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Topic Notes · Easy summaries with diagrams
Chapter 7 — Chapter 7 — Thermal Properties of Matter
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📘Easy summary
Matter is made of tiny molecules in constant motion with forces of attraction between them; they have K.E. (motion) and P.E. (attraction). Solids: molecules closely packed, vibrate about fixed mean positions, strong forces → fixed shape and volume. Liquids: slightly farther apart, slide over each other → fixed volume, no fixed shape. Gases: far apart, very weak forces, move randomly at high speed in all directions → no fixed shape or volume. Plasma: ionized gas with equal positive and negative charges (Sun, stars, lightning); KMT applies partly (particles move randomly) but electric forces dominate.
⭐Key points
- Heating a liquid increases molecular K.E. → expansion, faster evaporation.
- Gas molecules collide, so speeds differ.
🔬Diagram
🌿Real-life example
The Sun is matter in plasma state.
💡Exam tip
- Use spacing, motion and forces in comparisons.
✅Quick check
1. Molecules in solid:
2. Plasma is:
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