GR8 PARTICLE & KINETIC THEORY OF MATTER by Lizelle Swanepoel

PARTICLE AND KINETIC THEORY - NOTES

lizellexs — 2021-02-09 08:00:02 UTC

What does the particle model of matter teach us?

lizellexs — 2021-02-09 08:05:23 UTC

Four important aspects of matter:

TINY PARTICLES - All matter is made up of particles that are incredibly small - much too small to see with the naked eye. The particles can be atoms or combinations of atoms that are bonded.
FORCES - There are forces between the particles.
MOTION - These particles are in constant and random motion. The higher the temperature of the substance, the higher the speed of the particles.
SPACES BETWEEN PARTICLES - The spaces between the particles are empty. They contain nothing at all - not even air!

TEMPERATURE

lizellexs — 2021-02-09 08:30:19 UTC

Definition:
Temperature is a measure of the average kinetic energy of the particles in a system.

The coldest possible temperature is when the molecules in a system are not moving at all. This happens at -273 ^oC. (ABSOLUTE ZERO)

The Kelvin Scale

This temperature scale uses divisions which are the same as the Celsius scale but instead of zero being the temperature of melting ice (0 ^oC) it is instead the coldest possible temperature: Absolute Zero (0 K).
T_K = T_^o_C + 273

CONVERTING BETWEEN CELSIUS AND KELVIN

lizellexs — 2021-02-09 08:30:50 UTC

Complete the table ABOVE:

https://youtu.be/Xy2qVIhTtG8

THREE PHASES OF MATTER

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CHANGING BETWEEN PHASES

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Latent Heat (“Hidden” heat for phase changes)

When a phase change is happening (e.g melting) the temperature stays more or less constant despite the fact that energy is being added or removed from the system. This energy is called “latent heat” because it seems to disappear.

This release of energy as steam condenses is why a scald from steam can cause such a terrible wound. All the energy released damages the skin and flesh below. Steam is therefore very dangerous.

The heating curve of water shows latent heat

lizellexs — 2021-02-09 08:42:47 UTC

Even though heat is added to water at constant rate, temperature of the water does not increase at a constant rate.
Heat and temperature are not directly proportional to each other.
Heat and temperature are not the same concepts.
Heat = TRANSFER of thermal energy from a hot to a cold substance.
Temperature = AVERAGE KINETIC ENERGY of the particles in a substance.
The plateaus on the heating curve shows the latent heat of phase changing.

The effect of adding impurities to substances on their melting and boiling point

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MELTING AND BOILING

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ENERGY EXCHANGE INVOLVED IN PHASE CHANGES

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Looking at the effect of adding or removing heat from different phases of matter:

SUBLIMATION OF IODINE

lizellexs — 2021-02-09 09:08:22 UTC

CHANGING PRESSURE CHANGES BOILING POINT OF A SUBSTANCE

lizellexs — 2021-02-09 09:11:08 UTC

Higher pressure gives a higher boiling point. Water boils at lower temperature the higher the altitude.

PRESSURE OF GASES

The pressure of a gas results from particles colliding with the sides of the container.
Therefore the greater the number of collisions and the greater the average force of the collisions, the greater the pressure.

a) Pressure and volume.
If the volume of a fixed mass of gas is decreased the pressure increases.
Explain why this happens in terms of collisions.

In a smaller volume, particles travel a shorter distance before colliding with the container.
They thus collide with the container more often, meaning that pressure increases.

b) Pressure and temperature.
If the temperature of a fixed mass of gas is increased then its pressure will increase.
Explain why this happens in terms of collisions.

particles gain kinetic energy and move faster.
They collide with the container:
- harder
- and more often
- and both factors increase the pressure.

BOILING POINT CHANGES WITH ALTITUDE DUE TO CHANGE IN PRESSURE

lizellexs — 2021-02-09 09:13:34 UTC

The boiling point of water at sea level is 100 ^oC.
The boiling point of water on top of Mount Everest is only 70 ^oC.

lizellexs — 2021-02-09 09:15:10 UTC

EVAPORATION

Definition: The loss of particles through the surface of a liquid into the gaseous phase.

It is the faster moving particles which leave a liquid. Therefore the particles left are moving slower on average and the liquid cools.

A liquid which evaporates readily is called VOLATILE. (e.g. ether)

List 4 factors which increase the rate of evaporation of a liquid like water.

1. ________________________________________________________________
2. ________________________________________________________________
3. ________________________________________________________________
4. ________________________________________________________________

DIFFUSION

lizellexs — 2021-02-09 09:16:34 UTC

DIFFUSION

Definition:
The spontaneous moving, mixing and spreading of one substance through another substance from a region of high concentration to a region of low concentration until the particles are evenly spread.

Liquids and gases diffuse – solids do not.

When a gas jar containing air (colourless) is placed on top of a gas jar containing a red-brown gas (e.g. nitrogen dioxide or bromine), the red-brown colour spreads up into the air until the gas in both jars looks the same colour.

Gases diffuse faster than liquids. Explain why.

DIFFUSION IN ACTION

lizellexs — 2021-02-09 09:18:19 UTC

Diffusion of ammonia gas and hydrogen chloride gas to form ammonium chloride.

HCl is heavier than NH3 molecule and move slower towards NH3.
NH3 is lighter molecule than HCl and moves faster.
Hence the two gases meet each other off centre in the tube to react.

PRESSURE OF GASES

lizellexs — 2021-02-09 09:19:01 UTC

The pressure of a gas results from particles colliding with the sides of the container.

Therefore the greater the number of collisions and the greater the average force of the collisions, the greater the pressure.

a) Pressure and volume.

If the volume of a fixed mass of gas is decreased the pressure increases.

Explain why this happens in terms of collisions.

________________________________________________________________

b) Pressure and temperature.

If the temperature of a fixed mass of gas is increased then its pressure will
increase.

Explain why this happens in terms of collisions.

_______________________________________________________________
_______________________________________________________________

SUBLIMATION OF DRY ICE

lizellexs — 2021-02-09 19:20:01 UTC

Dry ice is solid carbon dioxide

WHY DOES SUBLIMATION OCCUR?

lizellexs — 2021-02-09 19:28:00 UTC

Substances with very weak forces between their molecules will turn directly into the gas phase from solid phase upon absorbing heat, due to them requiring very little energy to overcome these weak intermolecular forces between its molecules.

DEFINITIONS:
Sublimation = The transition of a substance directly from the solid to the gas state, without passing through the liquid state.

Deposition = The reverse process of sublimation in which a substance passes directly from a gas to a solid phase.

DEFINITIONS

lizellexs — 2021-02-09 19:48:26 UTC

Matter:
Anything that takes up space and has mass.

Temperature:
A measure of the average kinetic energy of the particles in a system.

Melting point:
The temperature at which a solid becomes a liquid at a fixed pressure, usually standard pressure.

Boiling point:
The temperature at which a liquid becomes a gas at a fixed pressure, under atmospheric conditions.

Freezing point:
The temperature at which a liquid becomes a solid at atmospheric pressure.

Diffusion:
The spontaneous moving mixing and spreading of one substance through another substance from a region of high concentration to a region of low concentration, until the particles are evenly spread.

Brownian motion
The continuous movement of particles in liquids or gases by the impact of moving liquid or gas molecules striking the particles.

Absolute Zero
Temperature at which the particles stop moving in an object.

Evaporation:
This is the loss of molecules from the surface of a liquid into the gas phase. Evaporation is a slow process, does not produce bubbles, and results in cooling.

Boiling:
Boiling is the phase change from liquid to gas which happens faster than evaporation, produces lots of bubbles, and does not result in cooling.

Atom:
The smallest part of an element having the chemical properties of the element.

Element:
An element cannot be broken down into anything simpler by chemical means.

Compound:
A compound is made up of two or more DIFFERENT elements chemically combined (joined together).

Pressure:
Force per unit area.

Mass:
The amount of matter in an object.

Density:
Mass per unit volume.

IMPURITIES AFFECT M.P AND B.P

lizellexs — 2021-02-14 21:49:10 UTC

Melting points: DECREASE

E.g. When salt is added to ice, it melts and its temperature drops.
Salt is used to remove ice from roads - freezing point also decreases.

Boiling points: RISE

E.g. Salt water (103 ^oC) has a higher boiling point than fresh water (100 ^oC).

EVAPORATION

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ANSWERS TO NOTES

lizellexs — 2021-03-17 19:43:04 UTC

BROWNIAN MOTION

lizellexs — 2021-03-18 04:30:24 UTC

YOU WILL BE LEARNING ABOUT:

lizellexs — 2022-02-03 19:52:26 UTC

The Particle model of matter
Phases of matter
Melting, boiling, evaporation, sublimation
Diffusion
Brownian motion
Pressure and volume changes with temp
Celsius and Kelvin scale
Absolute zero

EVIDENCE THAT MATTER CONSISTS OF SMALLER PARTICLES

lizellexs — 2022-02-03 20:37:24 UTC

EVAPORATION

Crystallization = the addition of new atoms or ions into a repeating arrangement called a crystal lattice.

lizellexs — 2022-02-03 20:45:10 UTC

DIFFUSION ILLUSTRATES = intermingling of substances by the natural movement of their particles

lizellexs — 2022-02-03 20:51:41 UTC

lizellexs — 2022-02-08 07:08:58 UTC

Relationship between Pressure and Temperature

lizellexs — 2023-03-06 06:50:24 UTC

Relationship between Pressure and Volume

lizellexs — 2023-03-06 06:53:27 UTC

Graph of P vs V

lizellexs — 2023-03-06 06:55:57 UTC

Graph of P vs T

lizellexs — 2023-03-06 06:58:55 UTC

KELVIN TEMP SCALE

lizellexs — 2024-02-07 08:54:32 UTC

HOW AN AIRCON WORKS

lizellexs — 2024-02-19 07:04:31 UTC

ANIMATION ON AIRCON

lizellexs — 2024-02-19 07:05:51 UTC

BROWNIAN MOTION DEMO

lizellexs — 2024-02-19 07:15:57 UTC

BROWNIAN MOTION

Robert Brown noticed that pollen grains on water were seen to be moving in a random way when observed under a microscope. He concluded that invisible tiny particles were moving very fast and were colliding with the pollen grains causing them to move in a haphazard way.

The above observation provides some evidence for the kinetic theory.

Note: smoke in air produces the same effect. In it little ash particles are seen to move as the air molecules collide into them.

HOW A PRESSURE COOKER WORKS

lizellexs — 2025-02-10 07:49:18 UTC

Concentration increases Rate of Reaction

lizellexs — 2026-04-11 20:10:25 UTC