Summary

This activity explores the interaction between salt and water (ice) as a way to further investigate their impact on the state of matter of a substance. Students will use salt and ice to create a slushy lemonade drink without the use of a freezer. They will learn through this hands-on experiment how salt and ice can rapidly cool a liquid.

Grade Level

Middle school

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

• Science and Engineering Practices
• Analyzing and interpreting data
• Constructing explanations and designing solutions

Objectives

By the end of this lab, students should be able to

• Read and record temperature from a thermometer.
• Describe the effects of ice and salt interactions and the results of freezing point depression.

Chemistry Topics

This lab supports students’ understanding of

• States of Matter
• Freezing Point
• Phase Change
• Temperature
• Transfer of energy

Time

Teacher Preparation: 20 minutes

Lesson: 35 minutes

Materials

• Lemonade (one cup per 2 students)
• Gallon Ziploc bags (one per group)
• Quart Ziploc bags (one per group)
• Small cup (one per student)
• Spoon (one per student)
• Thermometer (one per group)
• Salt (1/2 to 1 cup per group)
• Ice (3-4 cups per group)

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Do not consume lab solutions, even if they’re otherwise edible products.*
• Food in the lab should be considered a chemical not for consumption.*

Teacher Notes

• Students will create a slushy lemonade drink without the use of a freezer. They learn through this hands-on experiment how salt and ice can rapidly cool a liquid. Salt-water has a lower freezing point than water/ice. Using this mixture will allow the lemonade to cool quickly, partially freezing it and creating a slushy drink.
• To make the activity less about “eating,” do not tell the students that the liquid is lemonade. You can tell them that it is citric acid (the part of lemonade that gives it the sour and tangy taste, found in citrus fruits). Then when it comes time to eat it, you can talk about why you called it citric acid.
• Each group should be given 1 gallon Ziploc bag, 1 quart Ziploc bag, and 1 thermometer. Each person should receive a cup and spoon at the end of the activity to eat their lemon ice. Each group needs about 1 cup of lemonade per two students or 2 cups per four students. It is suggested that groups are comprised of at least two but no more than four students so that everyone is involved. A liberal amount of ice should be placed in the gallon bag so that it covers the inside bag, but can still be shaken (about 3-4 cups). Salt should also be excessively added to the ice so that it is heavily coated (1/2 to 1 cup). Err on the side of too much salt.
• This lab can get very messy. To minimize the cleanup time, it is advised that the students do all pouring and shaking over a tray or large bin. Because the bags can get cold, it may be prudent for the current “shaker” to wear gloves.
• Remind students that lab materials are usually not consumed, but in this instance an exception is made. Also remind students that any lab equipment should not come in contact with the edible product.
• Discuss the Pre-Lab Questions as a class before beginning the activity. This will help the students think of additional real-world connections.