Key Concepts

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

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Students will certainly investigate a wax candle and also a item 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 the is not the load of the object, however its density compared to the density of water, the determines whether an object will sink or to rise in water.


Students will have the ability to determine whether an object will sink or rise by compare its thickness to the thickness of water.


Download the student task sheet, and also distribute one per student as soon as specified in the activity. The activity sheet will certainly serve as the “Evaluate” component of each 5-E great plan.


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

Materials for Each Group

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

Notes around the Materials

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


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

Materials for the demonstration

1 tea light candleClayClear plastic containerWaterLarge balance

Teacher preparation

Use a little enough item of clay so that you room sure that the candle weighs more than the clay.
Pour water right into a clear plastic container (or big cup) till it is about ½-full.


Place a piece of clay that weighs much less than a tea irradiate candle on one finish of a balance. Remove the candle indigenous its steel container and place the candle on the other finish of the balance.

Ask students i beg your pardon is heavier, the clay or the candle. Ask them to predict which will certainly sink and also which will certainly float. Then, ar the clay and candle in a clear container that water.


Expected results

Even though the candle weighs more than the clay, the candle floats and also the clay sinks.


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

Question come investigate

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

Materials for each group

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


Compare the density of wax and also waterRoll 2 pieces of tape and stick them to the center of the pan in ~ each end of the balance. Connect each tea irradiate candle to the tape so that each candle is in the center of the pan. Usage the wick to traction one candle the end of its container.

Carefully to water water right into the empty metal container till it filling the container to the very same level together the candle in the other container. You might use a dropper to add the last little bit of water and also prevent spilling. The score is to to compare the fixed of equal volumes of wax and also water.


Expected results

The water has actually a higher mass 보다 an equal volume that wax. So, the density of water should be better than the thickness of wax.

Ask students:

Which weighs more, wax or an same volume that water? Water weighs an ext than an same volume that wax.Which is more dense, wax or water?Water is an ext dense.

If students have trouble understanding this relationship in between the mass and density of equal volumes, have actually them think around the demonstration from chapter 3, great 1 through the aluminum and also copper cubes. Both had the very same volume, however the copper cube sweet more. Because the copper had an ext mass, it likewise had a greater density.

Compare the thickness of clay and also waterMake certain you have one item of ice in the center of each pan on the balance.

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

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Place an north container top top the tape at the opposite finish of the balance. Slowly and carefully add water come the north container till it is full.

Expected results

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

Ask students:

Which weighs more, the clay or an same volume the water?The clay weighs an ext than an equal volume of water. Which is an ext dense, clay or water?Clay is an ext dense.Knowing the density of an object can aid you suspect if it will certainly sink or float in water.If things is an ext dense than water, would certainly you suppose it come sink or float?Objects the are more dense 보다 water sink.If an item is less thick than water, would certainly you suppose it to sink or float?Objects that are less dense than water float.