Phase of Matter States of Matter There is a force of attraction between the atoms. In Solid the force of attraction is strongest while in gas the force of attraction is weakest. Solid got a fixed volume and shape. It cannot flow. Liquid got a fixed volume but not a fixed shape. It can flow. Gas has no fixed volume or fixed shape. It can flow. Changing of state Evaporation Molecules in liquid are always moving. Some moves fast, some moves slow. When fast moving molecules are near the surface, they can escape the force of attraction and turn into vapor. Evaporation is a cooling process. The slow moving molecules can also become faster during collision with a fast moving molecules. Condensation When gas molecules are near the surface of liquid, they are attracted to surface and they gain kinetic energy and become part of liquid. The fast moving gas molecules hits the slow moving liquid molecules and the excess kinetic energy is shared with liquid. This increase the temperature of liquid so it is warming process. Condensation in Atmosphere Humidity is the ratio of the amount of water vapor present in air to the highest amount of water vapor that the air can hold. Fast moving molecules tends to collide and do not stick but the slow moving molecules sticks together. Slow moving molecules are more likely to turn to liquid form. Warm air have more water vapor than cold air. Fog and Clouds The slow moving molecules can combine with dust or smoke in air to form a cloud droplets which then further turns into a cloud. If condensation happens near the surface, it creates a fog. Clouds does not fall down even if the density is high. This is because of upward wind or “updraft” However, if they are big enough, they will start dropping to earth by gravity. We know this as rain. Boiling The change of phase that is happening throughout the liquid. Bubbles are formed when the pressure inside bubble is able to resist pressure from surrounding. At temp below 100 C, the pressure in bubbles is not strong enough. Eg Geysers Melting and Freezing. In melting the molecules vibrates more when heat is supplied. The force of attraction cannot hold them together In freezing, the molecules moves slow enough that the force of attraction is regained. Impurities increase the boiling point but reduces the melting point of a substance. Relegation The process by which ice is melted by applying pressure and freezes again when the pressure is reduced. Energy in change of Phase Refrigerator Components Evaporator Part that cools the stuff kept inside refrigerator. It consists of a tubes made up of metal with high conductivity. They absorbs heat from the stuff that are kept inside. Here the liquid refrigerant (coolant) turns into vapor. Condenser Consists of coiled set of tubes with external fins and is located at the back of refrigerator. It condenses the hot gas by absorbing heat and releasing the heat to outside Expansion valve It is a flow control device. Control flows of coolant into evaporator. The sudden drop in pressure make it expand, cool and turn partly into gas. Compressor Consist of motor that takes in coolant and compress it to make a hot, high-pressure gas Latent heat of Fusion The amount of energy required to change a unit mass of substance from solid to liquid. Latent heat of Fusion Specific latent heat of fusion is 330 000 J/ Kg. How much energy is needed to melt 0.65 kg of ice ?
