What does the kinetic theory of matter say?

All matter is made of tiny particles that are always moving.

Describe the arrangement and movement of particles in a solid.

Closely packed in a regular pattern, vibrating about fixed positions.

Describe the arrangement and movement of particles in a liquid.

Close together in an irregular arrangement, sliding past each other.

Describe the arrangement and movement of particles in a gas.

Far apart, moving randomly at high speed in all directions.

Why does a solid have a fixed shape?

Its particles are held in fixed positions by strong forces.

Why can a gas be compressed?

There is a lot of empty space between its particles, so they can be pushed closer together.

Why can a liquid hardly be compressed?

Its particles are already touching, so they cannot be pushed closer.

Why does a gas have a low density?

The particles are far apart, so there are few particles in a given volume.

What happens to the particles in a solid when it is heated?

They gain kinetic energy and vibrate more strongly.

Give one limitation of the particle model.

Particles are drawn as hard solid spheres and the forces between them are not shown.

States of matter and kinetic theoryIB MYP Chemistry: Flashcards

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What are the three main states of matter?

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What are the three main states of matter?: Solid, liquid and gas.
What does the kinetic theory of matter say?: All matter is made of tiny particles that are always moving.
Describe the arrangement and movement of particles in a solid.: Closely packed in a regular pattern, vibrating about fixed positions.
Describe the arrangement and movement of particles in a liquid.: Close together in an irregular arrangement, sliding past each other.
Describe the arrangement and movement of particles in a gas.: Far apart, moving randomly at high speed in all directions.
Which state has particles with the most kinetic energy?: Gas.
Why does a solid have a fixed shape?: Its particles are held in fixed positions by strong forces.
Why can a gas be compressed?: There is a lot of empty space between its particles, so they can be pushed closer together.
Why can a liquid hardly be compressed?: Its particles are already touching, so they cannot be pushed closer.
Why does a gas have a low density?: The particles are far apart, so there are few particles in a given volume.
What happens to the particles in a solid when it is heated?: They gain kinetic energy and vibrate more strongly.
Give one limitation of the particle model.: Particles are drawn as hard solid spheres and the forces between them are not shown.

Exam questions on States of matter and kinetic theory

In a science lesson in Lagos, students seal the nozzles of two identical syringes. One syringe holds 20 cm³ of air and the other holds 20 cm³ of water. When the students push each plunger in firmly, the air syringe squashes to about 5 cm³ but the water syringe hardly changes volume. The teacher then draws the particles in each syringe as small hard spheres.
Explain why the water in the syringe hardly changes volume when the plunger is pushed.2 marks
A metal worker in Seoul heats a solid iron bar from 20 °C to 300 °C in a workshop. The bar becomes slightly longer but stays solid and keeps its shape. Later in the day the same bar is heated in a furnace until it melts.
Explain, using the particle model, why the iron bar becomes slightly longer when heated but stays solid.2 marks
Students in Santiago want to test the hypothesis that a gas is more compressible than a liquid. They seal the nozzles of two identical 50 cm³ syringes, one filled with 50 cm³ of air and one with 50 cm³ of water. They place the same 5 kg mass on each plunger, wait until the plunger stops moving and read the volume. Safety glasses are worn throughout.
Identify the independent variable, the dependent variable and one control variable in this investigation.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).