Density

Density of Water

The density of the material is defined as the weight of the material per unit volume of it. The density of any material indicates how tightly the molecules of the material adhere to each other. A higher value of the density indicates smaller the distance among the molecules. The unit for measuring density is \(gm/cm^{3}\) or \(kg/m^{3}\). In the definition of the metric system for measurement, the density of water is taken as a reference to define the density of other materials.

The density of pure water is \(1 gm/cm^{3}\) or \(1000 kg/m^{3}\). The density of pure water fluctuates with the temperature and it reaches to the maximum value at a temperature of \(4 ^{0}C\) which is \(1000 kg/m^{3}\). Contamination in the water disturbs the density of water. Due to contamination, the density of water increases and this fluctuation in density depends on the degree of contamination and temperature.

Density of Water

Density of Water

The Behaviour of the Density of Water

The formula of water is \(H_{2}O\) and it is a chemical compound. It is an inorganic polar compound which is tasteless and odourless liquid at room temperature. It is also known as the universal solvent and it is the main constituent of fluids found in all living organisms. Water is abundantly available on the Earth and is found in all forms, i.e., gas, liquid and solid. When the temperature decreases, water converts into solid and when the temperature increases, water converts into gas. At the room temperature, water is in the liquid state.

The behaviour of water density is unusual. In other materials, when they transform from gas to liquid and liquid to solid-state, their density increases. But in case of water, though density increases when it transforms from gas to liquid and it decreases when water becomes solid (ice). Because of this unusual behaviour of density, ice floats in the liquid water.

Concerning to the density of water, it is already mentioned that the density of water fluctuates with temperature. When the temperature decreases, the water density increases and reaches its maximum value of \(1000 kg/m^{3}\) at a temperature of \(4^{0}C\). When the temperature further decreases, it tends to expand and becomes less dense. At \(0 ^{0}C\), water becomes ice; the water molecules form a rigid but open pattern. As this structure is less dense as compared to normal water therefore ice floats on the surface of the water.

Water density also depends on the purity of water. Pure water is less dense as compared to the saline water. The decrease in the purity of water increases the density of water. The seawater is denser than pure water. In the deep oceans, the density of water increases in depths. This change or fluctuation in the density in oceans, produce the currents in the oceans. These currents circulate around the world.

Factors affecting Water Density

There are two factors which are affecting the density of water, namely, temperature and purity.

In the case of pure water, temperature plays a crucial role. The density of water varies with temperature but not in a linear way. Lowering the temperature reduces the thermal motion and allows the water molecules to form more hydrogen bonds that prevent the molecules to come closer to each other. A hexagonal structure formed which leaves some space in-between the molecules which tend to decrease the density. Due to this structure, ice is less dense as compared to the liquid water.

In the case of impure water, water density increases with respect to impurity. The density of the saline water is the best example of this. When the salinity increases, the water becomes denser. Seawater is a good example of saline water. Seawater density also varies with temperature and depth. It is denser than the pure water as it contains lots of chemicals packed in it. The depth of the sea also shows the variation in density. It has a lower density at the top and higher density at the bottom. Change in the temperature also impacts the density of seawater.

When the temperature rises in summers, the seawater becomes less dense. On the rise of temperature, water gets warmer and molecules spread out. When the temperature goes down in winters, the seawater becomes denser as most of the chemicals present in the seawater become denser.

Deepwater is denser than shallow water. In the deep, water molecules are more packed and tightly adhere to each other as the weight of water above them pushing down. A good example of the high density of seawater is the Dead Sea. In this sea, the density is so high that objects are floating on the surface. Its average density is \(1240 kg/m^{3}\) which is very high and swimming in this sea is like floating.

Benefits from the Water Density

It is, now, a well-known fact the density of water fluctuates unusually with temperature. It increases when the temperature decreases and reaches its maximum value at a temperature of \(4 ^{0}C\). When the temperature further goes down water density becomes less. Due to this, ice (solid form of water) floats on the surface. This property of water benefits to living creatures in the sea whose surface is frozen but under the surface, water temperature is at \(4^{0}C\), which helps to survive these sea creatures.

FAQs on Density of Water

Q.1: What is the meaning of density?

Answer: Density of any material is defined as the weight of the material per unit volume of it. The density of any material indicates how tightly the molecules of the material adhere to each other.

Q.2: How does the temperature affect the density of water?

Answer: The density of water varies with temperature but not in a linear way. Lowering the temperature reduces the thermal motion and allows the water molecules to form more hydrogen bonds that prevent the molecules to come closer to each other. A hexagonal structure formed which leaves some space in-between the molecules which tend to decrease the density.

Q.3: What are the factors which affect the density of water?

Answer: There are two main factors which affect the density of water, namely, Temperature and Purity. The density of pure water varies with temperature and attains its maximum value at a temperature of \(4^{0}C\). Impure water density increases with respect to impurity. The density of the saline water is the best example of this. When the salinity increases, the water becomes denser.

Q.4: Explain the effect of temperature on seawater density?

Answer: The effect of temperature on the seawater can be seen in winters. When the temperature goes down in winters, the seawater becomes denser as most of the chemicals present in the seawater become denser. The upper layer of seawater frozen but the temperature of the water layer underneath the surface is \(4^{0}C\) which helps to survive the sea creatures. And on the other hand, when the temperature rises in summers, the seawater becomes less dense. On the rise of temperature, water gets warmer and molecules spread out.

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