Question

Do we have to make changes in every time the temperature and pressure to change the state of matter?explain

Answer 1

Not necessarily. You can even change the state just by changing the temperature.
For example, boiling water by raising the temperature till its boiling point or reducing the pressure till such extent that it boils at room temperature.

Answer 2

Because a state of matter depends on the arrangement of its particles and to change the state of matter we have to change the arrangement of the particles and to change the arrange ment of the particle we need to change the temperature and pressure. As at low pressure and high temperature matter occurs in gaseous state and in high pressure and lower temperature it occurs in solid state.