Physical Properties Of Water

Physical Properties Of Water

The significance of water as the most important liquid is mainly due to its physical properties. Some important physical properties of water are discussed in detail, in the following section.

Nature Water is an odorless, tasteless, transparent liquid. However, the taste of water is attributes to the presence of dissolved salts in it. Volatile impurities also impart some odour to water. Water is colourless in thin layers but it appears bluish in thick layers.

• Freezing point: The freezing point of water is 0°C under normal atmospheric pressure. The freezing point of water decreases with an increase in external pressure. Presence of soluble impurities decreases the freezing point of water.
• Boiling point: The boiling point of pure water is 100°C under normal atmospheric pressure. The boiling point of water gets elevated due to the presence of soluble impurities. Increase in external pressure increase the boiling point of water.

DENSITY OF WATER:

The maximum density of water is 1 gm/cc and is obtained at 4°C. The density of water increases with increase in temperature upto 4°C. Later, density of water decreases with increase in temperature beyond 4°C. Water shows a unusual behavior between 0°C to 4°C. In this range of temperature, water expands on cooling instead of contracting. This phenomenon of unusual expansion of water between O°C to 4°C is called anomalous expansion.

CONDUCTIVITY:

Pure water is a bad conductor of heat and electricity. The electrical conductivity of water is due to the presence of dissolved salts in water.

SPECIFIC HEAT:

The amount of heat energy required to raise the temperature of unit mass of a substance through 1°C or 1K is called specific heat capacity of the substance. Specific heat capacity of pure water is 1 calorie/gram = 4.2 joule/gram. Water has the highest specific heat capacity among all the substances.

SOLVENT:

The significant of ‘solutions’ in chemistry originates from the universal solvent property of water. Water can dissolve many substances in it due to its high dielectric constant. Dielectric constant is the property of a solvent to reduce the force of attraction between the ions (Cations and anions) of inorganic compounds. It can also dissolve a large number of organic compounds like glucose, sugar, alcohol etc. Due to the ability to dissolve a wide range of substances in it, water is called the universal solvent.

LATENT HEAT OF FUSION AND LATENT HEAT OF VAPORISATION:

The amount of heat required to be supplied to unit mass of ice for converting it to water without any change in the temperature is called latent heat of fusion of ice. Latent heat of fusion of ice = 80 calories/ gram. The amount of heat required to be supplied to unit mass of water for converting it to steam without any change in the temperature is called latent heat of vaporization of water. Latent heat of vaporization of water = 540 calories/gram.