Solids Liquids And Gases

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Notes

Kinetic Theory & States of Matter

The **kinetic theory** describes matter as tiny particles in constant motion.
**Solids**: particles packed closely in a fixed, regular pattern; vibrate in position; high density.
**Liquids**: particles close but randomly arranged; slide past each other; adopt container shape; medium density.
**Gases**: particles far apart, move randomly and quickly (~500 m/s); low density; easily compressed.
Particle energy increases from solid (low) → liquid → gas (highest).

Changes of State

**Melting**: solid → liquid at a specific **melting point**; requires heat to increase particle kinetic energy.
**Freezing**: liquid → solid at the same temperature as melting point.
**Boiling**: liquid → gas at a specific **boiling point**; bubbles form throughout the liquid.
**Evaporation**: liquid → gas at the surface, below boiling point; faster with larger surface area and higher temperature.
**Condensation**: gas → liquid on cooling; particles lose energy and group together.
State changes are reversible (⇌).

Heating & Cooling Curves (Extended)

A **heating curve** shows temperature vs. time as a substance is heated.
Horizontal sections indicate a change of state with no temperature change (energy used to overcome forces).
A **cooling curve** is the mirror image of a heating curve.

Pressure & Temperature in Gases

Gas pressure is caused by particles colliding with container walls.
Increasing temperature increases particle kinetic energy → more frequent collisions → volume expands if container flexible.
Increasing pressure (same number of particles in smaller volume) decreases volume; particles hit walls more often.
If pressure is too high, container may leak or explode.

Diffusion

**Diffusion**: net movement of particles from high to low concentration due to random motion.
Occurs in liquids and gases; no energy input required; faster at higher temperatures.
Diffusion is faster in gases than liquids because gas particles have more kinetic energy.
Example: potassium manganate(VII) in water spreads until evenly coloured.

Diffusion & Molecular Mass (Extended)

At the same temperature, gases with lower **relative molecular mass** diffuse faster.
Example: ammonia (Mᵣ $= 17)$ diffuses faster than hydrogen chloride (Mᵣ $= 36.5)$ .
In a tube, NH₃ and HCl react to form NH₄Cl; the white ring forms closer to the HCl end.

Particle arrangement in solids, liquids, and gases.

Practice questions

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1.Which statement about the arrangement of particles in a solid is correct?
Easy
- AParticles are far apart and move randomly
- BParticles are close together and arranged randomly
- CParticles are close together in a fixed regular pattern
- DParticles are far apart and vibrate in fixed positions
2.Which statement about the movement of particles in a liquid is correct?
Easy
- AParticles vibrate about fixed positions
- BParticles move around each other
- CParticles move quickly in all directions
- DParticles do not move
3.In a gas, the particles are far apart and move randomly.
Easy
True or false?
4.State the term for the change of state from a solid to a liquid.
Medium
5.Water boils at 100 °C. What is the boiling point of water in Kelvin?
Medium
- A410
- B373
- C336
- D447
6.Complete the sentence about diffusion.
Medium
Diffusion is the movement of particles from an area $of ____$ concentration to an area $of ____$ concentration.
7.Match each state of matter with its particle arrangement.
Medium
- Solid
- Liquid
- Gas
- Randomly arranged
- Regular arrangement
- Randomly arranged
8.Place the following steps in the correct order to describe what happens when a solid is heated until it becomes a gas.
Hard
- Particles vibrate more and solid expands
- Solid melts into a liquid
- Particles gain enough energy to escape as a gas
- Liquid boils into a gas

Slides

Kinetic Theory of Matter

All matter is made of tiny particles in constant motion.
The arrangement and movement of particles differ in solids, liquids, and gases.
These differences explain the physical properties of each state.

Which state of matter has particles that are closely packed in a regular pattern and only vibrate in fixed positions?

Solid
Liquid
Gas
Plasma

Properties of Solids, Liquids, and Gases

Solids: fixed volume and shape, high density.
Liquids: fixed volume, shape of container, medium density.
Gases: no fixed volume, shape of container, low density, easily compressed.

Which of these are true about gases?

Gases have a fixed volume.
Gases are easily compressed.
Gas particles are far apart and move randomly.
Gases have high density.

State Changes

Melting: solid → liquid (heat energy absorbed).
Freezing: liquid → solid (heat energy released).
Boiling: liquid → gas (heat energy absorbed, bubbles form).
Condensation: gas → liquid (heat energy released).
Evaporation: liquid → gas at surface, below boiling point.

The temperature at which a solid changes into a liquid is called $the ____$ point.

Heating and Cooling Curves

Heating curves show temperature change over time as a substance is heated.
Horizontal sections indicate a change of state (no temperature change).
Cooling curves are the mirror image of heating curves.

On a heating curve, what does a horizontal section represent?

Increase in temperature
Change of state
Decrease in temperature
No energy change

Pressure and Temperature in Gases

Increasing temperature increases gas volume (if flexible container).
Increasing pressure decreases gas volume (e.g., bicycle pump).
Gas pressure is caused by particles colliding with container walls.

Which statements about gases are correct?

Gas particles expand when heated.
Pressure increases as volume decreases at constant temperature.
Higher temperature gives particles more kinetic energy.
Gas particles stop moving when compressed.

Diffusion

Diffusion is the movement of particles from high to low concentration.
Occurs in liquids and gases due to random particle motion.
Faster at higher temperatures (more kinetic energy).
Faster in gases than liquids.

Diffusion is fastest in which state?

Solid
Liquid
Gas
Same in all

Diffusion and Molecular Mass

Lighter gases (lower relative molecular mass) diffuse faster.
Heavier gases diffuse slower.
Example: ammonia $(M_{r}=17)$ diffuses faster than hydrogen chloride $(M_{r}=36.5)$ .

A gas with a lower relative molecular mass will diffuse ____ than a heavier gas.

Summary of State Changes

Melting and freezing occur at the same temperature for a pure substance.
Boiling occurs at a specific temperature; evaporation occurs over a range.
Condensation is the reverse of evaporation.

Which process is the reverse of melting?

Boiling
Condensation
Freezing
Evaporation

Flashcards

What are the three states of matter?

Solid, liquid, gas.

Describe the arrangement and movement of particles in a solid.

Particles are packed very closely together in a fixed, regular pattern and vibrate about fixed positions.

Describe the arrangement and movement of particles in a liquid.

Particles are close together but randomly arranged, and they move around each other, allowing the liquid to flow.

Describe the arrangement and movement of particles in a gas.

Particles are far apart, randomly arranged, and move quickly in all directions at around 500 m/s.

Why can gases be easily compressed?

Because there is a lot of space between the particles.

What is melting?

Melting is when a solid changes into a liquid at a specific temperature called the melting point.

What is freezing?

Freezing is when a liquid changes into a solid at the same temperature as the melting point.

What is boiling?

Boiling is when a liquid changes into a gas at a specific temperature called the boiling point, with bubbles forming throughout the liquid.

What is evaporation?

Evaporation is when a liquid changes into a gas at the surface, occurring over a range of temperatures below the boiling point.

What is condensation?

Condensation is when a gas changes into a liquid on cooling, over a range of temperatures.

How does heating affect the particles in a solid?

Heating causes the particles to vibrate more until the structure breaks and the solid melts into a liquid.

How does heating affect the particles in a liquid?

Heating causes the particles to move more and spread out; at the boiling point, all particles gain enough energy to escape as a gas.

What happens to the temperature during a change of state?

During a change of state, the temperature remains constant even though heat is being added or removed.

How does temperature affect the volume of a gas?

Increasing temperature increases the kinetic energy of particles, causing them to move faster and spread out, increasing the volume.

How does pressure affect the volume of a gas?

Increasing pressure decreases the volume because the same number of particles are forced into a smaller space.

What causes gas pressure inside a container?

Gas pressure is caused by particles colliding with the walls of the container.

Define diffusion.

Diffusion is the movement of particles from an area of high concentration to an area of low concentration due to random motion.

Why does diffusion occur faster in gases than in liquids?

Because gaseous particles have more energy and move faster than liquid particles.

How does molecular mass affect the rate of diffusion?

Gases with lower relative molecular mass diffuse faster (travel further in the same time) than those with higher molecular mass.

In the ammonia and hydrogen chloride diffusion experiment, where does the white smoke form?

The white smoke (ammonium chloride) forms closer to the hydrogen chloride end because ammonia $(M_{r}=17)$ diffuses faster than HCl $(M_{r}=36.5)$ .

What is the kinetic theory of matter?

The kinetic theory describes matter as tiny particles in constant motion; the arrangement and movement differ in solids, liquids, and gases.

Why do liquids have a fixed volume but not a fixed shape?

Particles are close together (fixed volume) but randomly arranged and able to slide past each other, so the liquid takes the shape of the container.

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