Purpose: To give students experience planning and executing experiments, thinking in terms of independent and dependent variables, recording and interpreting data, keeping a scientific journal, divergent and convergent thinking, and fostering their natural curiosity.
Providing students with real science experience is difficult for a number of reasons. Equipment and materials are expensive and results are often imperfect with in-experienced scientists. The beauty of this experiment is that students probably do not know if it is possible to make vegan ice cream but they can come to a solid conclusion after a number of quick trials.
The first step in this experiment is to ask the student the experiment question, is it possible to make vegan ice cream at home?. It is important to have a discussion on this. The consistency of the ice cream is the real question and it will be hard to lead the student to ask this question on his own. Of course if you put sugar and soy milk in the freezer it will freeze, but you want ice cream not ice cube.
After the initial discussion, have the student research how to make home made ice cream on his own. Youtube has plenty of videos on this. He will find that you put milk and sugar in a small bag and put that bag in a larger bag of ice and salt and shake for ten minutes. Ask the student what the purpose of each step is and how substituting soy milk for cow milk might effect the result. The most important questions are:
Q: Why do you add salt to the ice?
A: The salt dissolves into water and changes the shape of the water molecules which lowers the freezing point of the water. Water conducts heat twice as strong as ice so lowering the temperature of the water in the bag will freeze the ice cream faster. Do not let the student be content with this simple explanation. Tell him that a deeper understanding of how the shape of a molecule effects its freezing point needs knowledge of quantum mechanics and the speed at which liquids freeze has to do with thermodynamics.
Q: What does shaking do?
A: If you were to just put the milk and sugar in the freezer then you’d get an ice cube. You want the milk to freeze but only in small bundles so that it is like sand.
Before the first trial, make sure a hypothesis is recorded in a bound journal. The hypothesis should note the dependent and independent variables and how the student foresees the independent variable effecting the dependent.
Complete a couple initial trials in order to finalize the experiment procedure. Label all experiments and record all observations. Then, complete multiple trials with varying milks. Discuss what variables might effect the outcome and how they can be minimized.
Have the student review the results and use the recorded data and observations to come to a conclusion. This is an exercise in convergent thinking which is bringing multiple ideas together. Make sure the student refers to his data in his conclusion. Have the student consider how the experiment could have been done better. Experiments need to be replicated many times before a solid conclusion could be formed. Ask the student to record advice for his peers that may wish to replicate the experiment. This is an exercise in divergent thinking.