Change of states of a substance or a compound
Melting: Solid matter changes its state to liquid.
Freezing: Liquid matter loses heat and changes its state to solid.
Boiling (vaporization): Liquid matters gain heat and change their states to
Condensation: Gas molecules lose heat and change its phase to liquid.
Sublimation: Solid matter changes directly to gas.
Ice melts and vaporizes quickly on hot griddle
Three states of H2O are Ice, water and vapor.
720 cal/gm is needed to first melt the solid, then vaporize the liquid water. The energy is absorbed by individual molecules of water to break the H bonds holding the crystal together resulting in a liquid and then a gas.
Change of states in matter
As you know, a molecule of water is made up of two
hydrogen atoms and one oxygen atom. At ordinary temperatures, water is in liquid
form. Take little amount of water in a container. If we heat the container to 100°C, the water inside will boil and
become steam. The binding between each molecule of water is broken due to heat and
therefore the distance between each molecule becomes large. Steam is the gaseous
state of water. If we reduce temperature, the steam will condense to become water
again. Now, if we reduce the temperature of the container to 0°C, the
water will solidify into ice. Thus the three states of matter for a water molecule
are ice in solid state, water in liquid state and steam in gaseous state.
It is good to remember that the states of matter depend on its temperature, the
pressure that is exerted on it, and transfer of energy or heat accompanies changes
of state. Matter changes form when heat is supplied or removed.
The change from solid
gas is called a
change of state of a substance or a compound.
We know by now that solids are bound together by tight bonds. As we supply energy,
the bonds start to stretch. This transforms the solid into liquid state. As more
energy is given to the system, the bonds stretch even more and ultimately break.
The liquid then is turned into gaseous matter. The inter–molecular forces become
weaker as we go from solid to liquid to gaseous state.
The process of converting a solid into liquid is known as melting. The temperature
at which melting occurs is called the melting point. The reverse of melting is called
freezing or solidification. If solidification makes the solid into properly structured
crystals, it is also known as crystallization process. The process of converting
liquid into gas is called vaporizing. The reverse of vaporizing is known as condensation.
The temperature at which the liquid turns into gas is called the boiling point of
Some solids like dry ice, iodine, frozen carbon dioxide, naphthalene balls convert to gaseous
state directly from their solid state. They jump the liquid state. The process of
going from solid state to gaseous state directly is known as sublimation. Reverse
of sublimation is called condensation.