Why do higher density objects sink

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Funding to support the advancement of the chemical sciences through research projects. ACS-Hach Programs Learn about financial support for future and current high school chemistry teachers. 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. Students will also be able to explain that density is a characteristic property of a substance.

Assessment does not include density or distinguishing mass and weight. Although the standard does not call for density to be used as a characteristic property to identify a substance, a basic introduction to density is included here as an optional element of a learning progression leading up to a middle school understanding of density.

Download the student activity sheet and distribute one per student when specified in the activity. The activity sheet will serve as the Evaluate component of the 5-E lesson plan. Students will record their observations, and answer questions about the activity on the activity sheet. If students dip the tiny piece of clay in the water beforehand and then put it back on the surface of the water, it should sink.

Show the Animation — Density: Clay and Water. Explain that density has to do with how heavy something is compared to its size. As you show the animation, explain that since a piece of clay weighs more than the same amount, or volume, of water, clay is more dense than water.

Since clay is more dense than water, a ball of clay sinks in water, no matter how big or small the ball of clay is. Show the Animation — Density: Wood and Water. If you compared the weight of wood and an equal amount, or volume, of water the sample of wood would weigh less than the sample of water.

This means that wood is less dense than water. Since wood is less dense than water, wood floats in water, no matter how big or small the piece of wood is. The key to floating is being light for your size. So if you can add size to an object without adding much weight, the object will be lighter relative to its size.

This means that the density of the overall object will decrease and be more likely to float. Ask students to describe how this principle can be used to explain how a lifejacket can help someone float in water.

The key to sinking is being heavy for your size. If you can add weight to an object without adding much size, the object will be heavier relative to its size. Mass is the amount of matter in an object. Volume is the amount of space that an object takes up in three dimensions. If we take the same volume one cubic centimetre of foam, wood and concrete, we can see that each has a different mass. Less Dense, More Dense If something is heavy for its size, it has a high density. If an object is light for its size it has a low density.

Imagine a big bowl of popcorn, compared to a big bowl of pebbles, which would feel heavier? It is easy to estimate relative densities if you keep either the volume or the mass of two objects the same.

If you filled one bag with a kg of feathers and another with a kg of lead you would see that the feathers take up much more room, even though both bags have the same mass. This because feathers are less dense, they have less mass per volume.

If you made a copper cube and an aluminum cube of the same volume and placed one in each hand, you would be able to feel that the copper cube would be heavier. Copper has more mass per volume than aluminum. How can one substance have more mass per volume than another? There are a few possibilities:. Any one or a combination of these explanations could be the reason why one substance has a higher density than another.

In the case of copper and aluminum, their atoms are arranged similarly, but copper atoms are smaller and have more mass than aluminum atoms, giving it a higher density. Density, Sinking and Floating Why do some things float, while others sink?

You might expect heavier objects to sink and lighter ones to float, but sometimes the opposite is true. The relative densities of an object and the liquid it is placed in determine whether that object will sink or float.

You can really see relative densities at work when you look at a heavy object floating and a lighter one sinking. For example, imagine putting a small piece of clay and a large, heavy wax candle in a tub of water. Sinking and floating applies to liquids too. For example, if you add vegetable oil to water, the oil floats on top of the water because the oil has a lower density than the water.

The water pushes upward against the object with a force buoyancy equal to the weight of water that is displaced. When the ball is submerged in the water, it displaces its volume in water. However, the weight of the ball is more like 55 N.

A beach ball may have the same volume as a bowling ball, but it has a much smaller mass. 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? Babble Dabble Do has a fabulous ship building activity to demonstrate how displacement helps objects float. Can you make a superhero float? We made out superhero arm bands and a raft,. Rainy Day Mum has a lovely activity using boats made from pie tins.

Try a p irate themed sink and float investigation. Find out how many coins it takes to sink a foil boat. Learn about density with this easy investigation, can you find something to float on each layer? Instead of making an object less dense by adding bubble wrap, try changing the density of water to help an object float.