... Or a fun expedition of volume, mass, density, floatation, an international warming, and how come float in a swimming pool.

You are watching: An ice cube floats in a glass of water. as the ice melts, what happens to the water level?

by Jared Smith


Archimedes" Principles:

Any floating thing displaces a volume the water equal in load to the object"s MASS.Any submerged thing displaces a volume of water same to the object"s VOLUME.


Mass / thickness = Volume

Melting ice cube

If you ar water and an ice cube in a cup so that the cup is entirely full to the brim, what wake up to the level the water as the ice melts? does it climb (overflow the cup), continue to be the same, or lower?

The ice cube is floating, so based on Archimedes" rule 1 above, we understand that the volume that water gift displaced (moved out of the way) is same in mass (weight) to the fixed of the ice cube. So, if the ice cream cube has a mass of 10 grams, then the mass of the water it has actually displaced will certainly be 10 grams.

We recognize the thickness (or compactness, load per unit) the the ice cube is much less than the of the liquid water, otherwise it wouldn"t be floating. Water is one of the very few solids that is less dense than once in its fluid form. If you take it a one pound bottle of water and also freeze it, it will certainly still weigh one pound, yet the molecule will have spread personally a bit and it will be less dense and take up more volume or space. This is why water bottles expand in the freezer. It"s comparable to a Jenga tower. As soon as you start playing it contains a fixed number of blocks, but as you pull out blocks and place castle on top, the tower i do not care bigger, however it still has the same mass/weight and number of blocks.

Fresh, fluid water has actually a density of 1 gram every cubic centimeter (1g = 1cm^3, every cubic centimeter liquid water will certainly weigh 1 gram). By the formula over (Mass / thickness = Volume) and straightforward logic, we understand that 10 grams of liquid water would certainly take increase 10 cubic centimeter of volume (10g / 1g/cm^3 = 10cm^3).

So let"s say that our 10 gram ice cream cube has a thickness of only .92 grams every cubit centimeter. By the formula above, 10 grams of mass that has a density of .92 grams every cubic centimeter will take up around 10.9 cubic centimeters of an are (10g / .92g/cm^3 = 10.9cm^3). Again, the volume the 10 grams the frozen water is much more than the volume of 10 grams of its liquid counterpart.

The floating ice cream cube has actually a fixed of 10 grams, so based upon Archimedes" rule 1, the is displacing 10 grams of water (which has 10cm^3 the volume). Friend can"t squeeze out a 10.9cm^3 ice cream cube right into a 10cm^3 space, therefore the rest of the ice cube (about 9% of it) will certainly be floating over the water line.

So what happens as soon as the ice cube melts? The ice cream shrinks (decreases volume) and also becomes an ext dense. The ice thickness will boost from .92g/cm^3 to the of liquid water (1g/cm^3). Note that the weight will not (and cannot) change. The mass just becomes an ext dense and smaller - comparable to placing blocks earlier into their original positions in ours Jenga tower. We understand the ice cream cube sweet 10 grams initially, and also we know it"s density (1g/cm^3), therefore let"s use the formula to determine exactly how much volume the melted ice cube takes. The answer is 10 cubic centimeters (10g / 1g/cm^3 = 10cm^3), i m sorry is exactly the same volume together the water that was initially displaced by the ice cream cube.

In short, the water level will not adjust as the ice cream cube melts

Other oddities

Anchors away

Using this exact same logic, there space some funny analogies. Think about an aluminum watercraft in a swim pool. If you put a 5 gallon bucket complete of 100 pounds of lead or some various other metal into the boat, the boat will acquire lower in the water and the additionally displaced water in the pool will cause the pool level to rise. And based on Archimedes" principle 1 because that floating objects, it would climb by the volume the water equal in load to the 100 lb lead bucket. Water weighs 8.3 pounds per gallon, therefore the watercraft will displace an additional 12 gallons the water (12 gallons * 8.3 pounds every gallon = 100 pounds).

What would happen if you litter the bucket of lead overboard into the pool? will certainly the swimming pool level increase, decrease, or continue to be the same?

When us toss the bucket of lead overboard, the swimming pool level goes under 12 gallons (the volume of water no much longer displaced through the load in the boat). However when it enters the water, it will certainly be submerged, so us now require to use Archimedes" principle 2 for submerged objects (it will displace a volume that water same to the object"s volume). The water level will then walk up by the volume the the lead bucket, which is 5 gallons. So, the net difference is the the swimming pool level will certainly go under by 7 gallons, even though the bucket is still technically in the pool.

Just remember the mass and density don"t issue for submerged objects. Volume is everything. Consider dropping a brick of clay and a brick the gold right into a bucket. The gold has an ext mass and is more dense than the clay, yet if both bricks space the same size, both will certainly displace the exact same amount the water.

A sinking ship

Similarly, if your aluminum boat weighed 100 pounds, it would displace 100 pounds that water (12 gallons) as soon as floating. But if the watercraft springs a leak and sinks, the swimming pool level would certainly decrease 12 gallons minus the volume that the aluminum in the boat. The boat"s volume (amount of room comprised of aluminum metal) would certainly be much much less than 12 gallons. In fact, based on the thickness of aluminum (.1 pounds/in^3), we have the right to determine utilizing our formula the the volume of ours 100 pound boat will be about 1000 cubic inch (100/.1 = 1000). There space 231 cubic inches every gallon, therefore the watercraft is comprised of around 4.3 gallons that aluminum (1000/231 = 4.3) and also thus displaces 4.3 gallons of water as soon as submerged, much much less than the 12 gallons that very same aluminum displaced as soon as floating. In conclusion, when our watercraft sinks, the swimming pool level goes under by 7.7 gallons.


As one experiment, fill a sink with 5 or 6 inches of water and also note the water level. Next collection a hefty glass down into the sink if balancing it right side increase (i.e., so it doesn"t pointer over and fill with water). The water level will especially rise to do room because that the empty glass and you"ll note that it"s challenging to obtain the glass come sink while likewise it is upright. The hefty glass displaces a most water due to the fact that of the heavy mass of the glass (Archimedes" rule 1), however it quiet floats because of it"s low density (don"t forget around all the air inside the glass). The glass will certainly feel lighter come you since of the buoyancy principle (the pressure of the displaced water advertise up versus the weight of the thing displacing it). It will float perfectly in the water as soon as the load of the glass equates to the load of the water the is displacing.

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Now lay the glass under sideways and let the submerge in the sink. The water level will certainly be only barely greater than the original level. It now displaces very tiny water due to the fact that the glass has actually a an extremely low volume (Archimedes" principle 2).

A marble in ice

Back to our initial scenario, what if the ice cream cube had actually a little marble embedded inside that it? when the ice melts, would certainly the water level increase, decrease, or continue to be the same?

Let"s say we have actually the very same ice cube as before (10g through a density of .92g/cm^3 and also volume of 10.9cm^3) and also a 1 gram marble with a thickness of 2g/cm^3. Using the formula above, we recognize the marble has to have a volume of .5 cubic centimeters (1g / 2g/cm^3 = .5cm^3). Clearly the marble would simply sink if we tossed the in the glass due to the fact that its density (2g/cm^3) is greater than water"s (1g/cm^3). And also we know when submerged it would displace .5cm^3 of water (Archimedes" principle 2). However when embedded in the ice cream cube, what happens?

Will it float?

First, we need to identify whether the ice cube will sink or float currently that it has the marble in it. To execute this, we require to figure out the combined density that the ice cube and also marble. We understand that the ice cube has actually a massive of 10 grams and also the marble has actually a massive of 1 gram, for a combined mass that 11 grams. We also know the the ice cream cube has actually a volume the 10.9cm^3 and also the marble has actually a volume of .5cm^3, for a an unified volume of 11.4cm^3. Making use of the formula, we have the right to determine that the combined density is .965g/cm^3 (11g / density = 11.4cm^3, or 11/11.4 = .965). In other words, the little marble obviously rises the linked density, yet it"s still much less than the density of water, therefore the point will definitely float!