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Glass is recycled by crushing it into cullet and heating it with sand and limestone, and metals by melting them down. Free notes and 10 questions answered.
Recycling in Practice: Glass and Metals is part of Life cycle assessment and recycling in GCSE AQA Higher Chemistry.
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Glass is recycled by crushing it into cullet and heating it with sand and limestone, and metals by melting them down. Free notes and 10 questions answered.
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Use this lesson to stay inside Life cycle assessment and recycling while connecting the detail back to the wider Topic 10: Using resources topic.
Read the core explanations from Recycling in Practice: Glass and Metals before testing yourself from memory.
Every year, millions of glass bottles and metal cans end up in landfill sites. But here's the thing - these materials never truly 'wear out'. A glass bottle can be recycled endlessly without losing quality, and metals like aluminium can be melted down and reformed countless times.
This isn't just about being environmentally friendly. Recycling saves massive amounts of energy compared to making new materials from scratch. For example, recycling aluminium uses 95% less energy than extracting it from bauxite ore.
Glass has a unique advantage - it can be reused directly or recycled completely. When you return a milk bottle to be refilled, that's reuse. The bottle keeps its original form and function.
Here's how glass recycling works: collected bottles are sorted by colour (clear, brown, green), then crushed into small pieces called cullet. This cullet is mixed with raw materials like sand and limestone, then heated to around 1500°C in a furnace. The molten glass can then be shaped into new bottles, jars, or even fibreglass.
The beauty of glass recycling is that it's a closed loop. One bottle can become another bottle, which can become another bottle, indefinitely. The quality never degrades.
Metals are recycling superstars. Unlike paper or plastic, which degrade each time they're recycled, metals maintain their properties no matter how many times they're melted down and reformed.
Worked example: The Metal Recycling Process
How does a discarded aluminium can become a new car part?
Answer: The aluminium can is transformed into high-quality metal that can be used for car parts, new cans, or any other aluminium product.
Here's where it gets clever. Some scrap steel can be added directly to iron from a blast furnace. This reduces the amount of iron ore that needs to be mined and processed. It's like adding recycled ingredients to a recipe - you need less of the raw materials.
Not all recycling needs the same level of separation. The amount of sorting required depends on what you're making and what properties you need.
For high-quality products like food containers, you need very pure materials. Glass bottles for wine must be made from perfectly clean, colour-sorted cullet. But for construction materials like concrete aggregate, mixed glass colours work fine.
The same applies to metals. Aircraft parts need ultra-pure aluminium alloys with precise compositions. But for making park benches or road barriers, mixed scrap steel works perfectly well.
Let's look at some impressive numbers. Recycling metals and glass saves significant energy compared with extracting raw materials and processing them from scratch.
In the UK, we recycle about 67% of glass packaging and 75% of steel cans. But there's still room for improvement - especially with aluminium cans, where we only recycle about 72%.
The steel industry is particularly clever with recycling. Electric arc furnaces can produce new steel using 100% scrap metal, while traditional blast furnaces typically use about 25% scrap steel mixed with iron ore. This flexibility means steel is one of the most recycled materials on Earth.
Exam questions on recycling often test your understanding of the difference between reuse and recycling, plus the factors affecting separation requirements. Here's how to tackle them.
Watch out for questions asking you to evaluate recycling processes. Structure your answer by discussing benefits (energy savings, reduced mining), limitations (collection costs, contamination issues), and overall conclusions about sustainability.
Not every glass product can simply be reused in its original form. Broken glass, mixed-colour glass, and some coated or laminated products are often recycled into different products instead. This is still useful because it reduces the need for fresh raw materials and lowers the energy needed for manufacture.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-19.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Aluminium melts at 660°C, much lower than iron at 1538°C. In metal recycling, scrap is heated to its melting point, which breaks down the original shape but keeps the metal's properties, then poured into moulds.
Glass is recycled by sorting bottles by colour, crushing them into small pieces called cullet, mixing the cullet with sand and limestone, and heating it to around 1500°C. The molten glass is shaped into new bottles, jars or fibreglass.
Metals are recycled by collecting and sorting scrap by type, cleaning off labels and coatings, melting the metal (660°C for aluminium, 1538°C for iron), removing impurities, then pouring it into moulds to make ingots or sheets. Metals keep their properties however many times they are recycled.
Cullet is crushed waste glass used in glass recycling. It is mixed with raw materials like sand and limestone, then heated to around 1500°C in a furnace to make new bottles, jars or fibreglass.
The UK recycles about 67% of glass packaging and 75% of steel cans, but only about 72% of aluminium cans. Recycling saves significant energy compared with extracting and processing raw materials.
Glass can be recycled endlessly without losing quality, making a closed loop where one bottle becomes another bottle indefinitely. Broken, mixed-colour or coated glass is often recycled into different products instead.
Reusing glass means using it again in its original form, such as returning a milk bottle to be refilled. Recycling means crushing waste glass into cullet and melting it to make new glass products.
The amount of separation needed depends on the end product. Wine bottles need clean, colour-sorted cullet, while mixed glass colours work for concrete aggregate; in the same way, aircraft parts need ultra-pure aluminium alloys, but mixed scrap steel works for park benches.
Some scrap steel is added directly to iron from a blast furnace, which reduces the amount of iron ore that needs to be mined. Electric arc furnaces can make new steel from 100% scrap metal, while blast furnaces typically use about 25% scrap steel mixed with iron ore.
Glass is sorted by colour (clear, brown, green) because high-quality products like wine bottles must be made from perfectly clean, colour-sorted cullet. For construction materials like concrete aggregate, mixed glass colours work fine.