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change of state Ice skating and the change of state In general, when pressure increases the forces of attraction between the particles increases and hence melting and boiling points of many substances increase. But for the substances like ice, the melting point decreases with increase in pressure. Increase in pressure favours decrease in volume. As the volume decreases when ice melts, melting is favoured by increase in pressure. This phenomenon helps to make ice skating possible. As the skater exerts pressure on ice (with his weight on skate), it melts and the film of water formed under the runner facilitates the movement of the skater over ice.

Learning Objectives

After completing the topic, the student will be able to:

  • List different states of matter − gaseous, liquid, solid, Bose−Einstein condensate and plasma.
  • Compare the characteristics of different states of matter.
  • Recognize how Bose–Einstein condensate is different from other states.
  • Define the interconversion processes such as melting, boiling, sublimation etc.
  • Predict the conditions that are required to convert one state of matter to another state.
  • Discuss the effect of temperature and pressure on equilibrium state of phase transitions of matter.
  • Define and calculate the latent heats of fusion and vaporization.
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Three states of matter - Solids, Liquids and Gases

Matter is the amount of stuff in an object. The physical appearance of matter in five different states is referred as 'States of matter'. Among the five states, solid, liquid and gas are considered as the primary states due to their existence at room temperature.

In a solid, matter maintains a fixed volume and shape. In liquid state, matter has fixed volume but adapts the shape of its container. The inter-molecular attractions keep the molecules in proximity, but do not keep them in fixed relationship. In the gaseous state, matter expands to occupy the available volume. In this state, the inter–molecular attractions among the molecules are relatively less that effects their motion.Change in temperature and pressure favors the inter conversion of states, as observed in the water cycle.

Plasma and Bose–Einstein Condensate are the fourth and fifth states of matter that occur at extremely high and super low temperatures respectively.

What is plasma? Plasma occurs in the stars, including the Sun. Inside the Sun, temperature is so high that the constituent Hydrogen and Helium molecules break their bonds and gives free electrons. As a result, electrically charged particles called ions are generated. The mixture of free electrons and ions gives plasma which is responsible for the glow. It is characterized by a complexity that is not exhibited by a solid, liquid and gaseous state.
Plasma and BEC states

One may wonder that the primary states of matter contribute to minor part of the Universe, while a major portion is composed of plasma. Plasma contains ionized gases and can exist at extremely high temperature (105 K). Plasma, like gas, does not have definite shape or volume. It can generate electromagnetic forces and can be accelerated. It provides many practical uses, new technologies, consumer products and also promises for abundant energy.

Plasma can also be made on the earth by passing electricity through gases at very low pressures taken in a glass tube (called discharge tube). The fluorescent tubes and neon sign bulbs form plasma when they are switched on. A fluorescent tube may contain helium gas (or some other gas), and a neon sign bulb contains neon gas. When electricity is passed through a fluorescent tube (or neon sign bulb) it glows.

In 1920, an Indian scientist Satyendra Nath Bose calculated for the fifth state of matter. On the basis of these calculations, Albert Einstein predicted the existence of a new state of matter called Bose–Einstein Condensate (BEC). This fifth state of matter was finally achieved by three USA Scientists: Cornell, Ketterle and Wieman. They cooled a gas of extremely low density (about one hundred thousandth the density of normal air) to super low temperature (<10– 7 K).