Matter in Our Surroundings
Anything that has mass and occupies space is called matter. Matter is made up of particles.
These particles are so small that they cannot be seen with naked eyes. They have spaces between them and they are in state of constant motion. The particles of matter are held together attractive forces.
On the basis of differences in the physical characteristics of the particles of the matter, matter exists in three states namely solid, liquid and gaseous state.
Diffusion is the process of movement of particles from the region of their high concentration to the region of low concentration. Factors which affect the rate of diffusion are nature of substance and temperature.
States of matter are interconvertible. One state of matter can be changed to another by altering the temperature or pressure.
Temperature is a measure of the degree of hotness or coldness of a body or environment. The most common scales which are used to measure the temperature are Kelvin scale and Celsius scale
On changing the temperature of the system, the states of matter also vary. This is due to the fact that the kinetic energy of the particles changes and they start moving with different speeds.
The temperature at which a solid converts into its liquid state is called its melting point.
The temperature at which a liquid changes to its gaseous state is called its boiling or vaporisation point.
The temperature at which a liquid converts into its solid state is called its freezing point.
Sublimation is the process of conversion of a solid to its gaseous state without changing into liquid.
Latent heat is the minimum amount of energy that changes the state of substance without bringing any change in the temperature.
An increase in the pressure decreases the space between the particles of the matter therefore, a gas can be converted to a liquid and a liquid can be converted to a solid.
Evaporation is the process of conversion of a liquid into its gaseous state at any temperature below its boiling point. It is a surface phenomenon.
Factors that affect rate of evaporation are surface area, temperature, humidity and wind speed.