Cold Pack Design Lab

Designing a Cold Pack Group Investigation

Background: An instant cold pack is a first aid device used to treat injuries.  The pack that we used in class contains two plastic bags: one contains an ionic compound (salt) and the smaller bag contains water.  When the water bag is broken, the water reacts with the salt to create an endothermic reaction.

Your task: Your group will investigate different salts for potential use in a cold pack.  Using data from your own experimentation along with the cost data below, your group must decide which salt is the best choice for your product.  You must keep in mind that you are deciding:

1)     Which salt will be used

2)     The quantity of salt and water to be used

3)     What your laboratory set up and procedure will be and what equipment will be used

4)     What data will be collected and who will be in charge of each job for the group

Your goal/Guiding Question: Make an effective cold pack that is also low cost for your company and have evidence in order to defend your choice to your classmates.

Salt	Amount (in grams)	Cost:
NH4Cl (ammonium chloride)	1,000	$13.90
NH4NO3 (ammonium nitrate)	500	$8.95
MgSO4 (magnesium sulfate)	100	$1.07
NH4SCN (ammonium thiocyanate)	500	$8.55

Materials:

Consumables:                                                            Lab Equipment:

·        NH₄Cl (ammonium chloride)                       Graduated cylinders (100 mL or 25 mL)

·        NH₄NO₃ (ammonium nitrate)                      Stirrers

·        MgSO₄ (magnesium sulfate)                        Thermometers

·        NH₄SCN (ammonium thiocyanate)             Scale

·        Distilled water                                               Weighing dish

Styrofoam Cups w/ beaker for stability

Safety Precautions:

Follow all normal lab safety rules. All of the salts are corrosive to your skin and moderately toxic to ingest. In addition, take the following safety precautions:

§  Wear chemical-splash goggles the entire time in the laboratory.

§  Handle all glassware with care.

§  Wash your hands with soap and water before leaving the laboratory.

Getting Started: You have three main tasks to reach your goal.

Task 1: What type of data you need to collect:

1.      What type of measurements or observations will you need to make during your investigation?

2.      Is it important to know the change in temperature of the solution or just its final temperature?

3.      How does the amount of salt or the amount of water influence your potential results?

Task 2: How will you collect the data:

1.      How often will you collect data and when will you do it?

2.      How will you make sure that your data are of high quality (reduce the errors)?

3.      How will you keep track of the data you collect and how will you organize it?

Task 3: How will you analyze the data:

1.      How will you calculate the heat energy change in the mixture?

2.      What type of graph could you create to help make sense of your data?

3.      How will you use the cost information to influence your decision?

Your guidelines (the rules):

Ø  Your company wants to produce a small, portable cold pack that can easily fit into a small first aid kit. Thus the pack cannot be too big and/or too heavy.

Ø  Your company is planning to use 60 mL of water in the cold pack.  This is the amount that you must use in your investigation.

Ø  For the cold pack to be effective, the temperature must drop rapidly as close to zero (O°C) as possible.

Ø  Your company wants to spend as little as possible to produce the cold packs to maximize their profits.

Ø  Write out your team’s plan for each of the tasks above.  You may write in paragraphs for each or bullet points.

Ø  Use your prior knowledge from conducting lab investigations about temperature and heat. 

Ø  Your group must work as a team to fulfill your investigation and prepare to defend your choice of cold pack.  Remember that you will need to make a claim and have evidence to back it up.

Ø  You will need sign off from Ms. Cotta on your initial plan before any testing 

Requirements in your lab report:

1.     Plan for experimentation

2.     Jobs for each person

3.     Data Table

4.     Graph

5.     Evidence

6.     Argument template

Argument Template: (what is written in bold is what you need to answer)

The guiding question: What salt is the most effective and low cost to use in a cold pack?

Claim: (What salt are you choosing and explain why)

Evidence: (give at least two pieces of evidence why you chose that salt for your cold pack)

Justification: Explain why your evidence is relevant and important to your claim.