Specific Heat

Purpose:

To determine the specific heat of an unknown object.

Objectives

To understand the flow of energy as related to heat transfer and the factors affecting it.
To understand the relationship between heat transfer and temperature change.
To be able to measure all the necessary quantities for the calculation of heat transferred.
To understand the factors that limit the accuracy of the experimental results in relation to measuring heat.

Equipment

Hot plate
A metal cube
Styrophoam cup with lid
Thermometer

Theory

When two objects are brought into physical contact, energy flows from the hotter object into the colder object until they reach an equilibrium temperature. The amount of energy transfered is called heat and in the event of changing temperatures, it is calculated as

Heat = (mass) ×(specific heat) × (change in the temperature)

Here the specific heat refers to the amount of energy that needs to be transferred into a 1-kg object in order to raise its temperature by 1^oC. In symbols, it is written as:

Q = (m) ×(c) × (ΔT)

Experiment

In this experiment, students will balance the heat released from a hot metal cube into a cool cup filled with water. Neglecting any losses into the environment, the heat released by the hot metal cube must be absorbed by the cool water in the cup. When the temperature of the hot cube – water system has reached equilibrium, the balance of the heat will be:

Q_absorbed + Q_released = 0

That leads to the following equation:

(m_water) ×(c_water) × (ΔT_water) + (m_metal) ×(c_metal) × (ΔT_metal) = 0

Since the goal of the experiment is to determine the specific heat of the metal, everything else in the formula above will be measured.

Measurements

Measure the mass of the metal cube.

Fill the metal container with water, hang the metal cube so that it is completely submerged in water, place the container with the cube on the hot stove and bring it to boil. When it is boiling, the temperature of the water and the metal cube will remain constant at 100^oC.

In the meantime, fill in a styrofoam cup with water, and measure the mass of the water and its temperature. Note. Make sure you do not count the mass of the styrofoam cup. Also, wait a few minutes for the water in the cup to settle to room temperature before measuring it.

Carefully remove the hot metal cube and place it into the styrofoam cup with water. Close te cup with a lid and wait until the temperature settles down.

Results and Calculations

Result for the specific heat of the metal:

Talk to your class mates and record their values for the specific heat. Discard any values that look “suspicious” , e.g. you suspect that the students may have made a mistake, and average the remaining values. Record the specific heat for the class:

Questions

Question 1. Can you identify the metal?

Question 2. Does the object have the same density as your identified metal? You may use the lab calipers and mass scales to calculate the density.

Question 3. List all the factors that you think could have affected the accuracty of the result. Order them according to their impact on the accuracy, starting with the most important.

Mass of water (kg)	Specific Heat (kcal/kg)	Temperature change (C)	Heat absorbed by water (kcal)

Mass of metal cube (kg)	Specific Heat (kcal/kg)	Temperature change (K)	Heat released (kcal)

Lab Bench 1	Lab Bench 6
Lab Bench 2	Lab Bench 7
Lab Bench 3	Lab Bench 8
Lab Bench 4	Lab Bench 9
Lab Bench 5	Lab Bench 10
Average Specific Heat