why do some objects float and some sink in water

Try this experiment: fill a small tub with water. Gather a few materials from around your house like a paper clip, a penny and a wooden block. Which objects do you think will sink? Which will float? Will the bigger objects sink, while the smaller objects float? Place the objects on the water and find out. Were you right? It seems logical that bigger objects should sink while smaller objects float, but this isnвt always true. Whether an object sinks or floats depends on its density. Everything is made of molecules. Molecules are tiny particles that can only be seen with a. Some objects have molecules that are packed closely together. Others have molecules that are packed more loosely. This is density. Objects with tightly packed molecules are denser and sink. A paper clip or a penny is dense. Objects with more loosely packed molecules are less dense and float. Wood, cork or sponges float. Fun Facts about Sink and Float for Kids Liquids vary in their density too.

Try mixing corn syrup, oil and water together. The corn syrup sinks to the bottom because it is the densest. The water is in the middle and the oil floats to the top because it is the lightest. The shape of an object can also determine if it sinks or floats. A ball of clay sinks right away. However, if you flatten the clay out into the shape of a, it floats. Objects filled with air also float. Sink and Float Vocabulary Logical Molecules Dense Vary Learn More All About Sink and Float A video explaining why some things float. Sink and Float Q A Question : Do things float better in salt? Answer : Salt water is denser than freshwater, so things do float better. Enjoyed the info? and. For lengthy info click.
Students are given a plastic tub filled with a variety of materialsвwood of different sizes and shapes, a pencil, a marble, a styrofoam ball, a cork, a plastic spoon, a rubber band, a penny, a toothpick, a paper clip, and whatever else is handy.

They are asked to predict which objects will float and which will sink when placed under the level of the water and let go. Students perform the experiment and compare the results to their predictions. They discuss why they thought certain objects would sink/float. The class brainstorms a list of properties of the different objects that may affect whether the object floats or sinks. Using the objects they already have, students do simple tests to rule out some of the properties (such as color, shape, etc). In the end, it should be apparent that the most important properties are mass and volume (the instructor needs to guide the class to this conclusion). The students are then given a second set of materials, five film canisters and at least 50 pennies, with which to test the effect of changing the mass and volume of an object (or system, in this case) on whether the object floats or not (See Activity 2 handout).

Students are asked to design and perform an experiment that only changes one of these properties (mass or volume) while keeping the other constant and then seeing how a change in the property affects whether the object sinks or floats. Before running their experiment, they make a prediction and record why they think their prediction is correct. They run their experiment, take data, and record their observations. They then compare their results to their prediction. Next, they go back and design a second experiment to test the other property (mass or volume), record predictions, run the experiment, make observations, and then compare their results to their prediction. After they have completed both experiments, they do a Check your Understanding question and predict how many film canisters they would need to use to float 50 pennies. After making a prediction, they test it by performing the experiment.

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