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Q = MCΔT – Specific Heat & CALORIMETRY Burnin’ Up
20

Q = MCΔT – Specific Heat & CALORIMETRY

Dec 30, 2015

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Steven Edwards

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?. - PowerPoint PPT Presentation
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Page 1: Q = MCΔT – Specific Heat & CALORIMETRY

Q = MCΔT – Specific Heat & CALORIMETRY

Burnin’ Up

Page 2: Q = MCΔT – Specific Heat & CALORIMETRY

What is heat?Thermal energy (kinetic) produced by the

movement of molecules

Page 3: Q = MCΔT – Specific Heat & CALORIMETRY

Why might we want to measure heat?

Page 4: Q = MCΔT – Specific Heat & CALORIMETRY

We’re going camping…I can only take 1L of gas.

Should I takePROPANE GAS?or BUTANE GAS?

How might I decide?

Page 5: Q = MCΔT – Specific Heat & CALORIMETRY

How about another example…

Page 6: Q = MCΔT – Specific Heat & CALORIMETRY

How many calories are in our food?

Page 7: Q = MCΔT – Specific Heat & CALORIMETRY

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

Page 8: Q = MCΔT – Specific Heat & CALORIMETRY

How do we determine the caloric content of food?

BURN IT!!!

Nowadays they use more sophisticated methods to determine the componentsProteins 4 cal/gCarbohydrates 4 cal/gFats 9 cal/g

Page 9: Q = MCΔT – Specific Heat & CALORIMETRY

It’s Experiment Time!

VS

Page 10: Q = MCΔT – Specific Heat & CALORIMETRY

Comparing itCHEETOS

550cal for 95 grams

= 5.78cal/gram

x 4.184KJ/cal

= 24.18 KJ/gram

CHIPS

390cal for 75 grams

= 5.2cal/gram

x 4.184KJ/cal

=21.76kJ/gram

Page 11: Q = MCΔT – Specific Heat & CALORIMETRY

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

Page 12: Q = MCΔT – Specific Heat & CALORIMETRY

Examples of Calorimeters

Page 13: Q = MCΔT – Specific Heat & CALORIMETRY

Bomb CalorimeterOften used for combustion reactions

(not necessarily for ‘bombs’!)

Page 14: Q = MCΔT – Specific Heat & CALORIMETRY

Calorimetry Questions

Page 15: Q = MCΔT – Specific Heat & CALORIMETRY

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.

Page 16: Q = MCΔT – Specific Heat & CALORIMETRY

Steps we followedSix Steps of Preparation

1. What do we need to find?

2. What numbers do we have?

3. What ‘hidden numbers’ do we have?

4. What equation(s) can we use?

5. Do we need to rearrange the equation?

6. 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?

Page 17: Q = MCΔT – Specific Heat & CALORIMETRY

Question 2: On your ownOn 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.

Page 18: Q = MCΔT – Specific Heat & CALORIMETRY

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?

Page 19: Q = MCΔT – Specific Heat & CALORIMETRY
Page 20: Q = MCΔT – Specific Heat & CALORIMETRY

HomeworkFinish 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