Polar ice blocks and icebergs drift in the ocean, and even in drinks the ice never sinks to the bottom. It can be concluded that ice does not sink in water. Why? If you think about it, this question might seem a little strange, because ice is solid and - intuitively - should be heavier than liquid. While this statement is true for most substances, water is the exception to the rule. Water and ice are distinguished by hydrogen bonds, which make the ice lighter in the solid state than when it is in the liquid state.
Scientific question: why does ice not sink in water
Let's imagine that we are in a lesson called "The World Around" in 3rd grade. “Why doesn't ice sink in water?” the teacher asks the children. And the kids, not having deep knowledge in physics, begin to reason. "Perhaps it's magic?" says one of the children.
Indeed, the ice is extremely unusual. There are practically no other natural substances that, in the solid state, could float on the surface of a liquid. This is one of the properties that makes water such an unusual substance and, frankly, it is what changes the path of planetary evolution.
There are some planets that contain huge amounts of liquid hydrocarbons such as ammonia - however, when frozen, this material sinks to the bottom. The reason why ice does not sink in water is that when water freezes, it expands, and with it, its density decreases. Interestingly, the expansion of ice can break rocks - the process of glaciation of water is so unusual.
Scientifically speaking, the freezing process sets up rapid weathering cycles and certain chemicals released on the surface can dissolve minerals. In general, there are processes and possibilities associated with the freezing of water that the physical properties of other liquids do not imply.
Density of ice and water
So the answer to why ice doesn't sink in water but floats on the surface is that it has a lower density than liquid - but that's a first level answer. To better understand, you need to know why ice has low density, why things float in the first place, how density leads to floating.
Recall the Greek genius Archimedes, who found out that after immersing a certain object in water, the volume of water increases by a number equal to the volume of the immersed object. In other words, if you place a deep dish on the surface of the water and then place a heavy object in it, the volume of water that will be poured into the dish will be exactly equal to the volume of the object. It doesn't matter if the object is completely submerged orpartially.
Properties of water
Water is an amazing substance that basically feeds life on earth, because every living organism needs it. One of the most important properties of water is that it has the highest density at 4°C. Thus, hot water or ice is less dense than cold water. Less dense substances float on top of denser substances.
For example, while preparing a salad, you will notice that the oil is on the surface of the vinegar - this can be explained by the fact that it has a lower density. The same law is also valid for explaining why ice does not sink in water, but sinks in gasoline and kerosene. It's just that these two substances have a lower density than ice. So, if you throw an inflatable ball into the pool, it will float on the surface, but if you throw a stone into the water, it will sink to the bottom.
What changes happen to water when it freezes
The reason ice doesn't sink in water is due to the hydrogen bonds that change when water freezes. As you know, water consists of one oxygen atom and two hydrogen atoms. They are attached by covalent bonds that are incredibly strong. However, the other type of bond that forms between different molecules, called a hydrogen bond, is weaker. These bonds form because the positively charged hydrogen atoms are attracted to the negatively charged oxygen atoms of neighboring water molecules.
When the water is warm, the molecules are very active,move a lot, quickly form and decompose bonds with other water molecules. They have the energy to approach each other and move quickly. So why doesn't ice sink in water? Chemistry hides the answer.
Physical chemistry of ice
As the temperature of the water drops below 4 °C, the kinetic energy of the liquid decreases, so the molecules no longer move. They do not have the energy to move and are as easy as at high temperature to break and form bonds. Instead, they form more hydrogen bonds with other water molecules to form hexagonal lattice structures.
They form these structures to keep negatively charged oxygen molecules apart. In the middle of the hexagons formed as a result of the activity of molecules, there is a lot of emptiness.
Ice sinks in water - reasons
Ice is actually 9% less dense than liquid water. Therefore, ice takes up more space than water. Practically, this makes sense because the ice expands. This is why it is not recommended to freeze a glass bottle of water - frozen water can create large cracks even in concrete. If you have a liter bottle of ice and a liter bottle of water, then an ice water bottle will be easier. The molecules are farther apart at this point than when the substance is in the liquid state. That's why ice doesn't sink in water.
When the ice meltsthe stable crystal structure breaks down and becomes denser. When the water warms up to 4°C, it gains energy and the molecules move faster and farther. This is the reason why hot water takes up more space than cold water and floats on top of cold water - it has less density. Remember, when you are on the lake, while swimming, the top layer of water is always nice and warm, but when you put your feet down, you feel the coldness of the bottom layer.
The significance of the process of freezing water in the functioning of the planet
Despite the fact that the question "Why doesn't ice sink in water?" for grade 3, it is very important to understand why this process is happening and what it means for the planet. Thus, the buoyancy of ice has important implications for life on Earth. Lakes freeze in winter in cold places - this allows fish and other aquatic animals to survive under the ice sheet. If the bottom were frozen, then there is a high probability that the entire lake could be frozen.
In such conditions, not a single organism would have survived.
If the density of ice was higher than the density of water, then the oceans would sink in ice, and the ice caps that would then be at the bottom would not allow anyone to live there. The bottom of the ocean would be full of ice - and what would it all turn into? Among other things, polar ice is important because it reflects light and keeps planet Earth from getting too hot.
