Page 33 - Understanding NCERT Science 09

• Mixtures can be separated into pure substances using
appropriate separation techniques.
• A solution is a homogeneous mixture of two or more
substances. The major component of a solution is called the
solvent, and the minor, the solute.
• The concentration of a solution is the amount of solute present
per unit volume or per unit mass of the solution.
• Materials that are insoluble in a solvent and have particles
that are visible to naked eyes, form a suspension.
A suspension is a heterogeneous mixture.
• Colloids are heterogeneous mixtures in which the particle
size is too small to be seen with the naked eye, but is big
enough to scatter light. Colloids are useful in industry and
daily life. The particles are called the dispersed phase and
the medium in which they are distributed is called the
dispersion medium.
• Pure substances can be elements or compounds. An element
is a form of matter that cannot be broken down by chemical
reactions into simpler substances. A compound is a substance
composed of two or more different types of elements,
chemically combined in a fixed proportion.
• Properties of a compound are different from its constituent
elements, whereas a mixture shows the properties of its
constituting elements or compounds.

Exercises

1. Which separation techniques will you apply for the separation
of the following?
(a) Sodium chloride from its solution in water
(b) Ammonium chloride from a mixture containing sodium
chloride and ammonium chloride
(c) Small pieces of metal in the engine oil of a car
(d) Different pigments from an extract of flower petals
(e) Butter from curd
(f) Oil from water
(g) Tea leaves from tea
(h) Iron pins from sand
(i) Wheat grains from husk
(j) Fine mud particles suspended in water

22 SCIENCE

Rationalised 2023-24