1. Heat Calculations Agenda Review specific heat Look at lab sections M&M and Results Learn about heating curve

2. What is specific heat? The energy to raise one gram of a substance one degree Celsius.

3. What has a higher specific heat: the ocean or the beach? The OCEAN – it takes a lot of energy to warm it up!

4. What has a higher specific heat: aluminum foil or the glass pan? The GLASS PAN – holds the heat for a much longer period of time

5. Define energy. The ability to do work!

6. When a reaction releases energy in the form of heat, it is said to be… EXOTHERMIC This means it’s negative!

7. When a reaction absorbs energy in the form of heat, it is said to be… ENDOTHERMIC This means it’s positive.

8. What is the formula for finding heat? q = m*s*  T

9. What are the different units used to measure energy? Joule and Calorie Related? 1 cal = 4.184 J

10. What happens if there is a phase change????? This is where the heating curve comes in…

11. Heat Calculations Date:

12. E N E R G Y TEMPERATURETEMPERATURE

13. TEMPERATURETEMPERATURE SOLID LIQUID GAS FREEZE MELT CONDENSE VAPORIZE 0OC0OC 100 O C

14. E N E R G Y TEMPERATURETEMPERATURE SOLID LIQUID GAS FREEZE MELT CONDENSE VAPORIZE 0OC0OC 100 O C ENDOTHERMIC  EXOTHERMIC 

15. E N E R G Y TEMPERATURETEMPERATURE SOLID LIQUID GAS FREEZE MELT CONDENSE VAPORIZE 0OC0OC 100 O C ENDOTHERMIC  EXOTHERMIC  q = m*s*  T s ice = 0.5cal/g o C q = m*s*  T s liquid = 1cal/g o C q = m*s*  T S gas = 0.4cal/g o C q = m*  H fusion  H fusion = 80 cal/g q = m*  H vap  H vap = 540cal/g

16. Solving Problems  Read question and determine number of “lines” involved.  Calculate the amount of heat required for each “line”  Determine the sum of all “lines” used.  IF ENERGY IS RELEASED, you MUST make  H fus and  H vap negative!!!!

17. Calculate the amount of heat necessary to raise 20g H 2 O from -10 o C to 45 o C  Determine lines: -10 o C = solid, 45 o C = liquid so 3 lines used.  Solid: q = m*s ice *  T q = (20g)(0.5cal/g o C)(0 o C – (-10 o C)) =  Melt: q = m*  H fus q = (20g)(80cal/g) =  Liquid: q = m*s liquid *  T q = (20g)(1cal/g o C)(45 o C – 0 o C) = TOTAL AMOUNT OF HEAT =

18. Calculate the amount of heat released when 30g H 2 O are cooled from 115 o C to 65 o C  Determine lines: 65 o C = liquid, 115 o C = gas so 3 lines used.  Gas: q = m*s gas *  T q = (30g)(0.4cal/g o C)(100 o C – 115 o C) =  Condensed: q = m*  H fus q = (30g)(-540cal/g) =  Liquid: q = m*s liquid *  T q = (30g)(1cal/g o C)(65 o C – 100 o C) = TOTAL AMOUNT OF RELEASED HEAT =

19. Suppose the heat needed to melt 38.0g of ice is absorbed from water contained in a glass. If this water has a mass of 210. g and an initial temperature of 21.0 o C, what is the final temperature of the water? Remember the ice melts and then warms up as a liquid.

20. Check homework

21. Lab  M&M: –how was calorimeter constructed –when were temperature and mass readings made – not what but when –don’t list supplies –does it make sense – can you picture the lab like a movie  Results: Charts –Data used for calculations – Table 1 –Temperature over time GRAPH!!!!! Graph 1 –Show a sample calculation (q = ms  T)

22. Metal sample Mass of metal Volume of water Mass of water T I metal (Boiling water) T I water/calorimeter T f system  T metal  T water/calorimeter s water q water q metal s metal

23. Homework  Heat Calculations worksheet  Make corrections to MM and Results –Put data into spreadsheet from wiki  Work on conclusions