Page 150 - ICSE Chemistry 8

7 Hydrogen

Learning Outcomes Key Concepts
Students will be able to
• Occurrence of Hydrogen
• describe the prepara on of hydrogen from electrolysis of water.
• Discovery of Hydrogen
• prepare hydrogen in the lab, using zinc and acid.
• Preparation of Hydrogen
• describe proper es and uses of hydrogen.
• Properties of Hydrogen
• correlate concepts of oxida on and reduc on with addi on and removal
of oxygen or removal and addi on of hydrogen. • Oxidation and Reduction
• Uses of Hydrogen

Warm Up Activity

Name any three compounds which consist of hydrogen as an element.
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What is the valency of hydrogen? ______________

Give any two uses of hydrogen.
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The fi rst element in the periodic table, hydrogen is the simplest and the lightest element. It is also the
most abundant of all the elements in the universe. The sun which is the ul mate source of energy is a
big ball of hot gases, mainly composed of hydrogen and helium. The stars and giant gas planets are also
made up of hydrogen. An atom of hydrogen consists of one proton around which one electron revolves.
Two atoms of hydrogen combine to form a hydrogen molecule (H ).
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OCCURRENCE OF HYDROGEN
Thirst for Knowledge
Hydrogen makes up almost 90% of the ma er in the universe.
Symbol of hydrogen atom: H
The outer atmospheres of the sun and the stars are majorly
composed of hydrogen. However, it makes up only 1.0% of the Symbol of hydrogen molecule: H 2
earth’s crust, oceans and atmosphere. There is prac cally no Atomic number: 1
hydrogen in the earth’s atmosphere. This is because the free Valency: 1
hydrogen is so light that it has escaped far above the earth into Atomic mass: 1.00794 amu
the outer atmosphere. Atomicity: 2

On earth, hydrogen occurs in free state in very small quan es, mainly in volcanic gases and clouds.

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