1. Energy A Give and Take

2. 10.1 The Nature of Energy Energy: the ability to do work or produce heat Potential energy (store energy): energy due to position or composition

3. Kinetic energy (motion energy): energy due to motion of the object and depends on the mass of the object and its velocity KE = ½ (mv 2 ) Law of conservation of energy: that energy can be converted from one from to another but can be neither created or destroyed. Energy of the universe is constant

4. The nature of energy Work: force acting over a distance w = F x d State function: property of the system that changes independently of its pathway

5. Temperature and Heat Temperature: is a measure of the random motions of the components of a substance E.g H 2 O molecules move rapidly in hot water than in cold water Heat: a flow of energy due to a temperature difference T final = average temp from mixing (hot & cold temp)

6. Exothermic and Endothermic Process System – everything we focus on in experiment Surroundings – everything other the system exothermic (energy flows out of system to surrounding (via heat) endothermic ( energy flows into system from surrounding (via heat)

7. Examples Identify whether these process are exothermic or endothermic Your hand gets cold when you touch ice The ice melts when you touch it Propane is burning in a propane torch Two chemicals mixing in a beaker give off heat

8. Thermodynamics Is the study of energy. First law of thermodynamics: the energy of the universe is constant Internal energy – energy of the system ∆E = q + w ∆ => change in the function q => represents heat w => represents work

9. 10.5 Measuring Energy changes calorie: the amount of energy (heat) required to raise the temperature of one gram of water by 1 o C 1Calorie = 1000 calories Joule (J) – SI unit 1 calories = 4.184 joules

10. Converting Calories to Joules Express 60.1 cal of energy in units of Joules How many calories of energy corresponds to 28.4 J? 60.1 cal4.184 J= 251 J 1 cal 28.4 J1 cal= 6.79 cal 4.184 J

11. Calculating Internal Energy Calculate ΔE for q = 34 J, w = -22 J ΔE = q + w ΔE = 34 J + (-22 J) = 12 J Is this exothermic or endothermic? ΔE > 0, therefore it is endothermic

12. Specific heat The amount of energy required to change the temperature of one gram of a substance by 1 o C Denoted as s Heat required = specific heat x mass x change in temp Q = s x m x ∆T

13. Calculating Energy Requirements Determine the amount of energy (heat) in joules required to raise the temperature of 7.40 g water from 29.0 o C to 46.0 o C Energy required or Q = s x m x ΔT s water = 4.184 J/g o C Q = 4.184 J x 7.40 g x 17°C g °C = 526 J

14. A 5.63 g sample of solid gold is heated from 21 o C to 32 o C. How much energy in Joules and calories is required? Q= s x m x ΔT s gold = 0.13 J/g o C Q = 0.13 J x 5.63 g x 11°C g °C = 8.1 J

15. A 55.0 g aluminum block initially at 27.5°C absorbs 725 J of heat. What is the final temperature? Q= s x m x ΔT ΔT= T final – T initial s aluminum = 0.89 J/g o C 725 J = 0.89 J x 55.0 g x T f -27.5°C g °C 725 J = T f – 27.5 °C 48.95J/°C

16. 725 J = T f – 27.5 °C 48.95J/°C 14.8 °C = T f – 27.5 °C T f = 42.3 °C

17. A sample of gold requires 3.1 J of energy to change its temperature from 19 o C to 27 o C. What is the mass of this sample of gold? Q = s x m x ΔT s gold = 0.13 J/g o C

18. 3.1 J = 0.13 J x m x 8 °C g °C 3.1 J = m 8 °C x 0.13 J/g°C m = 2.98 g or 3.0 g