NCERT Solutions for Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry

Chemistry is the branch of science that deals with the properties, composition, and structure of elements and compounds, how they can change, and the energy that is released or absorbed when they change.

Chemistry is essential for meeting our basic needs of food, clothing, shelter, health, energy, and clean air, water, and soil. Chemical technologies enrich our quality of life in numerous ways by providing new solutions to problems in health, materials, and energy usage.

The following is the nature of matter: Atoms that have protons, neutrons, electrons and a nucleus consist of matter. It generally exists in four states i.e. liquid, solid, gaseous and plasma state. The universe itself is a matter. Not all forms of energy are matter.

matter can exist in three physical states viz., solid, liquid and gas. different states of matter exhibit the following characteristics:

• (i) Solids have definite volume and definite shape.
• (ii) Liquids have definite volume but do not have definite shape. They take the shape of the container in which they are placed.
• (iii) Gases have neither definite volume nor definite shape. They completely occupy the space in the container in which they are placed.

• Physical Properties
  Examples of physical properties are temperature, malleability, appearance, texture, odour, colour, shape, solubility, melting, freezing, and boiling point. Volume, mass, length, density, pressure, viscosity, and hardness are a few more physical properties.
• Chemical Properties
  Chemical properties are those that get observed or measured when the substance undergoes a chemical change. Examples of chemical properties are – toxicity, chemical stability, the heat of combustion, flammability, reactivity, and enthalpy of formation.

Avogadro proposed that equal volumes of all gases at the same temperature and pressure should contain equal number of molecules.

The following are the Dalton’s Atomic Theory:

1. Matter consists of indivisible atoms.
2. All atoms of a given element have identical properties, including identical mass. Atoms of different elements differ in mass.
3. Compounds are formed when atoms of different elements combine in a fixed ratio.
4. Chemical reactions involve reorganisation of atoms. These are neither created nor destroyed in a chemical reaction.