What is the most abundant gas in the air?
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What is the most abundant gas in the air?
The most abundant gas in the earth's atmosphere is nitrogen.
True or False?
The atmosphere consists of approximately 80% oxygen.
False.
Oxygen makes up 20% of the earth's atmosphere, with nitrogen making up 80%.
True or False?
The proportion of gases in the air has changed significantly in the last 200 million years.
False.
The proportion of gases in the air has not changed much in 200 million years.
Give the percentage of nitrogen in the air.
The approximate percentage of nitrogen in the air is 78-80%.
How do scientists know the historic composition of air?
Scientists know the historic composition of the air by analysing tiny air bubbles trapped in ice cores taken at the poles.
State what is meant by the term combustion.
Combustion is the process of burning a substance in oxygen.
True or False?
Combustion reactions can also be classified as oxidation reactions.
True.
Combustion reactions can also be classified as oxidation reactions as the elements in the fuel react with oxygen.
Write the balanced symbol equation equation for the combustion of magnesium.
The balanced symbol equation equation for the combustion of magnesium is:
2Mg (s) + O2 (g) → 2MgO (s)
Define the term exothermic.
The term exothermic relates to a chemical reaction that releases heat energy.
Why are combustion reactions exothermic?
Combustion reactions are exothermic because they give out heat energy.
Write the word equation for the combustion of sulfur.
The word equation for the combustion of sulfur is:
sulfur + oxygen → sulfur dioxide
Give two observations you would make when magnesium undergoes combustion.
Two observations you would make when magnesium undergoes combustion are:
A white flame
A white powder is produced
Define thermal decomposition.
Thermal decomposition is the break down of a substance using heat.
What happens during the thermal decomposition of a metal carbonate?
During the thermal decomposition of metal carbonates, the metal carbonate decomposes on heating to produce the metal oxide and carbon dioxide gas.
State the general equation for the thermal decomposition of metal carbonates.
The general equation for the thermal decomposition of metal carbonates is:
metal carbonate → metal oxide + carbon dioxide
Write the word equation for the thermal decomposition of copper(II) carbonate.
The word equation for the thermal decomposition of copper(II) carbonate is:
copper(II) carbonate → copper oxide + carbon dioxide
Write the balanced symbol equation for the thermal decomposition of copper(II) carbonate.
The balanced symbol equation for the thermal decomposition of copper(II) carbonate is:
CuCO3 (s) → CuO (s) + CO2 (g)
Describe a test that could be used to identify the carbon dioxide gas produced during thermal decomposition.
A test that could be used to identify the carbon dioxide gas produced during thermal decomposition is to bubble the gas through limewater and it should turn cloudy.
What observations could be made when copper(II) carbonate undergoes thermal decomposition?
The observations which could be made when copper(II) carbonate undergoes thermal decomposition are that the green copper(II) carbonate powder darkens to form black copper(II) oxide.
True or False?
Making cement increases the amount of atmospheric CO2.
True.
Making cement releases CO2 when calcium carbonate is turned into calcium oxide.
Name three greenhouse gases.
Three greenhouse gases are carbon dioxide, water vapour and methane.
What is the greenhouse effect?
The greenhouse effect refers to greenhouse gases in the atmosphere absorbing and trapping infrared radiation emitted from the Earth's surface, causing warming.
Give the environmental effect of the increased amount of greenhouse gases in the atmosphere.
The environmental effect of the increased amount of greenhouse gases in the atmosphere is climate change / global warming.
Give two activities which release carbon dioxide into the atmosphere.
Two activities which release carbon dioxide into the atmosphere are:
combustion of fossil fuels.
respiration.
thermal decomposition.
deforestation.
What happens to infrared radiation emitted from the Earth's surface in the greenhouse effect?
It gets absorbed and trapped by greenhouse gases in the atmosphere.
What is the difference between the greenhouse effect and the enhanced greenhouse effect?
The greenhouse effect maintains a suitable average global temperature.
The enhanced greenhouse effect refers to increased warming due to higher levels of greenhouse gases.
What type of radiation from the sun gets absorbed and re-emitted as infrared by the Earth's surface?
The type of radiation from the sun which gets absorbed and re-emitted as infrared by the Earth's surface is short wavelength radiation / UV.
True or False?
Energy from the sun is absorbed and re-emitted at shorter wavelengths.
False.
Energy from the sun is absorbed and re-emitted at longer wavelengths in the form of infrared radiation.