Experiment Nine

Energy and Changes of State

Procedural Tips

FAQs

Introduction/Goals

Background

Pre-lab

Calculations

Additional Questions

Supplies and Chemicals

Safety Precautions

Waste Disposal Instructions

Chem 106 Lab Homepage

We will determine the specific heat of a metal.                                               The heat of fusion of water will also be determined.

Print a copy of the Grading Sheet for this lab.

Procedural Tips:

Using the Bunsen Burner

How to Use the Top-Loading Electronic Balance

The Calorimeter

Note: In Step A.2, the mass of your calorimeter = the mass of your Styrofoam cup

Use of the thermocouples

Setting up a Boiling Water Bath

FAQ:

Why do I have to wear safety goggles?

Introduction/Goals:

Introduction:

In this experiment, you will determine the specific heat of a metal by making a Styrofoam cup calorimeter. From the calculated specific heat, you will identify the type of metal.

In the second part of the expeiment, the heat of fusion for water will be determined with the use of a calorimeter. The mass of water, temperature change occurring during the cooling of water and the specific heat of water will be used to calculate the heat of fusion.

Goals:

Background:

Heat is a form of energy. When a substance is heated, its temperature will rise. Not all substances will have their temperatures rise to the same extent when an equal amount of heat is applied to them. The specific heat of a substance in the amount of heat that is required to raise the temperature of 1 g of the substance by 1 ° C. Water has a high specific heat of               1.00 cal/g ºC. Since the body is composed mainly of water, it is possible for humans to absorb large quantities of heat without causing a large change in body temperature. In other words, the large specific heat of water assists us in the regulation of our body temperature.

The specific heat of a substance may be determined by heating the metal and placing it into a measured quantity of water. The resultant temperature change of the water, along with the mass of the water and the specific heat of water may be used to calculate the specific heat of the metal.

The metric measure of heat energy is the calorie. The calorie is the amount of heat required to raise the temperature of 1 g of water by 1 ° C.  Nutritionists express the calories in food products as large calories (Cal). The Calorie, as referred to in nutrition, is equal to 1 kilocalorie (kcal). Measurement of the Caloric value of food may be made by burning the food and measuring the amount of temperature change in water in a calorimeter. The Caloric value of a food is dependent upon the amount of fats, proteins, and carbohydrates that the food contains.

When energy (heat) is added to a solid, its molecules move faster and the temperature rises. If enough energy is added, the molecules will be moving fast enough to break free from one another and the substance becomes a liquid. The temperature at which this occurs is called the melting point. When the melting point is reached, additional heat must be added to the substance to completely melt it. This energy is called the heat of fusion.

Pre-lab:

Read the introductory material on the webpage.

Read Experiment Nine in the laboratory manual.

Answer the pre-lab study questions on for Experiment Nine

You are encouraged to do the Application Questions at the end of Experiment Nine before coming to lab.

Calculations:

Calories = grams of water (A.3-A.2) X DT for water x 1.00 cal/g ºC

Specific heat = calories lost by metal object/mass of metal x temp. change of the metal

Specific heat in joules = specific heat in calories x 4.18

Additional Questions:

1. How many calories are required to heat 40 g of water from 20 ºC to  45ºC?

2. A 45 g sample of metal is heated to 186 ºC , then transferred to a calorimeter containing 50 g of water at 15 ºC. The water is heated to a temperature of 22 ºC. What is the specific heat of this metal object?

3. The heat of fusion of ice is 80 cal/g. How much heat in kilcalories is required to melt 1 pound of ice?

4. Answer 8.95 and 8.99 in your McMurray textbook.

Supplies and Chemicals:

Safety Precautions:

SAFETY GOGGLES MUST BE WORN AT ALL TIMES DURING THE LAB.

Use caution when boiling water.

Waste Disposal Instructions:

Return the unknown metal objects to the appropriate container.