• Anything in the universe that has mass and volume is made up of matter. Matter can exist in different forms due to the internal and external factors.
• At a given temperature and pressure a substance can exist mainly in one of three major states of matter: solid state, liquid state, and gaseous state of matter.
• All matter is composed of atoms, each of which has a central nucleus and one or more electrons moving around the nucleus.
• There are two major types of chemical bonds: covalent bonds and ionic bonds.
• A molecule is the simplest unit of a covalent compound that contains the physical and the chemical properties of the compound.
• One important application of kinetic theory is that it helps to explain why matter exists in the three different phases and how matter can change from one state to the next.
• Intermolecular forces are forces between interacting molecules and can be either attractive or repulsive. This force is attractive between neighboring molecules until they are very close and electrostatic forces come into play.
• The magnitude of the repulsion rises very rapidly as the distance separating the molecules decreases. This is the reason that liquids and solids are hard to compress.
• Attractive intermolecular forces are known as van der Waals forces. The van der Waals forces or van der Waals bonds in water are due to unsymmetrical charge distribution in the molecule that leads to a net attraction between polar molecules.
• Thermal energy is the energy of a body arising from motion of its atoms or molecules. It is directly proportional to the temperature of the substance. This movement of particles is called thermal motion.
• Thermal motion in a substance produces a dispersive force. This force acts opposite to the attractive intermolecular force.
• The attractive intermolecular forces tend to keep the molecules together by canceling out the dispersive force due to their thermal energy.
• The attractive forces between like molecules or atoms are referred to as cohesive forces. Attractive intermolecular forces between unlike atoms or molecules are said to be adhesive forces.
• Elasticity is the property of matter by virtue of which the deformed body returns to its initial configuration after the removal of the deforming force.
• The maximum force that the object can withstand without being permanently deformed is called the elastic limit.
• Plastic deformations are deformations where irreversible changes occur on shape or size after it is being deformed.
• The relative displacements of the various parts of a body under the action of an external force produce an internal force tending to restore the body to its original configuration.
• According to Newton’s third law, the internal force is equal in magnitude but opposite in direction to the applied force. Stress is measured at equilibrium.
• Tensile deformation occurs when two forces of equal in magnitude and opposite in direction act perpendicularly on the cross-sections of opposite ends of a material such as a rod or a wire.
• Tensile stress is defined as the ratio of tensile force F to the cross – sectional area A of the wire.

• Tensile strain is defined as the fractional change in length; i.e., the ratio of the extension L produced by the tensile stress to the original length (L0) of the wire.

• The stress applied to a wire produces a strain in it. Young’s modulus measures how much the wire stretches. It is defined as

The SI unit of Young’s modulus is N/m².

• Hooke’s law is stated as the stretch on a body is directly proportional to the applied force, provided that the applied force is below the elastic limit of the material.

F = Kx

where the proportionality constant k is known as the stiffness of the material and its SI unit is N/m.

• Surface tension is caused by the forces of attraction between the particles of the liquid and the other substances with which it comes in to contact.
• Surface tension is defined as a cohesive effect of the surface of the liquid due to the forces between the liquids atoms or molecules.
• The magnitude of surface tension of a liquid is large when the attractive intermolecular forces between the molecules are large. Hence surface tension can be reduced by heating the liquid
• Diffusion is the spreading out or mixing of a substance with another substance caused by the motion of its particles.
• The process of diffusing a substance into another substance continues until a homogeneous mixture is achieved.
• The higher the density of the diffusing substance, the lower the rate of diffusion
• As the temperature rises, diffusion rate increases.
• Viscosity arises due to the internal friction between layers of fluid as they slip past one another while fluid flows.
• In liquids, this resistance is due to the strong intermolecular forces between molecules.
• The greater the viscosity, the more slowly the liquid flows. Hydrogen bonding and van der Waals forces are strong enough to cause high viscosity.
• Increase in temperature reduces viscosity.
• Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation.