Homework Help

Why does ice float in water?Ice has more density than water.

user profile pic

sili | Student, Grade 10 | eNotes Newbie

Posted April 10, 2010 at 5:33 PM via web

dislike 2 like

Why does ice float in water?

Ice has more density than water.

5 Answers | Add Yours

user profile pic

krishna-agrawala | College Teacher | Valedictorian

Posted April 10, 2010 at 9:23 PM (Answer #1)

dislike 3 like

Ice floats on water because density of ice is less than water. In common language we can say ice floats on water because it is lighter than water.

Any solid when place in a liquid buoyancy force that is equal to the weight of volume of liquid displaced by it. An object with density less than that of the liquid is able to displace volume of water that is less than volume of the object. AS a result such object floats on the liquid. A solid, which has higher density than the liquid, displaces volume of liquid which is equal to the volume of the solid. But the buoyancy force exerted on the solid by this is less than the downward gravitational force acting on the solid because of its weight. As a result the solid sinks to the bottom. A solid with density exactly equal to the liquid will be able to remain suspended any where within the liquid, without rising to the top of the liquid or sinking to the bottom.

While on this subject, it is worthwhile explaining the phenomenon which makes ice lighter than water. All solids and liquids including water expand when heated and shrink when cooled. As a result, density of any substance is higher at lower temperature. However, water between temperature 0 degrees to 4 degrees centigrade presents an exception to this universal rule. In this temperature range, water expands when cooled. As a result the density of water at 0 degrees as well as that of ice at 0 degrees is lower than the water.

user profile pic

neela | High School Teacher | Valedictorian

Posted April 10, 2010 at 6:39 PM (Answer #2)

dislike 1 like

All things that have a specific gravity less than that of water, float in water which is natural property of water and the material of the things. The specific gravity of ice is 0.9168 . The water when it freezes expands in volume and therefore,its specific gravity reduces. Therefore , by the principle of buoyancy the ice gets an upward thrust by a  weight of its equal  volume of water as against its weight which is less than the equal volume of water. That makes the ice float in water.

user profile pic

giorgiana1976 | College Teacher | Valedictorian

Posted April 10, 2010 at 6:48 PM (Answer #3)

dislike 1 like

A simple property, but unique and very important for the environment, is that in solid form of ice,it floats on the liquid water.The solid form of water has a lower density than liquid water, because the geometry of the hydrogen bridges  which are forming only at lower temperatures.

For almost all substances and all other 11 unusual  forms of water,except ice-XI, the solid state is denser than the liquid one. Fresh water is most dense at 4 ° C, and it will sink by convection as it will cool to that temperature and if it's cooled further, it will rise.

Because of this property,depth water will be warmer than  surface ice water, so the ice will be formed from the surface and it will extend down and most of the water underneath will remain constant at 4 ° C. Thus, the bottom of a lake, sea or ocean is virtually isolated from the cold, allowing the survival of animal species.

Although this behavior may seem trivial, it should be noted that almost all other chemicals are denser in solid state and they are freezing from bottom to top.

user profile pic

pre123 | Student | eNoter

Posted June 15, 2011 at 12:53 AM (Answer #5)

dislike 0 like

if we form ice of 1 lit water ... its weight will reduce or not ... ? m taking about weight not mass .......... plz reply
user profile pic

run582 | Student, Grade 9 | Honors

Posted April 2, 2012 at 7:14 PM (Answer #6)

dislike 0 like

its because the chemical bonds between the H2O molecules are forced into being longer, expanding the water and forming a crystal (ice). When something at constant mass increases in volume, its density decreases. Thus, ice is less dense than water, causing it to float.

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes