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Lemon Ice (3 Favorites)

LAB in Freezing Point, Phase Changes, Physical Change, Temperature. Last updated February 4, 2019.


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

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.

For the Student

Lesson

Background

In this activity you will explore the interaction between salt and ice as a way to experience its effect on the state of matter of a substance.

Prelab Questions

  1. Why do people put salt onto icy and snow roads, sidewalks, and driveways?
  2. How does ice make other things cold?

Problem

How can ice and salt be used to rapidly cool another substance?

Materials

  • Lemonade
  • Salt
  • Gallon Ziploc bags
  • Quart Ziploc bags
  • Cups
  • Spoons
  • Ice
  • Thermometers

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of 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.

Procedure

  1. Each group of students should collect one set of supplies.
  2. Measure 1 cup of lemonade into the small bag and seal it tight (so that salt does not get in).
  3. Fill the large Ziploc bag with ice.
  4. Using the thermometer measure the temperature for the bag of ice and record it in the data table.
  5. Place the lemonade bag inside the ice bag. Make sure that you place the entire sealed lemonade bag inside the big bag. Do not pour the lemonade onto the ice.
  6. Add ½ cup of salt over the ice and seal the ice bag tight.
  7. Take turns shaking the bags.
  8. Stop and record the temperature inside of the ice bag at 1 minute intervals.
  9. After 10 minutes (when the lemonade starts to turn opaque), measure the temperature one last time.

Data

Use the following data table to record the temperature within the ice and salt mixture at one minute intervals. Calculate the temperature change after each reading by taking the initial temperature and subtracting the new temperature reading.

Temperature from thermometer Change in temperature=Initial Tem (minus) current temp
Initial temperature
1 minute
2 minutes
3 minutes
4 minutes
5 minutes
6 minutes
7 minutes
8 minutes
9 minutes
10 minutes

Analysis

  1. Can the ice itself (without salt added) make the lemonade slushy? How long do you think it would take?


  2. Compare the temperature of the ice before adding salt and the temperature after adding salt. Why did the temperature decrease?

Conclusion

Provide a conclusion to the results of your experiment: