Key Concepts

The density of an item determines even if it is it will certainly float or sink in another substance. An item will float if it is less dense than the liquid it is inserted in.An object will certainly sink if it is more dense 보다 the liquid it is put in.

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Students will certainly investigate a wax candle and a item of clay to understand why the candle floats and also the clay sinks also though the candle is heavier than the piece of clay. Student will uncover that it is not the load of the object, yet its density contrasted to the density of water, that determines whether an object will sink or float in water.


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


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


Make certain you and your students wear appropriately fitting goggles.

Materials because that Each Group

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

Notes around the Materials

A simple balance is required for the demonstration. Among the least expensive is Delta Education, stackable Balance (21-inch) Product # 020-0452-595. Students can use the smaller sized version that the very same balance, Delta Education, main Balance (12-inch), Product #WW020-0452. Friend will need tea light candles because that the demonstration and for each student group. Look because that candles in i m sorry the wax fully fills the metal container.


Do a demonstrate to show that the wax is heavier than the clay yet that the wax floats and the clay sinks.

Materials because that the demonstration

1 tea irradiate 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 large cup) till it is around ½-full.


Place a piece of clay that weighs less than a tea light candle on one finish of a balance. Eliminate the candle native its steel container and place the candle top top the other finish of the balance.

Ask students which is heavier, the clay or the candle. Asking them to predict which will certainly sink and also which will float. Then, place the clay and also candle in a clean container that water.


Expected results

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


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

Question come investigate

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

Materials for each group

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


Compare the thickness of wax and also waterRoll 2 pieces of tape and also stick them to the center of the pan in ~ each finish of the balance. Affix each tea light candle to the ice cream so the each candle is in the center of the pan. Usage the wick to traction one candle out of that container.

Carefully to water water right into the empty steel container till it filling the container come the exact same level together the candle in the various other container. You may use a dropper to add the last little of water and also prevent spilling. The goal is to to compare the massive of equal volumes of wax and also water.


Expected results

The water has a greater mass 보다 an equal volume of wax. So, the density of water have to be better than the thickness of wax.

Ask students:

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

If students have actually trouble expertise this relationship between the mass and also density of equal volumes, have actually them think about the demonstrate from chapter 3, class 1 with the aluminum and also copper cubes. Both had actually the very same volume, however the copper cube sweet more. Due to the fact that the copper had much more mass, it also had a better density.

Compare the density of clay and waterMake certain you have actually one piece of tape in the center of every pan ~ above the balance.

Fill one container with clay and place it on the ice cream so the it is in the center of the pan.

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Place an empty container ~ above the tape in ~ the opposite finish of the balance. Slowly and also carefully add water to the north container till it is full.

Expected results

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

Ask students:

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