Define melting point .

The melting point is the fixed temperature at which a substance changes state between solid and liquid. Melting and freezing both occur at this temperature.

True or False? Particles in a liquid are arranged in a regular pattern.

False. Particles in a liquid are randomly arranged. It is solid particles that are held in a regular arrangement.

How do particles move differently in a solid compared to a gas?

In a solid , particles only vibrate about fixed positions. In a gas , particles move quickly and randomly in all directions with large spaces between them.

Evaporation can occur at .......... temperature. It is a .......... process, unlike boiling which occurs throughout the liquid.

Evaporation can occur at any temperature. It is a surface process, unlike boiling which occurs throughout the liquid.

Define physical change .

A physical change is a change in a substance that does not alter the identity of the substance. No new chemical substance is formed and the change is usually easy to reverse.

Why are state changes classed as physical changes rather than chemical changes?

State changes are physical changes because the particles themselves remain the same — only the forces between particles change. No new substance is formed so the change is reversible.

True or False? In a chemical change, the reactants are converted into products.

True. In a chemical change , one or more reactants are converted into new substances called products . This is different from a physical change, where no new substances form.

What are the names for the state changes from gas to liquid and from liquid to solid?

Gas to liquid is called condensing . Liquid to solid is called freezing .

In the simple particle model, particles are represented as small, solid .......... .

In the simple particle model, particles are represented as small, solid spheres .

What is meant by the particle model ?

The particle model is a scientific model that explains how matter behaves in different states. It represents particles as small, solid, inelastic spheres and uses the energy and forces between them to explain state changes.

Give two limitations of the particle model. (Higher Tier Only)

It represents all particles as solid, inelastic spheres — it does not account for their real shapes or elasticity. It does not account for the forces of attraction between particles. It does not accurately show particle size relative to the spaces between them. (Any two of the above.)

True or False? (Higher Tier Only) The particle model accurately represents the size of particles relative to the space between them.

False. One key limitation is that the particle model does not accurately represent the size of particles relative to the space between them. Real particles are much smaller relative to the gaps than the model suggests.

When a solid is heated, particles vibrate more until the .......... break and the solid .......... . (Higher Tier Only)

When a solid is heated, particles vibrate more until the bonds break and the solid melts .

Why does the temperature stay constant during a state change on a heating curve? (Higher Tier Only)

During a state change, the energy supplied is used to break the forces between particles rather than raise the temperature. The temperature only rises again once the state change is complete.

True or False? (Higher Tier Only) Substances with stronger forces between their particles require more energy to melt and boil.

True. The stronger the forces of attraction between particles, the more energy is needed to overcome them. This results in higher melting points and boiling points .

Why does the particle model not fully explain the behaviour of real substances? (Higher Tier Only)

The particle model treats all particles as identical, rigid spheres and ignores intermolecular forces . Real particles vary in shape and do exert attractive forces on each other, which affect how substances behave when heated or cooled.

When substances are heated, particles absorb .......... energy which is converted into .......... energy. (Higher Tier Only)

When substances are heated, particles absorb thermal energy which is converted into kinetic energy.

GCSEScienceOCRCombined Science A (Gateway)ChemistryFlashcardsParticlesThe Particle Model

The Particle Model (OCR GCSE Combined Science A (Gateway): Chemistry): Flashcards

Exam code: J250

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FrontThe Particle Model
Define melting point.

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Cards in this collection (17)

Define melting point.
The melting point is the fixed temperature at which a substance changes state between solid and liquid. Melting and freezing both occur at this temperature.
True or False?
Particles in a liquid are arranged in a regular pattern.
False.
Particles in a liquid are randomly arranged. It is solid particles that are held in a regular arrangement.
How do particles move differently in a solid compared to a gas?
In a solid, particles only vibrate about fixed positions. In a gas, particles move quickly and randomly in all directions with large spaces between them.
Evaporation can occur at .......... temperature. It is a .......... process, unlike boiling which occurs throughout the liquid.
Evaporation can occur at any temperature. It is a surface process, unlike boiling which occurs throughout the liquid.
Define physical change.
A physical change is a change in a substance that does not alter the identity of the substance. No new chemical substance is formed and the change is usually easy to reverse.
Why are state changes classed as physical changes rather than chemical changes?
State changes are physical changes because the particles themselves remain the same — only the forces between particles change. No new substance is formed so the change is reversible.
True or False?
In a chemical change, the reactants are converted into products.
True.
In a chemical change, one or more reactants are converted into new substances called products. This is different from a physical change, where no new substances form.
What are the names for the state changes from gas to liquid and from liquid to solid?
Gas to liquid is called condensing. Liquid to solid is called freezing.
In the simple particle model, particles are represented as small, solid ...........
In the simple particle model, particles are represented as small, solid spheres.
What is meant by the particle model?
The particle model is a scientific model that explains how matter behaves in different states. It represents particles as small, solid, inelastic spheres and uses the energy and forces between them to explain state changes.
Give two limitations of the particle model. (Higher Tier Only)
1. It represents all particles as solid, inelastic spheres — it does not account for their real shapes or elasticity.
2. It does not account for the forces of attraction between particles.
3. It does not accurately show particle size relative to the spaces between them.
(Any two of the above.)
True or False?
(Higher Tier Only) The particle model accurately represents the size of particles relative to the space between them.
False.
One key limitation is that the particle model does not accurately represent the size of particles relative to the space between them. Real particles are much smaller relative to the gaps than the model suggests.
When a solid is heated, particles vibrate more until the .......... break and the solid .......... . (Higher Tier Only)
When a solid is heated, particles vibrate more until the bonds break and the solid melts.
Why does the temperature stay constant during a state change on a heating curve? (Higher Tier Only)
During a state change, the energy supplied is used to break the forces between particles rather than raise the temperature. The temperature only rises again once the state change is complete.
True or False?
(Higher Tier Only) Substances with stronger forces between their particles require more energy to melt and boil.
True.
The stronger the forces of attraction between particles, the more energy is needed to overcome them. This results in higher melting points and boiling points.
Why does the particle model not fully explain the behaviour of real substances? (Higher Tier Only)
The particle model treats all particles as identical, rigid spheres and ignores intermolecular forces. Real particles vary in shape and do exert attractive forces on each other, which affect how substances behave when heated or cooled.
When substances are heated, particles absorb .......... energy which is converted into .......... energy. (Higher Tier Only)
When substances are heated, particles absorb thermal energy which is converted into kinetic energy.

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