Science of Conflict

Calcium oxide and water
Exothermic reaction
The aim of this experiment is to find the relationship between the ratio of reactants used and heat given off.

We will investigate the reaction between calcium oxide and water.

Apparatus :
-50ml measuring cylinder
-100ml beaker
-electronic balance
-thermometer
-calcium oxide
Calcium oxide and resealable bags

 

Step 1- Measure 5 grams of calcium oxide and place it in a 100 ml beaker.


Step 2- Measure 20 ml of water, using a measuring cylinder.


Step 3- Measure the temperature of the water using a thermometer.

Step 4- Pour the water into the beaker containing the calcium oxide and stir with the thermometer.

 

Step 5- Record the maximum temperature of the water.

Take care not to place the glass beaker on a metal surface as heat will escape.

 
Repeat the steps above but now use different amounts of water. Complete the table below.
Mass of calcium oxide
Volume of water
Maximum temperature
5.0 grams
10 ml
  
5.0 grams
20 ml
  
5.0 grams
40 ml
  
5.0 grams
60 ml
  
5.0 grams
80 ml
  

 

Complete the table below

Mass of calcium oxide
Volume of water
Maximum temperature
5.0 grams
40 ml
  
10.0 grams
40 ml
  
15.0 grams
40 ml
  
20.0 grams
40 ml
  
30.0 grams
40 ml
  

Graph the results shown in the tables above. Use proper labeling. Click for more information on graphs

Describe your observations.
What happened to the temperature increase of the water as more water was added to 5 grams of calcium oxide?
What happened to the temperature increase of the water as more calcium oxide was added to 40 ml of water?

Consider your graphs. What mass of calcium oxide must be added to 40 ml of water in order to increase the temperature of the water by 20oC?

Specific Heat
The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The relationship between heat and temperature change is usually expressed in the form shown below.

Heat added = specific heat X mass of water X temperature change


The specific heat of water is 4.2 joule/gram/ °C, which is higher than any other every day substance. What this means is that, water can absorb more energy than most substances before its temperature increases by one degree Celsius. As a result, water plays a very important role in temperature regulation.

Consider your table of values above. Calculate the amount of heat energy generated by the reaction when 10 grams of CaO (calcium oxide) is dissolved in 40 ml of water.
As a chemical engineer working for the military you are asked to design a self heating food container to be used by soldiers operating in remote areas where the temperature is 0 oC. The food can contains 50 ml of chicken soup and must be heated to a temperature of 50 oC. Using the data you have collected, above, state the amount of CaO needed in your can assuming the specific heat of water is 4.2 J/g/C. Explain how you can insulate your food container and why insulation is important.