Chemistry Topic 2C - Gasses in the Atmosphere

Combustion

A chemical reaction where a substance is burnt in oxygen, releasing (heat) energy

Thermal decomposition

A chemical reaction where a substance is broken down into two or more products when heated up

Greenhouse gas

A gas that absorbs infrared radiation (heat) from the sun and traps it in the atmosphere, warming the planet

How do we know that there was no oxygen in Earth's early atmosphere

Some ancient rocks contain iron compounds that break down in the presence of oxygen. They could have only formed if there was little or no oxygen at the time.

% of nitrogen in the air

78%

% of oxygen in the air

21%

% of argon in the air

0.9%

% of carbon dioxide in the air

0.04%

What are the two types of energy formed during combustion?

Light and heat

Complete combustion

Occurs when there is an unlimite supply of air so that elements in the fuel react fully with oxygen

What is produced when hydrocarbons undergo complete combustion

Carbon dioxide and water

During complete combustion of hydrocarbons, what happens to the carbon?

Carbon will oxidise to form carbon dioxide

During complete combustion of hydrocarbons, what happens to hydrogen?

Hydrogen will oxidise to form water

Hydrocarbon

A compound made of only hydrogen and carbon atoms

Incomplete combustion

Combustion when there is a limited supply of air so that elements in the fuel do not react fully with the oxygen

What is formed during imcomplete combustion of hydrocarbons

Water and carbon monoxide or soot

Carbon monoxide

A poisonous, colourless, odourless gas

What colour is a flame during complete combustion

Blue

What colour is a flame during incomplete combustion

Yellor/orange

Energy release during complete combustion

Unlimited

Energy release during incomplete combustion

Limited

During complete combustion, where should the air hole be on a bunsen burner

open

During incomplete combustion, wehre should the air hole be on a bunsen burner

Closed

Observation during the combustion of magnesium

Bright white flame, and the production of a white solid (magnesium)

Observation during the combustion of hydrogen

A bright orange/red flame that leaves little droplets of water. Makes a squeaky pop sound

Observation during the combustion of sulphur

A bright blue flame which produces clouds of fumes (sulphur dioxide)

Observation during thermal decomposition of copper carbonate

Green solid turns black and bubbles

Word equation for the complete combustion of magnesium

Magnesium + Oxygen --> Magnesium oxide

Word equation for the incomplete combustion of a hydrocarbon

Hydrocarbon + oxygen --> Water + carbon monoxide + carbon

Observation during the therml decomposition of zinc carbonate

White solid turns yellow, but returns to white when cooled