Provide each student with a 20-ounce plastic soda bottle with a cap and a glass eyedropper. Fill the bottle to the top with water and fill the eyedropper 1/4 full of water. Place the eyedropper into the soda bottle, which should cause the bottle to overflow. Push the floating eyedropper in so the cap can be screwed on the bottle. Squeeze the sides of the bottle until the eyedropper sinks, then release the bottle and observe what happens. Use the experiment to discuss Pascal's Principle and the effects of increasing and decreasing pressure in the air and water.
Biology students can use eyedroppers to regulate the amount of food received by small creatures and determine whether the benefits of diet techniques extend to life forms other than humans. Gather two obese frogs, two overweight birds and two heavy snakes or lizards. Allow all creatures to eat at will for one week, providing a food supply and observing how much is consumed at each meal. Record weights of all species. Feed one of each species a smaller regulated amount of food with an eyedropper during the second week. Record weights of all species and increase portions to the same amount the other species received every day for the final week to determine if the diet curbed appetites. Check final weights to confirm or refute theories.
Help young children understand the scientific principle of water surface tension using an eyedropper and penny. Ask students to predict how many drops of water a penny can hold. With an eyedropper, slowly add water to the surface of a penny and count each drop out loud until the water spills over the edge. Determine which student was closest to the correct number and use the experiment to discuss practical applications of surface tension, such as the ability of water strider insects to cross the surface of a pond without sinking.
Students discussing meteorology can observe the water capacity of clouds with an inexpensive experiment suitable for home or classroom use. Students need to fill an eyedropper with water and pinch one corner of a cotton ball. Hold the cotton ball over a paper towel and predict how many drops it will take to saturate the cotton ball. It may be necessary to refill the eyedropper multiple times before the cotton ball begins to drip. Discuss precipitation and flash flooding based on experiment results.