 In this section we're going to look at colligative properties. Colligative properties are those physical properties that are influenced by how many particles you have in solution. For example at home or in your automobile you probably put antifreeze in your radiator. How much antifreeze that you put in your radiator determines how cold the water can get before it freezes. And so that's why you put it in there to protect your radiator from freezing and bursting. Another thing that is a colligative property and this is finally a lab that you can do at home is making ice cream. So what I have here is a mixture of our milk and cream, sugar and vanilla. I'll give you the recipe, you can get it from the documents folder. So once we have mixed our ice cream mixture what we want to do now is to change it from a liquid to a solid form. To do that I'm going to take another ziplock bag, just a little larger than that one, and put this inside it. I'm going to fill this with ice and I'm going to add some salt. Now you may have made homemade ice cream at home and done the same thing in your ice cream maker. You put in the ice and then you mix the salt in there. And what this salt is doing is lowering the freezing point. So as what it does is it appears to make the ice melt but in order for the ice to melt it has to gain energy. So where do you think it's getting the energy from? You're right it's getting it from the milk mixture. So it's taking heat from the milk mixture and melting the ice and as it does that we're going to be able to get ice cream. We want to constantly be mixing our ice cream because if you don't do that when the crystals are forming they're nice big crystals and that would give you an icy tasting ice cream. We want it to be smooth and little tiny crystals of ice. So you keep doing this for about five or six minutes. Okay well it looks like we have a nice creamy consistency now so let's taste our ice cream. Good stuff.