2.7 Metals and non-metals

Natural sciences

Grade 8

Matter: classification

Module 20

Metals and non-metals

• A metal typically is a hard, shiny and strong element that is able to conduct heat and electricity.
• Iron is the most commonly used metal in the world in which we live, though not in its pure form. When iron is combined with a small amount of a non-metal like carbon we obtain an alloy .
• The study of metals is known as metallurgy .
• Gold is generally regarded as a metal that symbolizes wealth and prosperity, while platinum and palladium are valuable because of their use in electronics and specialized engineering.
• Steel is known everywhere and millions of tons of steel are used annually to manufacture items such as washing machines, cars, ships and trains. Stainless steel is also used for cutlery. For this, it is made into an alloy with the use of hard, shiny chromium .
• A variety of substances can be added to iron to form alloys , e.g. manganese, phosphorus, silicon and sulphur.
• Aluminium , again, is used extensively for cold drink cans, ladders and objects that are required to be light and rust free. Aluminium is the third most common chemical element on earth as much of the earth’s crust is made up of it. Copper and magnesium are usually added to aluminium to make it suitable for industrial use.
• Metals can be recycled successfully to protect our natural resources – the gold and silver used in electrical circuits (and in false teeth!), particularly.
• Bronze – a mixture of copper and tin - is one of the most ancient of alloys.
• Brass is an alloy of copper and zinc.

Class activity

Recognition of metals and non-metals

• Identify as many substances as possible from the illustration and classify them as metals and non-metals according to the main element of their substance.

1. Which feature did you consider to determine whether substances were metals or non-metals?

2. Do you think the secretary is prosperous? Provide a reason for your answer?

3. Which substance is taking over from this metal in industry? From what is it made?

4. What is metallurgy?

5. What is steel?

6. The following are the distinctive features of metal. Write down the distinctive features for non-metals:

METALS

hard and shiny

pliable and malleable

conducts heat

conducts electricity

7. What is the difference between pliable and malleable?

Assessment of recognition

Were you able to do the classification correctly and to apply your knowledge?

[LO 2.2; LO 2.4]

Assessment

Learning outcomes 2: Constructing science knowledge

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

We know this when the learner

• is able to categorise information;

2.4 is able to apply knowledge.

Memorandum

Metals:

Non-metals:

1. shiny, hard

2. gold

3. demand

4. study of metals

5. alloy

6. NON-METALS

Hard and shiny - Different colours; not very hard

Pliable and malleable - Brittle, breaks

Conducts heat – No

Conducts electricity - NO

7. Pliable – long threads stretched out.

Malleable – hammered into thin plates/sheets.