Denisty of Water

Water is an essential substance that has been behind the sustenance of life on this planet earth. It has been the cradle of life. Life originated from the oceans, and water has been the constant supporter of life on this planet either directly (by forming the prominent part of living cells) or indirectly (by maintaining the living conditions on this planet even this planet went through varied extreme weather cycles).

This chemical compound comprises two atoms of hydrogen covalently bonded with a single molecule of oxygen. The compound is tasteless, transparent (in its pure state), insulator of electricity, colourless, and odourless. Moreover, the compound is a universal solvent as it can dissolve many things.

Definition of Density

We can define density as the ratio of volume and mass. Physicists also state it as the mass of a unit volume of the substance.
Density is a temperature-dependent value because the volume of a substance depends upon temperature.

Density of Water

The density of water is the mass of water per unit volume at a given temperature. The standard density of water is taken at 4℃ because water is supposed to have the highest density at this temperature.

Relation of Water Density and Temperature

The density of water varies with temperature. The density of water decreases in the solid-state, and as the temperature in the liquid stage increases, the volume also increases drastically, which decreases the density.
Water has its highest density at 4℃ because water molecules start drifting apart to form the ice below this temperature.

Properties of Water

The formula for the compound is H2O.
The boiling point for the compound is 100℃ at 1-atmosphere pressure.
The freezing point of water is 0℃ at 1-atmosphere pressure.
The density of water at 4℃ is 1000kg/m3 or 1g/cc.
The molar mass of water is 18.015g/mol.

Decrease in the Density of Water or Anomalous Expansion of Water
Water has two significant forces acting in the liquid phase- the Van Der Waals' forces and the Hydrogen Bonding. As temperature decreases, the Van Der Waals' forces become stronger (strongest at 4℃), but hydrogen bonding is always more substantial in the molecule. As the water enters the solid phase, it needs to form layers of water molecules held together in a cage-like structure by hydrogen bonding. Thus, the molecules gain space during the arrangement, which leads to a decrease in density.
This property of water has led to the preservation of life on this planet. Since ice is lighter than water, water's surface usually freezes, and life continues in the depths of water where water is still liquid and warmer than the surroundings since ice is a terrible conductor of heat. The ice is 9 percent lighter than water.

What is Heavy Ice and Why Does It Sink In Water?
Heavy Ice is the ice formed by D2O where the process replaces the hydrogen from normal water with deuterium, which is heavier than hydrogen. The density of Heavy Ice is about 10.6 more than ordinary water, and thus it sinks in water.

What is Specific Gravity?
Since water has always been available in abundance throughout the world, physicists have taken it as a standard for density and densities of other substances have been compared with water to see whether they would float or sink in water.
The specific gravity of a substance is the ratio of the given substance and the density of a standard substance which is usually the density of water at 4℃.

Experiment to Understand the Importance of Specific Gravity
Take some amount of water, cooking oil, maple syrup. In a beaker or test tube, add the maple syrup, followed by the water and oil. Allow the three liquids to settle. Do not agitate the mixture. Then, you would be able to see the three liquids separated. Maple syrup has the highest density, and thus it settles at the bottom. Oil is less dense; thus, it floats on water.

Frequently Asked Questions About Density of Water

Ques: Does seawater have a higher density than water?
Yes, seawater has a higher density than freshwater. This is because the higher the amount of salt dissolved in water, the higher is the density of the water. This is the primary reason the rejected brine in desalination plants sinks in the seawater.

Ques: Why doesn't water have an absolute density?
Since the volume of water is highly dependent on the temperature of the water, the density of water keeps on changing, which is why water doesn't have an absolute density.