Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
An alloy is a mixture of a metal with one or more other elements, which can be other metals or non-metals like Carbon ().
In a pure metal, atoms are of the same size and are arranged in a regular lattice. These layers of atoms can easily slide over each other when a force is applied, making pure metals relatively soft and malleable.
Alloys are harder and stronger than pure metals because the different-sized atoms of the added element(s) disrupt the regular arrangement of the metal lattice.
The disruption of the lattice prevents the layers of atoms from sliding over each other easily, which increases the material's resistance to deformation.
Brass is an alloy made of Copper () and Zinc (). It is harder than pure copper and is used in musical instruments and electrical plug pins.
Bronze is an alloy of Copper () and Tin (). It is used in making statues and ornaments due to its durability and resistance to corrosion.
Stainless steel is an alloy of Iron (), Chromium (), and Nickel (). The Chromium forms a thin, invisible layer of Chromium(III) oxide () that prevents the iron from rusting.
📐Formulae
💡Examples
Problem 1:
Explain why pure gold (-carat) is not typically used for making jewelry, whereas -carat gold ( and or ) is commonly used.
Solution:
Pure gold is too soft because its atoms are arranged in regular layers that slide easily. -carat gold is an alloy.
Explanation:
In -carat gold, the atoms of Silver () or Copper () have different sizes compared to Gold (). These atoms disrupt the regular lattice layers of the gold, making it harder for the layers to slide, thus making the jewelry more durable and resistant to wear.
Problem 2:
Determine the mass of Chromium () required to produce of stainless steel if the alloy must contain by mass.
Solution:
Mass of .
Explanation:
Using the percentage composition formula: . This amount of Chromium ensures the formation of the protective oxide layer.