What Are Alloys?

An alloy is a mixture of two or more elements, where at least one is a metal.

🧪 In the Chemical and Physical Change Gizmo, what were the elements that were used?

• copper

• zinc metal

• zinc chloride

Alloys are created to improve properties such as strength, durability, corrosion resistance, and appearance.

They can be formed by melting and mixing metals together, then allowing them to cool and solidify.

⚛️ What was the purpose for creating the alloy of copper and zinc?

• Silver appearance: Zinc deposits onto the copper surface, forming a thin layer of zinc metal.

• Gold appearance: When heated, the zinc and copper mix to form brass (a copper-zinc alloy), which has a golden color.

Why Are Alloys Used?

Pure metals often have limitations, such as being too soft, prone to rust, or too heavy. Alloys are created to:

✅ Increase strength (e.g., steel is stronger than pure iron)

✅ Improve corrosion resistance (e.g., stainless steel doesn’t rust)

✅ Reduce weight (e.g., aluminum alloys for aircraft)

✅ Enhance appearance (e.g., brass in decorative items)

Types of Alloys

• Substitutional Alloys – Some metal atoms are replaced by other metal atoms of similar size.

➡ Example: Brass (Copper + Zinc)

• Interstitial Alloys – Small atoms fill spaces between larger metal atoms.

➡ Example: Steel (Iron + Carbon)

Physical & Chemical Properties of Alloys

Physical Properties:

🔹 Harder and stronger than pure metals

🔹 More resistant to wear and corrosion

🔹 Can have different colors and textures

Chemical Properties:

🔹 More resistant to oxidation and rusting

🔹 Less reactive than pure metals

Interesting Facts About Alloys

💡 The Bronze Age (3300–1200 BCE) was named after an alloy—bronze!

💡 The Eiffel Tower is made of wrought iron, an early form of steel.

💡 Gold jewelry is usually an alloy—pure gold (24K) is too soft, so it's mixed with copper or silver.

💡 Stainless steel’s chromium content prevents rust by forming a protective layer.

Objective:

Students will work in groups to research and explore what happens when two metals are mixed together, focusing on the formation of alloys, reactions, and changes in properties. Each group will then present their findings.

Instructions:

1. Group Formation (5 Minutes)

   1. Divide the class into small groups (3-4 students per group).

   2. Assign each group two metals to research. Some example metal pairs include:

      1. Copper + Tin (Brass)

      2. Copper + Zinc (Brass)

      3. Iron + Carbon (Steel)

      4. Aluminum + Copper (Aluminum Alloys)

      5. Lead + Tin (Solder)

      6. Nickel + Iron (Stainless Steel)

2. Research (15 Minutes)

   1. Each group will research the following questions using the internet:

      1. What happens when these two metals are mixed together?

         1. Does the mixture form a new substance or an alloy?

         2. What properties change when the metals are combined (e.g., strength, corrosion resistance, appearance)?

      2. Why do people mix these metals together?

         1. What are the benefits of creating an alloy with this particular combination of metals?

      3. Where are these alloys or mixtures used in everyday life?

         1. List real-world applications of the alloy or mixture you are researching.

      4. What are some examples of chemical or physical changes that occur when these metals are combined?

         1. Describe any chemical reactions, changes in physical properties, or new material properties formed when these metals are mixed.

3. Group Presentation Preparation (5 Minutes)

   1. After conducting the research, groups will prepare a brief (2-3 minute) presentation of their findings.

   2. The presentation should answer the questions above and use visual aids (e.g., pictures of alloys, examples of products made from them, diagrams showing chemical reactions).

4. Group Presentations (5 Minutes)

   1. Each group will present their findings to the class. They should:

      1. Explain what happens when the two metals are mixed.

      2. Describe how the combination forms an alloy or mixture and why this is beneficial.

      3. Provide real-world examples of where the alloy or mixture is used.

      4. Share any chemical or physical changes that occur.

5. Reflection & Discussion (Optional, 5 Minutes

   1. After all groups have presented, have a brief class discussion on:

      1. Why are alloys important in modern technology?

      2. How can understanding the properties of metal mixtures benefit industries like construction, electronics, and transportation?

Helpful Websites for Research:

• Khan Academy – Alloys

• Royal Society of Chemistry – Alloys

• Chemistry LibreTexts – Alloys

1.4: Chemistry at Home