Do Water And Ice Weigh The Same?

As organisms that live on a planet mostly covered in water, we often take it for granted. Water is perhaps the most essential ingredient for all forms of life on Earth, and there isn't a single organism that can survive without it. Not only is water necessary for all living things, but it also happens to be composed of the most unique molecules in the cosmos. Interestingly, water is the only non-metallic fluid with a density that decreases as temperature decreases. This property creates differences between water in its liquid form and solid form. The following is a simple yet profound question: do water and ice weigh the same? 

The Density Of Water And Ice

ice floats
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Consider you have a bucket that contains one pound of water. If you were to freeze all the water in that bucket, would the weight of the water change or stay the same? According to the law of conservation of mass, after the water freezes, there will still be one pound of water since no water has been created or destroyed. All that has occurred is a change from a liquid state to a solid one. Thus, the weight will certainly not change.

However, ice is less dense than liquid water, a property that is unique to water. Having a lower density means that ice floats when placed in liquid water. When water freezes, it occupies more space than in its liquid form because its molecules expand. Therefore, if we have 1 liter of ice and 1 liter of water, the water will weigh more because it is denser.

How The Density Of Water Affects Life

baikal frozen lake
Baikal Lake in Russia, with Frozen layers on Top due to Cold Winter Temperatures

Water's unique property of being less dense in its solid state profoundly impacts life on Earth. For example, in winter, frozen water does not sink; it forms a layer of ice on top of liquid water. This allows bodies of water to maintain stable temperatures throughout the year beneath the ice. 

If ice had a density greater or equal to that of liquid water, lakes, rivers, streams, and even the oceans would freeze all the way through. This is because each time the top layer freezes, it sinks. Eventually, all of the water would turn to ice. This would make life in the oceans virtually impossible, and life on Earth probably wouldn't exist. Thankfully, ice floats and life can flourish as a result.

The difference in liquid water and ice density is an often overlooked property of water. It is something most of us do not think twice about. Next time you find yourself looking at a frozen lake or simply placing ice cubes in a drink, think about how the density of that ice is one of the reasons that we, and all other forms of life, exist.