Ch 3.1 Classification of Matter

8/21/2019 Ch 3.1 Classification of Matter

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Chapter 3.1 Classification of Matter

Name: ______________________( ) Class: ______ Date: ____________

CHAPTER MAP & OVERVIEW

Wan Yong, L., & Kwok Wai, L. (2013). All About Physics 'O' Level. Malaysia: Pearson Education

South Asia Pte Ltd., pages 162 to 164,

M. Heyworth Rex, & J G R Briggs. (2013). All About Chemistry 'O' Level. Malaysia: Pearson

Education South Asia Pte Ltd., pages 30 to 43,

CHAPTER 3.1

CLASSIFICATION OF MATTER

Kinetic ParticleTheory

Chapter 3.1.4Change of State

Used to explain

States of Matter

Gas

Melting

Freezing

Boiling

Condensation

Solid Liquid

Chapter 3.1.3

Molecular Model


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Learning Outcomes

3.1 Classification of Matter

Pupils are expected to:

(a) describequalitatively the molecular structure of solids, liquids and gases, relating their properties to theforces and distances between molecules and to the motion of the molecules

(b) describethe relationship between the motion of molecules and temperature(c) useof Kinetic Particle Theory (kinetic model of matter) to explain changes of states and the three states

of matter(d) understand that the internal energy of a body consists of kinetic and potential energy(e) describe a rise in temperature of a body in terms of an increase in its kinetic energy(f) describe a change in state of a body in terms of its potential energy and without a change in

temperature

(g) showunderstanding that Brownian motion provides evidence for Kinetic Particle Theory (kinetic modelof matter)

(h) inferfrom Brownian motion experiment the evidence for the movement of molecules(i) explaineveryday effects of diffusion in terms of particles, e.g. the spread of perfumes and tea or coffee

particles in water

(j) understandgeneral interpretation of graphs of change of states e.g. melting, boiling, freezing,condensation

Advanced Topics

(a) Describe two additional states of matter (plasma and Bose Einstein Condensate) and explain their

inter-conversion in terms of the kinetic particle theory

What is Matter?

Matter is anything that has massand occupies space.

All matter can exist in 3 physical states: solid, liquid& gas, depending on the temperature andpressure of their surroundings.

States of Matter

When you leave a dish of water in a corner of a room it disappears after a few hours. When youleave a few copper(II) sulfate crystals on the bottom of a glass of water the crystals disappear ontheir own and the water becomes blue. There is obviously a movement of particles of water andcopper(II) sulfate crystals that we cannot see. How do we explain this?

Consider the differences among solids, liquids and gases.

A solid has a fixed shape and a fixed volume. Normally it is hard and rigid and a large force

is required to change its shape. It is not compressible.

A liquid has a fixed volume but it does not have a fixed shape. It can flow and takes

the shape of its container. A liquid has a definite surface. It is not compressible.

A gas has no shape, no surface and no fixed volume. It can flow and spread easily tofill any vessel it is in. It also takes the shape and volume of its container. It is highly

compressible.


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Kinetic Particle Theory (Kinetic Model of Matter)

The Kinetic Particle Theorystates that matter is made of large number tiny particles(atomsor molecules), which are in continuous and random motion

(Energy due to movement is known as kinetic energy.)

Evidences of particles in continuous motion:

These molecules are too small to be seen directly. However, the existence of particles incontinuous motion has been demonstrated by Brownian motion and diffusion. X-raydiffraction patterns of crystals and the striking photographs of crystals taken with electronmicroscopes provide further evidence of the particulate nature of matter.

Brownian Motion

Brownian motion is the constant and random motion of small solid particles in fluids(liquids and gases).

Brownian motion provided the evidence of molecular motion& proved the existence of particlesthat cannot be observed with a normal microscope.

Further informationBrownian motion is first observed in 1827 by Robert Brown. Through

the microscope, he observed the motion of pollen grains suspendedin water. However, it was not until 1905 that Einstein (making his first

major contribution to science) was able to explain it. He suggestedthat the irregular or random motion of the smoke particles was the

result of being hit by unseen fast-moving air molecules. Brownianmotion, therefore, provides evidence for the kinetic theory of matter.

If heat is supplied, the motion of the smoke particles becomes morevigorous. Careful observations also show that the smaller the smokeparticles, the more rapid their motion.

Brownian motion can also be observed by placing pollen grains orchalk powder in water. In this case the zigzag motion of the pollen

grains is due to bombardment by water molecules.

DiffusionIn diffusion, particles move randomly from a region of high concentration to lower

concentration.

Examples of Diffusion:If a bottle of perfume is opened in one corner of a room, we can smell it in another corner after a very

short time. Evidently the perfume molecules have travelled from the bottle to your nose through the air.The spreading of molecules by their own accord without any external aidis called diffusion.

Another example of diffusion is that of gases in the atmosphere. Air is a mixture of oxygen, carbon

dioxide and nitrogen. Even though carbon dioxide is denser than the others, it does not sink down toform a separate layer. This is because all the gas molecules are moving randomly all the time and they

move into any space that is available. Hence the gas molecules stay mixed and do not separate out.


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Bromine vapour can be used to show diffusion of gases.

Bromine is a red brown liquid at room temperature but itevaporates easily to form a brown vapour. When a little bromine

vapour is released into a vacuum, the brown vapour spreadsthrough the vacuum almost at once. This indicates that the

bromine molecules are moving at very high speed.

If bromine vapour is released into a similar space full of

air, the brown vapour still spreads quickly through thespace but very much slower than in a vacuum. This is

because the bromine molecules keep hitting the airmolecules which get in the way.

Note: Bromine vapour is harmful.

The rate of diffusion of gases depends on:

1) The temperature of the gases

The higher the temperature, the faster the rate of diffusion.

2) The density of the gasesThe greater the density of the molecules, the slower the rate of the diffusion.

For example, dense carbon dioxide diffuses more slowly than light hydrogen gas. Gases canalso diffuse through walls which have pores slightly bigger than the size of the gas molecule.

Diffusion also takes place in liquids, though at a very much slower rate. Even if you do not stira cup of coffee after you have added milk, it will become uniformly coloured after many hours.In the school laboratory, diffusion of liquids can be shown using copper (II) sulfate solution andwater as shown in the figure below. The two layers become uniformly mixed after a while.


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Molecular Model of the Three States of Matter

Particles in a Solid

Solid

Diagram

Arrangement Closely packed together in a fixed, regular patternThis results in solids having high densities

Movement Cannot move freely but vibrate about fixed positions.Held in position by very strong attractive forcesThis explains why solids have fixed volumes and shapes

Particles in a Liquid

Liquid

Diagram

Arrangement Randomly arranged with the particles slightly further apart as compared to that of

solids. This results in liquids having relatively high densitiesMovement Particles slide past one anotherFree to move about but confined within the vessel containing it.Have attractive forces between particles.This explains why liquids have fixed volume but will take the shape of vesselscontaining them.

Particles in a Gas

Gas

Diagram

Arrangement Very far apart. Particles are randomly arranged and will occupy any availablespace. This results in gases having relatively very low densities

Movement Particles have very little attraction between them and move about randomly at avery high speed.This explains why gases have no fixed volume and shape, and why they arehighly compressible.


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Advanced: (Taken from http://www.chem4kids.com/files/matter_plasma.html)

Plasma and Bose-Einstein Condensates (BEC)Other than solids, liquids, gases, there are two more states of matter:Plasmas and Bose-Einstein condensates (BEC)

Plasma Basics

Plasmas are a lot like gases, but the atoms are different, because theyare made up of free electronsand ions of an elementsuch as neon

(Ne).

Plasma is different from a gas, because it is made up of groups ofpositively and negatively charged particles.

In neon gas, the electrons are all bound to the nucleus.In neon plasma, the electrons are free to move around the system.

Example of Plasma:

1. Fluorescent light bulbs.Inside the long tube is a gas.Electricity flows through the tube when the light isturned on. The electricity acts as an energy source andcharges up the gas. This charging and exciting of theatoms creates glowing plasma inside the bulb. The

electricity helps to strip the gas molecules of theirelectrons.

Find out more about fluorescent light athttp://electronics.howstuffworks.com/plasma-display1.htm


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2. Neon sign. Just like a fluorescent lights, neon signs are glass tubesfilled with gas. When the light is turned on, the electricity flows throughthe tube. The electricity charges the gas and creates plasma inside ofthe tube.The plasma glows a special color depending on what kind of gas is

inside. Inert gases are usually used in signs to create different colors.Noble gases such as helium (He), Neon (Ne), Argon (Ar), and Xenon

(Xe) are all used in signs.

Bose-Einstein Condensate BasicsBose-Einstein condensate consists of unexcited and cold atoms.

The BEC happens at very low temperatures. At zero Kelvin (absolute zero) all molecular motionstops. Scientists have figured out a way to get a temperature only a few billionths of a degreeabove absolute zero. When temperature is very low, a BEC can be created with a few specialelements. Cornell and Weiman did it with rubidium (Rb).

When the temperature decreases to near absolute zero, something special

happens. Atoms begin to clump. When the temperature becomes that low,the atomic parts can't move at all. They lose almost all of their energy. Sincethere is no more energy to transfer (as in solids or liquids), all of the atomshave exactly the same level.

The result of this clumping is the BEC. The group of rubidium atoms sits in

the same place, creating a "super atom." There are no longer thousands ofseparate atoms. They all take on the same qualities and, for our purposes,become one blob.


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Change of State (Explained using the Kinetic Particle Theory)

When a pot of cold soup is heated over a stove, it gradually becomes hot. Thermal energy istransferred from the heating element to the soup. The hot soup contains more energy now thanwhen it was cold. The energy contained inside the soup is known as internal energy.

The internal energy of a body is the combination of the total kinetic energy and potentialenergy of the molecules in a body.

Kinetic energy is due to the vibration of molecules. It is directly related to temperature.

Potential energy is due to the stretching and compressing of the inter-molecular forces as themolecules vibrate.

Melting (Solid to Liquid)

When a solid is heated, the particles absorb heat.

The particles gain kinetic energy and start to vibrate faster andmove further apart.

At a certain temperature known as the melting point, the particles have enough potential

energy to overcome the strong inter-molecular forces holding the particles together in thesolid.

The particles start to break away from one another and the solid becomes a liquid.

At the liquid state, the particles start to slide past over one another.

Freezing (Liquid to Solid)

When a solid is cooled, the particles release heat energy.

The particles lose kinetic energy and vibrate slower.

At a certain temperature known as the freezing point, the particles no longer have enoughpotential energy to overcome the strong inter-molecular forcesholding them together.

The particles start to come together in a regular arrangement and the liquid becomes a

solid.

Boiling (Liquid to Gas)

Particles in a liquid are held by strong attractive forces.

When a liquid is heated, the particles absorb heat.

The particles gain kinetic energy and slide over each other more rapidly.

Eventually, the particles gain sufficient potential energy to overcome the strong inter-molecular forces between the particlesand move far apart rapidly in all directions.

Lets think!

A liquid expands and changes into gas during boiling. Does it mean that the particles in a liquidbecome bigger and change their shape?


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Summary

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Ch 3.1 Classification of Matter