Lesson 1.6 - Specific Heat Capacity Calculations

You have learned to calculate the heat required to change the temperature of a substance.  You can use this knowledge to predict temperature changes when heated objects transfer the heat to other substances.  Here is an example of making such predictions.   

Example 1:

Two balls of metal, one copper and one iron, have identical masses of 50 g.  They are placed in an oven and heated to 150°C. Two glasses of water are prepared with 100 mL of water each at 25°C. One heated metal ball is then dropped into each glass of water.

Which glass of water would be warmer after a few minutes?

Solution:

Table 6.1 gives the specific heat capacity of copper as 0.38 J/g" °C and iron as 0.45 J/g" °C.  Without any calculation, you should see that the iron ball will contain more heat at 150°C than copper at the same temperature because it has a higher specific heat capacity.  This means the iron ball has more heat to transfer to the water.  Therefore, the water in the glass that the iron ball was dropped into will be the warmer than the other after a few minutes.  (It may take a few minutes for the heat to transfer to the water.)    

Now, try these questions.

Question 1. Two balls of metal, one aluminum and one iron, have identical masses of 50 g.  The specific heat capacity of aluminum is 0.90 J/g" °C.   They are placed in an oven and heated to 100°C.  Two glasses of water are prepared; each glass contains 100 mL of water at 25°C.  The heated metals are then dropped into the water.  Which glass of water would be warmer after a few minutes?

Question 2. Two balls of metal, one aluminum and one lead, have identical masses of 50 g.  The specific heat capacity of aluminum is 0.90 J/g" °C.  The specific heat capacity of lead is 0.129 J/g" °C.   They are placed in an oven and heated to 100°C.  Two glasses of water are prepared; each glass contains 100 mL of water at 25°C.  The heated metals are then dropped into the water.  Which glass of water would be the warmer after a few minutes?

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Two balls of metal, one aluminum and one iron, have identical masses of 50 g.  The specific heat capacity of aluminum is 0.90 J/g" °C.   They are placed in an oven and heated to 100°C.  Two glasses of water are prepared; each glass contains 100 mL of water at 25°C.  The heated metals are then dropped into the water.  Which glass of water would be warmer after a few minutes?

The specific heat capacity of aluminum is higher than the specific heat capacity of iron. (From table 6.1, iron has a specific heat capacity of 0.45 J/g" °C.)  Therefore, the glass of water that the aluminum ball was dropped into will be warmer than the glass with the iron ball after a few minutes.

Question 2. Two balls of metal, one aluminum and one lead, have identical masses of 50 g.  The specific heat capacity of aluminum is 0.90 J/g" °C.  The specific heat capacity of lead is 0.129 J/g" °C.   They are placed in an oven and heated to 100°C.  Two glasses of water are prepared, each glass contains 100 mL of water at 25°C.  The heated metals are then dropped into the water.  Which glass of water would be warmer after a few minutes?

The specific heat capacity of aluminum is higher than the specific heat capacity of lead.  Therefore, the glass of water that the aluminum ball was dropped in will be warmer that the glass with the aluminum ball after a few minutes.

 


Go to the next page to continue Lesson 1.