Developing a New, Improved Cold Pack

Difficulty of Project

Medium

Cost

$10 - $15

Safety Issues

Wear Safety glasses and apron when handling chemicals. Do not mix the three chemicals used in this experiment.

Material Availability

The materials, equipment and the chemicals can be found in any high school lab.

Approximate Time Required to Complete the Project

One week. This includes collection, recording and analysis of data, summary of results and completion of bibliography.

Objectives

To determine (a) which of the following chemicals, ammonium chloride, calcium chloride or  sodium chloride  would be best for lowering the temperature of water in a cold pack and (b) if the amount of the best chemical affects its use in the cold pack.

Materials and Equipment Required

• 1 scoopful of ammonium chloride
• 3 teaspoons
• 1 scoopful of calcium chloride
• 3 stirrers
• 1 scoopful of sodium chloride
• 1 graduated cylinder
• 10 small plastic cups
• 1 thermometer
• water
• labeling dots
• a balance
• 1 pair of vinyl gloves
• clock or watch with a second hand
• paper towels
• splash-proof safety goggles and apron

All of the above materials and equipment are readily available for use in any high school chemistry lab. Additional chemicals can be purchased from companies such as Chem Scientific, a leading supplier of inexpensive apparatus, chemicals and materials for science education.

Introduction

Background Information

We can make our own cold pack by placing water in the freezer and producing ice cubes. However there are chemical reactions we can produce to make things cold. Certain chemicals when dissolved in water give off heat, while others become cold. These chemicals can be used in hot or cold packs. Reactions that absorb heat from the environment are called endothermic reactions. These chemicals can be used in hot or cold packs. Cold packs can be used to reduce swelling from a bruise or injury. The design and improvement of the cold pack is an excellent example of the practical application of scientific knowledge. Students profit greatly when they view their knowledge and exploration of knowledge in the context of practical applications to daily life.

This science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings. They take on the role of scientists and in the process they learn to act as one.

Research Questions

• What is a simple cold pack?
• What is a chemical cold pack?
• How are cold packs used?
• What is an endothermic reaction?
• What are hot packs?
• What is an exothermic reaction?
• On the average, how long do cold packs last?
• What are the common uses of each of the chemicals, sodium chloride, ammonium chloride and calcium chloride?
• Why shouldn`t we mix all three?
• Are there other chemicals used in cold packs? If so, what are they?

Terms, Concepts and Questions to Start Background Research

• What is a control?  A control is the variable that is not changed in the experiment.
• What purpose does a control serve? It is used to make comparisons as to what changed or possibly caused the change.
• What are variables?  Variables are factors that can be changed in an experiment.
• What is an independent variable? The independent variable is the one that is changed in the experiment.
• What is a dependent variable? The dependent variable is the one that changes as a result of the change in the independent variable.

Charting and Graphing Data

In each section of the experiment, use charts to display the obtained data such the following sample:

When comparing the chemicals to determine their effects on the temperature of water over time, graph the data.

Experimental Procedure

1. State the two problems you are going to investigate in this science fair project.
2. Create the data sheets you will use to record your observations.
3. Gather all your materials.
4. Put on your safety glasses and apron.
5. Start part 1 to determine which chemical makes the best cold pack. Set up four cups. Label all and one as the control. Pour 50 mL of water into each of the cups.  Measure the temperature of each cup. Record your data. Then add one teaspoon of each of the chemicals in each of the cups and then measure the temperature of the water in each cup again.  Record your findings
6. Start part 2 to determine what an increase in the amount of the chemicals would produce. Pour 50mL of water into each of three plastic cups, and measure the temperature in each Record data. Then add one teaspoon of each to each of the cups as labeled and measure the temperature again.  Wait a few minutes and take temperature readings again. Record your data. You may want to construct a bar graph showing the results after adding two teaspoons of the chemicals to each one. Prepare your report and include all of the following: a clear statement of the problems, your hypothesis, which chemical you expected to be the most effective and whether there would be a marked different when the amount was increased. List the materials used. Include the safety precautions taken. Describe the procedures used. Include all the data that were gathered. Include all charts and graphs. Formulate your conclusions.   For dramatic value, you may include photos of cold packs, of the materials used or of you in the process of conducting this investigation. Include a bibliography of sources you used. You may wish to assess what you did and describe what you would do differently if you were to do this project again.

Bibliography

1. CAPT Science Performance Task, Connecticut State Department of Education, released item 2002 for public use.
2. About.com Chemistry, Anne Marie Helmenstine, Ph.D.