Make Your Ice Cream!
Key Concepts
Materials:
½ cup Half-and-half
4 cups Ice (see note 2)
½ cup Ice Cream Salt (Rock Salt)
¼ teaspoon Vanilla
1 tablespoon Sugar
1 Spoon
1 Gallon-sized bag (see note 3)
1 Sandwich bag (see note 1)
Measuring spoons (1 tablespoon and ¼ teaspoon) and cups (½ cup)
Paper towels
Optional: gloves/cloths
Note 1: Bags that have a zipper on top are not as airtight when sealed as bags without the zipper (regular sealable sandwich bags).
Note 2: For brevity, a good estimate for the amount of ice can be obtained by filling the gallon bag up to about 4 inches.
Note 3: Some gallon bags may start leaking especially if you are aggressive with your shaking, so have extra bags to put the leaking bag in.
Activity Directions:
Discussion Questions & Science Explanations:
Additional Experimentation:
- First, put 4 cups of ice and ½ cup of ice cream salt into your gallon bag.
- Put ½ cup of half-and-half or half-and-half, ¼ teaspoon vanilla, and 1 tablespoon of sugar into your sandwich bag.
- Squeeze all the extra air out of the bag with the half-and-half and seal it very tightly. Then, put the half-and-half bag inside of the gallon bag with the ice and squeeze the air out and close it tightly.
- Shake the bag back and forth from side to side. Hold the bag on the seal and the sides so it will freeze the ice cream and not your hands. You can also use gloves, a cloth, or paper towels to make the bag easier to hold. Keep shaking the bag until the half-and-half has solidified into a mass with a doughy, gelatinous texture.
- Once the half-and-half feels like solid ice cream, it’s ready to eat! Carefully empty and dispose of the gallon bag with the ice then enjoy your ice cream!
Discussion Questions & Science Explanations:
- What happened to the half-and-half?
- It changed from a liquid to a solid.
- It changed from a liquid to a solid.
- How do particles in a solid behave, in terms of their movement and spacing?
- Particles in a solid are barely moving, just vibrating, and are pretty close together. Particles in a liquid are father apart and move faster than particles in a solid, and gas particles are even more spread out and move even faster than particles in a liquid or solid.
- Particles in a solid are barely moving, just vibrating, and are pretty close together. Particles in a liquid are father apart and move faster than particles in a solid, and gas particles are even more spread out and move even faster than particles in a liquid or solid.
- Where did the heat travel?
- Heat travels from hot objects to cold objects. A helpful tip to figure out where heat is traveling is to think out which object is hotter and which object is colder. In this situation, the hot object is the half-and-half and the cold object is the salty ice. The heat moved from the half-and-half into the ice and this reduced the temperature of the half-and-half, thus turning it into ice cream.
- Heat travels from hot objects to cold objects. A helpful tip to figure out where heat is traveling is to think out which object is hotter and which object is colder. In this situation, the hot object is the half-and-half and the cold object is the salty ice. The heat moved from the half-and-half into the ice and this reduced the temperature of the half-and-half, thus turning it into ice cream.
- Was this a chemical reaction? And if so, why?
- A chemical reaction occurs when the molecular bonds of a substance change. Changing the physical properties of a substance, such as state of matter, isn’t a chemical reaction because the substance is still the same. Some common examples of each include: burning wood (chemical), cooking an egg (chemical), iron rusting (chemical), ice melting (physical), cutting paper(physical), mixing play-doh (physical).
- Making ice cream is not a chemical reaction because the substances do not change. The half-and-half simply decreases in temperature and becomes solid ice cream.
- A chemical reaction occurs when the molecular bonds of a substance change. Changing the physical properties of a substance, such as state of matter, isn’t a chemical reaction because the substance is still the same. Some common examples of each include: burning wood (chemical), cooking an egg (chemical), iron rusting (chemical), ice melting (physical), cutting paper(physical), mixing play-doh (physical).
- Why did we shake the bag?
- Imagine what would happen if they just put the bag of half-and-half in the freezer. It would just freeze into a solid block of half-and-half, not ice cream. We shake the bag to prevent large ice crystals from forming, so we can make ice cream and not just frozen half-and-half cubes.
- Imagine what would happen if they just put the bag of half-and-half in the freezer. It would just freeze into a solid block of half-and-half, not ice cream. We shake the bag to prevent large ice crystals from forming, so we can make ice cream and not just frozen half-and-half cubes.
- Have you ever seen somebody sprinkle salt on the road on an icy winter day? Do you know why they do that?
- Salt lowers the melting point of the ice. Water freezes at 32 degrees Fahrenheit but saltwater freezes at 28.4 degrees Fahrenheit. This means that at about 30 degrees Fahrenheit, pure water will be ice, but saltwater will be liquid. The liquid saltwater can move around the bag more easily, and therefore cover more area of the half-and-half bag. This is a more efficient transfer of heat, which freezes the half-and-half into ice cream faster.
- Salt lowers the melting point of the ice. Water freezes at 32 degrees Fahrenheit but saltwater freezes at 28.4 degrees Fahrenheit. This means that at about 30 degrees Fahrenheit, pure water will be ice, but saltwater will be liquid. The liquid saltwater can move around the bag more easily, and therefore cover more area of the half-and-half bag. This is a more efficient transfer of heat, which freezes the half-and-half into ice cream faster.
Additional Experimentation:
- Try using milk instead of half-and-half. Does it still make ice cream?
- Repeat the same procedure except don’t add salt to your bag. How much longer does it take to make ice cream?
Published 7.18.2020
Author: Anna Hudson
