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LESSON PLANS
plastic
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covered in microscopic cracks which are perfect places for bubbles to grow. When you
drop Mentos into the liquid, millions of bubbles form on the surface and then expand
rapidly. What’s more, the Mentos are denser than the water, so they immediately sink to
the bottom of the bottle, causing the bubbles to rise in their millions, expanding as they
go, and spraying the liquid out of the bottle – an eruption!
Why not try varying the number of Mentos from 1 to 13? How does this affect the height
of the eruption? Try different soft drinks. Which is the best? Can you cause a fountain
with anything other than Mentos?
Lesson 2 : raisin submarines
Objective: to teach students that many liquids contain gases in solution, and that they
may be released under the right conditions. Some liquids are excellent solvents and
dissolve solids such as salt and sugar as well as gases such as CO2. Mass is conserved
when solids and gases dissolve in a liquid.
A 2-litre bottle of clear diet lemonade (doesn’t leave such a sticky mess if spilt!)
Small packet of dried raisins
Electronic scales, accurate to 0.1 grams and capable of recording up to 2.5kg
Dull and dirty copper coins.
Introduction: Ask students to recall the difference between a chemical change and a
physical change. Explain that the lesson is all about the physical change when dissolved
gas escapes from a liquid solvent. Explain that it’s a very slow process, but that it can
happen faster if you add a catalyst to the liquid.
Exercise 1:
Place a bottle of lemonade on an electronic scale and remove the cap.
Take an accurate measurement of the bottle’s mass. Add around a dozen
raisins to the bottle and measure again, noting that the mass
has increased.
Q. Why did mass increase when the raisins were added?
Students will notice that the raisins behave very oddly, diving down to
the bottom of the bottle and rising up. Although the raisins are small, they
have a large surface area with lots of wrinkles to trap air. CO2 bubbles
form quickly on the raisins, so they float up to the surface. Once there,
the bubbles burst and the gas escapes – so the raisin dives back down
to collect more bubbles.
Q. What is happening to the mass of the bottle?
As the raisins go up and down, the mass decreases because the gas is
escaping. A 2-litre bottle should lose about 4.4 to 4.8 grams by the end
of the lesson, proving that flat lemonade is lighter than fizzy lemonade,
even though many students think it would be heavier!
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LESSON PLANS
Resources required:
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Exercise 2:
Students could work in small groups, dropping dirty coins into fizzy
lemonade. The coins also cause nucleation, but are too heavy to rise to
the surface. After a few minutes, the dirty coins look much brighter and
cleaner. The gas bubbles form in the coins’ tiny cracks and crevices,
dislodging all the dirt!
Exercise 3:
Ask students to make a list of things with bubbles – not just fizzy drinks
but also in foods like bread, soufflés, meringues, puffed rice and, the
obvious one, Aero bars! What about the inedible bubbles that help us?
For example in soap, in the foam rubber in a pair of trainers, bubble-wrap
used in packaging, foam insulation, padding in cycle helmets, bubbles in
shampoo and some fire-extinguishers, to name but a few.
Lesson 3 : testing for CO2
Objective: CO2 gas is produced in many different ways – the most notorious one being
the burning of fossil fuels which, as we all know, is creating a glut of CO2 in our
atmosphere. In this lesson, we use several different methods to confirm the presence
of CO2 gas.
Resources required:
One 2-litre bottle of clear fizzy lemonade
Vinegar
Sodium bicarbonate
A small rubber bung (that will fit snugly into the mouth of the soda bottle)
and tubing
Beaker containing a solution of limewater
A straw
A conical flask and delivery tube
Introduction: Pupils will discover that the same gas is released from each of the three
sources. Encourage your students to time each experiment to see how long it takes the
limewater solution to change colour.
Exercise 1:
Prepare a beaker with some fresh limewater and invite one pupil to blow
gently into a straw, bubbling air through the solution. Since we exhale air
containing between 7 and 8% carbon dioxide, the solution will turn a
milky white colour.
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LESSON PLANS
Summary: Fizzy drinks contain a great deal of dissolved gas and store it under
pressure. Once we release the pressure, the gas starts to escape – but this is a slow
process. The raisins acted as a catalyst and released the gas more quickly. Coins also
helped to release the gas, but had a smaller surface area. The gas can be released
more quickly – ask students what happens if you shake a bottle of lemonade before
you open it.
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Open a bottle of fizzy lemonade and place the rubber bung firmly in the
neck of the bottle. Place a glass tube in the rubber bung and attach it to
a rubber tube leading into the beaker of fresh limewater. CO2 bubbles will
appear in the solution and, again, it will turn milky white. You can speed
up the process by adding some raisins to the lemonade, as in lesson 1.
Compare the bottle of fizz with raisins with another bottle without raisins.
Exercise 3:
Add some sodium bicarbonate to a conical flask and add vinegar. The
fizzing, bubbling reaction produces lots of CO2 gas, which can be piped
through the limewater solution.
some additional experiments to try
National curriculum: The below experiments are directly linked to the following
science curriculum within KS3. These are; National Curriculum: SC3 Materials and their
Properties: (1h) & (3e).
The rate of a chemical reaction will vary depending on several factors: the chemical
changes taking place; the temperature of the various solids and liquids; their
concentration; and the size of the particles.
The following experiments show fast and slow reactions using carbonated drinks and
common chemicals. As students work through the various tests, noting the time taken
for each reaction and answering some basic questions, they’ll be preparing for their
GCSE course work and having fizzy fun at the same time!
Materials:
Cardboard
Olive oil
Flasks and beakers
Fizzy lemonade or soda
Powdered poster paint
Washing-up liquid
Sodium bicarbonate
Tea-light candles and tapers
Vinegar
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LESSON PLANS
Exercise 2:
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Experiment 1: the fizzy volcano
Create a volcano from a cone of cardboard and sit a glass beaker in the centre to make
its crater. Pour in plenty of sodium bicarbonate, some red and yellow powdered poster
paint and a generous helping of vinegar.
As the acidic vinegar reacts with the sodium bicarbonate, CO2 gas is released and mixes
with the paint, which froths up and flows over the top of the beaker like lava. A
spectacular and a fun experiment for pupils working in groups of three or four.
As an extra touch, get pupils to write their names on the cardboard cone beforehand,
then see how many disappear under the lava!
Experiment 2: fizz control
Everyone knows it’s not a great idea to shake a can of fizzy drink before opening it. But
try this: shake the can, then tap the sides several times and wait a few moments before
pulling the tab. The tapping dislodges the bubbles from the side of the can, so there
should be less fizz.
Using the same principle, bar staff will often rinse glasses with water just before pouring
a beer. It cuts down on froth and creates a pint with less head. Some bar staff will even
put their finger in the glass while they are pouring lemonade. It gives the bubbles a
surface to form on so the lemonade can be poured much quicker – but it’s not exactly
the most hygienic of tricks!
Experiment 3: the fizzy fire brigade
An inert gas, carbon dioxide is an ideal fire extinguisher because it doesn’t react with
flames. Show pupils a simple demonstration by adding a generous helping of sodium
bicarbonate to a large glass beaker. Pop in a tea-light candle and light the wick with a
taper. Without splashing the candle, add some vinegar and wait for the chemical
reaction. CO2 will start to fill the beaker and, because it’s heavier than air, it will stay at
the bottom. When the gas reaches the flame, it will start to snuff it out from the base of
the wick.
Using the taper, try and reignite the candle. Every time it comes into contact with the
CO2, it’ll go out.
*DISCLAIMER
The Mentos Fountain experiment must be performed outdoors in a large open space, in the presence of an adult of at least 18
years of age, with appropriate safety equipment worn and with the permission of the landowner. The other experiments must
be performed with appropriate safety equipment worn, in a school classroom and under supervision and with permission of the
teacher. We accept no responsibility for accidents, injury or damage to person or property caused by performing these
experiments without precisely following our instructions and we shall not be liable for any losses or damages (consequential or
otherwise) caused by incorrectly performing these experiments. Nothing in this disclaimer excludes or limits our liability for death
or personal injury caused by our negligence, fraud or fraudulent misrepresentation. *For the full disclaimer and other items you
may need please visit www.nationalschoolspartnership.com/fizzintoscienceresources
LESSON PLANS
Bubbles form in a fizzy liquid because the container has a tiny crack, weakness or
surface where they can collect and expand. Coat the inside of a glass beaker with olive
oil, then pour in a fizzy drink. The result? Far fewer bubbles!
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