First Grade: Trimester 3 – Matter Ice Cream Making Objective: Discover how a liquid can change into a solid and a gas can condense into a liquid by making ice cream! Materials: (amounts for a class of approx. 30)  Gallon and sandwich sized Ziplocs with pull‐across sealer (one of each per child)  2 gallons of half and half  Vanilla extract  2‐3 cups of sugar  Bowls for vanilla and sugar – so kids can scoop out themselves  Rock salt – 3 boxes  Ice – enough to fill each gallon‐size bag about ½ full, approx. 3‐20lb bags  Spoons to taste  1 Tablespoon  ½ teaspoon  1 cup measuring cup Introduction:  What are the three types of matter? (solid, liquid, gas)  How do we describe a solid? (matter that holds its shape)  …..a liquid? (matter that can take the shape of the container it is in)  …..a gas? (matter that spreads out to fill all the space of whatever it is in)  Today we are going to make ice cream and watch for different states of matter! Our ice cream will starts as a liquid. When we make it cold it will change to a solid. And when we put it into our warm mouths it will turn back into a liquid.  And to tie it to the garden…..all parts of ice cream come from plants…sugar cane, grass‐cow‐
milk, vanilla bean Procedure:  Pass out the sandwich sized Ziplocs.  Make one long, long line.  Have the kids file through and put the ingredients for the ice cream into their sandwich sized Ziploc: 
2 Tablespoons sugar 
1 cup half and half 
1/2 teaspoon vanilla extract  Seal the sandwich sized Ziploc and gently smush the solution until most of the sugar has dissolved.  5th grade modification – When our sugar (which is a solid) is dissolved in our milk,(which is a liquid) a ___________ is formed (answer: solution) 
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5th grade modification – Solutions are formed by a solute getting dissolved by a solvent. In our solution of sweetened milk, which part is the solvent and which part is the solute? (answer: milk is the solvent and sugar is the solute) Have the students put the sandwich sized Ziploc into a gallon Ziploc. Have the kids form another long line to fill gallon Ziploc approx. half way with ice Add approx. ½ cup rock salt to the gallon Ziploc with the ice The kids should shake the two bags until the liquid starts to form a solid. While they shake ask the students…. 
What do you see in your bag? What type of matter is it? How can you tell? 
What do you think is happening to change the liquid milk into solid ice cream? (a liquid will freeze if it loses enough heat energy. This means the liquid milk changes to a solid ice cream). 
Do you feel the water on the outside of your bag? When gas in the air touches the cold bag it changes to liquid water. This is called condensation. 
When you eat the solid ice cream, what type of matter does it change into (answer: liquid.....the heat from your mouth turns the solid back into a liquid) 
When the ice cream is ready, take the sandwich sized Ziploc out of the gallon Ziploc and eat the ice cream right out of the bag. BACKGROUND:  How does it change from a liquid to a solid? The amount of heat removed is great enough that the attractive forces between molecules draw the molecules close together, and the liquid freezes to a solid  Coagulative properties are based on entropy. Entropy is how disordered a system is. If you add more molecules of stuff to a system, it becomes more disordered. For example, if you have a classroom of kindergartners they will run around a lot and there is a lot of disorder or the entropy in the classroom is high. Now, imagine turning off the heater in the classroom in winter, everyone starts to huddle together, and be still (this is sort of like molecules in a solid once we reduce its temperature). Now, if you do not want them to stay still, you either have to add energy by increasing the temperature or add molecules/children to the classroom. It is harder to get the greater number of children to stay still. This is an increase in the entropy.  Salt on its own will not make ice cream faster, however adding salt to ice will lower the freezing point of ice and the ice cream mixture can be colder and that is what helps make the ice cream faster