Key Concepts

The thickness of an object determines whether it will float or sink in one more substance. An item will to rise if that is less dense than the fluid it is put in.An object will sink if that is an ext dense 보다 the fluid it is inserted in.

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Students will certainly investigate a wax candle and also a piece of clay to understand why the candle floats and also the clay sinks also though the candle is heavier than the item of clay. Students will uncover that it is no the load of the object, but its density compared to the density of water, that determines whether an object will sink or to rise in water.


Students will be able to determine whether an item will sink or to rise by compare its density to the thickness of water.


Download the student activity sheet, and also distribute one every student when specified in the activity. The activity sheet will serve as the “Evaluate” ingredient of each 5-E great plan.


Make sure you and also your students wear correctly fitting goggles.

Materials because that Each Group

2 tea irradiate candles in their steel containers ClayWater in cupSmall balance TapeDropper

Notes around the Materials

A simple balance is compelled for the demonstration. One of the the very least expensive is Delta Education, stackable Balance (21-inch) Product # 020-0452-595. Students deserve to use the smaller sized version that the very same balance, Delta Education, primary Balance (12-inch), Product #WW020-0452. Friend will need tea irradiate candles because that the demonstration and also for each student group. Look for candles in which the wax totally fills the metal container.


Do a show to show that the wax is heavier 보다 the clay however that the wax floats and the clay sinks.

Materials because that the demonstration

1 tea light candleClayClear plastic containerWaterLarge balance

Teacher preparation

Use a small enough piece of clay so that you room sure that the candle weighs an ext than the clay.
Pour water into a clean plastic container (or large cup) till it is around ½-full.


Place a item of clay that weighs less than a tea light candle top top one finish of a balance. Eliminate the candle indigenous its metal container and place the candle ~ above the other end of the balance.

Ask students i m sorry is heavier, the clay or the candle. Questioning them come predict which will certainly sink and which will certainly float. Then, location the clay and also candle in a clear container of water.


Expected results

Even despite the candle weighs much more than the clay, the candle floats and the clay sinks.


Have students compare the density of water, wax, and also clay.

Question to investigate

Why walk a heavier candle float and also a lighter item of clay sink?

Materials because that each group

2 tea light candles in their metal containers ClayWater in cupSmall balance TapeDropper


Compare the density of wax and waterRoll two pieces of tape and also stick them to the center of the pan at each finish of the balance. Affix each tea irradiate candle come the ice so the each candle is in the center of the pan. Use the wick to pull one candle out of that is container.

Carefully to water water right into the empty metal container until it fills the container come the same level as the candle in the various other container. You might use a dropper to add the last bit of water and also prevent spilling. The score is to compare the fixed of equal quantities of wax and water.


Expected results

The water has a higher mass than an equal volume that wax. So, the thickness of water must be greater than the density of wax.

Ask students:

Which weighs more, wax or an equal volume the water? Water weighs an ext than an same volume of wax.Which is more dense, wax or water?Water is much more dense.

If students have actually trouble expertise this relationship between the mass and density of equal volumes, have them think around the demonstrate from thing 3, class 1 with the aluminum and copper cubes. Both had the same volume, however the copper cube weighed more. Because the copper had much more mass, it additionally had a better density.

Compare the density of clay and also waterMake certain you have actually one item of ice cream in the center of each pan top top the balance.

Fill one container through clay and place the on the tape so the it is in the facility of the pan.

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Place an north container on the tape at the opposite finish of the balance. Slowly and also carefully include water to the empty container until it is full.

Expected results

The clay has a greater mass 보다 an equal volume that water. So, the thickness of clay is greater than the density of water.

Ask students:

Which weighs more, the clay or an same volume of water?The clay weighs more than an same volume of water. I beg your pardon is an ext dense, clay or water?Clay is more dense.Knowing the thickness of an item can aid you guess if it will certainly sink or float in water.If an object is an ext dense 보다 water, would certainly you suppose it come sink or float?Objects that are much more dense 보다 water sink.If things is less dense than water, would you suppose it come sink or float?Objects that space less thick than water float.