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Q = MCΔT – Specific Heat & CALORIMETRY

Q = MCΔT – Specific Heat & CALORIMETRY. Burnin ’ Up. What is heat?. Thermal energy (kinetic) produced by the movement of molecules. Why might we want to measure heat?. We’re going camping…. I can only take 1L of gas. Should I take PROPANE GAS? or BUTANE GAS? How might I decide?.

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Q = MCΔT – Specific Heat & CALORIMETRY

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  1. Q = MCΔT – Specific Heat & CALORIMETRY Burnin’ Up

  2. What is heat? • Thermal energy (kinetic) produced by the movement of molecules

  3. Why might we want to measure heat?

  4. We’re going camping… • I can only take 1L of gas. Should I take • PROPANE GAS? • or BUTANE GAS? • How might I decide?

  5. How about another example…

  6. How many calories are in our food?

  7. What are ‘calories’ in food? • How much ‘energy’ you will gain if you eat it • How much heat will be produced if we burn it

  8. How do we determine the caloric content of food? • BURN IT!!! • Nowadays they use more sophisticated methods to determine the components • Proteins 4 cal/g • Carbohydrates 4 cal/g • Fats 9 cal/g

  9. It’s Experiment Time! VS

  10. Comparing it CHEETOS CHIPS 390cal for 75 grams = 5.2cal/gram x 4.184KJ/cal =21.76kJ/gram • 550cal for 95 grams • = 5.78cal/gram • x 4.184KJ/cal • = 24.18 KJ/gram

  11. We’ve been talking about Q=MC(delta)T • What is Calorimetry? • the technological process of measuring energy changes in a chemical system • What is a Calorimeter? • A device used to measure the energy change of a chemical system • Used to insulate the reaction against energy/product loss

  12. Examples of Calorimeters

  13. Bomb Calorimeter • Often used for combustion reactions (not necessarily for ‘bombs’!)

  14. Calorimetry Questions

  15. Question 1: Together It takes 41.8J to heat a 0.01869kg chunk of gold from 10oC to 27oC. Calculate the specific heat capacity of gold.

  16. Steps we followed Six Steps of Preparation • What do we need to find? • What numbers do we have? • What ‘hidden numbers’ do we have? • What equation(s) can we use? • Do we need to rearrange the equation? • Do we need to convert any units? Four Steps of Action 7. Sub in the numbers 8. Do the math – WITH UNITS! -- WITH SIGNS! (+/-) 9. Round the answer to the appropriate significant digits 10. Check your answer: Does it make sense? Does it answer the question that was being asked?

  17. Question 2: On your own On a mountaineering expedition, a climber heats water from 0oC to 50oC. Calculate the mass of water that could be warmed by the addition of 8.00kJ of heat.

  18. Let’s take it one step further I took a 0.400kg block of Aluminum, and heated it on a hot plate to 212oC. I then transferred it to 0.800L of water at 23.0oC. The final temperature of the system was 41.35oC. What is the specific heat capacity of aluminum?

  19. Homework • Finish pre-lab for NEXT CLASS (Friday) • No pre-lab = no lab • Calorimetry worksheet is due on TUESDAY • Look over ‘cheat sheet’ – it may help you understand the worksheet

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