ∆T = 0.001 ˚C ∆T = 1000 ˚C ∆T = 1000000 ˚C = Tf - Ti The specific heat : Water Gold Steel = nature of the substance Ability of a specific material to incorporate (absorb)heat Water 4.184 J Aluminum 0.897 J

Chapter 2, Table 2.8

Practice---using the heat equation A hot-water bottle contains 750 g of water at 65 °C. If the water cools to body temperature (37 °C), how many calories of heat could be transferred to sore muscles? STEP 1 Given: Need: 750 g of water ? heat transferred cools from 65 °C to 37 °C Conversion factor or equation STEP 2 plan: Heat = mass x Δ T x SH STEP 3 execute: the temperature change Δ T: 65 °C – 37 °C = 28 °C 750 g x 28 °C x 1.00 cal = 21 000 cal g °C

Example---using the heat equation What is the specific heat of a metal if 24.8 g absorbs 65.7 cal of energy and the temperature rises from 20.2 ° C to 24.5 ° C? STEP 1 Given: Want: mass 24.8 g, ? SH metal heat 65.7 cal, Ti 20.2 ° C Tf 24.5 ° C Conversion factor or equation STEP 2 Plan: Heat = mass x Δ T x SH STEP 3 execute: ΔT = 24.5 ° C – 20.2 ° C = 4.3 ° C 65.7 cal = 0.62 cal/g ° C (24.8 g)(4.3 ° C) 12

Food = Energy Potential Energy Chapter 2, Unnumbered Figure, Page 76 The FDA recommends 30% of total intake from fat calories. For a female adult the level is around 2,000 calories per day, with 600 fat calories. For a male adult the level is around 2,500 calories per day, with 750 fat calories.

Nutritional calorie (Cal) = 1 kcal = 1000 cal 2000 Cal = 2000 kcal = 2,000,000 calories 2 million cal Eating 14 crackers provides 120 Cal. 4 g fat x 9 Cal/g = 36 Cal 19 g carbs x 4Cal/g = 76 Cal 2 g protein x 4 Cal/g = 8 Cal 120 Cal 120 Cal x 1000 cal x 4.184 J = 502,080 J 1 Cal 1 cal 500 kJ % fat = 35 x 100 = 29% 120 14

Practice 5. What is the specific heat of lead if 13.6 cal are needed to raise the temperature of 35.6 g of lead by 12.5 ºC? 6. How many kilojoules are needed to raise the temperature of 325 g of water from 15.0 °C to 77.0 °C? 1) 20.2 kJ 2) 84.3 kJ 3) 105 kJ 7. Ethanol has a specific heat of 2.46 J/g °C. When 655 J are added to a sample of ethanol, its temperature rises from 18.2 ˚C to 32.8 ˚C. What is the mass in grams of the ethanol sample? 15

Practice 8. At a fast-food restaurant, a hamburger contains 37 g of carbohydrate, 19 g of fat, and 24 g of protein. What is the energy content for each food type and the total energy content, in kcal? Round off the kilocalories for each food type to the tens place. 9. Use table 2.12, to determine the number of hours of running needed to burn off the calories in this meal.

2.5 Classification of Matter Figure 02-T07 Title: Classification of Matter Caption: 02_T07.JPG 17

Three States of Water Solid Low E state No movement Rigid structure 2.6 States and Properties of Matter Three States of Water Physical change Physical change Solid Low E state No movement Rigid structure Gas High E Lots of movement Particles are free from one another Figure 02-CI3B Title: States of Matter Caption: Answer the following questions for the water samples A and B shown in the diagrams: a. Which sample has its own shape? b. When each sample is transferred to another container, what happens to its volume? c. Match the diagrams (1, 2, or 3) that represent the water particles with sample A and B. Give a reason for your choice. Liquid Intermediate E More movement of particles Physical change  the identity and composition of the substance do not change. 18

2.7 Changes of State When energy is absorbed by a solid or liquid, the T of the sample does not necessarily rise. Instead, the sample may change from one state to another. The amount of heat per unit mass that must be transferred for a sample to completely undergo a phase change is called heat of transformation, ΔH. q = m ΔH

Melting = change from the solid state to liquid state. Heat is required to free particles from their rigid structure. The heat of fusion= ΔHf For water: 334 J or 80. cal 1 g of water is the amount of heat needed to melt 1 gram of a solid is the amount of heat released when 1 gram of liquid freezes

vaporizing = change from the liquid state to vapor (gas) state. Heat is required to free particles from one another. The heat of vaporization = ΔHv For water: = 2260 J or 540 cal 1 g of water absorbed to vaporize 1 g of a liquid to gas at the boiling point released when 1 g of a gas condenses to liquid at the boiling point Boiling Point of Water = 100 °C

illustrates the changes of state as a gas is cooled Figure 02-13 Title: Heating Curve Caption: (a) A heating curve diagrams the temperature increases and changes in state as heat is added. (b) A cooling curve for water. A cooling curve illustrates the changes of state as a gas is cooled uses sloped lines to indicate a decrease in temperature uses plateaus (horizontal lines) to indicate a change of state A heating curve illustrates the changes of state as a solid is heated uses sloped lines to show an increase in temperature uses plateaus (horizontal lines) to indicate a change of state 02_13.JPG 22

To calculate the heat involved in a plateau  q = m ΔH To calculate the heat involved in a slope  q = m x ΔT x SH ΔH v = heat of vaporization =540 cal/g 100 ˚C ΔH f = heat of fusion = 80. cal/g 0 ˚ C Heat added  To calculate the heat involved in a plateau  q = m ΔH

Practice Using the graph, determine the following: 11. A plateau (horizontal line) on a heating curve represents 1) a temperature change 2) a constant temperature 3) a change of state 12. How many plateaus are there on the graph? 13. A sloped line on a heating curve represents 14. How many sloped lines are there on the graph? Figure 02-13-15UN Title: Heating Curve Problem Caption: The following is a heating curve for chloroform, a solvent for fats, oils, and waxes. 15. The physical state of the substance present in the sloped lines. 16. The physical change taking place in the plateaus. 02_13-15UN.JPG 24

Practice 17. Using the graph, determine the following: Assign the corresponding beaker number to a letter on the graph Figure 02-13-16UN Title: Heating Curve Problem Caption: Associate the diagrams shown with a segment on the heating curve for water. 02_13-16UN.JPG 25

18. Practice (HW problem #51 a) Using the values for the heat of fusion, specific heat of water, or heat of vaporization, calculate the amount of heat energy in each of the following: a. calories needed to warm 20.0 g of water at 15 ˚C to 72 ˚C