Matter exists in a state of solid, liquid, gas or suspension. Using different techniques, matter can be changed, either physically or chemically, from one state to another. Science teachers everywhere have been using various experiments to demonstrate a matter’s change of state. Even young children can grasp these important scientific concepts by participating in a guided activity.
Matter undergoes a change of phase from liquid to solid when the heat leaves the liquid. Molecular bonds are broken as heat is lost and the liquid freezes, solidifying the matter. Fortunately for teachers, the phase change of a liquid to a solid can be both a visual and a tactile process, making learning more interesting and enjoyable for students.
Freezing liquid in ice cube trays is a fun science experiment. Instruct children to help you fill an ice cube tray with fruit juice or water mixed with food coloring. Cover it with plastic wrap and insert toothpicks into each cube. When the liquid is completely frozen, remove the plastic wrap and pluck the cubes from the tray using toothpicks. The kids can eat the product of their experiment. An experiment can also be done to demonstrate the conversion of solids to liquids. A great experiment for younger kids is to add a small collection of their favorite things into a sandwich bag filled with water. Place the sealed bag in the freezer. Allow kids to view the bag periodically. Leave the bag overnight to ensure the bag completely freezes.
Congealing experiments are an excellent way of showing how liquids may solidify. Several simple experiments can be performed. Pudding, milk, eggs, ketchup and blood are examples of liquids that congeal. Pudding must be cooled first. A warm environment accelerates the congealing process of milk. To demonstrate phase change in a egg, crack open a raw egg to show its contents. Next, boil a second egg, and crack it open to show how heat resulted in solidification. The ketchup experiment can be demonstrated by placing a little ketchup on a plate to dry. Congealing can also be seen when blood clots. Simply mentioning the phase change of drying blood gives kids a vivid mental image.
Sometimes when you mix a liquid substance with a solid you create matter that’s difficult to classify as a solid or a liquid. It may have some properties of both. This is called a suspension. Making a substance commonly known as “goo” can demonstrate this concept. Mix together water, cornstarch and a couple drops of food color. The result is a highly viscous and nontoxic matter that kids can play with for a bit.