Fizz fountain

COKE AND MENTOS ERUPT!
When you add Mentos (chewy mints) to a bottle of coke the reaction is a giant eruption. The carbon
dioxide dissolved in the coke rapidly comes out of solution and tries to escape from the bottle.
OBJECTIVES
theory is.
To begin to understand what a scientific
To generate questions for enquiry.
STARTER
Play “Dinner Time”. Organise the class
into circle, ensure everyone is sitting on their
own chair. Then give each pupil a food label
(e.g. potatoes, chicken, rice, beans, fish,
cheese, carrots and peas). Make sure that at
least 3-5 children share the same label. Once
everyone has been allocated a label explain to
the children that when their food label is
called they must switch chairs with someone
(and it can’t be with the person beside them!)
When “Dinner Time” is called everyone must
swap chairs.
STIMULUS
Present the Coke and Mentos
demonstration to the class. For this you will
need; a roll of Mentos mints, a 2 litre bottle of
diet coke and a piece of paper.
This demonstration is best done
outside! Open the bottle of coke and position
it on the ground so that it does not fall over.
Unwrap the roll of Mentos and using the piece
Saving your teeth to make a
FIZZ FOUNTAIN
What makes the
coke erupt?
of paper form a tube large enough to hold the
mints loosely (the goal is to drop all the mints
into the coke at once). When all the pupils are
standing at a safe distance drop the Mentos
out of the paper tube into the bottle of coke
and run!
Present the class with several theories
that claim to explain why the coke erupts (see
supporting cards, page 2). Read the theories
together and ask the pupils to discuss in pairs
which they think is the best theory, and
explain to each other their reasons why.
Emphasise that we are looking for what
makes a good theory, not necessarily which is
“correct”. Ask the pupils to stand beside the
card that they think is the best theory and try
to convince others to move.
GENERATING QUESTIONS
Organise the children into pairs and give
them time to reflect and discuss how they felt
when they saw the coke explode out of the
bottle. Ask each pair to generate a question
relating to the stimulus and to record their
question on the flip chart/board.
SELECTING THE QUESTION
Give each pupil 3 stickers and ask them
to vote for the questions they most want to
Do all fizzy
drinks erupt
when mentos
are added?
discuss by placing them beside the
corresponding question. They can use all 3
votes on the 1 question or they can spread
them over 2 or 3 questions.
ENQUIRY
Manage turn taking by passing around a
speaking object (only the pupil holding the
object is allowed to speak).
CONCLUDING THE ENQUIRY
Encourage the children to think of their
final comments for now and complete a quick
round, giving everyone the chance to voice
these thoughts (note pupils can pass if they
do not want to speak).
REFLECTING ON THE ENQUIRY
The “Head in the Clouds” word cloud
(page 3) gives pupils a choice of many
adjectives to help them describe how they felt
during the enquiry. Allow them to reflect,
circle the appropriate words and then share
their reasons why they felt this way. Also
allowing pupils the chance to circle how they
would like to feel gives the group the
opportunity to identify ways that they can
improve the enquiry
Resource for Teachers 1 www.ulster.ac.uk/scienceinsociety/

TIME FOR THEORY
A theory is a scientific idea that can be used to explain an observation.
Here are some theories that attempt to explain what is seen when mentos are added to coke.
Print the cards below or copy them on to A4 paper. Place them on the floor and ask students to stand beside the
card that they think represents the best theory. Emphasize that it does not matter whether the theory is correct:
you are interested in their reasons for selecting the theory.
The mints are
coated with
magic sugar.
This cola is
special.
The mints provide a
place for bubbles to
form. Gas comes out of
the cola and builds up
pressure until the cola is
pushed out of the bottle.
The carbon dioxide
bubbles from the cola
attach on to the
surface of the mint
and lift it.
The mints react with
the coke creating a
gas. As the pressure
builds up, the liquid is
pushed out of the
bottle.
The mints expand when
they are put into the
cola and they push the
cola up out of the
bottle.
Resource for Teachers 2 www.ulster.ac.uk/scienceinsociety/

H E A D I N T H E C L O U D S
Resource for Teachers 3 www.ulster.ac.uk/scienceinsociety/
Circle any words that describe how you felt during the enquiry today.
If the adjective you want is missing, add it in.
Think about why you have circled these adjectives!

fizzing
&
foaming
THe
mentos
fountain
• There is much debate over the explanation for the coke eruption.
Scientists have made theories to explain the observation.
• It is thought to be a result of a physical change rather than a chemical
reaction.
• The Mentos have tiny bumps on their surface. These are called
nucleation sites.
• Carbon dioxide (the gas that makes the coke fizzy) is squeezed into the
liquid. It stays dissolved when the cola is sealed, but when the bottle is
opened, the gas can escape into the atmosphere. When the Mentos are
added to the coke, the carbon dioxide comes out of solution more
quickly.
• When the carbon dioxide comes out of solution it forms bubbles on the
tiny bumps on the surface of the Mentos. These bubbles are not dense
so they rise through the cola to the surface where they burst and carbon
dioxide escapes into the air.
• A mint has a good surface for the carbon dioxide to attach to as it is
covered with microscopic layers of liquid sugar, in other words there are
lots of little holes that our eyes cannot see but the gas form bubbles in.
• Mentos are more dense than coke and so they sink all the way to the
bottom of the bottle, reacting with the coke the whole way down. As the
gas is released the pressure builds and the liquid is pushed up and out of
the bottle, hence the coke eruption.
Watch closely
when you add one
mentos to some
sparkling water. What will
happen if you add a
whole packet to a
bottle?
FIZZ
1. Carbon dioxide gas is
dissolved in fizzy drinks. It
is put into the drink under
pressure and stays in
because fizzy drinks are
kept in a sealed container.
When fizzy drinks are left
open, they go flat as the
carbon dioxide escapes.
Resource for Teachers 4 www.ulster.ac.uk/scienceinsociety/
1
2
2. Adding mentos speeds up
the escape of carbon
dioxide. You can see the
bubbles of carbon dioxide
forming around a single
mentos when it is placed in
water. What is special
about mentos? Do other
objects do the same?