Metals and Alloys

Question 1

Metal structure

Answer 1

-giant structure of atoms arranged in regular pattern

-electrons on outer shells are delocalised and free to move through whole structure (so they can conduct electricty)

-sharing of delocalised electrons causes strong metallic bonding

Question 2

Properties of metals

Answer 2

-good conductors
-high melting/boiling points

Question 3

Why do metals have such high boiling/melting points?

Answer 3

-metallic bonding in the giant structure is very strong
-large amounts of energy needed to overcome the metallic bonds in melting + boiling

Question 4

Why do metals conduct electricity?

Answer 4

-have delocalised electrons that carry electrical charge through the metal

Question 5

Alloy

Answer 5

-mixture of 2+ elements, where at least one is a metal

Question 6

How do we make a soft pure metal hard for other uses?

Answer 6

-we add another element, so it forms an alloy

Question 7

Why are pure metals soft?

Answer 7

-same-sized atoms are arranged in layers
-layers can slide over eachother easily with little force, so the metal is less strong

Question 8

Why are alloys so hard?

Answer 8

-atoms are of different sizes (since they are from different elements)
-smaller/bigger atoms distort the layers of atoms in the pure metal
-so a greater force is required for the layers to slide over eachother
-means the alloy is harder and stronger than the pure metal

Question 9

Explain why steel, an alloy of iron, is harder than pure iron

Answer 9

-the iron has been mixed with different elements so all the atoms are different sizes
-the smaller/bigger atoms distort the layers of the iron atoms
-so a greater force is required for the layers to slide overachother easily compared to pure iron
-this means steel is harder and stronger than pure iron

Question 10

How to answer 6-mark evaluation questions

Answer 10

Observations & Explanations (What Happened & Why)
Positive Results: State what did happen and explain the factors that caused it (e.g., “Rust formed in tubes 1 & 5 due to oxygen and water; tube 5 rusted less due to reduced iron exposure”).
Negative Results (Controls): Highlight what didn’t happen and why (e.g., “No rust in tubes 2, 3, or 4—water was absent in tube 2, oxygen in tube 3, and tube 4 was coated”).

2. Conclusions & Prevention Methods
   Essential Conditions: Define the necessary conditions for the process (e.g., “Both oxygen and water are required for rusting”).
   Prevention Methods: Identify effective prevention strategies (e.g., “Barrier coatings prevent exposure to oxygen or water, stopping rust”).
3. Comparative Analysis & Deeper Explanations
   Method Comparison: Compare effectiveness of tested approaches and state the best one.
   Underlying Chemistry: Explain why one method is superior based on chemical principles.
4. Summary & Key Takeaway
   Effectiveness Recap: Reinforce main findings and highlight the best strategies (e.g., “While coatings work when intact, galvanising provides superior long-term protection”).

Question 11

Write a word equation for the reaction of iron with oxygen and water

Answer 11

iron + oxygen + water > hydrated iron oxide

Question 12

Sacrificial protection

Answer 12

a corrosion prevention technique where a more reactive metal is used to protect another metal from corrosion

Question 13

Explain why a bike chain is protected from rusting by oiling it, rather than by painting it.

Answer 13

-oil lubricates chain, it moves smoother
-paint would flake off once bike is ridden
>which would then expose the steel chain to air and water so it rusts

Question 14

Where are the strong electrostatic forces in metals?

Answer 14

-between positive ions and delocalised electrons