You can simply pour all of the contents down the drain all the chemicals used are harmless. NoteĬlean up for this activity is very easy, even though it can get messy. This reaction is quite impressive, so the students may want to do see it more than once. Have the students take notes on what they observe. Add a small tablespoon of iodine to the goop. When the students are done playing with the Oobleck and have come to a consensus on whether it is a liquid or a solid, it is time for the next step.
#Physical and chemical changes free#
Was this a physical or a chemical change? Feel free to add some food colour, but the reaction when we add iodine is more dramatic if the Oobleck is a light colour (yellow and plain white are very impressive). Experiment with it, and have the students make notes about the properties. Mix twice as much cornstarch in with water. The two step process of creating the cornstarch-water mixture followed by the addition of iodine illustrates the differences between chemical and physical changes. Common indications of chemical reactions are colour change, bubbles, the formation of a new substance or the emission of a gas. This is a common indication that a chemical reaction has occurred rather than a physical change. The details of this reaction are complicated, but the important observations to be made are the colour changes. Finally, when the reaction is over, it will settle into a dark purple. First the cornstarch mixture will likely turn bright yellow, and there will be interesting movement of the liquid. In order to discuss the differences between physical and chemical changes, you can cause a dramatic reaction by adding iodine to the mixture. There is no new substance produced, it is simply a property of cornstarch that it arranges itself in this way when mixed with water. When the cornstarch is mixed with water, you are causing a physical change, even though it may not be obvious. They go on to look again at phase change. When the students start to play with the Oobleck, they will likely be unsure whether it is a solid or a liquid, which is something they probably have not experienced before. First the students consider the difference between a bending nail and a rusting nail. As you will have discussed, a gas spreads out and takes up whatever volume it is contained in, a solid maintains a rigid volume and shape, and a liquid takes the shape of the container it is in, but maintains its volume. It is a liquid if left at room temperature, but it begins to solidify when pressure is applied (like when you squeeze it in your hands). The first thing to note is that the Oobleck is actually a very special kind of fluid.
Nothing that occurs in this activity is very complicated, and all of it is fun and dramatic. This activity is an excellent way to start your unit on physical and chemical changes.
You can also discuss physical and chemical weathering.In this activity, students will experience physical and chemical changes as cornstarch is mixed with water and iodine. We have also explored whether changes in states and mixtures and solutions are physical or chemical changes. This is not the only activity that we explore when talking about physical and chemical changes. The kids always enjoy this activity and always want to do it over and over! Over time the rest of the acetone evaporates out of it, and it becomes a bit more firm and solid. They squeeze the acetone out of the Styrofoam, and then I let them mold it into whatever shape they desire.
Theoretically, if you were to blow air back into the cup, it could be reversible. While it appears to be a chemical change because it produces bubbles, it’s actually the trapped air being released out of the Styrofoam. As you pour the acetone onto the cup, you see it start to bubble and dissolve very quickly.