In the Classroom

  PK – grade 3 students At this level the students can be asked about different physical states of matter. They can be asked to give examples of solids, liquids, and gasses. They can also be asked if they know how to change one state to another. Then, they can be asked about what they observed during the experiment. What phase change took place? Why did it happen? Also, the students can be asked what makes the soda bubbly. Thus, at this grade level teachers can focus the experiment around states of matter. They can describe the states of matter, their properties, and what it would take to change them from one state to another. Grade 4 – 6 students At this level the students will have already been introduced to, and have learned about the scientific method. Most of them will have also already conducted experiments in various science courses. So, ask them to go through the steps of the scientific method for this experiment. What happened to the soda when it was placed in the ice bath? How did the CO2 keep it from freezing long before the bottle was open? Have each student make their own observations and ask their own questions, and then allow them to draw their conclusions based on how they followed the steps of the scientific method. Middle school students At this level, students will have had some more science courses, and topics such how a phase change can occur can be discussed. A solid becomes a liquid when heat is added via melting, and a liquid becomes a gas in the presence of heat due to evaporation. A gas can also go back to being a liquid through condensation. To go a little further a solid can go straight to a gas through a process called sublimation, and a gas can become a solid via deposition. The last couple terms might be a little foreign to the students, but they should still be able to grasp the basic idea, and then they can be asked to explain which processes are occurring in this experiment, and how each component, such as the water and the carbon dioxide, plays a role. Middle school students can gain experience first hand with this experiment. It can easily be replicated in the classroom with the proper equipment, and students can see if they can recreate it. Science Discipline(s) Chemistry Topics States of matter, super cooling, freezing, Carbon Dioxide, instant freezing Activity Title Seltzer Freeze Materials:
  • 8 oz. Bottled Water
  • Large ice chests (2)
  • Club Soda
  • Pack of Seltzer/ Sparkling Water (5-6 dozen bottles) in plastic bottles, e.g. half-liter Perrier in plastic bottles.
  • 1 Cooler
  • 1 Bag of ice (2-3 x 5lb bags)
  • Rock Salt (5 – 6 boxes)
  • Roll of Paper Towels
  • Pairs of Thick Gloves
  • Thermometer
  • Safety Googles
Instructions: (Note: Start 1 hour prior to experiment)
  1. Peel Labels off Club Soda
  2. Keep soda refrigerated or stored in ice for as long as possible before the start of the experiment
  3. Place ice into the ice chests
  4. Add sufficient rock salt into the chest with ice so that you have a 5:1 to 8:1 ratio of volume of ice to volume of salt. Mix ice and salt well.
  5. Submerge unopened club soda bottles into the salt/ice combo for least 45 minutes before start of the experiment. As ice melts, drain water from the ice chest and add more ice/ salt mix in the same ratio as above. Add only minimum additional salt to ensure that the ice chest temperature is approximately -10°C to -8°C.
  6. Cool the bottle to a temperature of -10°C to -8°C. DO NOT cool past -10°C or the soda will freeze
  7. Remove the bottle from the ice using the thick gloves (note: club soda should still be in liquid form)
  8. Wipe off condensation on outside of bottle
  9. Open the bottle or have the participant open the bottle.
  10. Carbon dioxide gas will rapidly escape the bottle. The soda should begin to freeze immediately and be completely frozen within 30 seconds
Questions
  1. What are some of the experimental variables that affect this experiment? How could you design an experiment that could test the importance of these variables to the instant freezing of the seltzer water?
  2. What is a freezing point? What is the freezing point of water?
  3. What would happen if other liquids were used instead of soda? If other materials were dissolved?
  4. What is the purpose of the rock salt? What would happen without it?
  5. What is the importance of the CO2 being a gas and the water being a liquid?
Explanation
  1. Variables: how cold the seltzer water is chilled to, how much carbon dioxide is dissolved in the water in the seltzer water, and how long the seltzer water is chilled. Even though the ice chest temperature might read -10 degrees Celsius, the water in the bottle might be warmer.  A warmer temperature would mean that the water in the bottle might not freeze when the carbon dioxide escapes. A smaller amount of carbon dioxide dissolved in the water could mean that the bottle would freeze at a higher temperature, even while it is cooling in the ice chest. Some of the carbon dioxide could be released from a seltzer bottle to test the effect of dissolved carbon dioxide on the behavior of the freezing.
  2. The freezing point is temperature at which a substance turns into a solid from a liquid due to cooling. The freezing point of water is 0°C or 32°
  3. The effect of other liquids would depend on their physical properties such as their specific freezing points. It could be experimented with though to see how other dissolved substances, (safe ones) such as sugar, would effect the freezing points.
  4. The purpose of the rock salt is to bring down the temperature of the ice further. Without it, the ice would not be able to actually bring the temperature of the water down enough to freeze it.
  5. The importance of the CO2 being a gas is that in a gaseous form it can easily leave the bottle when opened. Liquid cannot, which is why it stays in the container and is able to freezer since the CO2 is gone.
Next Generation Science Standards Scientific Knowledge is Based on Empirical Evidence Science Models, Laws and Theories Explain Natural Phenomena Science Addresses Questions about the Natural and Physical World Science Investigations use a Variety of Methods Next Generation Science Standards
  • PK – grade 3 students
    • K-LS1, 1-LS1, 2-LS1, 3-LS1, 2-PS1
  • Grade 4 – 6 students
    • 4-LS1, 5-PSI, 5-LS1
    • MS-PS1, MS-LS1
  • Middle school students
    • MS-PS1, MS-LS1
  • High school students
    • HS-PS1, HS-LS1
PS1- Structure and properties of matter: LS1-Structure and Function