2.1 Elements, Compounds & Mixtures
Master the fundamental differences between pure substances and mixtures
🧱 The Lego Brick Analogy
ELEMENT
A single red Lego brick. Only one type of atom. Cannot be broken down into simpler substances by chemical means.
Example: Fe, O₂, Cu
COMPOUND
Red and blue bricks glued together. Two or more different atoms chemically bonded. Hard to separate.
Example: H₂O, CO₂, FeS
MIXTURE
Loose bricks in a bucket. Two or more substances not chemically bonded. Easy to separate.
Example: Air, Fe + S
🔬 Virtual Lab: Iron + Sulfur Experiment
🎯 Key Observations:
- 1.MIXTURE (Before heating): Iron responds to magnet. Easy separation. Physical change only.
- 2.HEATING: Glows red (exothermic). Atoms are bonding. Chemical change occurring.
- 3.COMPOUND (After heating): Black solid. Does NOT respond to magnet. Properties changed completely.
⚛️ Particle Sorter Challenge
Click on each example to classify it as an ELEMENT, COMPOUND, or MIXTURE. Check your understanding!
🔩 Alloy Explorer: Is Brass a Compound?
Brass is made of Copper (Cu) and Zinc (Zn). Let's zoom in to see if it's a compound or mixture.
🎯 Answer: Brass is a MIXTURE (Alloy)
- •Copper and zinc atoms are NOT chemically bonded together
- •They are simply mixed in a metallic lattice
- •An alloy is defined as a mixture of a metal with other elements
📚 Summary & Definitions
ELEMENT
A substance made of only one type of atom. Cannot be broken down into simpler substances by chemical means.
Examples: O₂, Fe, Cu, C, He
COMPOUND
A substance made of two or more different atoms chemically bonded together. Can only be separated by chemical means.
Examples: H₂O, CO₂, NaCl, FeS, CH₄
MIXTURE
Two or more substances not chemically bonded. Can be separated by physical means (filtration, distillation, magnetism).
Examples: Air, seawater, Fe + S, sand + salt
ALLOY
A mixture of a metal with other elements (usually other metals). Alloys are NOT compounds.
Examples: Brass (Cu + Zn), Steel (Fe + C), Bronze (Cu + Sn)
⚠️ Examiner Tips
✅ Better: "Mixture can be separated by physical means such as filtration, distillation, or magnetism."
✅ Better: "Compound is when two or more different atoms are chemically bonded."
✅ Better: "Alloys are mixtures because the metal atoms are not chemically bonded - they simply occupy the same metallic lattice."
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