Carbon Footprint – Worksheet

What is a Carbon Footprint?

Carbon is one of the building blocks of life. Humans, animals and plants are made up of organic compounds. We burn wood and fossil fuels to produce energy and power transport, inadvertently releasing the greenhouse gas, CO2 into the atmosphere.

We will look at a series of calculations that represent the carbon cycle and how CO2 production is related to energy. You will start to see the energy implications of various fuels and technologies and their CO2 footprint.

The associated information sheet will provide the data you need to answer the questions below. 

  1. How much CO2 is emitted by the following activities? (calculate them in kg of CO2)

  • Driving 100 miles?

(Using 13 litres of petrol or 10 litres diesel)

 

 

  • Using your LED TV for 5 hours a day during a week?

(A 50” LED TV uses 100 watts, to convert to kWh, multiply kW by number of hours)

 

 

  • Boiling water in the electric kettle for a family for a week?

(A kettle uses 1200 W and it takes 3 minutes to boil water and this is done 10 times a day – or does your household drink more hot drinks?)

 

 

  • Heating the water with natural gas for a week of daily 5 minute showers?

(Heating 30 litre of water to 40°C uses 1.1 kWh in the form of gas, where emissions  from natural gas are 0.2 kg CO2/ kWh burned)

 

 

  • Charging mobile phones for the family for a week. With an average of two full charges a day.

(Typical phone charges at 0.015 kWh and takes 2 hours to charge fully)

 

 

  • Play station for 20 hours a week

(A Playstation 4 Pro uses 139 W)

 

 

2.  How to quantify CO2 emissions in terms of volume and mass?

  • How many cubic metres of CO2 would 5000 kg CO2 occupy?

  • A factory states that it releases 10 tons C per year (as greenhouse gas emissions). How many m3 of CO2e is this?

  • If UK car emissions released 3 GtC in a year and all the CO2 remained in the atmosphere, by how much would the CO2 concentration increase?

  • Go to see last year´s UK Carbon emissions published by the government (Provisional GHG emissions). In 2019 it was 351.5 Mt CO2 Considering the UK population is 63 million and the world population is 8.3 billion, are our carbon emissions representative of global average emissions? ((World emissions in 2017 were 36 Bt) 

  • Why has CO2 not decreased in 2020 if CO2 emissions have dropped? Is there still last years and the decade before´s emissions in the air or are we still emitting more despite the drop in transport and industry in 2020?

3.  Steps towards reaching carbon neutrality

  • Do you think the UK is on its way to becoming a low carbon economy? Why do you think some countries like Estonia are way behind the UK and countries like Sweden are way ahead?
  • The UK has a goal of reaching Carbon neutrality by 2050- do you think we are on our way to reaching that?
  • What percentage of our man-made CO2 emissions are absorbed by the oceans?
  • If a fully grown tree absorbs 22 kg of CO2 per year and an acre of forests 2.5 tons of Carbon, if we wanted to neutralize our country-wide annual emissions of 351.5Mt* CO2, how many more trees or acres of forest would we need?**

*The latest government statistics on UK annual CO2 emissions (for 2019) was 351.5 Mt CO2 equivalent

**UK forests absorbed 21 million tonnes CO2 in total in 2020, so they are working away continuously at helping to neutralise our emissions!

 

Carbon Footprint – Teacher’s Notes

Carbon, fossils fuels and CO2

Carbon is one of the building blocks of life. Humans, animals and plants are made up of organic compounds. We burn wood and fossil fuels to produce energy and power transport, inadvertently releasing the greenhouse gas, CO2 into the atmosphere. Students will become more aware of the facts and figures that link the carbon cycle with CO2 emissions and the jargon that is used in the news and in global climate politics.

Chemistry curriculum links: AQA GCSE

3.2.1 Use of amount of substance in relation to masses of pure substances (Moles)

7.1 Carbon compounds as fuels and feedstock

9.2 Carbon dioxide and methane as greenhouse gases

9.2.4 The carbon footprint and its reduction

Chemistry in the activity

Calculating the energy from combustion of different fuels is related to the number of Carbon atoms these hydrocarbons contain. The amount of CO2 produced upon combustion is our way of measuring the Carbon footprint of energy sources. Electricity is generated from various forms of energy in each country´s electricity mix and the more renewables and the fewer inefficient coal power plants there are, the less CO2 is released per kWh electricity used. The UK is trying to go below 100 g of CO2 released per kWh by 2030 and is likely to achieve this before that date.

In the associated worksheet the students will carry out calculations based on a range of information they will find in the corresponding information sheet. They will become familiar with conversions between tons of Carbon and tons of CO2, the volume of CO2 and other factors they may hear in the news or that relate to their personal, a country´s or organisation´s carbon emissions.

They will go to websites that provide current global CO2 levels and a breakdown of the UK´s electricity supply, with the corresponding kg of CO2 this will emit per unit electricity used. Questions 1&2 use numeracy skills to evaluate and compare different forms of energy and different technologies.

Question 3 is best used as a classroom discussion and covers carbon neutrality, achieving the UK´s Carbon neutrality goals and calculate how many trees they would have to plant to neutralise this year´s CO2 emissions.

1.  Which fuels or activities produce more CO2?

QUESTIONS

 

Which of these activities produces more CO2 emissions? (calculate them in kg of CO2)

 

  • Driving 100 miles?

(Using 13 litres of petrol or 10 litres of diesel)

Petrol = 2.3 x 13, Diesel = 2.7 x 10 = 29.9 kg CO2 for petrol and 27 kg for diesel

 

  • Using your LED TV for 5 hours a day during a week?

(A 50” LED TV uses 100 watts, to convert to kWh, multiply kW by number of hours)

5 x 7 hours at 100 watts = 3.5 kWh = 3.5 kg CO2

 

 

  • Boiling water in the electric kettle for a family for a week?

(A kettle uses 1200 W and it takes 3 minutes to boil water and this is done 10 times a day – or does your family drink more tea?)

1200 x 10 x 3 x 7 = 210 minutes (3.5 hours) or 4.2 kWh  x 0.283 = 1.19 kg CO2

  • Heating the water with natural gas for a week of daily 5 minute showers?

(Heating 30 litre of water to 40°C uses 1.1 kWh in the form of gas, where emissions from natural gas are 0.2 kg CO2/ kWh burned)

Heating the water for a week uses 7.7 kWh so 0.2 x 7.7 is 1.54 kg CO2

  • Mobile phone usage for the family in a week. Assume the family does an average of two full charges a day.

(Typical phone charges at 0.015 kWh and takes 2 hours to charge fully)

4 x 7 x 0.005 = 0.014 kWh x 0.283 = 0.396 kg CO2

  • Play station for 20 hours a week

(A Playstation 4 Pro uses 139 W)

139 x 20 = 2.4 kWh = 7.87 kg CO2

2.  How to quantify CO2 emissions in terms of volume and mass?

QUESTIONS

  • How many cubic metres of CO2 would 5000 kg CO2 occupy? 2500 m3
  • A factory states that it releases 10 tons C per year (for its greenhouse gas emissions). How many m3 of CO2e is this? 10,000 kg x 44/12 = 36,667 kg CO2, so ½ x this is 18,333 m3
  • If UK car emissions released 3 GtC in a year and all the CO2 remained in the atmosphere, by how much would the CO2 concentration increase?

0.47 x 3 = 1.41 ppmv

  • Go to see last year´s UK Carbon emissions published by the government (Provisional GHG emissions). In 2019 it was 351.5 Mt CO2 Considering the UK population is 63 million and world population is 8.3 billion, are our carbon emissions representative of global average emissions? ((World emissions in 2017 were 36 Bt)

63m/8.3b =0.81 % of population and CO2 emissions are 351.5Mt/36000Mt = 0.98 %, so the population of the UK creates more CO2 than their population dictates, we produce 0.98/0.81 =1.21 times more CO2 than the average world population

(figures for 2020) 500 ppm; increase of 100 ppm between 1950 and 2020 (in 70 years), that is a 0.7 ppm average increase; it has increased 4 ppm since 2018 (in 2 years), 2 ppm increase per year. The rate of increase of CO2 concentration has increased since the 1950s.

  • Why has CO2 concentration not decreased in 2020 if CO2 emissions have dropped?

The lifetime of CO2 means that it stays around in the atmosphere for many years and you will not see a decrease in the CO2 from the year that you stop releasing it, it will gradually level off, that is why we need to reach our CO2 emission peak as early as possible, to see the results a few years later.

3. Steps towards reaching carbon neutrality

QUESTIONS to discuss as a class

  • Do you think the UK is on its way to becoming a low carbon economy? Why do you think some countries like Estonia are way behind the UK and countries like Sweden are way ahead? (http://www.globalcarbonatlas.org/en/CO2-emissions is a useful information source)

Estonia still burns a lot of coal, hence its high CO2 emissions. Sweden has 80 % of its electricity from nuclear and renewables

  • The UK has a goal of reaching Carbon neutrality by 2050- do you think we are on our way to reaching that?
  • What percentage of our anthropogenic (human) CO2 emissions are absorbed by the oceans?

31 %

  • If a fully grown tree absorbs 22 kg of CO2 per year and an acre of forest, 2.5 tons of Carbon, if we wanted to neutralize our country-wide annual emissions of 351.5Mt* CO2, how many more trees or acres of forest would we need?**

351500/2.5 = 140600 acres. There are 60 million acres in the UK, so actually, only adding 0.234 % of the land as forests would do this!

*The latest government statistics on UK annual CO2 emissions (for 2019) was 351.5 Mt CO2 equivalent

**UK forests absorbed 21 million tonnes CO2 in total in 2020, so they are working away continuously at helping to neutralise our emissions!

 

Carbon Footprint – Information Sheet

Carbon is one of the building blocks of life. Humans, animals and plants are made up of organic compounds. We burn wood and fossil fuels to produce energy and power transport, inadvertently releasing the greenhouse gas, CO2 into the atmosphere.

1.  Which fuels or activities produce more energy or CO2?

 

What are fossil fuels made up of?   Hydrocarbons with varying amounts of Carbon:

  • Coal contains large complex hydrocarbon molecules (with C:H:O ratios of ~85C:5H:10O)
  • Diesel is made up of alkanes containing 12 or more carbon atoms. (e.g. C13H28)
  • Petrol contains alkanes and cyclo-alkanes with between 5 and 12 Carbon atoms (with an average composition of C8H12 (octane))
  • The mass of one mole of pure Carbon is 12 g and the mass of one mole of CO2 is 12 + (2×16) = 44 g (to convert from CO2e to C multiply by 12/44)

What are the combustion reactions and how much energy and CO2 do they produce?

 

  • 1 kg of petrol burned yields about 47 MJ of energy (1litre, 34.2MJ)
  • 1 kg of diesel burned yields about 46 MJ of energy (1litre, 38.6MJ) (diesel is denser than petrol and has more energy per litre)
  • 1 kg of coal burned yields about 30 MJ of energy
  • 1 kg of wood burned yields about 19 MJ of energy
  • 1 kg of coal (containing 0.78 kg Carbon) will produce 2.4 kg of CO2
  • 1 litre of petrol (containing 0.63 kg of carbon) will produce 2.3 kg of CO2
  • 1 litre of diesel (containing 0.72 kg of carbon) will produce 2.7 kg of CO2

The most up-to-date information on the make-up of the UK electricity grid (which is a mix of sources) can be found at RENSmart and the value in February 2021 was that 1 kWh produces 0.23314 kg CO2. (kWh are calculated by multiplying kW by the number of hours). If you live in another country you could compare its CO2 emissions per kWh electricity factor. Here is a good comparison site for many countries but with older data.

 

2. How to quantify CO2 emissions in terms of volume and mass?

Volume and mass of CO2

You will often hear about kg of CO2 emitted, relating to the energy usage of different forms of transport, of a household, of a company, of a particular industry (like the cement industry) or of a country or a person.

From what we know about the combustion processes, their efficiency and our energy needs, we can use emission factors to calculate carbon footprints. We also know that a mole of any gas occupies 22.4 dm3 at ambient temperature. So we can express the emissions as a volume of CO2. If we know how much of a gas is emitted and what the original concentration of that gas was in the atmosphere, we can see whether the emissions will change the concentration.

  • 1 kg pure CO2 occupies a volume of half a cubic metre (500 dm3 (or litres))
  • CO2 emissions are often stated in GtC (109 tonnes (or Gigatonnes) of Carbon)
  • Concentrations of CO2 in the atmosphere are expressed in parts per million by volume (ppmv). 1 ppmv takes up 0.0001% of the volume of the atmosphere. Check out the Mauna Loa CO2 measurement station in Hawai for today´s level.
  • A release of CO2containing 1 GtC would increase the atmospheric CO2 concentration by 0.47 ppmv if all the CO2 remained in the atmosphere, BUT carbon sinks nearly balance out the sources
  • There was a CO2 increase of 2.5 ± 0.1 ppmv between 2017 and 2018
  • The lifetime of CO2 is 5 to 100 years

Don’t forget:

  • The mass of one mole of pure Carbon is 12 g and the mass of one mole of CO2 is 12 + (2×16) = 44 g (to convert from CO2eq to C multiply by 12/44)

Effects of the Covid-19 on the economy and thus CO2 emissions

  • Between 2019 and 2020 global CO2 emissions decreased due to the COVID-19 Pandemic (in the region of 4 Gt CO2 and the CO2 emissions fell by 7 % in 2020, the largest ever decrease since the Second World War!) 
  • A Carbon brief article suggests that in 2020 we reduced the annual increase in CO2 concentrations by 0.32ppmv, putting it at 2.48ppm.
  • Note the difference between emissions of CO2 and actual concentrations. The CO2 already in the atmosphere from previous year´s emissions (it lasts up to one hundred years).

3. Steps towards carbon neutrality

UK Fuel Source Mix

 

This Figure shows the latest (calculated every 3 months) fuel source mix for the UK electricity supply. Go to: OFGEM. Note the elimination of coal and the increase in wind and solar energy.

The UK electricity supply now has well over 20 % from renewables. The UK is trying to get to below 100 g CO2/ kWh by 2030 and we might achieve 5 % renewables by 2025. In late 2019 the electricity from British windfarms, solar panels and renewable biomass plants surpassed fossil fuels for the first time since the UK’s first power plant fired up in 1882.

We saw in section 1 that at RENSmart you can get the latest value for how many kg CO2 are produced per kWh of electricity. Let´s compare other countries from the table at the bottom of this website. Sweden currently has an emission of 0.013 kg CO2/ kWh (21 times lower CO2 emissions per kWh!). In Sweden 80 % of electricity comes from nuclear and renewables (with 66 % from renewables). By the way, renewables do have an embedded energy (of up to 50 g CO2/ kWh).

And look what these natural Carbon Sinks can do:

  • Between 1994 and 2007, the oceans absorbed 34 Gt CO2 (31 % of what humans put into the atmosphere during that time)
  • One acre of new forest can sequester about 2.5 tons of carbon annually. Young trees absorb CO2 at a rate of 6 kg per tree each year and after 10 years they absorb 22 kg of CO2 per year. At that rate, they release enough oxygen back into the atmosphere to support two human beings.

Particulate Matter, ice, albedo and melting – Worksheet

Have a look at these two glaciers, one has fresh snow over the glacier and the other is a dry glacier in summer with accumulated deposits of dust and Black Carbon from air pollution. Which one do you think is more vulnerable to melting? Does a bright white surface reflect more or less light than a darkened surface?

Silvretta Glacier with Fresh snow

Fresh clean snow on the Silvretta glacier,    Switzerland (Zoë Fleming)

Fox Glacier with dirty ice

Dirty ice on the Fox Glacier, New Zealand (Sylvia Knight)

Particulate Matter is solid particles that are so small that they float in the atmosphere. They are formed from incomplete combustion of wood and fossil fuels. When they are smaller than 2.5 microns (2.5 x 10-9 m, an eight the width of a human hair), this PM2.5 can enter into our lungs and be carried into the blood system and cause damage to the brain and the cardiovascular system.

When Particulate Matter (or Black Carbon, which is more or less soot or pure Carbon) settles on glaciers and snow it darkens the colour of the snow and hence changes the how much of the Sun’s light the snow reflects. In this experiment we will check to see whether dirty or clean ice melts faster.

Materials

 

Chemicals

Apparatus

3 ice cubes per group

3 bowls for placing ice cubes

Soot or Activated Carbon or burn a splint and gather the blackened combusted material

Spotlight

Soil or sand (as light coloured as possible)

Measuring scale

 

Spoon or forceps to move the ice cube between the bowl and the measuring scale

Method

  1. Take 3 ice cubes out of the freezer and place one in each bowl.
  2. Scatter soot over the ice cube in one bowl, covering it completely. Scatter the next ice cube with the soil. The last bowl will contain the control ice cube.
  3. Weigh each ice cube (using a spoon or forceps to place it on the scale).
  4. Shine the light bulb over the 3 bowls, trying to equally light/heat them all.
  5. After 5 minutes, remove each ice cube one at a time to weigh them.
  6. After 10 minutes, remove each ice cube one at a time to weigh them.
  7. If you have time to wait for the first ice cube to completely melt, note the time and note down how much was left of the other ice cubes (weigh them).

Results and Questions

  1. Which ice cubes melted faster?
  2. Does covering them with brown or black melt them faster?
  3. Thinking about a sunny day on snow, how do your eyes react to the sunlight? Does it seem like there is more light around or less than on a sunny day walking on bare soil? What about a sunny day on a boat? Do you think there is more or less light reflected back to your eyes than on land? The proportion of the Sun’s light which is reflected by a surface is called its albedo – a high albedo means a large proportion of the light is reflected and, therefore, only a small proportion is absorbed. 
  4. What about the difference between wearing white or black clothes on a sunny day- which one absorbs the sun rays and makes you feel warmer? Is that a small or large albedo?

Application for the world’s glaciers:

Glaciers around the world are more exposed to particulate matter now than they ever were before the industrial revolution. Covering them with a dark material changes the albedo. The darker the surface, the more of the Sun’s light is absorbed by the glacier, warming it and melting it. 

Particulates are tiny solid or liquid particles that are present in the atmosphere. They are sometimes termed aerosols as they float in the air. Black carbon (soot) is a particulate released from incomplete combustion. It absorbs the Sun’s light, which actually helps to cool the Earth. However, when it lands on ice, the absorption of radiation speeds up the ice´s melting as the light is absorbed by the dark colour and heats up the ice.

 

Social and political perspectives:

Knowing that air pollution that reaches glaciers is increasing their melting faster than what would happen from air temperature changes alone, what do you think we can do in terms of laws or behaviour change?

How can we reduce soot and Black Carbon reaching glaciers? Emission control of cars? Banning domestic wood-burning? Have you heard of smokeless coal that can be used in stoves in smoke-free zones? And pellet stoves, are there fewer emissions from these?

Note: You could carry out your own experiment if you are lucky enough to get snow. Prepare two neat snow blocks or two snow-balls of similar size and cover one with gravel or sand and leave the other clean. Watch which one melts first.

Particulate Matter, ice, albedo and melting – Teacher’s Notes

In this experiment the students will look at the effect of Particulate matter or other substances that have landed on ice and test how this can speed up the melting of ice by affecting its albedo. Particulate Matter and aerosols are made up of a variety of pollutants, some of them enhancing and some counteracting the greenhouse effect when they are in the atmosphere. But once they land on snow or ice, they will promote the melting of these surfaces.

Chemistry Curriculum Links AQA GCSE

9.2.3. Properties and effects of atmospheric pollutants

Particulate Matter is a pollutant that absorbs at many different wavelengths, some act as greenhouse gases and others actually reflect more light than they absorb, leading to a reduction in the temperature of the atmosphere. When they (or Black Carbon in particular) deposit on snow and glaciers, they change the albedo (the reflectivity) of the snow surface. This controls the heat balance at the surface of snow and ice surfaces as the darker colour of the ice will lead to it melting faster.

 

Particulate Matter is solid particles that are so small that they float in the atmosphere and can be measured as a concentration in the atmosphere. They are formed from incomplete combustion of wood and fossil fuels. PM smaller than 2.5 microns (2.5 x 10-9 m), PM2.5 , is much smaller than the width of a human hair and can enter into our lungs and be carried into the blood system and cause damage to the brain and the cardiovascular system.

Uncertainties to do with the quantities of the different particles in the atmosphere (and the fact that particles enhance cloud formation) are part of the biggest current uncertainty in climate models.

Class Practical 

This experiment can be carried out in pairs or larger groups and takes about 20 minutes.

Follow the notes in the student worksheet, allowing more time to discuss what particulate matter is, what is albedo and how sunlight is absorbed differently by different coloured substances.

Discussion Questions

  1. Which ice cubes melted faster? Was it what they expected?
  2. Did all groups get similar results? Can we compare the melting rates as a % of original mass and see if they are similar between groups? What is the error in the melting rate of the 3 types of ice cubes?
  3. Does covering them with brown or black melt them faster?
  4. What are the possible errors in the experiment?

Application to the World’s Glaciers:

Glaciers around the world are more exposed to particulate matter now than they ever were before the industrial revolution and the increase in industry and cars over the last century. Covering snow and ice with a dark layer changes the albedo and they absorb more heat and melt quicker than the pure ice.

Particulates are tiny solid or liquid particles that are present in the atmosphere. They are sometimes termed aerosols when they float in the air. Examples are dust, spores and pollen, salt from sea spray, volcanic ash and smoke. Black carbon (elemental carbon (soot) or organic carbon) from incomplete combustion in the atmosphere can actually absorb incoming solar radiation and cool the Earth. However, when these particles land on ice, the absorption of radiation will enhance the ice´s melting.

References

Iain Stewart BBC black ice experiment

UN Environment programme, 2019: Glaciers are melting and air pollution is the cause

See bar chart of radiative forcing of various gases or particulates in Fig 14.4 Ramaswami et al., 2019

Ocean CO2 Absorption – Worksheet

Does warm or cold water absorb CO2  better?

If the oceans are absorbing large quantities of water, and if we know the oceans are warming due to global warming, what is the effect of warmer oceans on CO2 absorption? Let´s check with this experiment that shows how much CO2 will dissolve in the water and how much will be in its gaseous form above the water.

Materials

Chemicals

Apparatus

Water

2 x 500 ml measuring cylinders

Effervescent fizz tablets (e.g. Alka Seltzer)

2 x Petri dishes that fit over the cylinders

Ice (optional)

Bowl or container of at least 5 litres

 

Stand and clamp to hold cylinders

 

Water heater

 

Funnel (optional)

Method

  1. Fill the basin half-full with cold  (or iced) water. Place the stand beside the basin.
  2. Fill the graduated cylinder to the brim with cold water and cover the top of the cylinder with the petri dish. Turn it upside down in the basin, making sure that no water spills out of the cylinder (so no air bubble forms). Remove the Petri dish when the cylinder is already underwater.
  3. Secure the graduated cylinder with the clamp to the stand and place the funnel in the mouth of the cylinder.
  4. Place an effervescent tablet carefully under the funnel. (Be sure your hands are dry so as to not set off the reaction prematurely).
  5. Observe the air space that develops at the top of the upside-down cylinder. Record the volume of the air space formed.
  6. Repeat the same procedure with warm water and record your results in the table. What happens to the air space when warm water is used? Is more or less air released than with cold water?
  7. Repeat the same experiment two or three times more with both cold and warm water.

Results table

 

Experiment number

WARM water (volume of air/ml)

Experiment number

COLD water (volume of air/ml)

1

 

1

 

2

 

2

 

3

 

3

 

4

 

4

 

AVERAGE volume

 

AVERAGE volume

 

 

Question: Does more CO2 escape from warm or cold water?

 

If more has escaped from the liquid, the water cannot absorb as much CO2.

Extension Question: With global warming and warmer oceans, will the oceans be able to absorb more or less CO2 than before?

What is the perfect pH of the oceans? Is it different depending on which ocean and whether it is in the deep ocean or the shallower coastal areas?

Ocean Acidification – Worksheet

Increased CO2 levels in the atmosphere are buffered by the oceans, as they absorb roughly 30 % of this CO2. The negative consequences of this are that the oceans become more acidic. The CO2 reacts with water and carbonate to form carbonic acid, reducing the available carbonate that shellfish, crabs and corals combine with calcium to make hard shells and skeletons.

Materials

Chemicals

Apparatus

Bicarbonate of soda (1/2 teaspoon)

2 x 500 ml Beakers

White vinegar (1 teaspoon)

Small plastic or paper cup (100 ml)

Indicator: Bromothymol blue

(Diluted with water: 8 ml bromothymol blue (0.04% aqueous) to 1 litre of water)

Masking tape

 

2 x Petri dishes or lid for large beakers

 

Safety glasses and lab coat

 

Teaspoon or 5 ml measuring cylinder

 

Two sheets of white paper

Method

  1. Pour 50 ml of the indicator solution into both beakers. 
  2. Add 1/2 teaspoon (2 grams) of bicarbonate of soda to the plastic cup.
  3. Tape one paper cup inside one beaker containing the indicator solution so that the top is about 1 cm below the top of the beaker. Make sure the bottom of the paper cup doesn´t touch the surface of the liquid in the plastic cup. The other beaker will be your control.
  4. Place both clear plastic cups onto a sheet of white paper and arrange another piece of white paper behind the cups as a backdrop (so you can see any colour change).
  5. Carefully add 1 teaspoon (5 ml) of white vinegar to the plastic cup containing the bicarbonate of soda. Be very careful not to spill any vinegar into the indicator solution. Immediately place a Petri dish over the top of each beaker.
  6. Position yourself so you are at eye level with the surface of the indicator solution, ready to see a colour change occurring.

Results

  1. What colour does the solution that contains the plastic cup change to?
  2. Vinegar (acetic acid) and bicarbonate of soda (Sodium bicarbonate) react to produce CO2 that is now present in the atmosphere of the large beaker, in contact with the indicator solution (the ocean). Some of the CO2 starts to absorb into the ocean, changing its pH.
  3. A colour change from blue to yellow represents a reduction in pH. Is the solution (the ocean) becoming more acidic or basic?

Application to the World’s Oceans

Corals and shellfish can be affected by ocean acidification, making it harder to create their shells, which will affect other fish up through the food web.

Corals and fish can be affected by slight changes in the temperature of the water and the next experiment also shows the effect of temperature increase on CO2 absorption, creating a positive feedback, a knock-on effect.

Ocean Acidification and CO2 Absorption – Teacher’s Notes

Increased CO2 levels in the atmosphere are buffered by the oceans, as they absorb roughly 30 % of this CO2. The negative consequences of this are that the oceans become more acidic. The CO2 reacts with water and carbonate to form carbonic acid, reducing the available carbonate that shellfish, crabs and corals combine with calcium to make hard shells and skeletons.

Curriculum Links: Core chemistry AQA GCSE

4.2.4 The pH scale

9.1.2 The Earth´s early atmosphere

9.2.3. Global climate change

Chemistry in the activity

Na2CO3 + 2 CH3COOH → 2 CH3COONa + CO2 + H2O (Bicarbonate of soda reacts with vinegar to form carbon dioxide)

In this experiment the students will initiate a reaction that produces CO2 in an enclosed water-air environment. The CO2 formed will be absorbed into the water, making it more acidic and changing the colour of the indicator. The experiment can be carried out in pairs and takes about 15 minutes. An additional experiment to test the solubility of CO2 in warm and cold water can be carried out afterwards, explaining how global warming can affect marine CO2 absorption.

Materials

  • Bicarbonate of soda (baking soda)
  • White vinegar
  • Bromothymol blue Indicator (diluted with water: 8 ml bromothymol blue (0.04% aqueous) to 1 litre of water)
  • 2 x 500 ml Beakers
  • Small plastic or paper cup (100 ml)
  • Masking tape
  • 2 x Petri dishes or lid for large beakers
  • Teaspoon or 5 ml measuring cylinder
  • Two sheets of white paper
  • Safety glasses and lab coat

See the student worksheets for the detailed preparation: Ocean acidification and CO2 Absorption

Application to the  World’s Oceans

The beaker is like an enclosed ocean-atmosphere and the CO2 from the reaction will equilibrate between the water and the air. Our oceans absorb more CO2 when the concentration in the atmosphere increases. But how much CO2 can they keep absorbing? Will they reach a saturation point?

Corals and shellfish are affected by ocean acidification, making it harder to create their shells, which will affect other fish up through the food web. Global warming caused by the increased CO2 effects the corals and fish as only slight changes in the temperature of the water can have effects throughout the ocean´s food chain. So there is a knock-on effect or a positive-feedback from the ocean heating and the ocean acidification.

If you want to illustrate more about the feedbacks and this double impact, the next experiment demonstrates the effect of a temperature increase on CO2 absorption, thus limiting the water´s capacity to absorb as much CO2.

CO2 Absorption in Water class practical

This experiment allows  students to determine how much CO2 dissolves in warm or cold water.

See the student worksheet for the detailed preparation.

Materials

  • Water
  • Effervescent fizz tablets
  • Ice (optional)
  • 2 x 500 ml measuring cylinders
  • 2 x Petri dishes that fit over the cylinders
  • Bowl or container (at least 5 litres)
  • Stand and clamp to hold cylinders
  • Water heater
  • Funnel

Application to the World’s Oceans:

More CO2 has escaped from the warm water, showing that it cannot absorb as much CO2. Warmer oceans will not be as effective buffers at removing CO2 from the atmosphere. However, this phenomenon does prevent these warmer oceans from being as acidic.

References

Measuring Raindrops

How big is a raindrop?

Collect data and analyse mode, mean and median, range, interquartile range and standard deviation

Introduction: There are many words and many descriptions for different types of rain: fine rain, heavy rain, pelting down, mizzling. In fact the BBC news magazine has an article entitled “Fifty words for rain”. But how big is a rain drop? Does the size vary depending upon the time of year or the type of rain?

Aim: To collect data, manipulate data and analyse data to calculate and compare the size of raindrops.

Equipment Required

  • A platform of area of about 0.5m2 with edges.
  • Enough flour to cover the platform to a depth of about 3cm
  • An accurate measuring device, e.g. electronic sliding callipers.

Collecting the data

  • Cover the platform with the flour.
  • Place the platform in the rain for about 90 seconds, long enough for about 200 raindrops to hit the platform.
  • Use your measuring device to measure the diameter of the raindrops and record the data.

Manipulating, analysing, displaying and interpreting the data

There follows a number of suggestions of how the data can be used depending upon the ability of the students.

1. Calculate the mode, mean and median diameter of raindrop. Which is the most appropriate measure to use? Compare results from different groups.

2. Group the data into appropriate groups. Represent the data using histograms. Discuss whether it is appropriate to have all the groups the same size of vary the size of the groups. Compare the results from different groups. Compare data collected at different times of year if possible.

3. Calculate the spread of the data using range, interquartile range and standard deviation.

4. Discuss different methods of displaying the data. Is the data discrete or continuous? Should a bar chart or a histogram be used? This activity is ideal for discussing when a histogram should be used and the reasons for using a histogram.

5. Draw box plots to show the distribution of the data. Compare the spread of different data sets. What does this information tell us?

6. Write a report comparing the size of raindrops.

Extension

It may be appropriate for Advanced level students to explore the log-normal distribution as discussed in the accompanying article A Low Cost Experiment for determining Raindrop size Distribution.

Further Background Information

Making rainfall features fun: scientific activities for teaching children aged 5–12 years.

This lovely animation explores integration through Is it better to walk or run in the rain?

With thanks to Stephen Lyon at the National STEM centre

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