Incorporate the scientific process into your child's floating object project. Simply placing an object in water and instructing the child to watch will not be enough to help her learn and develop new critical thinking skills. Instead, start with a discussion of the scientific principles at play when an object floats, such as buoyancy and gravity. Ask the child to make predictions and a hypothesis about which objects will sink and which will float when placed in water. Test the hypothesis and have the child make observations. At the end of the experiment, ask the child to discuss what happened and make conclusions.
Materials for a floating object kid's science project will vary depending on your specific experiment or activity. Most sink or float type of projects use plain water, but some may require soda, juice or another more or less dense liquid. You will also need a container to hold the liquid. Since the child will need to see what is happening to the object, a clear plastic or glass bowl or cup will work best. For comparisons, you will need objects of different weight that will fit into your container. Examples of objects are small toys, marbles, feathers, plastic spoons, keys and balls.
Kids can explore how objects float by experimenting with different types of liquids. These density experiments allow the student to discover how the chemical properties of a substance affect other liquids and objects placed into it. Choose different liquids such as water, juice, corn syrup and oil. Place each in a separate container. Put a small object such as a raisin into each container, predict and observe what happens. Discuss why the raisin sinks or floats in the various liquids. Take the object out and use the liquids themselves as additional objects to float. Pour the oil into the water or the corn syrup into the juice and watch what happens as they form layers, depending on their densities.
Simple sink or float comparisons are an easy way for kids in preschool through middle school to learn about how objects float. Use only one liquid medium. Water's clarity makes it ideal for children to make observations. Choose a variety of objects, such as marbles, coins, toy boats or string. Weigh the items on a scale and ask the students to predict which ones will sink and which ones will float. Invite the children to place the objects into the water one at a time and observe. Discuss plausible reasons why some of the objects floated. This should include weight, gravity, density and buoyancy concepts.