This term the lesson are all about the topic of Forces. + Introduction to The Scientific Method.


Ask the class to brainstorm for a few minutes and see what they know about ‘forces’ including


  • What is a Force
  • Where do Forces occur? Can they give examples?
  • What types of forces are there
  • How can we measure forces?
  • Is there a unit of Force?
  • Who is the most famous scientist associated with Force?


Continue the Brainstorming and Ask What is it that Scientists do and How do they do it? Do they have a specific ‘Way’ of doing what they do?


  • Introduce pupils to the scientific method and briefly go through the 3 main parts of the Lab Book / Report explaining that these are
    • Planning and Investigation
    • Collecting Data and Analysing it
    • Evaluating their investigation
  • This term they will be focusing on ‘Planning’ and Investigation and that this consists of the following parts
    • Forming a Hypothesis
    • Making a Prediction with Dependent / Independent variables (for younger pupils this can simply framed as ‘Asking a Question’ that can be tested using 1 thing they change and 1 thing they measure)
    • Attempting to justify the prediction
    • Deciding on a method + recording this
    • Writing an equipment list
    • Assessing the Risk Associated with the experiment

General- all students should be made aware of and confidently follow the core rules of conduct in a science lesson:

Wash hands regularly.
Put nothing in their mouths or eyes.
Follow all instructions given by adults.

Specific to this lesson:

Safety goggles to be worn during all demonstrations

· Demonstration 1.1
1. Spillages are a possibility so do this over a bowl.
2. Any spills must be cleaned and the affected area dry before continuing.

· Demonstration 1.2
1. Extinguish the match after lighting the candles.
2. After the egg has been removed from the flask, do not allow pupils to approach the conical flask as it will be very hot.
3. Dismantle the cartridge burner after it has cooled.

· Demonstration 1.3

· Investigation 2.1

1. Pupils must perform the experiment standing up, with chairs and bags tucked under desks.
2. Safety goggles MUST be worn.
3. Any spillages must be mopped up immediately until the affected area is dry.

Please see the individual demonstrations and investigations for potential Misconceptions and Corrections

Review all the stages to a scientific plan including:

  • Identifying Independent and Dependent Variables
  • Shaping a question, they can test
  • Making a Prediction / Hypothesis
  • Justifying their hypothesis
  • Method (plus research)
  • List of Equipment
  • Risk Assessment

Force - an influence on a body or system, producing or tending to produce a change in movement or in shape or other effects.
Balanced and unbalanced forces - equal or unequal influences acting on a body or system.
Pressure - the exertion of force upon a surface by an object, fluid, etc., in contact with it.
Air Pressure - the force exerted upon objects by the air.
Effervescence - the bubbling of a solution due to the escape of gas. The gas may form by a chemical reaction, as in a fermenting liquid, or by coming out of solution after having been under pressure, as in a carbonated drink.
Variable - something that may or does vary or change; a variable feature or factor.
Prediction - suggest a possible outcome in advance of the event.
Hypothesis - a justified prediction; a reasoned possible outcome with explanation.
Gravity - the force of attraction by which terrestrial bodies tend to fall toward the centre of the earth.

This demonstration introduces the idea that the air all around us exerts pressure in all directions.

Demonstrator will need access to:

Small Drinking Glass

Plastic Square

Step-by-step demonstration:

  1. Fill the glass completely (if you look at the glass at eye level the water is actually over the lip).
  2. Place the plastic square centrally on the glass.
  3. Hold one finger onto the centre of the plastic.

Question time!

  • What do you think will happen if I turn the glass upside down?
  1. Invert the glass (over the bowl may be a good idea!).

Question time!

  • What do you think will happen if I remove my finger?
  1. Remove the finger holding the plastic in place.
  • What did you expect to happen when I took my finger away?
  • Why do you think water didn’t splash everywhere?
  • Will it work with only half filled glass of water? Why/why not?
  1. Repeat with half-filled glass.

Question time!

  • Did the experiment result agree with your prediction?
  • Can you suggest what might be happening here? (Think about the forces involved)

Misconceptions & Corrections

When the glass is inverted, the water will fall out

The water is sticking/ sucking the plastic on to the glass

Science explanation

  1. Gravity is seeking to pull the water down.
  2. Something must be pushing on the plastic to stop this (some kind of upward pressure).
  3. The force is air pressure.
  4. Air pressure also acts equally on the outside surface of the glass.

This demonstration further illustrates air pressure is being exerted on objects in all directions.

Demonstrator will need access to:

Oil Vegetable 30ml

Pyrex Conical Flask 250ml

Rods Plastic Stirring

Candles Birthday

Step-by-step demonstration:

Show the students the peeled boiled egg balancing on the mouth of the 250 ml flask and ask them if they can suggest ways of getting the egg into the flask without breaking it.

  1. Rub some oil into the neck of the flask.
  2. Place the egg onto the flask with the narrow end pointing to the ceiling.

Question time!

  • Why is the egg not going into the flask?
  • What forces are acting on the egg? Are they balanced for unbalanced? How do you know?


  1. Carefully, without damaging the egg, stick the candles into the narrow end of the egg in close triangular formation (the candles must not be too far apart).

Question time!

  • How will these candles help me to get the egg in the flask?
  1. Light the candles.
  2. Holding the flask upside down, confidently place the egg into neck of the flask with the lit candles entering first.
  3. Ensure contact between the glass and the egg by keeping a finger on the bottom of the egg.
  4. Do not ram the egg into the conical, but do not do it slowly either!

Question time!

  • What has happened to the egg?
  • How did this work? Encourage students to consider the forces acting on the egg at the beginning, and how these have changed
  • Why did the balance of the forces change?
  • Can I get the egg back out again without breaking it up or smashing the glass? How? What would I need to change? The balance of forces
  1. Using the cartridge burner and a clamp stand, simply up end the flask ensuring the egg slides snugly into the neck, and heat the bottom of the flask vigorously for a few minutes, the egg will obligingly ‘squeeze’ back out!

Question time!

  • How did I change the balance of forces?
  • What effect did this have on the egg?

Potential Misconceptions & Corrections


  • A vacuum is being created
  • The glass expands as it heats up
  • The egg is being pulled into the flask
  • The egg is “sucked” in or out of the flask

Science explanation

  1. The candles heat the gas inside the flask (air) and this expands.
  2. The reaction produces carbon dioxide through reaction of the carbon in the paper and oxygen (O2) in the air and water vapour through a reaction with hydrogen in the paper and O2 in the air.
  3. When the flame goes out the air cools, the vapour condenses and occupies less space and so the pressure inside the flask drops.
  4. The greater air pressure outside the flask then easily forces the soft pliable egg into the flask.
  5. The opposite is the case when the up-ended flask is heated to extract the egg. The air molecules inside the flask receive lots of energy and start to move with much greater speed impacting with much greater force on the inside of the flask and surface of the egg than the air molecules outside the flask....and so, because the forces are imbalanced the egg is ‘forced’ out.

If it doesn’t work, possibilities are that you have done it too slowly, allowing a build-up of carbon dioxide into the flask. If this happens, simply fill the flask with water and empty out and/or use another egg. Or, perhaps the egg is shaped so that a perfect seal cannot be achieved on the flask.

This demonstration illustrates the force of air pressure.

Demonstrator will need access to:

Magdeburg Spheres (Pair)

Step-by-step demonstration:

  1. Put the hemispheres together
  2. You must ensure a perfect seal. Do this by running your thumb and finger around the rim, and push in the centre.
  3. Play tug-of war!

Potential Misconceptions & Corrections


  • The spheres are “stuck” together
  • They are sucking each other       

Science Explained:


  1. These are a brilliant way of introducing/consolidating force diagrams.
  2. Pupils should be getting that if things don’t move, forces are balanced.
  3. They only see the ‘pull-apart’ force of the tug of war.
  4. Therefore, there must be something pushing in,
  5. This force is air pressure again!

For each demonstration allow children time to discuss and agree where the force arrows should be on a diagram. You may extend some children by encouraging them to think about which is the greater force/are the forces equal, and the impact that has on the size of the force arrows used. Children could draw the demonstrations with force arrows as a record of their ideas.

Pupils will need access to:

Canister Plastic Film White with Lid

Vitamin C Tube

Measuring Cylinder Plastic 100ml

Step-by-step instructions

Part 1 (Lesson Guidance 1)

  1. Break off half a tablet of Vitamin C and place it in a dry film canister
  2. Pour about a third of the canister’s volume in water into the container
  3. Place the lid onto the canister. A snap can be heard otherwise the lid may not be on properly
  4. Turn the canister upside down and place it on the table
  5. Stand back!

Question time!

What has happened?

What forces are in play here? Try and link the theory learned in the previous lesson to observations and results.

How does the balance of forces change?

What does the observed fizzing mean?


Part 2 (Lesson Guidance 2)

  1. Ensure the canister is dry
  2. As method above, but pupils should investigate their own independent variable

Question time!

What are the variables in this experiment?

Which variables could be changed in a controlled way? candidates for the independent variable

How do you ensure your results are valid? repeat measurements, keep dependent variables constant

Try and devise a way of making the canister travel faster, further, higher etc.                              

  1. Obtain repeat results
  2. Pupils to record their results in a table

Science explained 

  • The tablet is a bicarbonate and acid mixture.
  • The bicarbonate reacts with the acid to produce carbon dioxide.
  • The CO2 fills the space in the canister.
  • As more CO2 is produced, the pressure increases inside the canister.
  • The pressure is suddenly enough to overcome the friction between the lid and the canister.
  • The lid pops off.
  • The liquid and gas escapes rapidly which produces thrust.
  • The canister launches into the air!
  • Gravity takes over so the canister falls.

  1. Ask the class what they learnt / discovered...providing the wherewithal so that children can say ‘I used to think ......... and now I think.......... because ......’ or ‘I used to think ......... and I still think .......... because ......’
  2. Suggest a list of variables that could have been changed if they had more equipment.
  3. Ask for volunteers to suggest how they could have improved the experiment and how this might change their results.
  4. Ask if anyone seemed to have discovered a pattern in their results.
  5. Discuss examples of air pressure in the real world.

Recap / Plenary  : Use of Ind vs Dep variables

  • Ask the class what they learnt / discovered
  • Ask for volunteers to suggest how they could have improved the experiment.
  • Ask if anyone seemed to have discovered a pattern in their results.
  • Ask what are all the steps in a Scientific Plan
  • Quickly check understanding of Depenedent and Independent Variables


  • Write instructions for the investigation for another year group.
  • Begin a class glossary of term used in the Forces topic. This could be used towards a science dictionary, for a particular audience, maybe for parents or younger children.
  • Research and write a fact file on Sir Isaac Newton.


  • Practise recording data.
  • Use of decimals and smaller units of time, such as tenths and hundredths of a second, and comparing them in size.
  • Introduction to the fact 1Kg = 10 Newton’s of Force (Weight). Pupils can work out simple mass to Newton equivalents.

Other subjects

  • Forces in balance, with stable and unstable shapes and identifying pushes and pulls in PE.
  • Taking pictures of themselves in action poses in a physical education session. Using IT, children could import three of their photographs and write about the forces that were evident during the session. 
  • Make a Powerpoint presentation about Newton. Show children this one for some ideas.