Activity 5
Steel speaking to you
Recycling
Context
Steel is an alloy made from iron and carbon. It requires a lot of energy to create.
The average Australian consumes 6 kilograms of drink cans each year – that’s more than 1.7 billion cans every
year. Only around 56% of these cans are recycled across Australia. But recycling steel makes sense. It’s 100%
recyclable and uses 75% less energy than producing steel from raw materials.*
Before you recycle your steel cans … why not reuse them to create a tin can phone, a great way of exploring how
sound travels.
* Steel and Aluminium Fact Sheet, www.cleanup.org.au
Resources required
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•
•
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two steel cans, clean and dry with no sharp edges
3–4 metres of small diameter string such as kite string
medium sized nail and a hammer
electrical tape (optional)
Teaching background
Sounds vibrate and make sound waves that ears can pick up. When you pull the string tight and talk into one of
the cans, the bottom of the cup vibrates back and forth with the sound waves which then vibrate across the taut
string to the other can. The ears of the person at the other end of the line collect the sound vibrations and send
them to the brain to be processed. That’s when you ‘hear’ the message.
Make sure the string is tight between the two cans. This normally means the distance is limited and the two
people have to be connected in a straight line.
Qualitative data is data that can be collected without tools, just using your five senses. For example describe the
can using the criteria of colour, size or texture, roughness of the edges (smooth, ribbed), feel to the touch.
Quantitative data is data that is measured using tools and always produces a number. For example measure the
length of string between the cans.
Consider how to ensure testing is ‘fair’. Generally, fair testing changes only the independent variable while
ensuring controlled variables stay the same.
All scientific investigations involve variables. The independent variable is the variable you purposely manipulate
(change). The dependent variable is the variable being observed, which changes in response to the independent
variable. The variables that are not changed are called controlled variables.
46 | Recycle Right is a program delivered by Zero Waste SA www.zerowaste.sa.gov.au
Activity 5
Steel speaking to you
Recycling
Teaching background cont...
When planning an investigation, to make it a fair test, we need to identify:
• one variable to change (independent variable)
• another variable to measure (dependent variable)
• variables to keep the same (controlled variables).
Brainstorm test factors that may be varied (independent variable):
1.the type of ‘cans’ used (eg paper cups or polystyrene cups)
2.the size of the cans (eg milo cans come in a variety of sizes)
3.the type of string used
4.the width of the string
5.the length of string (distance)
6.straight versus around corners.
What to do
[Optional] Start by watching a 5-minute episode of The Wombles Season 1, Episode 6 Peep Peep Peep in which
Uncle Bulgaria wants the Wombles to keep in touch with one another so Wellington invents a ‘talking tin can’.
1.Ensure that one end of each can has been removed. Be sure there are no sharp edges. Cover the rim with
electrical tape to be extra safe.
2.Punch a small hole in the bottom of each can with the nail and hammer just large enough for the string to go
through. Ensure an adult is present and keep your hands and fingers clear of the hammer.
3.From the outside, insert one end of the string into the hole in one can. Tie enough knots in the end of the string
or tape it to the can so it cannot go back through the hole. Do the same with the other end of the string in the
other can.
4.Each person holds a can and stretches the string so that it is taut. One person speaks into their can while the
other person listens through the other can.
Recycle Right is a program delivered by Zero Waste SA www.zerowaste.sa.gov.au | 47
Activity 5
Steel speaking to you
Recycling
Steel can telephone
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Student example:
Investigation Planner
What do we wish to investigate?
What do we predict will happen? (Hypothesis)
The materials that transmit sound the best.
We think paper will make the best transmitter of sound.
What will we change (the independent variable)?
The types of material used for each ‘can’
For telephone 1 we will use steel cans.
For telephone 2 we will use paper cups.
For telephone 3 we will use polystyrene cups.
What are we observing (the dependent variable)?
We will observe which is easiest to hear the sound of a bell from.
What will we keep the same (the controlled variables) to ensure the test is fair?
1.
2.
3.
4.
The length of string between the cans
The type of string between the cans
The bell sound (not our voices as these can change easily)
The volume of the cans (as much as possible) by measuring how many millilitres fit in each.
48 | Recycle Right is a program delivered by Zero Waste SA www.zerowaste.sa.gov.au
Activity 5
Steel speaking to you
Recycling
Conducting the investigation
1.Form teams and allocate roles.
2.Use the investigation planner to decide on what is being investigated and therefore what the team will change,
observe and keep the same.
3.Use the template to create 3 designs which vary the independent variable.
4.Make the designs and record the quantitative and qualitative data from each design.
Analysing the results
Once the telephones are made, test the properties of each telephone according to the criteria and record
results.
Decide how the data could be depicted (eg bar graph, line graph or pictograph) and then create a large
scale poster with analysis for presentation.
Use the observations and graphs to draw a conclusion about the different telephone performances and
compare the hypothesis with the conclusion.
Create a list of the pros and cons of different designs.
Consider questions you have come across during your investigations that you would like to explore. For
example, if paper cups and thinner string are both better transmitters of sound will paper cup telephones
with thin string make the best telephone?
Create the ULTIMATE telephone
Using the data you have collected can you create the ultimate telephone?
1.Create a list of materials needed to create the design.
2.Create a list of criteria that the telephone needs to meet to be considered ‘ultimate’ (eg variability of use, ability
to hear the sound).
Make the telephone and test it to see if it is the ultimate one.
• What do you like best about your telephone? What are its best features?
• What changes could you make to your telephone to improve it even further?
Evaluation
Students create one or more of the following:
•
•
•
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a scientific report of the exercise including aim, materials, method, results and summary
a manual/recipe for making one or more of the ultimate telephone
a mock newspaper headline and article about a new telephone
an advertisement, advertorial or infomercial for their telephone including explaining why their phone is the best
or easiest to use
• a letter to Wellington (Womble) who did not know how his ‘talking tin can’ phone worked explaining how it
works and how to make the best ‘talking’ phone.
Recycle Right is a program delivered by Zero Waste SA www.zerowaste.sa.gov.au | 49
Activity 5
Steel speaking to you
Recycling
Investigation PLANNER
What do you wish to investigate?
What do you predict will happen? (hypothesis)
What will you change (independent variable)?
What are you observing (dependent variable)?
What will you keep the same (the controlled variables) to ensure the
test is fair?
50 | Recycle Right is a program delivered by Zero Waste SA www.zerowaste.sa.gov.au