These notes cover the key properties of carbon allotropes and...
Chemistry88 views·Updated 24 Jun 2026·3 pagesGCSE Chemistry Unit 3: Quantitative Chemistry Notes
Erin@erin_agwa
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Carbon Structures and Mass Conservation
Ever wondered why pencil lead conducts electricity but diamond doesn't? It's all about how carbon atoms bond together! Graphite has each carbon atom making 3 bonds with delocalised electrons that can move freely, making it conductive and soft as its hexagonal sheets slide over each other.
Diamond takes a completely different approach - each carbon atom bonds to 4 others, creating an incredibly hard structure with no free electrons. That's why it can't conduct electricity but makes brilliant cutting tools.
Graphene is basically a single layer of graphite that still conducts electricity, whilst fullerenes like C60 are football-shaped molecules made of 60 carbon atoms. Silicon dioxide behaves similarly to diamond - high melting point but no electrical conductivity.
Key Point: The way atoms bond determines the material's properties - same element, completely different characteristics!
Here's something crucial for your calculations: no atoms disappear during chemical reactions. The mass of what you start with (reactants) always equals the mass of what you end up with (products). This is why balancing symbol equations matters so much for your exams.
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of 3
Calculations with Moles and Concentration
Calculating relative formula mass (Mr) becomes straightforward once you know the pattern. Take sodium oxide (Na₂O): you've got 2 sodium atoms (2 × 23) plus 1 oxygen atom (1 × 16) = 62. Always multiply the number of atoms by their relative atomic mass.
Moles represent Avogadro's constant (6.02 × 10²³) - that's an enormous number of particles! The key formula you'll use constantly is: Mass = Mr × moles. This relationship helps you predict how much product you'll get from any reaction.
Let's tackle a real example: if you start with 510g of Al₂O₃, you can work out that this equals 5 moles (510g ÷ 102). From the balanced equation, this produces 10 moles of aluminium, which weighs 270g.
Top Tip: Always start by finding the moles of what you're given, then use the balanced equation ratios to find what you need!
Concentration measures dissolved particles (solute) in a set volume of liquid (solvent). Use the formula: concentration = mass ÷ volume. Remember that 1000cm³ equals 1dm³. The limiting reactant runs out first and determines how much product you can make.
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Chemistry88 views·Updated 24 Jun 2026·3 pagesGCSE Chemistry Unit 3: Quantitative Chemistry Notes
Erin@erin_agwa
These notes cover the key properties of carbon allotropes and silicon dioxide, followed by essential quantitative chemistry concepts including mass conservation, moles, and concentration calculations. You'll also learn about metal reactivity and how different metals behave with acids, water, and...
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Carbon Structures and Mass Conservation
Ever wondered why pencil lead conducts electricity but diamond doesn't? It's all about how carbon atoms bond together! Graphite has each carbon atom making 3 bonds with delocalised electrons that can move freely, making it conductive and soft as its hexagonal sheets slide over each other.
Diamond takes a completely different approach - each carbon atom bonds to 4 others, creating an incredibly hard structure with no free electrons. That's why it can't conduct electricity but makes brilliant cutting tools.
Graphene is basically a single layer of graphite that still conducts electricity, whilst fullerenes like C60 are football-shaped molecules made of 60 carbon atoms. Silicon dioxide behaves similarly to diamond - high melting point but no electrical conductivity.
Key Point: The way atoms bond determines the material's properties - same element, completely different characteristics!
Here's something crucial for your calculations: no atoms disappear during chemical reactions. The mass of what you start with (reactants) always equals the mass of what you end up with (products). This is why balancing symbol equations matters so much for your exams.
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Calculations with Moles and Concentration
Calculating relative formula mass (Mr) becomes straightforward once you know the pattern. Take sodium oxide (Na₂O): you've got 2 sodium atoms (2 × 23) plus 1 oxygen atom (1 × 16) = 62. Always multiply the number of atoms by their relative atomic mass.
Moles represent Avogadro's constant (6.02 × 10²³) - that's an enormous number of particles! The key formula you'll use constantly is: Mass = Mr × moles. This relationship helps you predict how much product you'll get from any reaction.
Let's tackle a real example: if you start with 510g of Al₂O₃, you can work out that this equals 5 moles (510g ÷ 102). From the balanced equation, this produces 10 moles of aluminium, which weighs 270g.
Top Tip: Always start by finding the moles of what you're given, then use the balanced equation ratios to find what you need!
Concentration measures dissolved particles (solute) in a set volume of liquid (solvent). Use the formula: concentration = mass ÷ volume. Remember that 1000cm³ equals 1dm³. The limiting reactant runs out first and determines how much product you can make.
3
of 3Sign up to see the content. It's free!
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Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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