T540: Calorimetry – Specific Heat and Molar Capacity

Introduction

Equal masses of aluminum and lead are heated in boiling water.  The metals are then placed in separate beakers containing equal volumes of room temperature water.  The temperature change in each amount of water is measured and specific heats can be determined.

Equations 

Using the mass of the metal, the mass of water in the cooling beaker, and the change in temperature of the water, the specific heat capacity for the metal can be found.

qH2O = mH2O . cH2O . ΔTH2O

qmetal = -qH2O

cmetal = qmetal/(mmetal . ΔTmetal)

The ΔTmetal is Tf-Ti, where Tf is the final temperature and Ti is the initial.  The initial temperature is that measured in the boiling water.  The final temperature of the metal is that measured in the cooling beaker.

To Conduct Demonstration

    1. Bring an 800mL beaker of water to boiling.
    2. Place equal masses of lead and aluminum in the boiling water and allow them to heat for several minutes.  Measure the temperature of the water.
    3. Remove the metals and place them in separate beakers containing the same volume of room-temperature water.
    4. Stir water and measure the maximum temperature reached in each beaker.

Demo Time: 10 – 15  minutes

Safety 

Use tongs and/or heat-protective gloves to remove hot metals.

Reference 

A.B. Ellis et al Teaching General Chemistry, 1993.

Acknowledgment

Steven George, Fall 1995.