Rapid rockets – rocket fuel investigation
Name ..................................................................................... Date: ...............................
Water as a rocket fuel
What happens to an Alka-Seltzer when it is put into water?
Watch and note down what happens when you put the tablet
into water. Could you use any of the following words to
describe your observations?
fizz, boil, bubble, bend, crack, dissolve, disappear, sparkle, bang,
mix, float, freeze, foam, explode, froth, stretch.
Fuel
Observation notes and diagrams
Water
What do you think is happening?
I think ........................................................................................................................
...................................................................................................................................
...................................................................................................................................
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Rapid rockets – rocket fuel investigation
Name ..................................................................................... Date: ...............................
Rocket fuel observations
Watch and note down what happens when you add the Alka-Seltzer to each
rocket fuel. Look out for whether the tablet reacts, how quickly it reacts, how
much gas is produced, whether there are bubbles or if foam is formed.
Fuel
Time taken
to react
Observation notes and diagrams
I think .................................................................... will be the best rocket fuel because
.........................................................................................................................................
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Name ..................................................................................... Date: ...............................
Flying the rockets
Test each of your rocket fuels in turn. One member of the team can time
how long it takes for the rocket to launch. Place each rocket by a wall so
that another team member can measure the height each rocket reaches.
Fuel
Time taken
to react
Height
reached
Observation notes and diagrams
The best rocket fuel was ........................................ because ......................................
.....................................................................................................................................
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Rapid rockets – rocket fuel investigation
Teaching notes
Foams – Foam is a substance that is formed by trapping pockets of gas in a liquid or a solid.
Reaction between Alka-Seltzer and water – The fizzing that is seen when an Alka-Seltzer tablet is
dropped in water is the same sort of fizzing that can be seen when baking soda is mixed with
vinegar. If the ingredients for Alka-Seltzer are examined it is found that the tablets contain solid
forms of citric acid (vinegar) and sodium bicarbonate (baking soda). When a tablet is dropped in
water the water dissolves the solid form of the acid and the baking soda allowing them to mix and
react. The result is a reaction that produces carbon dioxide gas (CO2).
Factors that affect the rates of chemical reactions:
There are several factors that can influence the rate of a chemical reaction.

Concentration of reactants: Concentration means a higher amount of the reactants or, more
simply put, more of the stuff that is causing the chemical reaction. If there are more reactants,
there are more particles to collide with, or bump into each other, which will make the reaction
go faster.

Temperature: Usually, an increase in temperature is accompanied by an increase in the reaction
rate. An increase in temperature causes the molecules to move faster, which will cause the
reaction to happen faster.

Environment: The kind of solution the reaction takes place in can affect the rate of reaction.
Many reactions happen faster in a liquid, rather than in a solid or a gas.
Why does the “rocket” fly? – As the Alka-Seltzer and the water react, carbon dioxide (CO2) is
released. As the gas is released, the pressure inside the canister builds up until the lid pops off.
The height that the rocket may fly will depend on how quickly the pressure builds inside, so will
ultimately depend on how quick the reaction proceeds.
Learning outcomes
Working scientifically:

Draws conclusions and raises further questions that could be investigated, based on
their data and observations.

Uses appropriate scientific language and ideas to explain, evaluate and communicate
their methods and findings.
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POS Properties and changes of materials:

Explain that some changes result in the formation of new materials, and that this kind
of change is not usually reversible, including changes associated with burning and the
action of acid on bicarbonate of soda.
The investigation
Resources:
Film canisters
Beakers
Fairy Liquid?
Alka-Seltzer
Funnels
Stopwatches
Oil
Water
Vinegar
Milk
Activity 1 – Using water as rocket fuel
Split children into small groups. Show them the PowerPoint slides explaining that they are going
to be investigating a fuel to make a rocket fly. Give each group an Alka-Seltzer tablet and explain
that they are going to be making observations about what happens when it is placed in water.
Place the tablets in and watch what happens. (See PowerPoint slide 2 – Health and Safety).
Allow children time to discuss as a group and class about what they saw: fizzing, bubbles, tablet
“disappearing” etc. Some children may start to describe that the bubbles are gas, observing
direction of bubbles, what happens when they get to the surface etc. This part allows lots of
discussion about what is happening to the tablet, in that it hasn’t “disappeared” but has been
changed into something else (gas and sodium citrate).
Once the discussion has been had and the children have an understanding that the tablet is
emitting gas in water as part of an acid-base reaction, show children a film canister and ask: What
would happen if the reaction took place in here? Again, allow children time to discuss as a group
and feedback their ideas to the class. In simple terms, the children should understand that the gas
is still being released, but in a closed space it has nowhere to escape to. This builds pressure and
eventually, when the pressure gets too much, the lid will be forced off to release the gas.
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Activity 2 – Observing different rocket fuels
Now explain to children that, using the ideas of the acid-base reaction and build-up of pressure
inside the film canisters, they will investigate the best rocket fuel to make a film canister rocket fly
the highest.
Here there are opportunities for research to be done on actual rockets and how they work. The
ideas are the same, in which the fuel used is designed to burn and release gas quickly, so there is a
rapid build-up of pressure, which forces the rocket to fly upwards.
Show children a variety of liquids that they can test, by adding in a portion of Alka-Seltzer and
noting and observing what happens. Children should be looking at whether the tablet reacts, how
quickly it reacts, how much gas is produced, are there bubbles or is a foam formed? What impact
will formation of a foam have? Is it good or bad? (Foams are trapping gas, so will not build
pressure quickly).
Children can use an observation grid to write down what they notice about the “fuels”.
Depending on abilities, teachers can decide whether they want to give children a checklist of what
they should be looking for, or with HA children in particular, see if they can relate the observations
they see to potential effectiveness of the liquid as a rocket fuel.
Activity 3 – Flying the rockets:
Following on from the investigation phase, children can now take their chosen fuel and fly their
rockets! This may be best done outside, as it can be quite messy.
Teachers may need to model to children how to place the liquid and fuel in quickly, before the
reaction takes place. This stage can be done as a competition for fun or just simply as a data
collection exercise.

First, agree on a set amount of liquid to place in the canister. This can be another discussion
point as too much liquid will not allow for much gas to collect and thus lead to reduced
pressure. Too little liquid may mean the reaction not going to completion.

Secondly, agree on an amount of Alka-Seltzer to put in e.g. whole, half or a quarter. Again
this could lead to an interesting discussion: Does the amount of Alka-Seltzer effect how high
the rocket flies?

Finally, once the fuel and tablet is in, quickly place the rocket next to a wall and let it fly! A
measurement can be placed on the wall to the height the rocket went and then once all rockets
have been flown, a winner can be decided.
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Conclusions could be written up formally, as either letters to NASA, or as part of an on-going link
to a topic (Literacy link).
Results could be converted into graphs, repeat readings taken, and averages calculated
(Mathematics Link).
Further investigations:
The experiment allows plenty of scope for follow-on investigations. From their results and
observations, children should be encouraged to pose further questions that could be investigated,
such as:

Does the temperature of the liquid have an effect?

Does the amount of liquid make a difference?

Does the size/number of tablets have an effect?

What about using a mixture of liquids? (e.g. orange juice and vinegar)

Are there alternatives to Alka-Seltzer? (bicarbonate of soda, baking powder)
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