Again, lucky for us, as we would not hear that delightful tinkle of ice cubes against the side of a glass if the ice in our ice tea sank to the bottom. The density of ice is about 90 percent that of water, but that can vary because ice can contain air, too. That means that about 10 percent of an ice cube or iceberg will be above the water line. This property of water is critical for all life on earth. If water was most dense at the freezing point, then in winter the very cold water at the surface of lakes would sink, the lake could freeze from the bottom up.
And, with water being such a good insulator due to its heat capacity , some frozen lakes might not totally thaw in summer. The real-world explanation of water density is actually more complicated, as the density of water also varies with the amount of material that is dissolved in it. Water in nature contains minerals, gasses, salts, and even pesticides and bacteria, some of which are dissolved. As more material is dissolved in a gallon of water then that gallon will weigh more and be more dense— ocean water is denser than pure water.
We already said ice floats on water because it is less dense, but ice of a special kind can be denser than normal water. Heavy water, D 2 O instead of H 2 O, is water in which both hydrogen atoms have been replaced with deuterium, the isotope of hydrogen containing one proton and one neutron.
Heavy water is indeed heavier than normal water which contains a tiny amount of heavy water molecules naturally , and heavy-water ice will sink in normal water. The instrument to measure the density of a liquid is called a hydrometer. It is one of the simplest of scientific-measuring devices, and you can even make your own out of a plastic straws see links below.
More often, though, it is made of glass and looks a lot like a thermometer. It consists of a cylindrical stem and a weighted bulb at the bottom to make it float upright. The hydrometer is gently lowered into the liquid to be measured until the hydrometer floats freely. There are etched or marked lines on the device so the user can see how high or low the hydrometer is floating. In less dense liquids the hydrometer will float lower, while in more dense liquids it will float higher. Since water is the "standard" by which other liquids are measured, the mark for water is probably labeled as "1.
Hydrometers have many uses, not the least being to measure the salinity of water for science classes in schools. They are also used in the dairy industry to get estimates of the fat content of milk, as milk with higher fat content will be less dense than lower-fat milk.
Hydrometers are often used by people who make beer and wine at home, as it offers an indication of how much sugar is in the liquid, and lets the brewer know how far along the fermentation process has gone. Do you think you know a lot about water properties?
Looking at water, you might think that it's the most simple thing around. How to Calculate Concentration From Density. How Is Salinity Calculated?
Physical Properties of Household Ammonia. Third Grade Science for the Measurement of Density. Hydraulic Oil Density. Definition of Acidic Solution. How to Find the Percent of Concentration of Copper How to Calculate Percent Solids by Weight.
Ophardt; Chapter 3, Lesson 5 Multimedia Oil Oil is more dense than alcohol, but less dense than water. Water Water molecules are packed more closely together than the long molecules that make up oil.
The oxygen atoms in water are also smaller and heavier than the carbon atoms in oil. This would not only make ice-skating way less enjoyable but would kill off all the animals and plants that lived in it. The way it is now, water at 4 degrees Celsius sinks to the bottom and the coldest water rises up to the surface.
So fish can live in a comfortable for them environment, and get a free layer of ice that insulates the lake from cold in the same bargain. Seeing as life on Earth most likely evolved in the oceans , we should all be very grateful for this.
This also means that it has a very high liquid-to-gas volume change, increasing its volume When water is heated, thermal energy pushes its molecules apart, counteracting the effect of its hydrogen bonds.
This is why power plants boil water for their turbines and not alcohol, for example, even if it has a higher boiling point. This very large increase in volume on vaporization allows fine water mists to be used in fighting fires by displacing the oxygen with water vapor. Water is nothing if not spectacular. Stunningly charming pun connoisseur, I have been fascinated by the world around me since I first laid eyes on it.
Always curious, I'm just having a little fun with some very serious science.
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