Page 54 - Science Class 07
P. 54
v Water is a compound of hydrogen and Chemical compounds have dis nct proper es:
oxygen in the ra o 2:1. v Every compound has its components
v Sugar is a compound of carbon, hydrogen present in a definite ra o.
and oxygen in the ra o 12:22:11. v Every compound has its proper es that
v Carbon dioxide is a compound of carbon differ from those of its components.
and oxygen in the ra o 1:2. v A compound may be a solid, liquid or gas.
v Methane is a compound of carbon and v The cons tuents of a compound cannot be
hydrogen in the ra on 1:4. detected separately.
v Ammonia is a compound of nitrogen and v The cons tuents of a compound cannot be
hydrogen in the ra o 1:3. separated through simple methods, but
through chemical methods only.
We made a mixture of iron and sulphur in this
chapter. If we heat that mixture ll it begins to v As a compound is made up of different
glow, a new substance will be formed. It will be elements, its composi on is heterogeneos,
different from iron and sulphur both. This i.e., its molecules are made up of different
substance has a compound name iron sulphide. elements.
Iron + Sulphur Iron Sulphide v The smallest par cle of a compound is a
(grey) (yellow) (black) molecule, not atom.
Compounds can also be formed in various ways v The forma on of a compound is a chemical
and permanent change that cannot be
as the atoms can combine in different ways to
easily reserved.
form various compounds. In some cases, atoms
of the same elements can combine in different v Compounds occur in a variety of colours.
ra os to form different compounds. v Some compounds quickly undergo a
For example: chemical ac on, but other react slowly.
v Carbon and hydrogen combine in the ra o v Compounds fall into two major groups
1:4 to form methane, a major component organic and inorganic. Organic compounds
contain carbon, fats, carbohydrates and
of natural gas.
protein while inorganic compounds do not.
v Carbon and hydrogen combine in the ra o
How can you determine a substances is an
3:8 to form propane that is used in
element or a mixture or a compound?
torches.
As you know different elements have different
v Some compounds are made up of elements
physical proper es. Therefore, in case of a
only as sodium chloride is made up of
mixture, it is easy to dis nguish its form, an
sodium and chlorine.
element or a compound. But it is li le bit
v Compounds can also be made up of the difficult to dis nguish a compound from an
compounds. Such compounds are called element.
complex compounds. Living things have For this, it has two methods:
the property to make various compounds
v Decompose it into its cons tuent elements.
combine toghter.
Hydrogen + Oxygen Water
elements compound
54 Science-7
