States of matter and the kinetic molecular theory
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Question
What are the three states of matter?
Answer
**Solid**, **liquid** and **gas** — they differ in how close the particles are and how freely they move.
Question
Describe the particles in a solid.
Answer
**Packed** close in fixed positions; they only **vibrate**. A solid has a fixed shape and volume.
Question
Describe the particles in a liquid.
Answer
**Touching** but not fixed; they **slide** past each other. A liquid has fixed volume but takes the container's shape.
Question
Describe the particles in a gas.
Answer
**Far apart**, moving **fast and randomly**. A gas fills its container and is easily compressed.
Question
What is the kinetic molecular theory?
Answer
A model treating matter as **small particles in constant random motion**, with attractive forces between them that weaken as they spread apart.
Question
What does temperature measure?
Answer
The **average kinetic energy** of the particles — hotter means the particles move faster on average.
Question
How do you convert °C to kelvin?
Answer
**Add 273.15** (≈ 273): T(K) = θ(°C) + 273.15.
Question
What is absolute zero?
Answer
**0 K** (about −273 °C) — the lowest possible temperature, where particle motion is at a minimum.
Question
Why can a gas be compressed but a liquid cannot?
Answer
Gas particles are **far apart** with large gaps to close up; liquid particles are already **touching** with little space.
Question
Why does temperature stay constant during melting?
Answer
The added energy is used to **overcome the forces** between particles, not to speed them up, so the average kinetic energy (temperature) stays the same.
Question
Why does a liquid take the shape of its container?
Answer
Its particles are **not held in fixed positions**, so they **slide** and flow to fit the container.
Question
What happens to particles when a solid is heated?
Answer
They **gain kinetic energy** and **vibrate more**, until they have enough energy to break free of their fixed positions and the solid melts.
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Full study notes for States of matter and the kinetic molecular theory
Topic 1.1 hub
Introduction to the particulate nature of matter
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