Metals that mix when melted

The idea

Metals mix only when molten, solidifying into an alloy: a homogeneous mixture of two or more metals, or of a metal and a non-metal, whose components physical methods cannot separate.

Brass in a temple bell

Metals do not dissolve in each other at room temperature. Yet brass is made of two metals.

How could two metals be mixed together?

• Melt them at a high temperature and let them cool
• Press them side by side at room temperature
• Dip them in water

Make brass

Melt copper and zinc together, then let it cool. Then try to pull the zinc out.

Alloys

Metals do not dissolve in each other at room temperature, but molten metals can mix. When the hot mixture cools, it solidifies into a new material that looks like a single metal. A homogeneous mixture of two or more metals, or of a metal and a non-metal, is an alloy. Physical methods cannot separate the components of an alloy.

Alloys are made to be stronger, more rigid or more corrosion-resistant.

• Alloy | Approximate mixture
• Brass | 80 % copper + 20 % zinc
• Bronze | 80 % copper + 20 % tin
• Stainless steel | iron + carbon (0.03 to 0.8 %), chromium (16 to 18 %), nickel (10 to 14 %), molybdenum (2 to 3 %)

Notes

An alloy is a homogeneous mixture of metals (or a metal and a non-metal), made by melting and cooling. Physical methods cannot separate it.

Check yourself

An alloy is a…

Why are alloys made?

Can the components of an alloy be separated by physical methods?

• homogeneous mixture of metals, or of a metal and a non-metal — correct. Yes.
• single pure metal. An alloy is a mixture.
• heterogeneous mixture that can be sorted by hand. An alloy is uniform.
• To make metals dissolve in water. That is not the purpose.
• To get materials that are stronger, more rigid or more corrosion-resistant — correct. Yes.
• To make metals lighter than air. Not the purpose of alloys.
• Yes, with a magnet. A magnet cannot pull them apart in an alloy.
• Yes, by filtering. Filtering does not separate an alloy.
• No — correct. Yes. The components cannot be separated by physical methods.