Construct a model solar system to teach your class the distances among the planets and the relative sizes of the planets themselves. You might choose to use physical materials such as golf balls, strings, foam balls and the like to construct your model. Another option would be to use the students as their own demonstration by having them act as the planets, sun, moon and stars.
Students will inevitably have to use a magnifying glass at some point in their science classes. Gather several different types of items, such as leaves, rocks and soil. Demonstrate to your students how they should use a magnifying glass to examine these different types of materials. Construct a chart that shows what different elements they should study and observe.
Show students how to measure for density. Fill two 400 ml beakers halfway with water. Add 50 ml of vegetable oil to one beaker and 50 ml of sugar to the other. Place a raw egg in each of the beakers, and ask students to note which of them sinks and which floats. In the sugar water, the egg will float because the water has a higher density. Have the students experiment with different types of water.
Creating shiny coins is a demonstration that is quite popular in science classrooms. In front of the class, fill a cup with lemon juice. Put some dull copper coins into the juice and leave them there for a few minutes. When you take the coins out, put them on a paper towel. The lemon juice will have caused the copper coins to become shiny. Help students understand why this process happens.