Specific Heat of Lead

Introduction

How much heat must be added to a substance to make its temperature increase by one degree? If you compare several substances and always use the same mass of each substance when you make the measurement (1 gram), what you are measuring is the specific heat of the substance. The specific heat of a substance is the heat required to raise the temperature of 1 gram of a substance by 1 °C. Therefore, specific heat has units of or because Celsius has the same size units as Kelvin. The relationship between heat (q), temperature change (∆T), mass (m) and specific heat (C) is q = ∆T x m x C.

In this experiment, you will measure the specific heat of lead. You will do this by heating a lead sinker in boiling water, then placing it in a cup of room-temperature water in a calorimeter and measuring the change in temperature of the water. From the change in temperature of the water, you can calculate the amount of heat transferred from the lead sinker to the water. Then, with the known amount of heat, the measured mass of the lead and the measured change in temperature, you will calculate the specific heat of lead.

Safety

Be very careful not to spill the boiling water or to touch the hot plate or the hot lead sinkers. Wear safety goggles at all times while performing the lab. Avoid handling the lead sinker.

Procedure
  1. Place a Styrofoam cup inside a 250 mL beaker. This will serve as your calorimeter.
  2. Obtain a lead sinker. Measure and record its mass to the nearest 0.1 g in the data table.
  3. On a hotplate, heat to boiling several hundred mL of water in a beaker. Place the lead sinker in the boiling water (with the string outside the beaker) and let it heat up for at least 3 minutes. Measure the temperature of the boiling water and record the temperature to the nearest 0.1 °C.
  4. Place 50.0 mL of cold water in the calorimeter.
  5. Remove the thermometer from the boiling water and rinse it in running water to reduce its temperature, then place it in the calorimeter. Wait a minute or two for the temperature to stabilize, then measure and record the temperature of the cold water to the nearest 0.1 °C.
  6. Carefully remove the lead sinker from the boiling water and place the sinker in the cold water.
  7. Very gently swirl the water in the calorimeter while observing the temperature. Be very careful not to break the thermometer. Record the maximum temperature of the water to the nearest 0.1°C.
  8. Repeat this procedure and record the data in the Trial 2 column of the data table. It is not necessary to re-weigh the sinker or to replace the water in the calorimeter.
  9. Turn off the hot plate, clean your work area and wash your hands.
Data TableTrial 1Trial 2
Mass of lead sinker
Volume of cold water in calorimeter
Temperature of boiling water
Initial temperature of cold water
Final temperature of cold water
Calculations (set up all equations properly and show how all units cancel!)

Select whichever set of data has the largest temperature change.

  1. How much did the temperature of the cold water change when you put the lead sinker into it?
  1. How much heat must the lead sinker have transferred to the cold water to produce the temperature change you calculated in step 1?
  1. What was the temperature change of the lead sinker when it was removed from the hot water and placed in the cold water?
  1. Calculate the specific heat (C) of lead. This is the amount of heat released into the cold water by the lead sinker per degree Celsius and per gram of lead. Use C =

Questions

  1. What has the higher specific heat? Water or lead?
  1. What scientific law accounts for the assumption that the heat gained by the water in the calorimeter is equal to the heat lost by the lead sinker?
  1. How much heat energy is required to raise the temperature of your sinker by 1 °C? (Use the equation for q in the Introduction section.)
  1. A potato chip contains about 8 Calories of energy. If the chemical energy of one potato chip were entirely converted into heat energy and all of the heat transferred to your lead sinker, how much hotter would it get? (Hint: solve the q equation for ∆T. Don’t forget that 1 Cal = 1,000 cal and that 1 cal = 4.184 J.)

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