Particulate Nature of Matter

Question-and-answer flashcards covering particle types, states of matter, phase changes, and energy changes.

What two fundamental properties are shared by all matter?

All matter has mass and occupies space.

According to the particulate model, what composes all substances?

Tiny particles such as atoms, molecules, or ions.

What is an atom?

The smallest unit of an element that retains the element’s identity.

What is a molecule?

A particle made of two or more atoms chemically bonded together.

What is an ion?

An atom or group of atoms that has gained or lost electrons and carries an electric charge.

Describe the shape, volume, and compressibility of a solid.

Fixed shape, fixed volume, and essentially incompressible.

Describe the shape, volume, and compressibility of a liquid.

No fixed shape (takes the shape of its container), fixed volume, and essentially incompressible.

Describe the shape, volume, and compressibility of a gas.

No fixed shape, no fixed volume (fills its container), and highly compressible.

How are particles arranged and moving in a solid?

They are closely packed and vibrate about fixed positions.

How are particles arranged and moving in a liquid?

They are close together but can slide past one another, moving throughout the liquid.

How are particles arranged and moving in a gas?

They are far apart and move rapidly and randomly.

What is the melting point?

The temperature at which a solid becomes a liquid.

What is the freezing point?

The temperature at which a liquid becomes a solid.

What is the boiling point?

The temperature at which a liquid changes to a gas throughout the bulk of the liquid.

What is the condensation point?

The temperature at which a gas changes back into a liquid.

During melting, does a substance gain or lose energy?

It gains energy.

During freezing, does a substance gain or lose energy?

It loses energy.

During boiling, does a substance gain or lose energy?

It gains energy.

During condensation, does a substance gain or lose energy?

It loses energy.

How do boiling and evaporation differ?

Boiling occurs at the boiling point throughout the liquid with bubble formation; evaporation occurs at any temperature below the boiling point only at the surface with no bubbles.

What change of state skips the liquid phase and goes directly from solid to gas?

Sublimation.

Give two common substances that undergo sublimation.

Solid carbon dioxide (dry ice) and iodine crystals (moth balls also sublimate).

On a heating curve, what happens to the temperature during a phase-change plateau?

It stays constant while absorbed heat breaks intermolecular forces.

On a cooling curve, what happens to the temperature during a phase-change plateau?

It stays constant while released heat allows intermolecular forces to form.