Page 44 - Big Ideas Year 10 sciPAD 2025

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44 SCIPAD - BIG IDEAS - BOOK 2
BASIS OF CHEMICAL REACTIONS
Alloys
An alloy is a mixture of two or more elements, one or more of which is a metal.
Alloys often have properties that are different to the metals they contain. This
makes them more useful than the pure metals alone. For example, alloys are
often harder than the metal they contain. Steel is an alloy of iron and carbon.
It is used to make many things such as cars, ships, bridges and building frames.
Steel is harder, stronger and more flexible than iron and doesn’t corrode (rust)
as quickly as iron.
Recent advances in technology have created a new range of alloys - called
smart alloys . Smart alloys have unusual properties. Nitinol is an alloy of nickel and
titanium, and is known as a shape memory alloy. If nitinol is bent out of shape, it
returns to its original shape when it is either heated or an electric current is passed
through it. This property makes it useful for making spectacle frames because they return to their
original shape if they are put in hot water after bending them.
The table below lists some common alloys.
Alloy Metals Properties Uses
Tungsten steel Tungsten, iron,
chromium Very hard, resists wear
Stainless steel Iron, nickel,
chromium
Hard, very shiny lustre,
does not corrode
Bronze Copper, tin Hard, resists corrosion
even in salt water
Brass Copper, zinc Good acoustic
properties
Duraluminium Aluminium, copper,
magnesium
Lightweight, strong,
malleable
1. Using the words provided below, complete the table by writing in the common use for
each alloy.
High-speed drill bits - Cutlery - Ship propellers - Musical instruments - Aircraft bodies
2. Define the term ‘alloy’. 


3. Outline three advantages of using steel instead of iron in building ships and cars.
(a) 
(b) 
(c) 
4. New Zealand’s “gold” coins are actually an alloy of aluminium and bronze. Using the
information from the table above, and the information from the previous page, outline the
properties of these substances that make them suitable for use in coins.
Properties of aluminium: 

Properties of bronze: 

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