Heat Energy Associated with Chemical and Physical Changes



Introduction:

The purpose of this lab is to discover the amount of heat associated with chemical and physical changes. What was being tested in this lab was the heat changes of both chemical and physical processes and see if the energy is endothermic or exothermic. Physical change is when it changes the state the substance is in but not the substance itself. Chemical change is when a chemical reaction has occurred and there is a new substance. Endothermic is when energy is consumed. Exothermic is when energy is given off. Physical and chemical change, and endothermic and exothermic were used to find the heat capacity of the calorimeter. Specific Heat is the amount of heat used to raise the temperature of one gram of a substance. Specific heat was used to determine an unknown metal. Heat Capacity is the amount of heat used to raise the temperature of one mole of a substance. Heat Capacity was used to find the heat capacity of a calorimeter as well. Heat of Neutralization is the energy of a reaction coming from the neutralization of an acid and base. Heat of neutralization was used to find heat of neutralization of acid-base reaction. Heat of Solution is the change that is the dissolution of a substance in a solvent. Heat of Solution was used to find the heat of solution of KNO 3 .



Materials:

Goggles
Water (H 2 O)
Two Styrofoam Cups and Cover
Tweezers
2 Thermometer
Bunsen Burner
Ring Stand
Wire Gauze
Ring
Unknown metal
KNO 3
250 ml beaker
HCl
NaOH
Graduated Cylinder
Test Tube


Experimental:

Build the calorimeter as establish on page 12 in "Chemistry 112 Laboratory Book". Record the temperature of 25.0 ml of water in the calorimeter. Heat 25 ml of water to 50 °C in a beaker. Pour the 25 ml of hot water into calorimeter and record the temperature every 10 seconds until a constant is reached. Then record every 30 seconds for a total of 3 minutes.
For the Acid-Base reaction, measure 25 ml of NaOH and record the temperature and find the temperature of 25 ml of HCl . Before mixing the acid-base, make sure the temperatures are both equal. After both temperature is equal, mix the acid and the base. R ecord the temperature every 10 seconds until a constant is reached. Then record every 30 seconds for a total of 3 minutes.
For the Heat of solution, measure 25 ml of water and pour it into the calorimeter and record the temperature. Add 1 gram of KNO 3 into the calorimeter and record the temperature as done in the acid-base reaction.
For the unknown metal, pour 25 ml of water into the calorimeter. Take 2 grams of the unknown metal and place it into a test tube with a cork on it. Use a 250-ml beaker filled with water and place the test tube into the beaker until the water is boil. Using a tweezer, take the metal out of the tube and place into the calorimeter and record the temperature as did above in the earlier steps.


Results :
Heat Capacity of Calorimeter
Intial Temperature (°C)

23

Final Temperature (°C)

22.5

Change in Temperature (°C)

0.5

Temperature of cold water (°C)
23

Temperature of hot water (°C)

54

Joules lost by hot water (J)

1987

Joules gained by cold water (J)

1255

Heat Capacity of Calorimeter (J/°C)
61.026

*This is the calculations of the heat capacity of the calorimeter


*This is graph of the mixture of the hot and cold water. Temperature at zero time is 33°C.



Heat of neutralization in an acid-base reaction
Concentration of acid (M)

3.00

Concentration of base (M)

3.00

Temperature of HCl and calorimeter (°C)
23

Temperature of NaOH (°C)

23

# of Joules change in energy (J)
439.32

Heat absorbed by the calorimeter (J)
470.82

Total # of Joules for the energy change (J)
910.14

# of moles of HCl (mol)

1.46

# of moles of NaOH (mol)

1.6

Heat of neutralization (J/mol)

300.9

*These are the calculations of the Heat of Neutralization

*This is the graph for the Heat of Neutralization. Temperature at zero time is 38 °C



Heat of Solution
Temperature of calorimeter + water (°C)
25
Mass of KNO3 (g)


1.00
Total Volume of Solution

26