1. As you go through this lesson, you will be equipped with new knowledge of a heat measuring method that will help you get closer to planning a successful commercial hot or cold pack
Please go through this lesson sequentially in slideshow mode

2. At the end of this lesson, create a mind map that connects the concept learnt in THIS ppt

3. Types of Organic Reactions
Using Calorimetry to Study Energy Changes

4. Using Calorimetry to Study Energy Changes
A method of measuring the heat released or absorbed during a chemical or physical process
A calorimeter = a device used to measure the heat released or absorbed during a physical or chemical process
The term calorimeter comes from the word calorie, which was the original unit for heat transferred from one object to another.
A calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius
Not an SI unit
Therefore, no longer used by scientist.
H/w, still used by dieticians and nutritionists to express the energy content in food.
1 Calorie = 1000 calorie = 4184 J

5. 1 Calorie = 1000 calories = 4184 J

6. Using Calorimetry to Study Energy Changes
Ideally, a calorimeter is an isolated system
No matter or energy is exchanged with the surroundings
The water is one system; the reaction taking place in the water is the second system
The two systems are in thermal contact, but isolated from the surroundings
If the process is endothermic, thermal energy is transferred from the water to the reaction and the temperature of the water decreases
If the process is exothermic, thermal energy is transferred from the reaction to the water and the temperature of the water increases.

7. The Theoretical Basis of Calorimetry
Calorimetry is based on the 1st and 2nd laws of thermodynamics
Recall: 1st law is the law of conservation of energy & 2nd law is the law of thermal equilibrium
Q- Write what you know about the 1st and 2nd law of thermodynamics about?
The 1st law of thermodynamics ensures that any energy added to the system came from the surrounding and, likewise, any energy lost by the system went to the surroundings.
In relationship to calorimetry, the most useful statement of the second law of thermodynamics is: Thermal energy is spontaneously transferred from an object at a higher temperature to an object at a lower temperature until the two objects reach the same temperature

8. 1st and 2nd law of thermodynamics
1st law: energy is conserved; any energy added to the system came from surrounding and vice versa
2nd law:
Thermal energy is spontaneously transferred from an object at a higher temperature to an object at a lower temperature until the two objects reach the same temperature
The 1st law of thermodynamics ensures that any energy added to the system came from the surrounding and, likewise, any energy lost by the system went to the surroundings.
In relationship to calorimetry, the most useful statement of the second law of thermodynamics is: Thermal energy is spontaneously transferred from an object at a higher temperature to an object at a lower temperature until the two objects reach the same temperature

9. 1. Simple (coffee cup) calorimeter
Types of calorimeters
1. Simple (coffee cup) calorimeter
2. Flame calorimeter
3. Bomb calorimeter

10. Using a Simple Calorimeter
A simple calorimeter consists of two nested vessels (such as polystyrene cups) covered with a lid.
produces relatively accurate results when used carefully.
The reaction occurs in the inner cup which contains a known mass of water
covered with a lid with 2 holes for a thermometer & a stirrer
air b/t 2 cups adds insulation
under constant pressure
The inner vessel is where the reaction occurs and contains a known mass of water.
The polystyrene cups prevent the escape of thermal energy because they are excellent insulators.
Further, the air trapped between the cups provides additional insulation.
Liquids remain in the inner cup; however, due to the holes in the lid for the thermometer and the stirrer, gases can escape.
Because of gases can escape (or enter), the thermal energy changes measured using this type of calorimeter are at a constant pressure. 10

11. Assumptions Made When Using a Simple Calorimeter
Any thermal energy exchanged with the surroundings is negligible (So, would it affect the heat you’re trying to measure? Thoughts?)
Any thermal energy exchanged with the polystyrene cups, the lid, thermometer and stirrer is negligible
Since the reaction is occurring in water and the solutes are dilute, the reactants have the same properties as water (density, specific heat capacity)
The exchange of thermal energy takes place under constant pressure
When using a simple calorimeter, compounds are often dissolved in water.
Thus, the change in temperature of the water in which the reaction is occurring is being measured
If the temperature of the water increases, then the process is exothermic
If the temperature of the water decreases, then the process is endothermic
The amount of heat transferred is calculated using the specific heat capacity of water.
Thus, the solutions must be dilute so that the presence of the reactants and the products do not alter the specific heat capacity of water.
Important 11

12. ∆Hgiven off by reaction (system) = qgained by water (surrounding)
In simple calorimeter, the above assumptions lead to the following equations
Exothermic processes
∆Hgiven off by reaction (system) = qgained by water (surrounding)
- n ∆Hmolar = mH2O . cH2O . ∆T
Endothermic processes
∆Hgained by reaction (system) = qlost by system
n∆Hmolar = ̶ mH2O . cH2O . ∆T
Further explanation:
reaction = rxn you’re studying inside the calorimeter
System= water in the calorimeter
 Hr = molar enthalpy of reaction for a particular reactant or product

13. Q = mole of rxtant or product x molar enthalpy Or Q = n Hr
How to find molar enthalpy of reaction Hr for a particular reactant or product?
Once Q is found
Set up
Q = mole of rxtant or product x molar enthalpy
Or Q = n Hr
Then, Hr = Q / n 13

14. Using Flame Calorimetry to Determine the Enthalpy of Combustion
A flame calorimeter can be used to determine the enthalpy of combustion of a substance
It is flame-resistant (unlike a simple calorimeter)
The calorimeter absorbs a significant amount of heat and must be included in the energy calculation
The fuel being combusted is burned under a small can, heating both the can and water inside. 14

15. Using Flame Calorimetry to Determine the Enthalpy of Combustion
For pure substances, the molar enthalpy of combustion is used.
For foods, which contain a mixture of chemicals, the enthalpy of combustion is expressed in units of kJ/g or kJ/serving.
The fuel being combusted is burned under a small can, heating both the can and water inside. 15

16. Using Bomb Calorimetry to Measure Enthalpy Changes during Combustion
A bomb calorimeter precisely and accurately measures heat released during a combustion reaction at constant volume.
Contains more parts than a simple calorimeter.
All these parts can absorb or release small quantities of energy.
Therefore, the assumption that heat loss is negligible CANNOT be made.
A bomb calorimeter measures enthalpy changes during combustion reactions at a constant volume.
Works on the same principle as a simple calorimeter
H/w, the reaction takes place inside an inner metal chamber called a bomb
This bomb contains pure oxygen
The reactants are ignited using an electric coil.
The chamber is surrounded by a known volume of water, that absorbs the energy released by the reaction. 16

17. Calculations Using Data from a Bomb Calorimeter
For precise heat measurements, must know (or find out) the heat capacity, C, of the entire bomb calorimeter
Calibrated for a constant mass of water.
Therefore, no need for mass term, m, in heat capacity value as the mass of the other parts remains constant.
The heat capacity of the bomb calorimeter takes into account the heat capacity of all the components of the bomb: Cbomb calorimeter = Cwater + Cthermometer + Cstirrer + Ccontainer
The heat capacity of a particular bomb calorimeter is usually provided by the manufacturer.
Because C accounts for mass of the calorimeter, C is equivalent to mc and, thus, Q = CΔT
Heat capacity, C, is the amount of heat required to raise the temperature of a substance 1 degree Celsius. The heat capacity of 1 g of water would be much smaller than the heat capacity of 1 tonne of water; however, both have the same specific heat capacity. Heat capacity is an extensive property. 17

18. A Bomb Calorimeter is a Closed System
The bomb calorimeter is a closed system under pressure
Inside the calorimeter, processes are occurring at constant volume but not at constant pressure.
As the pressure can change significantly, Qsystem ≠ ΔHrxn
Therefore, a correction must be made to account for the change in pressure conditions: Q = CΔT + RTΔn(gas) Where R is the universal gas constant ( LkPa/molK) and Δn(gas) is the change in total moles of gas
For any calculations we do, we will assume that total moles of gas remains constant and that the equation Q = CΔT can be used to calculate enthalpy changes. 18

19. Hands-on activity 5.2 page 302
Determination of the Temperature of a Bunsen Burner Flame using a simple calorimeter
Introduction
A Bunsen burner flame is clearly too hot to measure by ordinary means; however, we can estimate its temperature by applying calorimetry and the Law of Conservation of Energy.
A strip of copper is heated in the hottest blue region of the flame and then quickly transferred into a calorimeter containing water.
By measuring the temperatures of the copper strip, water and final temperature, the initial temperature of the hot copper strip can be calculated and then ascribed to temperature of the flame.
The calorimeter (“heat measurer”) will consist of two nested Styrofoam cups set in a 250 mL beaker.
When the heated copper is dropped into the water, its heat is absorbed by the water.

20. Materials
A long strip of Cu
Graduated cylinder
Stir rod
Metal tongs/tweezer
Simple calorimeter
Thermometer
Balance
PROCEDURE:
You will be using a Labquest temperature probe to monitor the temperature change inside the calorimeter. Instruction will be given in class.
Please go over page 6-8 of the provided Labquest manual PRIOR to performing the procedure on the next slide

21. Important:
What are due on Nov (yes same day as the field trip)?
a flow chart showing the steps in the lab procedure (remember the flowchart I showed you during the soap lab?). This should help you rid the feeling of cluelessness
Pre-lab questions (see slide # 23)
The above items are to be handed in INDIVIDUALLY
Total marks: ____/8m, TI

22. Measure 100 mL water into the calorimeter and measure its temperature.
Procedure continued
Measure 100 mL water into the calorimeter and measure its temperature.
Ensure that the temperature probe stay submerged in the water.
Weigh the copper strip and determine its temperature.
Heat the copper strip for 5 minutes
Turn off the burner and SLOWLY lift the cup so that the hot metal becomes immersed in the water.
Do not touch the water inside the cup with the tongs/tweezers. Why?
Stir water briefly using thermometer and record highest temperature obtained.
Repeat the above step once more if there is enough time

23. Pre-lab Thoughts:
1. Is the process we study in this lab a chemical reaction or a physical one?
2. Identify the system and surrounding in this lab?
3. Which object gain/lose energy?
a) copper
b) water
4. How would you set up an equation that relates the amt of energy lost/gained by the system and the surrounding in this lab so you can find the temp of the Bunsen burner?
5. What assumptions must we make in this lab to be able to set up the equation in #4?

24. At the end of this lesson, create a mind map that connects the concept learnt in THIS ppt