NCERT Solutions for Class 9th Science
Chapter 2. Is Matter around us Pure
- The substance are the same in their chemical nature and consists of a single type of particles are called pure substance.
- Mixture: A mixture is a combination of two or more substances which show the properties of each of the substance combined. E.g: A mixture of iron powder and sulphur show the properties of both sulphur and iron.
- The concentration of a solution is the amount of solute present
per unit volume or per unit mass of the solution/solvent.
- There are two types of mixture. (i) Homogenous Mixture (ii) Heterogenous Mixture.
- Mixture having uniform composition are called homogeneous mixture.
- Those mixture that do not have uniform composition are called heterogeneous mixture.
- Type of solution: (i) Colloidal Solution (ii) Concentration Solution (iii) Suspention.
- Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods.
- Air is a homogeneous mixture of a number of gases. Its two main constituents are: oxygen (21%) and nitrogen (78%). The other gases are present in very small quantities.
- A solution of iodine in alcohol known as ‘tincture of iodine’.
- If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.
- Mercury is the only metal that is liquid at room temperature.
- Some elements have intermediate properties between those of
metals and non-metals, they are called metalloids. Examples:- Boron,
silicon, germanium etc.
- Elements, gallium and cesium become liquid at a temperature
slightly above room temperature (303 K).
- Crystallisation is a process that separates a pure solid in the
form of its crystals from a solution. Crystallisation technique is better than simple evaporation technique.
- A dye is a mixture of two or more colours. The coloured component that is more soluble in water, rises faster and in this way the colours get separated.This process of separation of components of a mixture is known as chromatography.