MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 9ga1
9Ga1 Investigating soils
Name _____________________________ Class ____________
Test soil samples taken from different locations, and record your results.
Recording your results
Soil sample
Texture
Appearance
pH
Stickiness when dry
Stickiness when damp
Mass when dry
Mass when wet
Mass of water held by soil
1 Which soil sample has the highest pH?
2 Which soil sample has the lowest pH?
3 List the soils in order of increasing acidity.
4 Which soil sample has the most grains of rock?
5 Which soil sample is the stickiest when it is damp?
6 Which soil holds the most water?
7 Which soil holds the least water?
Considering your results/conclusions
8 What do your results tell you? Can you see any patterns?
9 What do you think gives the soil a particular pH value? Where did this come from?
[ observing, considering ]
9Ga2 Acids and alkalis
Complete the following sentences, using words from the box.
Acids and alkalis are types of _______________ . The _______________ scale is used to measure
how acidic or _______________ a solution is. To test a solution we use an _______________
which changes _______________ as the pH changes.
colour pH indicator alkaline solution
Colour in the indicator chart below to show the colours of universal indicator at different pH values.
In this experiment you will find the pH of different solutions.
Apparatus
- Some common solutions
- Universal indicator liquid
- Dimple tile
- Eye protection
Method
1 Add a drop of a solution to a dimple in the tile.
2 Add a drop of universal indicator to the dimple.
3 Use a fresh dimple for each solution.
Wear eye protection.
Recording you results
Solution
Colour of indicator
Type of solution
[ knowledge, observation ]
9Ga3 Soil survey
Test the pH of the soil and record the plants you find in different locations around the school.
Location
Description of soil
Plants found
Is there any pattern in your results? If there is, what is the pattern?
_______________________________________________________________________________
Are any plants found only in more acidic soils or more alkaline soils?
9Ga4 Neutralising soil
Complete the sentences using words from the box.
Soil is a _________________ of different materials including _________________
_________________, humus and _________________.
The mixture of these materials makes some soils more _________________ or alkaline than others.
We can test the acidity of a sample of soil using a soil _________________ kit. This contains an
_________________ which changes colour with different pHs.
If the pH of a soil is _________________ than 7, the soil is acidic.
If the _________________ is more than _________________ , the soil is alkaline.
Some _________________ prefer to grow in soil of a particular pH. This may mean that you
cannot grow the plants you want in your soil.
The acidity of soil can sometimes be changed.
Acids can be _________________ by adding an alkali.
If a soil is too acidic, it can be neutralised by adding _________________ to _________________
the pH of the soil.
If the soil is too alkaline, the pH can be _________________ by adding some _________________
or some _________________ .
acidic indicator less lime lowered mixture
neutralised peat pH plants raise
rock particles manure 7 testing water
[ knowledge, literacy ]
9Ga5 Rocks and weathering
Complete the following paragraphs, using words from the boxes.
1 Both _________________ rocks and those used as _________________ materials become
over time. The _________________ up and _________________ away of rocks is called
_________________ and it happens in several different ways.
Some examples are shown below.
Weathering by
________________________ .
breaking building changed freezing natural rain wearing
weathering wind
2 The bits of rock are then _________________ away by streams and _________________
This is called _________________ . As the rocks are washed along they are
_________________ up into _________________ pieces. The smallest bits of rock are called
sand and _________________ . Eventually, the water flow _________________ down and
the sand, clay and gravel are. This is called _________________ . The bits of rock formed by
_________________ and erosion that are not washed out to sea become a home for
_________________ and tiny animals. Eventually soil is formed.
Sedimentation.
broken clay deposited erosion plants rivers
sedimentation slows smaller washed water weathering
9Ga6 At home in any soil?
Imagine that you have a plot of land, like an allotment, on which you must grow all the fruit and vegetables you need to feed yourself. Some plants only grow really well in soils which have a particular pH. You test the soil in different parts of the plot and find that the pH is 7.0 across the whole of the plot.
You need to grow a wide variety of fruit and vegetables in order to have a healthy and interesting diet, but these plants may need very different soil conditions in order to grow large enough to provide you with enough food.
The table below shows the conditions preferred by some fruit and vegetables.
Fruit or vegetable
Preferred pH
apples
6.5 -7.0
asparagus
6.5- 7.0
apricots
6.0 - 7.0
beans
5.0 - 6.5
grapes
broccoli
6.5 - 7.0
pears
brussels sprouts
5.6 - 6.5
rhubarb
cabbage
watermelon
5.0 - 5.5
cucumbers
potatoes
leeks
squash
onions
turnips
1 Which of these plants would not grow well in the soil found naturally on your plot?
2 Draw a block chart, like this, to show the preferred pHs of the plants.
3 What pH would be able to grow the widest variety of plants?
4 What would you do to the soil to get it to this pH?
5 Which plants will still not grow well, after you have treated the soil?
[ knowledge, numeracy ]
9Ga7 Growing hydrangeas
As a scientist, you have been asked to solve an argument. Fred has been growing flowers for 20 years but has never managed to grow blue hydrangeas. He says that they are very rare and although he has bought several hydrangeas in the past, they have always had pink or white flowers. Sylvia lives down the road. She has only been gardening for a couple of years, but she has several hydrangea plants, each of which has blue flowers. Sylvia says that she gets blue flowers because the pH of her soil is different from the pH of Fred's soil.
A hydrangea plant.
Read the following article from 'Judith's Gardening Tips'
'Hydrangeas are amazing plants and you can actually change the colours of the flowers. The flower colour in most hydrangeas relates to the pH of the soil. In acidic soil (pH 5 or less) the flowers are blue. In soil that has a pH of more than 5 the flowers are pink or red. You can buy a 'blueing tonic' which contains aluminium and acid and will turn pink or red hydrangeas blue. It should be applied once a month in March and April and then again in August, September and October. A cup of calcium carbonate added to the soil in spring will turn blue hydrangeas pink. White flowering hydrangeas will stay white no matter what the pH of the soil is.'
1 Is the pH of the soil in Fred's garden more than pH 5 or less than pH 5? Explain your reasoning.
2 Is the pH of the soil in Sylvia's garden more than pH 5 or less than pH 5? Explain your reasoning.
3 Write a letter to Fred and explain to him about hydrangeas and soil pH. Explain to him how to turn the flowers blue. Explain why this method works.
4 Write a letter to Sylvia and explain to her how to turn her hydrangeas pink. Explain why this method works.
9Gb1 Acid rain on materials
You are going to investigate what kinds of materials are affected by acid rain.
- Bottle of acid rain
- Samples of different rocks and metals
- Test tubes
- Test tube rack
- Forceps
1 You will be given a sample of acid rain and some different types of rocks and metals.
2 Using forceps place a small sample of each rock or metal into a different test tube.
3 Add a little acid rain to each of the substances in a test tube.
4 Watch what happens over a period of time. Record your observations in the table on the next page.
5 If possible, leave the experiment in a safe place and note what happens over an even longer period.
Substance
Effect of acid rain
Immediately
After 5 minutes
After 30 minutes
Acid rain affects certain rocks like ________________ and ________________ which contain metal
________________ . Some metals, like ________________ and ________________ , are also
affected by acid rain.
carbonates zinc marble magnesium limestone
9Gb2 Oxides
You are going to test some solutions of oxides of different elements and then make some predictions.
- Bottles of oxide solutions
- Universal indicator solution or test papers
- Pipettes
1 Add 1 cm3 of each solution to a separate test tube.
2 Add a few drops of universal indicator solution (or a piece of universal indicator paper) to each test tube.
3 Record the colours of the indicator in the table below and complete the table.
Complete the following table to show what pH each solution was and whether it is an acid or an alkali.
Indicator colour
Considering your results/conclusion
Write out a list of the solutions in pH order, starting with the most acidic.
Solutions of metal oxides are ___________________ and solutions of non-metal oxides are
___________________ .
Prediction
Your teacher will show you how sulphur dioxide and magnesium oxide are made. These oxides will then be dissolved in water. Complete the sentence below to say what you think will happen.
I predict that, when dissolved in water, sulphur dioxide will form an ___________________ and
magnesium oxide will form an ___________________ .
Was your prediction correct? ___________________
Write one or two sentences to sum up what you have learnt from this experiment.
9Gb3 Metals and acid rain
Acid rain reacts with many metals and eventually the metal can dissapear. For example, metals like magnesium react quickly with acids. You are going to carry out an investigation to find out how the concentration of acid rain affects the speed of the reaction with magnesium. The concentration of a solution is the amount of the solute dissolved in a certain volume of solvent.
1 How will changing the concentration of the acid rain affect the speed of reaction with magnesium?
Planning
2 Design an experiment to find out if your prediction is correct. Write out your plan and show it to your teacher before you start. You will need to think about these things:
a What variables could affect how quickly magnesium reacts with acids? Which variables are you going to use?
b What variables will you need to keep the same to do a fair test?
c What apparatus will you use? You may need some of the apparatus in the box below.
- Acid rain solutions - Pieces of magnesium
- Test tubes - Test tube rack
- 10 cm3 measuring cylinder - Dropper
- Emery paper - Stopwatch or stopclock
- Eye protection - Pipette
d You will need to make up a series of solutions of acid rain of different concentrations. You could use solutions like the ones shown in the table below. How many concentrations will you use?
Volume of acid
Volume of water
1
2 cm3
8 cm3
2
4 cm3
6 cm3
3
e How will you do your experiment safely?
f Show your plan to your teacher.
3 Draw up a table of your results. Remember to name the measurements and units that you used. Your teacher may help you with the table.
4 Draw a graph of the results to show how the time for the reaction changes as the concentration of acid changes.
5 Look at your results.
a As the concentration of acid rain changed what happened to the time taken for the magnesium to react until it had dissappeared?
b Copy and complete the following conclusion:
The ____________________ the concentration of the acid rain the
____________________ the reaction with metals.
6 a Compare this conclusion with other groups in the class. Do they all agree?
b Using the class results can you be sure whether your conclusion is correct?
If not, why not?
7 Was your prediction correct?
Evaluation
8 Can you suggest any improvements to the way you did your experiment to make the results even more accurate?
[ planning, observing, presenting, considering, evaluating ]
9Gb4 The formation of acid rain
1 Cut out the boxes at the bottom of the page. Stick them in the correct boxes to show the main stages in the formation of acid rain.
2 Look at your diagram. Colour in red all the ways that acidic gases are naturally released into the atmosphere. Colour in blue all the ways that acidic gases are released into the atmosphere by people.
[ knowledge ]
---------------------------------------------------------------------------------------------------------
Volcanoes release sulphur dioxide when they erupt.
Clouds cool and release acidic rain.
Living plants and animals release carbon dioxide.
Burning fossil fuels releases a lot of carbon dioxide and a lot of sulphur dioxide.
Car engines release nitrogen oxides.
Acidic gases are released into the atmosphere.
Acid rain falls onto the land and runs into streams and rivers.
Acidic gases dissolve in moisture in the air.
9Gb5 Limestone caves
The largest caves in Britain are formed by the action of acidic rain on limestone rocks. An interesting feature, found in many limestone caves, is the formation of stalactites and stalagmites.
Formation of limestone caves.
1 Write a report about limestone caves. The report should include answers to some or all of the following questions.
a What are limestone caves?
b Where are limestone caves found?
c How are the caves formed?
d What chemical reactions are involved in their formation?
2 Find out about the formation of stalactites and stalagmites and include it in your report.
You could get information for your report about limestone caves from textbooks, CD-ROMs and the Internet.
Your report should be about 300 to 400 words long and include labelled diagrams, drawings and chemical equations wherever possible.
[ knowledge, literacy, research ]
9Gb6 Where does it come from? 1
Sulphur dioxide is produced when fossil fuels are burned in places like power stations. The sulphur dioxide dissolves in water in the atmosphere to make acid rain.
1 What is acid rain?
__________________________________________________________________________
2 Give one example of a fossil fuel.
Look at this graph:
3 On the map of Europe shade in the two countries that produced the most sulphur dioxide.
4 Put an 'X' on the three countries which produced the least sulphur dioxide.
Look at this table:
Country
Amount of sulphur dioxide in the atmosphere (micrograms per m3)
Czech Republic
50
Germany
15
Greece
45
Iceland
Norway
20
Sweden
United Kingdom
25
5 On the map, put a 'Y' on the two countries that had the most sulphur dioxide in their atmosphere.
6 On the map, put a 'Z' on the two countries that had the least sulphur dioxide in their atmosphere.
7 What do you notice about the data for Germany?
8 What do you notice about the data for Norway and Sweden?
9 Where do you think the acid rain comes from that falls on Norway?
9Gb7 Where does it come from? 2
Sulphur dioxide produced in thousands of tonnes (1995)
1100
2100
550
30
40
90
2300
2 Give three examples of fossil fuels.
3 Plot the data in the table as a bar chart.
4 Which two European countries produced the most sulphur dioxide?
5 Which three countries produced the least sulphur dioxide?
The map shows the amount of sulphur dioxide present in the atmosphere in various countries in Europe. The data is also shown in the bar chart below.
6 Which two countries had the most sulphur dioxide in their atmosphere?
7 Which two countries had the least sulphur dioxide in their atmosphere?
8 What do you notice about the data for Germany?
9 What do you notice about the data for Norway and Sweden?
10 Where does the acid rain come from that falls on Norway?
11 Look at the data for Iceland. Iceland has a lot of geothermal activity. This means that there are sources of hot water and steam close to the surface of the Earth. Why do you think that Iceland does not produce a lot of sulphur dioxide?
9Gb8 The effects of acid rain
Acid rain has a pH value between pH 5.5 and pH 2 - in some cases, the rain is as acidic as vinegar! The acidity of the rain depends upon the amount of acidic gases dissolved in it. Some areas of the country, and even some countries around the world, will have a bigger problem than others.
When acid rain reaches streams and lakes, it makes them acidic. This may kill the water life, including any fish.
When acid rain falls on the ground, it soaks into the soil and reacts with the minerals in the soil. This may prevent plants from taking up minerals such as iron, zinc and magnesium which they need for healthy growth. As a result, plants and even well established trees may die.
When acid rain falls directly onto plants, it may damage new shoots and leaves. This also prevents the plant from growing.
When acid rain falls on buildings and other structures it also causes damage. The acid rain reacts with any carbonates contained in the rocks used for building. Acid rain also corrodes metals such as iron, weakening bridges and other large structures.
Choose Task A or Task B:
A Choose one of the effects of acid rain listed above, and research it in more detail. When you have researched your chosen effect of acid rain, produce a three-minute talk to tell another person of your age about your findings. Present your talk to your class, or another group of pupils.
B Produce a leaflet to explain the effects of acid rain. You should consider each of the effects in turn, explaining why it is important that the production of acidic gases should be reduced.
[ knowledge, research ]
9Gb9 Using symbols
Each element in the Periodic Table has a symbol and the same symbols are used all around the world.
1 Draw up a table and list the symbols shown below along with the elements' names. You may need a Periodic Table to help you.
Ni Zn Fe Au Mg
S N Ag O H
Cl Ca C Pb Cu
2 Symbols are often used as a shorthand way of writing down any substances - compounds or elements. Copy and complete the table below that lists the names and formulae of some common substances.
If a compound contains two elements, the second name often ends in -ide.
If the second name ends in -ate or -ite, then the compound contains two elements plus oxygen.
Name
Formula
_________________
O2
ZnSO4
carbon dioxide
CO2
CaCO3
H2
H2O
N2
ZnCl2
hydrochloric acid
HCl
SO2
sulphuric acid
H2SO4
NO2
Chemists often use the formula of substances in a chemical equation as it is quicker and gives more information. The following questions are about chemical reactions concerning the causes and affects of acid rain.
3 Copy the following symbol equations and write the correct word equations below them.
a C + O2 → CO2
b N2 + O2 → NO2
c HCl + Zn → ZnCl2 + H2
d H2SO4 + CaCO3 → CuSO4 + CO2 + H2O
4 Copy the following word equations and write the correct symbol equations below them.
a sulphur + oxygen → sulphur dioxide
b hydrochloric acid + calcium carbonate → calcium chloride + carbon dioxide + water
c sulphuric acid + zinc → zinc sulphate + hydrogen
9Gc1 Evidence of pollution 1
Our understanding of air pollution has improved since we set up a network of automatic monitoring stations. There are about 1500 stations at different sites around Britain. Their main job is to take samples of air and measure and record the levels of pollution.
Black smoke and sulphur dioxide are the two pollutants which have been measured for the longest period of time. The graph below shows how the levels of these two pollutants have changed over a 35-year period.
Trends in pollution: mean levels of pollution of black smoke and sulphur dioxide (1962-1996).
1 Which forms of pollution have been monitored for the longest time?
2 What were the trends in the levels of black smoke and sulphur dioxide between 1962 and 1996?
3 By how much did the black smoke levels drop between 1962 and 1996?
4 By how much did the sulphur dioxide levels drop between 1962 and 1996?
5 During which year was the drop in black smoke levels greatest? _______________________
6 During which year was the drop in sulphur dioxide levels greatest? _____________________
7 Suggest a possible reason for the drop in pollution levels.
9Gc2 Evidence of pollution 2
The main sources of air pollution are industry, domestic (people's homes) and transport (cars, trains and aeroplanes). The charts below show the percentage of smoke, sulphur dioxide and nitrogen oxides produced from the different sources.
Sources of pollution from (a) smoke, (b) sulphur dioxide and (c) nitrogen oxides.
1 What is the largest source of each of the following pollutants?
a smoke _______________________________________________________________
b sulphur dioxide _________________________________________________________
c nitrogen oxides _________________________________________________________
2 Complete the table below using information from the pie charts.
Pollutant
% from transport
% from industry
% from domestic
% from other sources
smoke
sulphur dioxide
nitrogen oxides
3 Describe ways in which we could reduce the amount of energy we use, and so reduce pollution:
a in our homes
______________________________________________________________________
b in our use of transport
c in industry
9Gc3 Sources of information
Cheaper electricity 'threatens pollution target'
Financial Times; 4 Feb, 2002
By ANDREW TAYLOR
The government's aim of cutting carbon dioxide emissions by 20% by 2010 is likely to be missed by an even wider margin than previously predicted, according to Cambridge Econometrics, the privately owned economic and industrial forecasters.
Tony Blair's long-awaited energy review, due to be published later this month, is expected to call for a six-fold expansion in wind farms and other renewable sources as an important plank of government strategy to reduce greenhouse gases.
Cambridge Econometrics, however, warns that cheaper power, due to increased
competition and the
introduction last year of new electricity trading arrangements, could derail carbon reduction policies. It also revealed that a big increase in coal burning by power stations, in response to higher gas prices, prompted a sharp rise in carbon emissions last year. It now forecasts that carbon emissions will fall by only 6.4% between 1990 and 2010 - well short of the government's 20% target.
Professor Paul Ekins, Cambridge Econometrics senior consultant, said: 'Measures to encourage greater efficiency in the generation and trading of electricity are to be
welcomed'.
However, lower prices would promote higher demand 'unless accompanied by fiscal measures to encourage prudent use of energy'. 'The government appears not yet to have learned this lesson', he added. Carbon emissions from power stations fell by 23.5% between 1990 and 2000 as generators switched from coal to cheaper, cleaner natural gas. This trend had now reversed, said the forecasters, who now expected carbon emissions from power stations to rise by 8.9% between 2000 and 2010.
Copyright: The Financial Times Limited 1995-2002
1 By how much did the government want to cut carbon dioxide emissions by the year 2010?
2 What is the revised predicted cut in carbon dioxide emissions by the year 2010?
3 Give two reasons for the fall in electricity prices.
4 How will cheaper electricity lead to greater carbon emissions?
5 Why are power stations now using more coal?
6 How could the government use the tax system to:
a encourage people to use less electricity
b force power stations to use less coal?
[ literacy ]
9Gc4 Air quality monitoring
The following passage and graph came from a website in the UK.
Air quality monitoring is designed to provide data in support of a health study and a buildings study.
The graph below shows the nitrogen dioxide measurements from a street in the city centre. This is a daily (24-hour) profile for nitrogen dioxide averaged over a whole month. (ppb stands for parts per billion.)
The following table shows the standards and limits set by some of the relevant monitoring organisations.
Daily (24-hour) pollution profile for nitrogen dioxide averaged over a whole month.
Nitrogen dioxide (NO2) recommended limits.
Standard
Pollution concentration (ppb)
EC Directive Standard
limit value
104.6
Department of the Environment
air quality bands
very good
good
poor
very poor
peak hourly average concentration
<50
50-99
100-299
>300
1 Which two studies will use the data from the air quality monitoring stations?
2 What might the city change as a result of these studies and the data?
3 At what times of the day are the nitrogen dioxide levels in the 'very good' air quality band as set by the Department of the Environment?
4 a At what time of the day are nitrogen dioxide levels at their highest?
b Why do you think the nitrogen dioxide levels are at their highest at this time?
5 Do the nitrogen dioxide levels ever exceed the EC Directive Standard limit value?
6 Which air quality band of the Department of the Environment describes the nitrogen dioxide levels in Cornmarket street when they are at their highest?
[ literacy, numeracy ]
9Gc5 Pollution in the past
Finding evidence about levels of pollution in the past can be difficult, as there were no direct measurements made. We therefore have to look for other information that may be linked to pollution levels. Where we do have direct measurements we can use them to see if there are links.
Look at the graph below.
Think about what the graph tells us about the effects of pollution.
1 Write a paragraph, about 100 to 150 words long, describing what the graph tells us about pollution and its effects. Describe the trends in the graph and how they are linked.
2 Think about the health problems caused by air pollution. What kinds of records might we use to get information about pollution in the past?
[ considering, literacy ]
9Gd1 The global warming debate
The global warming debate.
These are all important questions. Your task is to find out about what scientists think will happen to our climate in the future.
There are many possible sources of information. You could start your search with the following websites:
- The US Global Change Research Information Office
www.gcrio.org/ - look at 'Common questions asked about climate change'
- The Met Office home page
www.meto.gov.uk/
- Department for Environment, Food and Rural Affairs.
www.defra.gov.uk/environment/climatechange/schools/index.htm
You can also use a search engine by trying combinations of these words
and phrases:
global warming - schools - debate - greenhouse effect - the facts - the truth
Write a report on what you find out about these problems. The report should have the title, 'The global warming debate' and should cover four sides of A4 paper. Include relevant data, graphs, diagrams and quotations wherever possible.
[ literacy, research ]
9Gd2 Global warming 1
1 Complete the following sentences, using words from the box.
Mean world _____________ have increased by about _____________ in the last 100 years
and scientists have predicted a _____________ rise of between 2 and 5 °C during the next
century. This rise in temperature has been called _____________ _____________ and if it
happens it would have a great affect on all _____________ on Earth.
life 0.6 °C greater global warming temperatures
A mean temperature for the period 1961-1990 has been calculated. This is shown by 0 on the graph. The line on the graph shows how each year's mean temperature compares with the 30-year mean.
2 Label the graph to indicate where the following statements apply:
a the mean temperature this year
b mean temperatures start to rise.
3 What has been the general trend in mean world temperatures over the last 100 years?
4 What does the graph predict will happen to mean temperatures over the next 100 years?
5 Using only the information on the graph, do you think that this prediction is correct?
[ knowledge, considering ]
9Gd3 Global warming 2
1 What do most scientists think is causing the rise in mean global temperatures?
2 What is meant by the greenhouse effect?
3 What are the main causes of rising levels of carbon dioxide in the atmosphere?
4 Look at the graphs below. Graph 1 shows the changes in carbon dioxide levels over the last 1000 years. Graph 2 shows the mean temperature of each year compared to the mean temperature for the years 1961-1990 (this is set at 0 on the graph).
Graph 1: How carbon dioxide levels have changed in the last 1000 years.
Graph 2: Changes in mean world temperatures from 1860 until 2100.
a i In what year did carbon dioxide levels start to rise?
ii In what year did mean temperatures start to rise?
b Describe the current trend in carbon dioxide levels.
c What has been the general trend in mean world temperatures over the last 100 years?
d What does the graph predict will happen to mean temperatures over the next 100 years?
e Using the graphs, describe any link between the mean world temperatures and the carbon dioxide levels.
f Do you think these graphs provide good evidence that rising temperatures are caused by rising levels of carbon dioxide?
g Briefly explain your answer to f.
9Gd4 Climate history
The climate of the Earth has gradually changed over millions of years.
Graph 1: Mean world temperatures over the last 160 000 years.
Graph 2: Mean world carbon dioxide levels over the last 160 000 years.
We are currently in a warmer period during an ice age. The term 'ice age' is used to describe generally cool periods of the Earth's history. These can last hundreds of millions of years, and during these times large areas of the Earth are covered in sheets of ice (glaciers). At present these glaciers are only found in certain areas, like the North and South Poles. However, about 160 000 years ago, the glaciers covered most of the Earth. Over the last 2 million years there have been 20 glacial advances and retreats.
These changes in temperature cannot be linked to human activity or pollution. However, look at the graphs above, which shows carbon dioxide levels over the last 160 000 years. Can you see a link between the two graphs?
1 Explain what Graph 1 tells us about the Earth's mean temperatures over the last 160 000 years.
2 Explain what Graph 2 tells us about the carbon dioxide levels over the last 160 000 years.
3 Describe the link between the two graphs.
4 Do you think changes in temperature cause changes in carbon dioxide levels, or do changes in carbon dioxide levels cause changes in temperature? Can you be sure which it is?
5 Give one reason why scientists cannot be sure if global warming will occur.
9G Summary Sheets
Environmental chemistry
Types of soil
Soil is a mixture of:
- broken up bits of rock (including sand and/or clay)
- humus (the decaying remains of plants and animals)
- air, water and dissolved chemicals
- plants and animals.
Different soils will contain different chemicals and can be acidic, alkaline or neutral. Universal indicator can be used to test the pH of soil.
Farmers and gardeners need to know the pH of their soil so their plants will grow well. Acids can cancel out alkalis. This is called neutralisation. If a soil is too acidic then lime, an alkali, is added to neutralise the acid.
Rocks and building materials
Different rocks are formed in different ways. Many rocks are used as building materials. Both natural rocks and those used as building materials wear away over time. This is called weathering and can occur in different ways:
- The rain and wind slowly break up the rocks (physical weathering).
- Changes in temperature cause cracks in the rock (physical weathering).
- Acids, and other chemicals in rain or soil, damage rocks (chemical weathering).
- Plants and animals damage rocks (biological weathering).
The sand and clay that make up the soil are produced by weathering and erosion.
Acid rain
The air contains small amounts of the following gases:
- carbon dioxide, produced by combustion of fuels and respiration
- sulphur dioxide, formed when sulphur burns in volcanoes
- nitrogen oxides, produced during lightening storms.
These gases dissolve in water to form acids, so rainwater is naturally acidic (pH between 5.6 and 5.9).
Our rainwater has become even more acidic (pH between 3 and 5.5) due to air pollution from burning fossil fuels. This is what we call acid rain. The main sources of this pollution are power stations and cars. Both burn large amounts of fossil fuels and release more carbon dioxide, sulphur dioxide and nitrogen oxides. Sulphur dioxide and nitrogen oxides are the main contributors to acid rain.
Problems caused by acid rain
Acid rain causes damage to our environment in several ways:
- Metals and carbonate rocks (like limestone and marble) react faster with acid rain than with normal rainwater.
- Plants and water life are damaged and killed by acid rain.
Pollution has been reduced by several actions:
- reducing the sulphur content in diesel and petrol so less sulphur dioxide is produced by combustion
- fitting catalytic converters in car exhausts, which change harmful gases into harmless gases
- spraying the gases from power station chimneys with an alkaline mixture to remove sulphur dioxide.
Measuring air pollution
A network of air quality monitoring stations provides us with information on levels of air pollution. A range of pollutants is measured, including rainwater pH. The data collected tells us that our air quality is improving but there are still serious problems.
Using less energy would help reduce pollution as we would burn less fossil fuels.
Global warming
There has been a small, but steady increase in mean world temperatures in the last 100 years.
These rising temperatures have been linked to increasing levels of carbon dioxide in the
atmosphere. Carbon dioxide and other gases trap the Sun's energy. This is sometimes called the greenhouse effect.
Some scientists believe that this will lead to global warming.
This means that there will be even greater rises in mean world temperatures in the future. If global warming does happen it will cause changes in weather and rising sea levels.
The increased levels of carbon dioxide in the atmosphere are
caused by burning more fossil fuels, and destroying large areas of forest. Scientists and politicians are trying to find ways to reduce the amount of carbon dioxide that is produced and so reduce the chances of global warming. The situation is complex, however, and not all scientists agree that global warming will definitely occur.
9G Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
9Ga
Know how to test the pH of a soil.
Know how the pH of the soil can affect plant growth.
Know ways of reducing the acidity of soils.
4
Know different ways that rocks and building materials can be weathered.
9Gb
Know why rainwater is naturally acidic.
Know what causes acid rain.
Know about the effects of acid rain on rocks, metals and living things.
Know how acid rain can be reduced.
9Gc
Know why air pollution is monitored and controlled.
Know some ways of monitoring pollution.
Know what pollution data can be used for.
Know how individuals can help reduce air pollution.
9Gd
Know the meaning of global warming.
Know what factors contribute to the greenhouse effect.
Know some possible effects of global warming.
Know why some scientists have different views about global warming.
9G Word sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
9Ga - Types of soil/Rocks and buildings
Word
Pronunciation
Meaning
acid rain
Rain that is more acidic than usual (pH less then 5.6) due to high amounts of dissolved acidic gases.
biological weathering
Weathering caused by plants and animals.
chemical weathering
Weathering caused by chemicals.
clay
Very fine particles of rock.
erosion
e-row-shun
The movement of pieces of rock by the wind, water, etc.
humus
hew-mus
A mixture of rotting plant material and animal remains found in soil.
lime
Calcium oxide (made by roasting limestone or chalk).
loam
The best soil for growing plants. Mixture of humus, clay and sand.
mineral
A chemical found in rocks. Rocks are mixtures of minerals.
neutralisation
A reaction in which an acid cancels out an alkali.
A scale which measures how acidic or alkaline a solution is.
physical weathering
Weathering caused by physical processes, such as changes in temperature.
sandy soil
A soil that contains larger particles than clay soils. Water passes through it easily.
sedimentation
Depositing of broken up pieces of rock, sand and clay.
soil
A mixture of rock fragments, humus, air, water and dissolved minerals.
universal indicator
A mixture of dyes which turns different colours as the pH of a solution changes.
weathering
The break up of rocks into smaller pieces by natural processes.
9Gb - Acid rain/The effects of acid rain/A cure for acid rain?
catalytic converter
A device fitted to a car's exhaust to change harmful gases into harmless gases.
carbon dioxide (CO2)
A slightly acidic gas formed when carbon reacts with oxygen (and during respiration).
combustion
The scientific word for burning.
corrosive
A substance that is corrosive reacts with certain substances and wears them away.
Acidic gases formed when nitrogen reacts with oxygen. Includes nitrogen dioxide (NO2).
photosynthesis
foto-sinth-e-sis
Process in plants which takes in carbon dioxide and water and, using the Sun's energy, makes glucose and oxygen.
respiration
res-per-ay-shun
Process which occurs in all living cells that releases energy from food. Carbon dioxide is one of the products.
sulphur dioxide (SO2)
An acidic gas formed when sulphur reacts with oxygen.
sulphur precipitator
pre-sip-it-ate-or
A device used in power stations to remove sulphur dioxide gas from the gases coming out of the chimney.
9Gc - Measuring air pollution
air pollution
Substances released into the atmosphere which should not be in air.
9Gd - Global warming
global warming
The gradual increase in mean (average) global temperatures.
greenhouse effect
The Sun's energy being trapped by gases in the atmosphere, thought to lead to global warming.