Teaching sequence

Work through this resource material in the following sequence:

10 minutes

Tune In: What can go into glass recycling?

20 minutes

Find Out: Why can only some types of glass be recycled?

25 minutes

Take Action: Science communication for effective glass recycling

5 minutes

Reflection

Learning intentions and success criteria

Students will:

identify the properties of different materials by understanding their structure and composition
understand how the properties of different materials affect their recyclability.

Students can:

describe the properties of different materials in terms of their particle arrangement
outline how the properties of different materials affect their recyclability
design a piece of science communication to raise awareness around the importance of correct glass recycling.

Tune In: What can go into glass recycling?

Step 1

Allocate students into groups of 4-5 and give them a selection of the materials listed below without labelling what category they belong to.

If you don’t have these materials available, give each group of students a copy of this handout, with images of all the materials listed that can be printed and cut up. You can also find images of these materials in the attached visual explainer.

Glass	Glass bottles (green, amber, clear), Glass jars, drinking glasses, reading glasses, window glass, glass cookware, ceramic/porcelain bowls and plates, lightbulbs, mirrors
Metal	Food cans, soft drink cans, empty aerosol cans, foil trays, aluminium foil
Plastic	Plastic drinking bottles, plastic packaging
Paper/cardboard	Plain paper, cardboard, paper food packaging, empty milk cartons, egg cartons

Step 2

Invite each group to sort the materials into 1 of 5 categories:

glass recycling
metal recycling
plastic recycling
paper/cardboard recycling
can’t be recycled

Of the images provided, all of the non-glass materials are recyclable. Of the glass materials, the following are NOT recyclable: Drinking glasses, reading glasses, window glass, glass cookware, ceramic/porcelain bowls and plates, lightbulbs and mirrors.

Step 3

Discuss as a class how each group sorted their materials. Determine if there is a consensus about what materials can be recycled.

Step 4

Share with students which materials can be recycled using the slides on the attached visual explainer.

Discuss the answers with your students by asking them if they are surprised by any of the results. You might like to brainstorm some reasons why the particular materials are not recyclable.

Find Out: Why can only some types of glass be recycled?

Step 1

Explain to your students that glass is an extremely important and versatile material. While we might think all glass is the same, there are, in fact, many different types of glass made in different ways with different properties to make them suitable for different purposes.

Watch the video below with your students to learn a little more about the composition and structure of glass. Ask them to pay attention to the video for the answers to the following questions in order to discuss them once the video is finished.

What is the main ingredient in glass?	Silicon dioxide (Quartz often found in sand).
What is an amorphous solid?	A solid that has a chaotic structure, like a liquid and doesn’t have a clearly defined shape or form. This means molecules can get really close to each other and fill any gaps, making the surface very smooth. It also means light can hit the glass without scattering in many directions.

Why is glass transparent - Mark Miodownik - TED-Ed (youtube.com/watch?v=VwRLIt6jgdM)

You might like to show your students the image of the difference between crystalline structure and amorphous structure on the attached visual explainer.

Step 2

Explain to your students that the average glass we see in bottles and jars is usually soda-lime glass. This is made from silicon dioxide (sand), soda ash (sodium carbonate), and limestone (calcium carbonate).

The melting point of sand is extremely high, around 1700℃. The soda ash reduces the sand's melting point, which helps to save energy in the manufacturing process, and the limestone stops the unwanted chemical effects of the soda ash from becoming a problem (soda ash makes a glass that would dissolve in water!) (Source: Explain that stuff, explainthatstuff.com/glass.html)

Step 3

Glass is a material that can be infinitely recycled (when it is in the right form). When glass is recycled, it can be added to the mixture of ingredients to create new bottles and jars.

Watch the following video with your students from 1:13 mins until 3:50 mins, which shows Visy's process of creating glass out of recycled materials. As your students watch the video, ask them to note down some answers to the questions on their student worksheet (also included below).

Visy - How We Make Glass (https://vimeo.com/563048506)

Question	Suggested answer
What do they use the optical sorters for?	To remove small contaminants.
How does the glass get sorted?	By colour (green, amber and clear).
What material does the remanufacturing process start with?	Cullet (Reclaimed and sorted glass in small pieces).
What materials get made at the plant?	Glass bottles and jars.
What temperature is the furnace at?	1550 degrees Celsius.
Why are the final glass products inspected?	To check for imperfections, thickness and strength.

Step 4

Remind your students that all types of glass can’t be recycled, just as they found out in the Tune In of this lesson. The reason has to do with their chemical properties and composition. When cullet is used in the remanufacture process, it cannot contain any contaminants. If these unwanted materials make their way into the final product, it causes imperfections in the glass that make them unstable!

Allocate students into groups of 6. Task each group with researching why different types of glass can’t be recycled using the method Visy used in the video. Ensure each group assigns one group member to each type of glass and encourage them to use the resources below and any other information they come across to find the description and properties of the different types of glasses, focusing on their melting point, what materials they are made with and if there is anything added to the material. (A worked example has been provided below).

	Description	Properties
Bottle and jar glass made from recyclable materials	Note: This type of glass can be recycled.Use an average soda-lime glass, which can be substituted with recycled glass.	The mixture melts in the furnace at approximately 1550℃. It is hard, has a high temperature and chemical resistance, and is transparent.
Ceramic glasses	Inorganic non-metallic solid that is made up of metal or non-metal compounds that have been shaped and hardened by heating to high temperatures. It contains clay.	Hard, corrosion-resistant, and brittle, have a melting temperature above 2000℃, which means they can be used in places that require high temperatures.
Glass cookware - e.g Pyrex	Made of borosilicate glass, which has ingredients similar to normal glass but with added boric oxide, gives it unique properties. Type of glass that is resistant to heat, chemicals and electricity. Used to make cookware, thermometers and science lab equipment.	High melting point, more heat resistant than normal glass, can expand more than normal glass, which means it doesn’t break after rapid temperature changes.
Lightbulb glass	Thin glass that can withstand high heat from the temperature in the globe.	Incandescent globes contain small amounts of metal and glass that aren’t easily separated from each other, halogen bulbs are made of a different type of glass that doesn’t melt at the same temperature as bottles and jars. Fluorescent bulbs can contain mercury which is toxic.
Window glass	Thicker, flat glass used in doors, windows and other building applications.	It can have many different properties depending on how it is made and for what purpose. E.g. laminated glass has a coating of a chemical between layers, screen-printed glass can be tinted with ceramic ink, and mirrored glass has a coating of metal.
Mirrors	Flat glass surface that is coated with a reflective metal or substance such as aluminium	Reflective due to coating which makes it not able to be recycled as these components can’t be separated from each other.

Suggested resources

	Resources
Bottle and jar glass made from recyclable materials	Visy Explain That Stuff
Ceramic glasses	Science Learning Hub UNSW Sydney
Glass cookware - e.g Pyrex	Britannica Swift Glass
Lightbulb glass	Treehugger
Window glass	St. Cloud Window Innovative Aluminium and Glass
Mirrors	Metal Men Recycling Recycle Nation

Step 5

Once your students have finished collecting their information, bring everyone back together for a class discussion.

Ask your students what they found out about the different types of glass that would mean they can’t be recycled using the methods mentioned before.

Suggested answer: The main point of their research should be that lots of these types of glass have different substances added to their structure or placed on them, which cause them to have different properties and also make them have different melting points, which means they wouldn’t melt in the furnace with the bottle and jar glass and would cause imperfections in the new glass.

Take Action: Science communication for effective glass recycling

Step 1

Students will be tasked with creating an effective piece of science communication to educate their family, school or community about what types of glass can be recycled.

Show your students this Household Recycling Poster from Visy and ask them to perform a ‘Good, Bad, Better’ on the glass recycling section, discussing their responses. Lead students to understand that whilst the poster gives good information about what can and can’t be recycled, it doesn’t indicate why. Most people don’t transform their habits until they know the consequences of those habits. People might be throwing these materials into recycling because they aren’t aware, or they don’t understand why they cannot recycle them.

A ‘Good, Bad, Better’ activity prompts students to observe something that is good about what they are looking at, something that is bad, and something that could be better.

Step 2

Explain to your students that their task is to create a poster or other piece of science communication, such as a social media post, that educates their chosen audience about the scientific reasons behind glass recycling. Their goal should be to raise awareness of correct glass recycling and inform their audience why it is important, focusing on the chemical and physical properties they have learnt about in this lesson.

Extension opportunity: Students requiring extension can dive more deeply into this and find if there are any alternative methods by which different types of glasses can be recycled and where these items need to go for this to happen.

Reflection

Reflect on the lesson with your students by asking them to answer the following questions.

What did you learn from today's lesson?
What surprised you the most?
What can you do with the information you now know?

Visy Glass - Physical and Chemical Properties of Glass

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Visy Glass - Physical and Chemical Properties of Glass

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