The World of Metals and Non-metals
Iron, copper and gold behave very differently from sulphur or carbon. This Class 7 Curiosity chapter compares metals and non-metals — their physical and chemical properties, how they react with oxygen, water and acids, and the many ways we use them.
Learning objectives
- Compare physical properties of metals and non-metals.
- Describe chemical properties of each.
- Explain reactions with oxygen, water and acids.
- Give common uses of metals and non-metals.
Key concepts
Physical properties
Metals are usually shiny (lustrous), hard, malleable (can be beaten into sheets), ductile (can be drawn into wires), good conductors of heat and electricity, and sonorous (ring when struck). Non-metals are generally dull, brittle, poor conductors, and not malleable or ductile. There are exceptions, such as mercury (a liquid metal) and graphite (a non-metal that conducts).
Reaction with oxygen
Metals react with oxygen to form metal oxides, which are usually basic — for example, iron forms iron oxide (rust) and magnesium burns to give magnesium oxide. Non-metals react with oxygen to form oxides that are usually acidic, such as the oxide formed when sulphur or carbon burns.
Reaction with water and acids
Some metals react with water, vigorously or slowly, and reactive metals react with acids to release hydrogen gas, which burns with a 'pop' sound. Most non-metals do not react with acids in this way. These differences help us classify a substance as a metal or non-metal.
Uses of metals and non-metals
Metals are used in making tools, machinery, wires, vehicles, utensils and jewellery because of their strength and conductivity. Non-metals are essential too: oxygen for breathing, nitrogen and phosphorus for fertilisers, and carbon (as graphite) in pencils. Both groups are vital in daily life.
Important formulas
Metal + oxygen
metal + oxygen → metal oxide (usually basic)
Metal + acid
reactive metal + acid → salt + hydrogen gas
Key definitions
- Malleable
- Able to be beaten into thin sheets without breaking.
- Ductile
- Able to be drawn into thin wires.
- Sonorous
- Producing a ringing sound when struck.
- Metal oxide
- The compound formed when a metal reacts with oxygen.
Solved examples
Q1. Why can copper be drawn into wires?
Solution: Because it is ductile, a property of metals.
Q2. What gas is released when a reactive metal reacts with an acid?
Solution: Hydrogen gas (it burns with a 'pop').
Q3. Name a non-metal that conducts electricity.
Solution: Graphite (a form of carbon).
Common mistakes to avoid
- Assuming all metals are solid (mercury is a liquid metal).
- Thinking no non-metal conducts (graphite does).
- Believing metal oxides are acidic (they are usually basic).
- Forgetting that the 'pop' test shows hydrogen gas.
The World of Metals and Non-metals — MCQ Quiz
10 questions with instant feedback. Use number keys 1–4 to answer.
A property of metals is that they are:
Practice questions
Short answer
Name two physical properties of metals.
Lustre and malleability (also ductility, conductivity, sonorousness).
What forms when a metal reacts with oxygen?
A metal oxide, usually basic.
Which gas burns with a 'pop'?
Hydrogen.
Long answer
Compare the physical properties of metals and non-metals, noting exceptions.
Metals and non-metals differ in many physical properties. Metals are usually lustrous (shiny), hard, malleable (can be hammered into sheets), ductile (can be drawn into wires), good conductors of heat and electricity, and sonorous (ring when struck). Non-metals are generally dull, brittle, poor conductors, and neither malleable nor ductile. However, there are notable exceptions that show these are general trends rather than strict rules: mercury is a metal but is liquid at room temperature, and graphite is a non-metal yet conducts electricity well. These exceptions are why we look at several properties together before classifying a substance.
Describe how metals and non-metals react with oxygen and acids.
Metals and non-metals can be distinguished by their chemical reactions. When metals react with oxygen they form metal oxides, which are usually basic in nature — for instance, iron slowly forms rust and magnesium burns brightly to give magnesium oxide. Non-metals react with oxygen to form oxides that are usually acidic, such as those formed when sulphur or carbon burns. With acids, reactive metals react to release hydrogen gas, which burns with a characteristic 'pop' sound, whereas most non-metals do not react with acids in this way. These contrasting reactions are a reliable guide to whether a substance is a metal or a non-metal.
HOTS (Higher Order Thinking)
A shiny solid is hammered into a thin sheet and conducts electricity. Metal or non-metal? Why?
A metal — lustre, malleability and conductivity are all metallic properties.
Why is graphite an unusual non-metal?
Unlike most non-metals, graphite conducts electricity, which is why it is used in pencils and electrodes.
Quick revision
Revision notes
- Metals: lustrous, malleable, ductile, conductors, sonorous.
- Non-metals: dull, brittle, poor conductors.
- Metal + oxygen → basic oxide; non-metal oxide is acidic.
- Reactive metal + acid → hydrogen ('pop' test).
Key takeaways
- Metals and non-metals differ in look, feel and reactions.
- Metal oxides are basic; non-metal oxides acidic.
- Exceptions (mercury, graphite) show trends aren't absolute.
Frequently asked questions
What does ductile mean?
Able to be drawn into thin wires.
Are all metals solid?
No — mercury is a liquid metal at room temperature.
Which gas does a metal–acid reaction give off?
Hydrogen gas.