Chemistry of Ice Cream

1. Chemistry of Ice Cream Shelly Hopper, IBM Learning Leader Laura Montero, New Hire Onboarding Success Partner

2. Our Plan • In this activity we will do some simple chemistry and make delicious ice cream! • We will: • Observe changes in states of matter • Look at chemical reactions • Explore the properties of ice and salt

3. The Science!! • We will be changing milk and sugar into frozen ice cream using ice and salt • Why do we add salt? • Let’s start by asking: What is the freezing point of water? • The freezing point of water is 0 degrees Celsius (32 degrees Fahrenheit) • To make milk and sugar freeze quickly we need to make it colder than 0 degrees • But how can we make ice colder? • We can add a solute to the water (salt (or sugar)) to make a salty-water solution • The freezing point of salty-water is lower than 0 degrees Celsius • So once our ice becomes salty-ice-water it will be colder than just plain ice and water

4. Our Hypothesis: What Do We Expect To See? • What states of matter do you expect to change? • What will happen to the various ingredients? • Half & half • Sugar • Vanilla • Ice • Salt • What else do you expect to see?

5. Ingredients & Supplies • ½ cup half & half milk • 1 tbsp sugar • 1 tsp vanilla extract or chocolate syrup • 2 cups crushed ice or ice cubes • 6 tbsp salt • 1 small Ziploc bag • 1 large Ziploc bag • Paper towels • Spoon

6. Group Demonstration: How To Mix Our Ice Cream Mixture • Combine ½ cup half & half milk, 1 tablespoon sugar, and 1 tsp vanilla extract or chocolate syruptogether in a small Ziploc bag • Seal the bag (remove as much air as possible from the bag) • Combine 2 cups of crushed or cubed ice and 6 tablespoons salt in a large Ziploc bag • Put the small baggie into the large baggie • Shake it! Hint: Keep moving the ice cream to transfer energy from your hands to the mixture and to stop large ice crystals from forming

7. Let’s Do It! • Each table group has the supplies necessary for each person to make a baggie of ice cream • We are going to go through each of the four steps together as a large group… please don’t jump ahead • Make note of any observations as your ice cream comes together • What does it look like over time? • When does it look good enough to eat? • What happens to the ice cubes? • Before you return to your tables, let’s mix up the variables!!! What happens if we: • Don’t add salt to the ice? • Don’t shake or squish the mixture as it freezes?

8. Experiment: Step 1 • Combine ½ cup half & half milk, 1 tablespoon sugar, and 1 tsp vanilla extract or chocolate syruptogether in a small Ziploc bag • Seal the baggie Hint: Remove as much air as possible from the small baggie

9. Experiment: Step 2 • Combine 2 cups of crushed or cubed ice and 6 tablespoons salt in a large Ziploc bag Hint: Remove as much air as possible from the large baggie

10. Experiment: Step 3 • Put the small baggie into the large baggie

11. Experiment: Step 4 • Shake it!! Hint: Keep moving the ice cream to transfer energy from your hands to the mixture and to stop large ice crystals from forming

12. Our Observations • What did your ice cream look like as it was changing? • 1 minute – at the beginning • 5 minutes – about half way through • 10 minutes – at the end • What happened to the ice cubes during our experiment? • When did your ice cream look good enough to eat? • What other changes did you observe? • What happened when we changed the variables? • Don’t add salt to the ice? • Don’t shake or squish the mixture as it freezes?