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Make Your Own Ice Cream

You may not have thought of it this way, but every recipe is really it’s own science experiment! Combining things in different ways, adding heat or cold, predicting and then seeing what happens – all with the added bonus of getting to eat the results! This science task is no different: in this activity, we’ll learn about the different phases of matter, all while making some delicious ice cream to actually taste our results!

The Different States of Ice Cream. Also Matter.

Matter is a fancy word for the stuff everything around us is made out of. The phases, or states, of matter are solid, liquid and gas.  When we make our ice cream, we’ll explore 2 of those phases – solid (the way it is when we eat it – yum!), and liquid (the way it starts before it’s frozen into a solid). Each phase of matter has different properties. Here are a few of those properties for each phase:

Phases of Matter
SolidLiquidGas
Confined shapeTakes the shape of their containerTakes the shape and volume of their container
Particles packed into a tight patternParticles have some space between them Particles have large spaces between them 
Particles have little ability to move around (only vibrate)Particles are able to vibrate and slide past each other

Particles move at high speeds freely around their container

The Role of Salt in Our Activity

As you’ll see, we’re going to add salt to our ice in this activity, but why?  How do you think the salt will affect the ice?  

The salt has the role of lowering the freezing point of ice.  In other words, the salt will coat the ice, and cause some of the ice to melt. The water/salt mixture that results will not re-freeze until it has reached a lower temperature than the normal freezing point of water (zero degrees Celsius).  Another part of that process that’s really important to our activity, is that as the salt causes the ice to melt, heat is absorbed (or transferred) from its surroundings – in this case, our liquid ice cream mixture. That causes the temperature of the liquid ice mixture to drop, eventually making the ice cream mixture reach a temperature low enough where it will freeze. Pretty neat!

As well, when salt and water are combined, the salt prevents the melted ice from refreezing. This happens because the salt (NaCl) prevents water molecules (H2O) from forming bonds and packing tightly to form solid ice.

Using salt to melt ice so the water/salt mixture stays a liquid at lower temperatures than water alone can, has applications beyond just making a delicious dessert. In Canada in the winter, salt is often spread on our roadways to melt the ice, and keep us safe from slipping when driving in our cars or walking on sidewalks.  Who knew that something most of us have in our kitchens has so many different and useful purposes!

Did You Know:

Everything around us is made of matter, from the air we breathe to the water we drink – even our own bodies are made our of matter!

Did You Know:

States of matter can change. For example, water – a liquid – can turn to ice, which is a solid. Heat it up and it becomes steam, which is a gas.

Did You Know:

Different types of matter behave differently when moving between states. For example, iron is solid at room temperature, becomes a liquid when it is heated to 1,538°C, and boils and turns into vapour at 2,862°C. That sure is hot!

Let's Make Some Ice Cream!

Materials

To make our ice cream, you will need the following materials:

  • 1 medium Ziploc bag (1 quart)
  • 1 large Ziploc bag (1 gallon)
  • 4 cups ice
  • 6 tablespoons Kosher or rock salt
  • 1/2 cup of half-and-half cream
  • 1 tablespoon vanilla extract 
  • 1 tablespoon white sugar
  • Pinch of table salt
  • Food colouring (optional)
  • Favourite ice cream toppings
  • Bowl
  • Spoon

Procedure

  1. Add 4 cups of ice and 6 tablespoons of salt to the large Ziploc bag.

  2. Close the bag and give it a good shake. All of the ice should be coated with salt.

  3. In the medium Ziploc bag, add ½ cup of half-and-half cream, 1 tablespoon of sugar, 1 tablespoon of vanilla extract and a pinch of salt. Here you can also add a few drops of your favourite colour of food colouring.

  4. Let all of the air out of the medium Ziploc bag, seal the bag and give it a good shake.

  5. Open the larger Ziploc bag and nestle the smaller one inside of it. Make sure that the ice surrounds it. Seal the large bag.

  6. Now shake the large bag! Do this for about 5 minutes. Try to keep the smaller Ziploc bag surrounded by ice the whole time. 

  7. Open the larger bag and take a look at the smaller one. If the contents in the bag are of an ice cream consistency, then your treat is almost ready! If not, continue shaking a little longer.

  8. Using the spoon, scoop out all of the ice cream into a bowl and add your favourite toppings. Enjoy!

Try This!

To make this activity a true experiment, repeat the procedure again, this time using a different type of salt or even no salt with your ice cubes. Make a prediction – what do you think will happen differently? Record your observations (what happened differently and what happened the same?). Try adding different flavourings (for example, peppermint extract for a mint ice cream, strawberry extract or pureed strawberries for strawberry ice cream, etc.) to your ice cream, or different colours to make a different flavour with each batch!

Science never tasted so good!

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