Page 53 - Science Class 07

MIXTURES mixture. It will a ract the iron-dust that will

A mixture is formed of li le bits of one or more s ck to it leaving the sulphur-powder behind.
substances mixed together. Usually, the parts Mixtures can be of various types as under:
can be separated from each other by physical
No. Types of Mixtures Example
means, because it does not involve any
1. mixtures of gases air
chemical reac ons or bonds.
2. a gas and a liquid aerated water
Kinds of Mixtures
3. a mixture of liquids lemonade
Heterogeneous mixture : A mixture that shows 4. a solid and a liquid sugar solu on
visible boundaries of its cons tuents when 5. a mixture of solids rice and pulse
examined closely under the microscope or 6. a solid and a gas smoke
even by naked eyes, e.g., the mixture of air an
carbon par cles (smoke), mixtures of iron and A mixture has the following proper es:
sulphur, mixture of sand and water shows v It has its cons tuents present in any ra o.
visible boundaries between them even when
v Its cons tuents have their par cles lying
examined by naked eyes.
side-by-side.
Homogeneous mixture : Homogeneous
v Its cons tuents can be separated by simple
mixture has the same composi on throughout
mechanical methods.
the sample. It does not show any visible
v Its cons tuents show their respec ve
boundaries of its cons tuents even when
proper es, e.g, lemonade has the sour
examined under the microscope.
taste of a lemon and also the sweet taste of
For example, salt solu on, sugar solu on,
sugar.
carbonated water (carbon dioxide dissolved in
v Heat is generally not involved in the
water), etc.
forma on of a mixture.
Let us take two elements — iron and sulphur in
v Forma on of a mixture is a physical
their powdered form. If we mix them in any
ra o, their par cles will not combine through temporary change in which no new
any ac on, but remain laying side-by-side. substance is formed. So, this change is
reversible.
v The composi on of a mixture is uniform,
i.e., homogeneous.

v A mixture is generally made up of atoms
of more than one element par cle of
compound or both.
v A mixture can be a solid, liquid or gas.

CHEMICAL COMPOUNDS
A chemical compound is a chemical substance

Mixture of Iron and Sulphur consis ng of two or more different chemically
bonded chemical elements, with a fixed ra o
We can separate the two components of this
determining the composi on.
mixture simply by bringing a magnet near the

Science-7 53