Question

State the two factors, which determine the state of a substance.

Answer 1

Hint: We know that there are three states of a substance: solid, liquid and gas. Solids have their own shape and volume. They have highly ordered structures. Liquids take the shape of the container but they have definite volume. Gases are free to move anywhere. They have low density and high compressibility.

Complete step by step answer:
Solids, liquids and gases are the three physical states of a matter.
Solids have low density and high compressibility.
Liquids have high density and low compressibility.
Gases have high density and low compressibility.
Two factors determine whether a substance may be a solid, a liquid or a gas.
Kinetic energy
Intermolecular force
The kinetic energies of the particles (atoms, molecules (or) ions) make up a substance. The particles move apart from each other due to kinetic energy.
The substance would not condense to form a liquid (or) solid, if the average kinetic energy is bigger than the attractive forces between the particles. If the kinetic energy is less than the attractive force, the formation of solid (or) liquid takes place.
The energy passed by matter due to heat energy is known as thermal energy. The thermal energy increases, and hence, it tries to keep the particles apart.
We know that kinetic energies depend on the temperature and it tends to keep particles apart and moving interparticle attractions draw particles together.
The attractive intermolecular forces between particles tend to draw the particles together.
In gases, the average kinetic energy of the particles is sufficient to overcome the forces of attraction between them. The molecules of a gas move from each other on collision.
In liquids (or) solids, the average kinetic energy of the particles is small and the attractive force between them is enough to hold the particles close together. Liquid molecules (or) solid molecules do not move apart.
The interparticle attraction is known as intermolecular force.
The increase in temperatures forces the molecules to be closer with each other. Increase in temperature, also increases the strength of intermolecular force.

Note:
In solids, the intermolecular forces are stronger since the particles are tightly packed with each other. In liquids, the intermolecular forces are not strong enough to keep the molecules from moving particles, hence liquids hold the shape of the container. In gases, the intermolecular forces are very weak, and the weak intermolecular force allows gases to expand. The types of attractive forces/intermolecular forces are,
-Dipole-Dipole forces
-Induced-dipole forces
-Hydrogen bonding
-London dispersion forces