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Lesson 9: Compounds What is a compound? Difference between element and compound Examples (water, CO₂, NaCl)
Year 8 • Chemistry
Compounds
In this lesson, students learn what compounds are, how they differ from elements, and how common compounds such as water, carbon dioxide, and sodium chloride are formed.
Lesson Objectives
- Define what a compound is.
- Explain the difference between elements and compounds.
- Identify compounds using examples.
- Understand compounds using particle diagrams.
1. What Is a Compound?
A compound is a substance formed when two or more different elements are chemically bonded together.
[ Image Placeholder – Compound Particle Diagram ]
Key points:
• Compounds contain different elements
• Elements are chemically joined
• Compounds have fixed compositions
• Compounds contain different elements
• Elements are chemically joined
• Compounds have fixed compositions
2. Difference Between Elements and Compounds
[ Image Placeholder – Element vs Compound Diagram ]
Element:
• One type of atom only
• Cannot be broken down chemically
• Example: oxygen (O₂)
• One type of atom only
• Cannot be broken down chemically
• Example: oxygen (O₂)
Compound:
• Different atoms joined together
• Can be broken down chemically
• Example: water (H₂O)
3. Examples of Compounds
[ Image Placeholder – Water, CO₂, NaCl ]
Water (H₂O): hydrogen + oxygen
Carbon dioxide (CO₂): carbon + oxygen
Sodium chloride (NaCl): sodium + chlorine
Carbon dioxide (CO₂): carbon + oxygen
Sodium chloride (NaCl): sodium + chlorine
Each compound has its own properties that are different from the elements it is made from.
4. Compounds and Particle Diagrams
Particle diagrams help us understand compounds.
[ Image Placeholder – Compound Particle Model ]
• Different coloured particles show different elements
• Joined particles show chemical bonding
• Repeating patterns show a compound
• Joined particles show chemical bonding
• Repeating patterns show a compound
Practice Questions
A. Fill in the Blanks
- A compound contains __________ elements.
- Elements in a compound are __________ bonded.
- Water is made of hydrogen and __________.
- CO₂ contains __________ oxygen atoms.
- NaCl is also called __________.
B. True or False
- A compound contains only one type of atom.
- Water is a compound.
- CO₂ is an element.
- Compounds can be broken down chemically.
- NaCl contains sodium and chlorine.
C. Short Answer
- What is a compound?
- How is a compound different from an element?
- Give one example of a compound.
- What does a particle diagram of a compound show?
- Why is water not an element?
✅ Show Answer Key
A. Fill in the Blanks
- different
- chemically
- oxygen
- two
- salt
B. True or False
- False
- True
- False
- True
- True
C. Short Answer
- A substance made of different elements chemically joined.
- Elements have one atom type; compounds have more than one.
- Water / CO₂ / NaCl.
- Different atoms joined together.
- Because it contains hydrogen and oxygen.
© Aviate Learning – Compounds (Year 8)
🧪 Element vs Compound Sorting
Decide whether each substance is an Element or a Compound.
Think carefully about how many types of atoms are present.
Substance will appear here
Click a button to classify the substance.