Most kids enjoy a bowl of ice cream, particularly on a hot day. Making their own treat allows fourth-graders to grasp the concept of the effect that temperature has on the solidity of the ingredients. To make ice cream, combine ice with rock salt in a large container. In another smaller container, place 1 pint of half-and-half, 1 1/2 teaspoons of vanilla, and 1/3 cup and 2 tablespoons of sugar. Put the smaller container inside the larger one and seal both tightly. Roll or shake the larger container until the mixture inside becomes solid. Fourth-graders will see how the rock salt effects the rate at which the ice melts and how the cold temperature of the ice turns a liquid into a solid.
Fourth-grade students build on previously learned information about organisms, their parts and how they play a role in our world. Plant cells are one type of organism that children at this age begin to look at. Creating a plant cell with different colors of gelatin allows students to create a visually appealing project that demonstrates their knowledge on the topic and gives the class a tasty treat at the end of the lesson. Make a variety of different colors of gelatin and allow them to firm up in the refrigerator. Use a sharp knife to cut the gelatin to form the nucleus, cytoplasm, Golgi apparatus and the other parts of a plant cell. Arrange them on a plate or cookie sheet and cover them with plastic wrap for transport to school.
Popping popcorn the old-fashioned way -- with oil in a pan -- is an ideal way to reinforce the process of developing a hypothesis, which an important concept in fourth grade. Heat a pan and add 100 kernels of popcorn. Challenge the students to guess how many will pop. Allow them to eat their experiment. Ask students to make a guess on what would happen if the kernels were wet when they were added to the pan or how much longer it would take for them to pop at a lower temperature. Use caution with this project to prevent students from getting splattered with hot oil when the popcorn is placed in the pan.
Making crystals is a science project that teaches fourth-graders about the process of evaporation and how the presence or absence of liquid alters the appearance of sugar. To make the candy, mix 1 cup of sugar with 1/3 cup of water in a pan and stir it until the sugar dissolves. Boil the mixture to make this process faster. Wet a piece of string and squeeze out most of the water. Lay the middle of the string in the sugar water, leaving the ends exposed. Cover it with plastic wrap and allow to sit overnight. Check for crystals. Once the string is covered with sugar crystals, allow your fourth-graders to eat their project.