So if a material like steel is shaped into a boat and made larger and larger, it will displace more and more water. When it is large enough to displace a volume of water that has a mass equal to the mass of the boat, the boat will float. Careers Launch and grow your career with career services and resources.
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Lesson 2. Inquiry in Action. Lesson Overview for Teachers View the video below to see what you and your students will do in this lesson. Objective Students will be able to explain that the density of a substance has to do with how heavy it is compared to the size of the object. Key Concepts Density is a measure of how heavy something is compared to its size.
If an object is more dense than water it will sink when placed in water, and if it is less dense than water it will float. Summary Students are introduced to the concept of density and that density has to do with how heavy something is relative to its size.
Students are also introduced to the idea that whether a substance sinks or floats in water is a characteristic property of that substance and does not depend on the amount of the substance.
Students also learn that if an object is more dense than water it will sink when placed in water, and if it is less dense than water it will float. Evaluation Download the student activity sheet and distribute one per student when specified in the activity. Safety Make sure you and your students wear properly fitting safety glasses or goggles. Clean-up and Disposal Remind students to wash their hands after completing the activity. All common household or classroom materials can be saved or disposed of in the usual manner.
Materials Clay 1 ball for each group Clear plastic container of water Popsicle sticks 20 Rubber band. Generally the more of the outside of an object that is touching the water the more buoyant it is. Water pushes back up against objects so the more surface area an object has the more water pushes back against it helping it to float.
When an object floats, it pushes water out of the way displacement. Have you ever noticed that when you climb into a bath the water level rises? This easy activity demonstrates how reducing the density of a heavy object allows it to float. Place the bubble wrapped ball on the surface of the water, you should find it now floats. Although the bubble wrap makes the ball weigh a little more, it also displaces extra water making the ball more buoyant.
The pockets of air in the bubble wrap mean that the ball and bubble wrap together are less dense than the water, which means the ball floats! Can you think of a different way to make the ball float? What if you made it a boat with plasticine? Buoyant forces are why we feel so much lighter when we are in a swimming pool. Our bodies are mostly water, so our density is fairly close to that of water.
Because of this, an average person needs only a little bit extra buoyancy to float. A life jacket provides this extra lift. Changing Density You can change the density of a substance by heating it, cooling it, or by adding something to it. There are two possible ways to make that object float, however:. Archimedes : Greek mathematician, physicist, engineer, inventor and astronomer c. In other words, the buoyancy is equal to the weight of the displaced fluid. For example, when an object goes into water, it displaces the water.
EDinformatics Mass, Volume, Density. ProTeacher Collection Density. Objectives Demonstrate how the distribution of molecules in a substance determines its density. Investigate the relative densities of liquids and the relative densities of solids.
Demonstrate understanding of the relationship between density and buoyancy by building a boat. Materials see individual activities for materials. There are a few possibilities: Atoms of one substance might be a similar size yet have more mass than the atoms of another substance.
Atoms of one substance might be a similar mass but be smaller, so more of them fit within the same volume. Atoms of one substance might be arranged in a way that allows more of them to fit in the same volume. There are two possible ways to make that object float, however: Increase the density of the water so that the water becomes denser than the object. For example, an egg will usually sink in a glass of water, because it is denser than water.
The oxygen atoms are bonded to the silicon and aluminum to make molecules with a lot of mass. These are packed closely together, which makes the clay more dense than water. Students should realize that if an object weighs more than an equal volume of water, it is more dense and will sink, and if it weighs less than an equal volume of water, it is less dense and will float. Predict whether the following objects will sink or float.
Read more about sinking and floating in the teacher background section. Note : Students may wonder why boats made out of dense material like steel can be made to float. This is a good question and there are several ways of answering it. A key to understanding this phenomenon is that the density of the material and the density of an object made of that material are not necessarily the same. If a solid ball or cube of steel is placed in water, it sinks.
But if that same steel is pounded and flattened thin and formed into a big bowl-like shape, the overall volume of the bowl is much greater than the volume of the steel cube. The mass of the steel is the same but the big increase in volume makes the density of the bowl less than the density of water so the bowl floats.
This is the same reason why a steel ship is able to float. The material is shaped in such a way so that the density of the ship is less than the density of water. The American Chemical Society is dedicated to improving lives through Chemistry. Skip Navigation. Lesson 3. Engage Do a demonstration to show that the wax is heavier than the clay but that the wax floats and the clay sinks. Materials for the demonstration 1 tea light candle Clay Clear plastic container Water Large balance Teacher preparation Use a small enough piece of clay so that you are sure that the candle weighs more than the clay.
Procedure Place a piece of clay that weighs less than a tea light candle on one end of a balance. Remove the candle from its metal container and place the candle on the other end of the balance. Expected results Even though the candle weighs more than the clay, the candle floats and the clay sinks. Explore Have students compare the density of water, wax, and clay. Question to investigate Why does a heavier candle float and a lighter piece of clay sink? Materials for each group 2 tea light candles in their metal containers Clay Water in cup Small balance Tape Dropper Procedure Compare the density of wax and water Roll two pieces of tape and stick them to the center of the pan at each end of the balance.
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