Sankey Diagrams for Physics

Energy and Climate Change

Energy is needed in the form of electricity to power our lives, and to fuel our travel and industry. Since 1990, total world energy consumption has increased by over 55% and is projected to increase by another third by 2040.

Globally, oil accounts for over 30% of total energy use, followed by coal, gas and nuclear at 4%. This mix is different when you look only at electricity production, and different again on a country by country level.

A sustainable energy transition is a shift from an energy intensive society based on fossil fuels to energy efficiency with low carbon and renewable energy sources.

The Paris Agreement is a legally binding global climate change agreement, adopted by 189 nations at the Paris climate conference (COP21) in December 2015. It sets out a global framework to avoid dangerous climate change by limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C.

Significant changes in energy production, transmission and use are necessary to achieve these commitments.

This should lead to co-benefits including improved air quality and reductions in energy poverty.

Since 2019, the costs of developing new power plants based on hydroelectric power, onshore wind, solar photovoltaic (PV), biomass and geothermal energy have become comparable to the costs of new oil and gas fuel plants.   

Physicists play an essential role in all aspects of climate change research and policy decisions as well as in development of technologies and new ideas for preventing and mitigating the effects of future, damaging climate change.

Energy and Core Physics


Energy is a fundamental concept in physics and a key topic in any physics curriculum. The Earth’s climate system is driven by energy stores and transfers. Development of clean, sustainable energy generation and distribution methods relies on understanding the core physics involved. The climate system and sustainable energy production therefore provide engaging and relevant sources of examples for enhancing the teaching and learning of energy as a topic in Physics. They give teachers an obvious opportunity to engage their students in an appreciation of the importance of the physics already in the school curriculum in solving many of the problems surrounding accelerated climate change, as illustrated in the following, brief summary of potential links.

Energy is transferred by radiation from the Sun, increasing the thermal store in the Earth’s atmosphere and ocean systems. Energy transfers within these systems take place through the physical processes of conduction, convection, radiation and changes of state. Seasonal and longer term, natural variations in heating and cooling of the Earth are a result of the alignment of the Earth in space and its orbital motion around the Sun. Land and ice surfaces are heated differentially according to the absorptive or reflective nature of the surface type and rocks are heated internally due to energy released during radioactive decay and large scale, convective motion of the Earth’s interior.

Successful and sustainable, low carbon generation of electricity to meet current and future demands relies on understanding and exploiting many of these natural, physical processes. Atmospheric convection causes winds to drive wind turbines and also generates the ocean waves exploited in wave power devices. The relative motion of the Earth, Moon and Sun causes the ocean tides exploited in tidal barrages and undersea-current driven turbines. Seasonal changes, weather patterns and latitude can all affect the output of solar energy devices as can reflection and absorption of radiation by the materials they are made from. Geothermal energy relies on energy transfers due to radioactive heating of rocks, local volcanism or simply the heat capacity of the soil acting as a thermal store of energy.

Many large-scale electricity generation methods depend on the basic principle of a turbine turning a generator which relies on understanding the principles of electromagnetic induction and factors affecting potential power output and efficiency. Electricity distribution on a large scale, via the National Grid, involves minimising energy dissipation into the surroundings by transmitting electricity at very high potential difference and low current thus reducing thermal transfers of energy within the cables. Domestic uses of electricity involve devices with varying levels of energy efficiency and informed choice of the most efficient appliances and how long they are used for can lead to reductions in an individual’s energy demands, carbon footprint and household bills.

Energy Efficiency

Improving energy efficiency saves individuals money, reduces waste, conserves resources and cuts emissions of greenhouse gases and other pollutants. Discussing personal, financial savings and more immediately obvious environmental impacts can lead to engagement with climate change by an indirect route with valid applications in the physics curriculum. This is also a good opportunity to reinforce accurate vocabulary using the terms energy stores, transfers and pathways as well as the concept of energy dissipation and avoiding terms such as energy saving ( Examples can be given of more relevant applications of the Sankey Diagram as a tool for accounting for energy transfers in the atmosphere:

(see also and

Sankey energy diagram

By Cmglee – Own work, CC BY-SA 3.0

This could be used to illustrate a more complex example of a Sankey diagram and lead to a discussion of the possible effects of changes to some of the pathways, reinforcing the concept of energy conservation as both sides must remain balanced.

Wind Turbine Example 

In a wind turbine, 20% of the energy from the wind is converted to electricity. Lost wind leads to a loss of 30 % of the energy, friction between the wind and the blades of the turbine and the wind leads to a loss of 25% of the energy, and the rest of the energy is lost due to friction in the electric generator.

  1. How much energy is lost due to friction in the generator?

2.   Draw a Sankey diagram for the wind turbine, considering that the output in electrical energy is 20 kJ.



Climate Change Graph


You will need: 120 multicoloured lollipop sticks (at least 10 sticks each of 6 colours), PowerPoint, lollipop.xls, blue tack or similar

  1. Beforehand, mark on the middle of each lollipop stick. On each stick, write the year and the temperature for one of the data points in the spreadsheet (e.g. 1970 14.47), differentiating between global and CET data. Use a different coloured lollipop for each decade – so the 60s are all one colour etc.
  2. You’ll also need to print a blank graph – the spreadsheet supplied will work on A3 paper.
  3. Divide the students into two groups. Within each group, divide out the lollipop sticks.
  4. They should then work together to stick the sticks to the graphs in the right places.
  5. When they’ve finished, ask them to complete the table on the ppt.
  6. What does their graph show? What surprises them? What are the similarities and differences between the graphs?
  7. Next, they should take the sticks back off the graph and, within their groups, line the sticks up in temperature order with the coldest on the left and the warmest on the right.
  8. What does this show?

Leaves as Thermometers

Leaves as thermometers

Leaf shape changes with climate. Generally smoother leaves are found in warmer climates and more jagged leaves are found in cooler climates.

Because the shape of the leaves change with climate, fossilised leaves are used to help learn about past climates.

By studying different types of plant they can gather climate information, such as annual temperature range and water availability that corresponds to the time when the plant was living.

This graph shows the relationship between the temperature and the percentage of smooth leaves found together:

leaf graph

The main problem with this method is that lots of samples are needed to get a good picture of the past climate. 

Using the graph, work out the approximate mean annual temperature if the following leaves were found together:


smooth and jagged edged leaves

This resource was originally developed by the Climate Change Schools Project

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.


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 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.




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


  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.


  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 more 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 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.





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)


  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)

















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 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.


  • 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.


  • 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.


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.





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


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


  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.

Transition Resources for Year 6/ Post SATS

Transition Resources for Year 6/Post SATS

These resources are designed to be used in one session with year 6 (10/ 11 year old) students. Although they will support numeracy, literacy and various other aspects of the curriculum, they are designed to prepare students for secondary school rather than support the year 6 curriculum.

There are 6 suggested activities. Although they are designed to be run sequentially, you may choose to use only some of the activities, or to supplement them with your own ideas.
It should be possible to use these activities with any class size.

Many people, including Ellie Highwood, Cristina Charlton-Perez, Helen Johnson and Laila Gohar, have contributed to these resources.

Guidance Notes – START HERE!

Activity 1 – the Difference between Weather and Climate

Powerpoint: Weather-or-Climate

Word Doc: Weather-or-Climate

Activity 2 – Climate Change Graphs

Powerpoint: Climate Change Picture

Excel: Lollipop

Activity 3 – Climate Change Lucky Dip

No resources required

Activity 4 – Weather Risk Game

Powerpoint: Weather Risk Game

Word Document: Money

Activity 5 – Flooding/ Floating Gardens

Powerpoint: Floating Garden Challenge

Activity 6 – Greenhouse Bulldog

No resources required

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!