Page 35 - ICSE Chemistry 6

• A compound always contains the same elements combined together in a fi xed ra o.
For example, the composi on of water always remains the same. It always contains hydrogen and
oxygen in the ra o of 2:1.
• A compound is pure and homogeneous.

• The proper es of a compound are diff erent from those of Thinking Fountain
What is the diff erence between
its cons tuent elements. For example, hydrogen and oxygen
the molecules of an element and
combine to form water. Here hydrogen and oxygen are gases
the molecules of a compound?
but the compound water is a liquid.

• The cons tuents of a compound cannot be separated by physical means like boiling, fi ltra on,
evapora on, etc. A compound can be broken down into its cons tuent elements by chemical
methods. For example, we cannot separate oxygen and hydrogen from water by simple physical
means like boiling.
To break down water into its cons tuents, electricity is passed through water mixed with an acid,
and as a result, the molecules of water split to give hydrogen and oxygen.
• Energy is either absorbed or given out when a compound is formed. For example, oxygen
and hydrogen combine chemically to form water and during this process energy is produced in the
form of heat and light.

Table 2.5: Diff erences between Elements and Compounds
Element Compound

• A compound contains two or more elements
• An element is made up of only one kind of substance.
combined together in a ϐixed ratio.
• An element cannot be broken down into simpler • A compound can be broken down into its constituent
substances by chemical methods. elements by chemical methods.
• The properties of a compound differ from those of its
• An element has its own set of properties.
constituent elements.

• An element is represented using a symbol. • A compound is represented using a formula.

Take a Break!

Write/Choose the correct answer.

1. An element cannot be __________ into simpler substances by normal chemical means.
2. Most of the metals are found in the earth’s __________.

3. __________ do not react chemically with other elements.
4. __________ possess some proper es of metals and some proper es of non-metals.

5. Water is a compound. (True/False)
6. A compound is represented using a _______________.

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