What Happens To The Entropy Of A Sample Of Matter When It Changes State From A Solid To A Liquid?

extra advanced notes on gas laws, ideal and non-ideal gases

GASES, LIQUIDS and SOLIDS

A pplication of the particle model to the three states of matter

Using the particle models to describe and explain the properties of gases, liquids and solids and state changes betwixt them

See besides P-V-T pressure level-volume-temperature gas law calculations

Doc Dark-brown'due south Chemical science KS4 scientific discipline GCSE/IGCSE Revision Notes

Sub�index for Parts 1 to three (this folio) :

0 Introduction What are the three states of thing?

ane.1 3 states of matter - what can we look from particle models and are in that location limitations?

1.1a Properties of gases - particle model and properties explained and diffusion experiments

1.1b Properties of liquids - particle model and properties explained and diffusion experiment

1.1c Properties of solids - particle model and properties explained

2. State changes - a summary diagram

2a Evaporation and boiling - explained using particle model

2b Condensation - explained using particle model

2c Distillation - explained using particle model

2d Melting - explained using particle model

2e Freezing-solidifying - explained using particle model

2f Cooling and heating curves - state changes and relative energy changes

2g Sublimation - explained using particle model

2h Comparison of latent heat changes in physical changes of state for different substances

3a-d. (a) Dissolving, (b) Solutions, (c) Miscible liquids & immiscible liquids, (d) Separating funnel

Appendix 1. Particle pictures of elements, compounds & mixtures

GCSE multiple choice QUIZ on states of matter � gases, liquids & solids

GCSE�AS (basic) chemistry KEYWORD index for Office one (this folio): Boiling * Humid point * Brownian motion * Changes of state * Condensing * Cooling curve * Diffusion * Dissolving * Evaporation * Free energy changes & change of state * Freezing * Freezing indicate * Gas particle moving picture * Heating curve * Liquid particle picture show * Melting * Melting signal * miscible/immiscible liquids * Particle pictures of elements, compounds & mixtures * Properties of gases * Properties of liquids * Backdrop of solids * solutions * sublimation * Solid particle picture

Sub�index for Part 2 (on dissever more advanced pages): A Level 4. Introduction to the kinetic particle theory of an ideal gas * Kelvin temperature scale * 4a Kelvin temperature calibration and Boyle'southward Law * 4b. Charles'south�Gay Lussac's Law and the combined gas law equation * A Level only 4c. The ideal gas equation PV=nRT * 4d. Dalton'south Law of fractional pressures * 4e. Graham'south Police force of improvidence * 5a. The deviations of a gases from platonic behaviour and their causes * 5b. The Van der Waals equation of state * 5c Compressibility factors * 5d The Critical Signal � The Critical Temperature and Critical Pressure *

Doc Brownish'southward chemistry revision notes: basic school chemistry scientific discipline GCSE chemistry, IGCSE chemistry, O level & ~United states of america grades 8, 9 and 10 schoolhouse scientific discipline courses or equivalent for ~14-16 year quondam science students for national examinations in chemical science

part 0 Introduction

You should know that the three states of thing are solid, liquid and gas. Melting and freezing take place at the melting point, boiling and condensing take place at the boiling point. The three states of matter tin can exist represented past a simple model in which the particles are represented by small solid spheres. Particle theory can help to explain melting, boiling, freezing and condensing.

The corporeality of energy needed to change state from solid to liquid and from liquid to gas depends on the forcefulness of the forces between the particles of the substance and the nature of the particles involved depends on the blazon of bonding and the structure of the substance. The stronger the forces between the particles the college the melting bespeak and boiling betoken of the substance. For details see structure and bonding notes.

The force of the forces betwixt particles depends on the material (structure and type of bonding), the temperature (affects the energy of the particles) and pressure (how shut the particles are compressed together east.m. in a gas).

The physical state a fabric adopts depends on its construction, temperature and pressure.

State symbols used in equations: (k) gas (l) liquid (aq) aqueous solution (due south) solid

aqueous solution ways something dissolved in water,

a skilful case of how to use the state symbols correctly is calcium carbonate dissolving in hydrochloric acid:

CaCO₃ (south) + 2HCl(aq) ====> CaCl₂ (aq) + H_iiO(l) + CO₂ (k)

Most diagrams of particles on this page are 2D representations of their construction and state

EXAMPLES OF THE Three PHYSICAL STATES OF Matter

GASES eastward.g. the air mixture effectually us (including the oxygen needed for combustion) and the high pressure steam in the banality and cylinders of the steam locomotive. All of the gases in air are 'invisible', being colourless and transparent. Notation that the 'steam' you meet exterior of a kettle or steam locomotive is actually fine liquid droplets of water, formed from the expelled steam gas condensing when it meets the cold air � the 'land change' of gas to liquid (aforementioned effect in mist and fog germination).

LIQUIDS eastward.one thousand. water is the almost common case, but so are, milk, hot butter, petrol, oil, mercury or booze in a thermometer.

SOLIDS due east.g. stone, all metals at room temperature (except mercury), condom of walking boots and the majority of physical objects around y'all. In fact almost objects are useless unless they accept a solid structure!

On this page the basic physical properties of gases, liquids and solids are described in terms of structure, particle motion (kinetic particle theory), effects of temperature and pressure changes, and particle models used to explain these backdrop and characteristics. Hopefully, theory and fact will match up to give students a clear understanding of the material world effectually them in terms of gases, liquids and solids � referred to as the three physical states of matter.

The changes of state known as melting, fusing, boiling, evaporating, condensing, liquefying, freezing, solidifying, crystallising are described and explained with particle model pictures to assistance understanding. There is as well a mention of miscible and immiscible liquids and explaining the terms volatile and volatility when applied to a liquid.

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i.1. The Iii States of Matter, gas�liquid�solid particle theory models

The 3 states of matter are solid, liquid and gas. Either melting and freezing tin take place at the melting bespeak, whereas boiling and condensing accept place at the boiling signal. Evaporation can take place at whatsoever temperature from a liquid surface. Y'all tin can represent the three states of thing with a simple particle model. In this model�diagrams, the particles are represented by small solid inelastic spheres (electron structure is ignored).

Kinetic particle theory can assist to explain changes of state like melting, boiling, freezing and condensing. The amount of energy needed to alter country from solid to liquid or from liquid to gas depends on the force of the forces between the particles of the substance.

These inter-particle forces may be relatively weak intermolecular forces (intermolecular bonding) or potent chemical bonds (ionic, covalent or metallic). The nature of the particles involved depends on the type of chemical bonding and the structure of the substance. The stronger the bonny forces between the particles the higher the melting indicate and boiling point of the substance

WHAT ARE THE THREE STATES OF Matter?
- Nigh materials can be simply described as a gas, a liquid or a solid.
WHY ARE THEY LIKE WHAT THEY ARE?
- But knowing isn't enough, we demand a comprehensive theory of gases, that can explain their behaviour and make predictions about what happens eastward.g. if we alter temperature or force per unit area.
HOW CAN We EXPLAIN HOW THEY Carry?
- We need a theoretical model east.thousand. 'particle theory' that is supported past experimental evidence.
Can PARTICLE MODELS Help Us Empathise THEIR PROPERTIES and CHARACTERISTICS?
- In a word, Yes!
WHY IS It IMPORTANT TO KNOW THE Backdrop OF GASES, LIQUIDS AND SOLIDS?
- It is important in the chemical manufacture to know about the behaviour of gases, liquids and solids in chemic processes e.g. what happens to the different states with changes in temperature and pressure.
What is the KINETIC PARTICLE THEORY of gases, liquids and solids?
- The kinetic particle theory of the states of thing is based on the thought of all materials existing as very very tiny particles which may exist individual atoms or molecules and the their interaction with each other either by collision in gases or liquids or by vibration and chemical bonding in solids.
CAN Nosotros Brand PREDICTIONS BASED ON THEIR CHARACTERISTIC Properties?
- This page introduces general physical descriptions of substances in the simplest physical (non�chemic) classification level i.e. is it a gas, liquid or a solid.
- But, this spider web page likewise introduces 'particle models' in which a modest circle represents an atom or a molecule i.east. a particular particle or simplest unit of a substance.
- This department is quite abstract in a way because you are talking about particles you lot can't see as individually, you lot only the 'majority' cloth and its concrete character and properties.
Are at that place LIMITATIONS to the particle model?
- Well, yes! e.yard.
- The particles are treated every bit elementary inelastic spheres and but deport like minute snooker assurance flying around, not quite true, only they do wing around non-stop at random!
- Although the particles are assumed to be hard spheres and inelastic, in reality they are atoms, ions or molecules.
- Apart from lone atoms, they can be all sorts of shapes and twist and bend on standoff with other particles and when they react they separate into fragments when bonds break.
- The simple model assumes no forces between the particles, but this is untrue, the model takes little business relationship of the forces betwixt the particles, even in gases you get very weak intermolecular bonding forces.
- The particle model takes no account of the actual size of the particles e.k. ions/molecules can be widely different in size e.m. compare an ethene molecule with a poly(ethene) molecule!
- Neither does information technology take account of any space that may exist between the particles.

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WHAT IS THE GASEOUS STATE OF MATTER?

WHAT ARE THE PROPERTIES OF A GAS?

HOW DO GASEOUS PARTICLES BEHAVE?

How does the kinetic particle theory of gases explain the backdrop of gases?

A gas has no stock-still shape or book, but always spreads out to fill any container - the gas molecules will diffuse into any infinite available.

At that place are almost no forces of attraction between the particles so they are completely gratis of each other.

The particles are widely spaced and scattered and always moving speedily at random throughout the container and so there is no order in the organization.

The particles motion linearly and rapidly in all directions, and oft collide with each other and the side of the container.

The collision of gas particles with the surface of a container causes gas pressure level, on billowy off a surface they exert a force in doing so.
With increase in temperature, the particles movement faster as they gain kinetic energy, the rate of collisions betwixt the particles themselves and the container surface increases and this increases gas pressure eg in a steam locomotive or the volume of the container if it tin can expand eg similar a balloon.

Using the particle model to explain the properties of a Gas

Gases have a very low density (�light�) because the particles are and then spaced out in the container (density = mass / volume).

Density gild: solid > liquid >>> gases

Gases flow freely because there are no effective forces of attraction between the gaseous particles � molecules.

Ease of flow order : gases > liquids >>> solids (no real flow in solid unless you finely powder it!)
Considering of this gases and liquids are described as fluids.

Gases have no surface, and no fixed shape or volume , and because of lack of particle attraction, they always spread out and make full whatsoever container (so gas volume = container volume).

Gases are readily compressed because of the �empty� infinite between the particles.
- Ease of compression lodge : gases >>> liquids > solids (about impossible to compress a solid)

Gas pressure level

When a gas is confined in a container the particles will cause and exert a gas force per unit area which is measured in atmospheres (atm) or Pascals (1.0 Pa = i.0 N/kⁱⁱ), pressure is force/area i.e. the outcome of all the collisions on the surface of the container.
- All particles take mass and their motility gives them kinetic energy and momentum.
- The gas pressure is caused by the strength created by millions of impacts of the tiny individual gas particles on the sides of a container.
- For example � if the number of gaseous particles in a container is doubled, the gas pressure is doubled because doubling the number of molecules doubles the number of impacts on the side of the container so the total impact force per unit area is too doubled.
  - This doubling of the particle impacts doubling the pressure is pictured in the two diagrams below.

Effect of temperature change
If the volume of a sealed container is kept constant and the gas within is heated to a higher temperature, the gas pressure level increases.
- The reason for this is that equally the particles are heated they proceeds kinetic free energy and on average move faster.
- Therefore they will collide with the sides of the container with a greater force of impact, so increasing the pressure.
  - There is also a greater frequency of standoff with the sides of the container BUT this is a small-scale factor compared to the upshot of increased kinetic energy and the increase in the average force of affect.
- Therefore a fixed amount of gas in a sealed container of constant volume, the higher the temperature the greater the pressure and the lower the temperature the lesser the pressure.
- For gas pressure�temperature calculations see Function two Charles's/Gay�Lussac'southward Police force

If the �container� volume can alter, gases readily expand* on heating because of the lack of particle attraction, and readily contract on cooling.
- If in that location is no volume restriction the expansion on heating is much greater for gases than liquids or solids because in that location is no significant allure between gaseous particles. The increased average kinetic energy will make the gas pressure rising then the gas will try to expand in volume if allowed to east.thou. balloons in a warm room are significantly bigger than the same airship in a common cold room!

DIFFUSION in Gases:
- The natural rapid and random movement of the particles in all directions means that gases readily �spread� or lengthened.
  - Di ffusion continues until the concentrations are uniform throughout the container of gases, merely ALL the particles keep moving with their always present kinetic energy!

Improvidence is faster in gases than liquids where there is more space for them to move (experiment illustrated beneath) and diffusion is negligible in solids due to the shut packing of the particles.
- Other prove for random particle motion including diffusion:
  - A long glass tube (two�4 cm diameter) is filled at one stop with a plug of cotton fiber wool soaked in conc. hydrochloric acid sealed in with a rubber bung (for health and rubber!) and the tube is kept perfectly still, clamped in a horizontal position. A similar plug of conc. ammonia solution is placed at the other end. The soaked cotton wool plugs will give off fumes of HCl and NH₃ respectively, and if the tube is left undisturbed and horizontal, despite the lack of tube movement, due east.g. NO shaking to mix and the absence of convection, a white deject forms most ¹/₃rd forth from the conc. hydrochloric acid tube end.
    - Note the rule: The smaller the molecular mass, the greater the average speed of the molecules (merely all gases have the same average kinetic energy at the same temperature).

A demonstration of diffusion

A coloured gas , heavier than air (greater density), is put into the bottom gas jar and a 2nd gas jar of lower density colourless air is placed over it separated with a glass cover. Diffusion experiments should be enclosed at constant temperature to minimise disturbance by convection.

If the drinking glass encompass is removed and then (i) the colourless air gases diffuses downwardly into the coloured brown gas and (2) bromine diffuses upwards into the air. The random particle move leading to mixing cannot be due to convection considering the more dense gas starts at the bottom!

No 'shaking' or other means of mixing is required. The random movement of both lots of particles is enough to ensure that both gases somewhen become completely mixed by diffusion (spread into each other).

This is articulate evidence for improvidence due to the random continuous motility of all the gas particles and, initially, the internet movement of one type of particle from a higher to a lower concentration (' down a diffusion gradient '). When fully mixed, no further colour change distribution is observed Only the random particle movement continues! Come across besides other evidence in the liquid department later the particle model for diffusion diagram below.

Oestrus conduction in gases
- All gases are very poor conductors of thermal energy, energy which is due to the kinetic energy of the moving particles.
- Heat free energy is transferred by 'hotter' higher kinetic energy gas particles colliding with 'cooler' lower kinetic energy particles and so raising their kinetic energy and spreading the rut energy.
- However, the density of gases is very depression, and so the density or rate of 'standoff transfer' is quite low.
- Therefore gases are very good insulators e.g. think of their used in house insulation where air is trapped in various ways like foam or fibre glass loft insulation.
Electrical conduction in gases
- Electrical conduction requires the presence of free IONS or free ELECTRONS i.east. particles that tin carry an electrical charge.
- Gases are poor conductors of electricity because they are usually not in an ionic or ionised course.
- Notwithstanding, applying a very high potential difference of thousands of volts, peculiarly with a low gas pressure, can cause the formation of complimentary ions and electrons and electrical conduction can happen.
- Strip lighting and neon signs use this result.

A note on 'forces'

Forces between particles are mentioned on this page and some ideas will seem more abstract than others � merely think near it ...
- A gas spreads everywhere in a given infinite, then there can't exist much attraction between the molecules/particles.
- Something must hold liquid molecules together or how tin can a liquid grade from a gas?
- In fact betwixt liquid molecules there are really weak electrical forces of attraction called intermolecular forces, but they can't be stiff enough to create a rigid solid structure.
- However, in solids, these forces must exist stronger to create the rigid construction.
- Intermolecular forces are likewise called 'intermolecular bonds' BUT these are not the same as covalent, ionic or metallic bonds and they are much weaker than these true chemical bonds.

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WHAT IS THE LIQUID Country OF Matter?

WHAT ARE THE Backdrop OF A LIQUID?

HOW Exercise LIQUID PARTICLES Bear?

How does the kinetic particle theory of liquids explain the backdrop of liquids?

A liquid has a fixed book at a given temperature but its shape is that of the container which holds the liquid.

There are much greater forces of attraction between the particles in a liquid compared to gases, but not quite every bit much as in solids and the particles are sufficiently gratuitous to move past each other.

If there were no intermolecular forces, liquids could not exist!

The particles are quite close together but notwithstanding arranged at random throughout the container due to their constant random movement, there is a little close range order every bit you can get clumps of particles clinging together temporarily (as in the diagram above).
As well as moving chop-chop in all directions, they collide more oftentimes with each other than in gases due to shorter distances betwixt particles � much greater density - particles closer together.

With increase in temperature, the particles move faster equally they gain kinetic energy, so increased collision rates, increased collision energy, increased rates of particle diffusion, expansion leading to subtract in density.

Using the particle model to explain the backdrop of a Liquid

Liquids have a much greater density than gases (�heavier�) considering the particles are much closer together considering of the bonny forces.

Most liquids are just a little less dumbo than when they are solid

H2o is a curious exception to this general rule, which is why ice floats on h2o.

Liquids usually menstruum freely despite the forces of allure betwixt the particles but liquids are non as �fluid� as gases.

Note 'sticky' or viscous liquids have much stronger bonny forces betwixt the molecules BUT not strong plenty to form a solid.

Liquids have a surface , and a fixed volume (at a particular temperature) because of the increased particle attraction, but the shape is not stock-still and is only that of the container itself.

Liquids seem to accept a very weak 'skin' surface effect which is caused by the majority molecules attracting the surface molecules disproportionately.

Liquids are not readily compressed because there is so petty �empty� space between the particles, so increase in pressure has only a tiny effect on the volume of a solid, and you need a huge increase in pressure to meet any real contraction in the volume of a liquid.

Liquids will expand on heating but zip like as much equally gases, only more than than solids, because of the greater particle attraction restricting the expansion (volition contract on cooling).
- Note: When heated, the liquid particles gain kinetic energy and hit the sides of the container more oftentimes, and more than significantly, they striking with a greater force, and then in a sealed container the pressure level produced in a liquid can exist considerable!

Diffusion : The natural rapid and random movement of the particles means that liquids �spread� - lengthened. Diffusion is much slower in liquids compared to gases because in that location is less space for the particles to move in and more �blocking� collisions happen.
- Just dropping lumps/granules/powder of a soluble solid (preferably coloured!) volition resulting in a dissolving followed past an appreciable improvidence issue.
- Once again, the net flow of dissolved particles will be from a college concentration to a lower concentration until the concentration is uniform throughout the container.

Diffusion in liquids � bear witness for random particle motion in liquids :
- If coloured crystals of e.one thousand. the highly coloured salt crystals of potassium manganate(Vii) are dropped into a beaker of h2o and covered at room temperature.

Rut conduction in liquids

Near liquids are poor conductors of thermal free energy, free energy which is due to the kinetic energy of the moving particles.
Heat energy is transferred past 'hotter' college kinetic energy liquid particles colliding with 'cooler' lower kinetic energy particles so raising their kinetic energy and spreading the estrus energy.
However, the density of liquids is much greater than gases (particles much closer together), so the density or charge per unit of 'collision transfer' is much higher, and so liquids are meliorate rut conductors than gases.
Liquid metals are very skillful heat conductors because of the freely moving electrons that can carry the kinetic energy rapidly through the liquid. For more details come across 'metal structure'.

Electrical conduction in liquids

Electrical conduction requires the presence of free IONS or free ELECTRONS i.east. particles that tin can conduct an electrical accuse.
Most liquids are poor conductors of electricity (practiced insulators), but at that place are important exceptions.
For example, if a liquid contains ions eastward.g. table salt solutions, then electric conduction tin take place
Liquid metals are very good electrical conductors because of the freely moving electrons that can deport the electrical electric current speedily through the liquid metal.
For more details see 'electrolysis' and 'metallic construction'.

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WHAT IS THE SOLID State OF Thing?

WHAT ARE THE Backdrop OF A SOLID?

HOW DO SOLID PARTICLES Conduct?

How does the kinetic particle theory of solids explain the backdrop of solids?

A solid has a fixed volume and shape at a item temperature unless physically subjected to some force.

The greatest forces of attraction are betwixt the particles in a solid and they pack together as tightly as possible in a groovy and ordered arrangement called a lattice.

The particles are as well strongly held together to allow movement from place to place merely the particles vibrate near their position in the structure.

With increase in temperature, the particles vibrate faster and more strongly as they gain kinetic free energy, so the vibration increases causing expansion.

More on the kinetic particle theory of an platonic gas

Using the particle model to explain the backdrop of a Solid

Solids accept the greatest density (�heaviest�) because the particles are closest together.

Solids cannot flow freely like gases or liquids because the particles are strongly held in fixed positions.

Solids take a stock-still surface and book (at a particular temperature) considering of the strong particle attraction.

Solids are extremely difficult to compress because there is no real �empty� infinite between the particles, then increase in pressure has virtually no event on the volume of a solid.

Solids volition expand a little on heating only goose egg similar as much every bit liquids because of the greater particle attraction restricting the expansion and causing the wrinkle occurs on cooling.
- The expansion is caused by the increased kinetic energy of particle vibration, forcing them further apart causing an increase in volume and corresponding decrease in density.
- Although t he expansion of a solid is due to the higher average kinetic energy of the particles and the more energetic vibrations, they are still held together by the intermolecular bonding forces (or much stronger strong ionic or covalent bonds), which restricts the expansion - this is non part of the kinetic particle theory!

Diffusion is nearly incommunicable in solids because the particles are too closely packed and strongly held together in a lattice. The immobile particles cannot move effectually because there is no random movement into �empty space� for them to move through.

Its quite a dissimilar situation in gases and liquids where diffusion readily takes identify because of the freedom of the particles to move around at random and 'fustigate' each other aside!

Heat conduction in solids

Apart from metals, most solids are poor conductors of rut energy, energy which is due to the kinetic free energy of the vibrating particles in the crystal structure � recall, unlike gases and liquids, the particles tin can't move effectually, they just vibrate almost a fixed bespeak.
Heat energy is transferred by 'hotter' higher kinetic free energy vibrating particles colliding against 'cooler' lower kinetic free energy vibrating particles and so raising their kinetic energy and spreading the rut energy through the solid structure.
The density of solids and club of particles is are greater than liquids (particles closest together), and so the density or rate of 'collision transfer' vibration is much college, and so solids are better heat conductors than liquids (and much greater than gases).
However, although virtually not-metal solids are poor heat conductors, metals are exceptionally good oestrus conductors because of the freely moving electrons that can bear the kinetic energy chop-chop through the crystal structure.
For more than details see 'metallic structure'.

Electrical conduction in solids

Electrical conduction requires the presence of free IONS or gratis ELECTRONS i.e. particles that can acquit an electric charge within a solid structure. Which of course is impossible in near solids (except metals) because ALL particles tin can't movement effectually, and so even solid ionic compounds cannot deport electricity.
Most non-metallic solids are poor conductors of electricity (expert insulators), but at that place are important exceptions.
All metals are relatively expert electric conductors considering of the freely moving electrons that tin comport the electric electric current rapidly through the liquid metal. For more details see 'metallic structure'.
Graphite and graphene, forms (allotropes) of the non�metallic element carbon, are electrical conductors due to complimentary moving electrons in the solid structure, a rare exception of conducting solids autonomously from metals.

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2. Changes of Country for gas <=> liquid <=> solid

You need to be able to predict the state of a substance at dissimilar temperatures given appropriate data.

FREEZING

MELTING

SUBLIMING -the contrary is degradation or 'reverse sublimation'

BOILING or EVAPORATING

SUMMARY of the CHANGES of Country betwixt a gas, liquid and solid

All mass conserved in these PHYSICAL CHANGES

CONDENSING

These are Not chemical changes !

A alter of state ways an interconversion between ii states of matter, namely gas <=> liquid <=> solid

A 'triangular' summary of of import state changes is illustrated above.

due east.k. solid ==> liquid is melting or fusing

liquid ==> gas/vapour (vapor) is boiling, evaporation or vapourisation (vaporisation)

and the contrary processes

gas/vapour (vapor) ==> liquid is condensation, liquefaction/liquefying

liquid ==> solid is freezing, solidifying or crystallising

and there is also

solid ==> gas is sublimation

We tin can use the country particle models and diagrams to explicate changes of land and the energy changes involved.

These are Non chemical changes But PHYSICAL CHANGES, e.g. the water molecules H₂O are just the aforementioned in ice, liquid water, steam or water vapour. What is dissimilar, is how they are arranged, and how strongly they are held together past intermolecular forces in the solid, liquid and gaseous states.

2a. Evaporation and Boiling (liquid to gas)

Explained using the kinetic particle theory of gases and liquids

Evaporation is when particles of a liquid escape to course a gas or vapour i.e. water evaporating into the air.
Because of random collisions, the particles in a liquid have a diversity of speeds and kinetic energies. On heating, particles proceeds kinetic energy and motility faster and are more than able to overcome the intermolecular forces between the molecules i.e. some particles will have plenty kinetic energy to overcome the bonny forces holding the particles together in the bulk liquid.
- Even without further heating, evaporation occurs all the time from volatile liquids, but it is however the college kinetic energy particles that tin overcome the attractive forces between the molecules in the bulk of the liquid and escape from the surface into the surrounding air.

In evaporation and humid (both are vaporisation) it is the highest kinetic energy molecules that can �escape� from the attractive forces of the other liquid particles.
- The particles lose whatsoever guild and become completely free to form a gas or vapour.

Free energy is needed to overcome the attractive forces betwixt particles in the liquid and is taken in from the environment.
- In boiling, heat free energy must be continually supplied e.g. from an electric heating element or Bunsen burner etc.
- In the case of evaporation, the estrus is taken from the liquid, so an evaporating liquid cools - the lower speed/kinetic free energy particles are left behind.

This means heat is taken in, so evaporation and humid are endothermic processes (ΔH +ve).

If the temperature is loftier plenty humid takes place and bubbles of gas class in the bulk liquid � something you don't see in evaporation, because that can only occur on the surface of a liquid.

Boiling is rapid vapourisation anywhere in the bulk liquid and at a stock-still temperature called the boiling point and requires continuous add-on of oestrus.
- B oiling point depends on the ambience force per unit area, the lower the gas pressure above the liquid, the lower the humid indicate of the liquid.
- This is why tea brewed on the elevation of high mount isn't quite as adept as at sea level, the water boils at a lower temperature and doesn't extract substances from the tea leaves as efficiently!
- In the past, measuring the boiling point of water was used to gauge the peak of land to a higher place sea level!

The charge per unit of boiling is express past the rate of heat transfer into the liquid.

Evaporation takes place more slowly than boiling at any temperature betwixt the melting point and boiling point, and but from the surface, and results in the liquid becoming libation due to loss of higher kinetic energy particles.

Factors affecting the rate of evaporation of a liquid.

The higher the temperature of the liquid, the faster it evaporates, because more than particles take sufficient kinetic energy to overcome the intermolecular forces of the bulk liquid and can escape from the liquid surface.
The larger the surface area of given volume of liquid, the faster information technology evaporates, because at that place is a greater probability of particles escaping.
The greater the airflow over a liquid the faster it evaporates because its stops a build�up of vapour particles which may hit the surface and condense! The airflow lowers the concentration of evaporated particles past sweeping them away and so more readily replaced past freshly evaporated particles.
Delight note that the best atmospheric condition for drying washing are a warm sunny twenty-four hour period, a good breeze, and spreading the clothes out every bit much as possible to increase their surface area (I get told off about this one!).

More details on the e nergy changes for these physical changes of state for a range of substances are dealt with in a section of the Energetics Notes .

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2b. Condensing (gas to liquid) � the process of condensation

Explained using the kinetic particle theory of gases and liquids

On cooling, gas particles lose kinetic energy, they slow down and eventually become attracted together via intermolecular forces to form a liquid i.due east. they haven't enough kinetic free energy to remain free in the gaseous state.

In that location is an increment in social club equally the particles are much closer together and can grade clumps of molecules.

The procedure requires heat to be lost to the surroundings i.e. heat given out, so condensation is exothermic (ΔH �ve).
- This is why steam has such a scalding effect, its not only hot, but you go extra oestrus transfer to your skin due to the exothermic condensation on your surface!

Factors affecting the rate of condensation of a gas�vapour

The lower the temperature of the gas the faster it condenses because the particles on average accept less kinetic free energy to overcome the attractive intermolecular forces i.e. they gas particles are more likely to aggregate into drops of liquid.
The colder the surface the gas condenses on, the faster the estrus transfer to reduce the kinetic energy of the gas particles, and so the faster the gas/vapour can condense.
The college the concentration of vapour in air, the faster condensation can have identify. The particles are closer together and more chance of combining to form liquid droplets.

2c. Distillation � the procedure of distilling a liquid

Simple and fractional distillation involve the processes of boiling and condensation and are described on the Elements, Compounds and Mixtures Office two page, where other methods of separation are also described.

The procedure of distillation involves boiling (liquid ==> gas/vapor) and the reverse procedure of condensation (gas/vapour ==> liquid)

2d. Melting (solid to liquid)

Explained using the kinetic particle theory of liquids and solids

When a solid is heated the particles vibrate more strongly as they gain kinetic energy and the particle attractive forces are weakened.

Eventually, at the melting bespeak, the attractive forces are likewise weak to hold the particles in the structure together in an ordered way and and so the solid melts.
- Note that the intermolecular forces are still there to hold the bulk liquid together � simply the effect is not strong enough to course an ordered crystal lattice of a solid.

The particles go costless to move around and lose their ordered arrangement.

Energy is needed to overcome the attractive forces and give the particles increased kinetic energy of vibration.

So heat is taken in from the surroundings and melting is an endothermic process (ΔH +ve).

Free energy changes for these physical changes of state for a range of substances are dealt with in a section of the Energetics Notes.

2e. Freezing (liquid to solid)

Explained using the kinetic particle theory of liquids and solids

On cooling, liquid particles lose kinetic energy and then can become more strongly attracted to each other.

When the temperature is depression enough, the kinetic energy of the particles is bereft to preclude the particle bonny forces causing a solid to course.

Somewhen at the freezing point the forces of attraction are sufficient to remove any remaining freedom of movement (in terms of one place to another) and the particles come together to class the ordered solid arrangement (though the particles even so take vibrational kinetic free energy.

Since heat must be removed to the surroundings, and then foreign equally it may seem, freezing is an exothermic process (ΔH �ve).

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2f . Cooling and Heating Curves and the comparative free energy changes for changes of land: gas <=> liquid <=> solid

2f(i) Cooling curve : What happens to the temperature of a substance if it is cooled from the gaseous land to the solid state?

Note the temperature stays constant during the country changes of condensing at temperature Tc, and freezing/solidifying at temperature Tf. This is considering all the oestrus energy removed on cooling at these temperatures (the latent heats or enthalpies of land modify), allows the strengthening of the inter�particle forces (intermolecular bonding) without temperature autumn. The rut loss is compensated past the exothermic increased intermolecular force allure. In betwixt the 'horizontal' state change sections of the graph, yous can see the energy 'removal' reduces the kinetic free energy of the particles, lowering the temperature of the substance. See section two. for detailed description of the country changes.

A cooling curve summarises the changes:

gas ==> liquid ==> solid

For each modify of state, energy must be removed, known equally the 'latent heat'

Bodily free energy values for these physical changes of state for a range of substances are dealt with in more particular in the Energetics Notes .

2f(ii) Heating curve : What happens to the temperature of a substance if it is heated from the solid state to the gaseous state?

Note the temperature stays abiding during the state changes of melting at temperature Tm and boiling at temperature Tb. This is because all the energy captivated in heating at these temperatures (the latent heats or enthalpies of state change), goes into weakening the inter�particle forces (intermolecular bonding) without temperature rise The rut gain equals the endothermic/heat absorbed energy required to reduce the intermolecular forces. In between the 'horizontal' country modify sections of the graph, you tin encounter the energy input increases the kinetic energy of the particles and raising the temperature of the substance. See department 2. for detailed description of the state changes.

A heating bend summarises the changes:

solid ==> liquid ==> gas

For each change of land, energy must be added, known as the 'latent rut'

Actual energy values for these physical changes of land for a range of substances are dealt with in more detail in the Energetics Notes .

SPECIFIC LATENT HEATS - refer to diagram below

The latent oestrus for the state changes solid <=> liquid is called the specific latent estrus of fusion (for melting or freezing).

The latent heat for the state changes liquid <=> gas is called the specific latent estrus of vaporisation (for condensing, evaporation or boiling)

For more on latent heat meet my physics notes on specific latent oestrus

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2g. Sublimation

Explained using the kinetic particle theory of gases and solids

Sublimation:
- This is when a solid, on heating, directly changes into a gas without melting, AND the gas on cooling re�forms a solid directly without condensing to a liquid. Sublimation unremarkably just involves a physical change BUT its not always that elementary (see ammonium chloride!).

Theory in terms of particles:

When the solid is heated the particles vibrate with increasing force from the added thermal energy.
- If the particles have enough kinetic energy of vibration to partially overcome the particle�particle attractive forces yous would expect the solid to melt.
- HOWEVER, if the particles at this point have enough energy at this point that would accept led to humid, the liquid will NOT form and the solid turns directly into a gas.
  - Overall endothermic change, energy absorbed and 'taken in' to the arrangement.
On cooling, the particles motility slower and have less kinetic energy.
- Eventually, when the particle kinetic energy is depression enough, information technology volition allow the particle�particle attractive forces to produce a liquid.
- BUT the energy may be low plenty to permit direct formation of the solid, i.eastward. the particles practice Non take enough kinetic energy to maintain a liquid country!
  - Overall exothermic change, free energy released and 'given out' to the surround.

Examples:

Fifty-fifty at room temperature bottles of solid iodine testify crystals forming at the top of the canteen above the solid. The warmer the laboratory, the more than crystals form when it cools downwards at dark!

The formation of a detail form of frost involves the directly freezing of h2o vapour (gas). Frost can as well evaporate straight back to h2o vapour (gas) and this happens in the 'dry' and extremely cold winters of the Gobi Desert on a sunny day.

Solid carbon dioxide (dry ice)
is formed on cooling the gas down to less than �78^oC. On warming it changes directly to a very cold gas!, condensing whatever water vapour in the air to a 'mist', hence its use in stage effects.
- CO_{ii (s)} CO_{2 (grand)} (physical alter only)

On heating strongly in a test tube, white solid ammonium chloride, decomposes into a mixture of ii colourless gases ammonia and hydrogen chloride. On cooling the reaction is reversed and solid ammonium chloride reforms at the cooler pinnacle surface of the test tube.

Ammonium chloride + heat free energy ammonia + hydrogen chloride
NH_ivCl_(south) NH_3(yard) + HCl_(k)
This involves both chemical and concrete changes and is so is more complicated than examples 1. to 3. In fact the ionic ammonium chloride crystals change into covalent ammonia and hydrogen chloride gases which are naturally far more volatile (covalent substances generally take much lower melting and humid points than ionic substances).

The liquid particle picture does not figure here, merely the other models fully utilize apart from state changes involving liquid formation. GAS particle model and SOLID particle model links.

Delight NOTE, At a college level of study, you need to study the g�l�s stage diagram for water and the vapour force per unit area curve of ice at particular temperatures. For example, if the ambient vapour pressure is less than the equilibrium vapour force per unit area at the temperature of the ice, sublimation tin can readily take place. The snow and water ice in the colder regions of the Gobi Desert exercise not melt in the Sunday, they just slowly 'sublimely' disappear!

The germination of hoar frost - the reverse of sublimation

Frost is a thin layer of water ice on a solid surface.

Hoar frost forms directly from water vapour in air higher up 0^oC, coming in contact with a solid surface whose temperature is below freezing (<0^oC).

The water vapor changes directly from gas (vapour) to solid (ice) as it comes into contact with the solid surface.

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2 h. More on the latent estrus changes of physical changes of state

Changes of physical state i.e. gas <==> liquid <==> solid are as well accompanied by energy changes.

To melt a solid, or boil/evaporate a liquid, rut energy must be absorbed or taken in from the surroundings, and so these are endothermic free energy changes. The organisation is heated to issue these changes.

To condense a gas, or freeze a solid, heat free energy must be removed or given out to the surround, and then these are exothermic energy changes. The system is cooled to effect these changes.

Generally speaking, the greater the forces betwixt the particles, the greater the free energy needed to effect the state change AND the higher the melting point and boiling betoken.

A comparison of free energy needed to melt or boil different types of substance

(This is more for avant-garde level students)

The heat energy change involved in a land change can exist expressed in kJ/mol of substance for a fair comparison.

In the table below

ΔH_melt is the energy needed to melt ane mole of the substance (formula mass in m).

ΔH _vap is the energy needed to vaporise past evaporation or boiling one mole of the substance (formula mass in m).

These are the latent heats required to alter the physical land of a substance.

For simple minor covalent molecules, the energy captivated by the material is relatively small to melt or vaporise the substance and the bigger the molecule the greater the inter�molecular forces.

These forces are weak compared to the chemical bonds belongings atoms together in a molecule itself.

Relatively low energies are needed to melt or vapourise them.

These substances have relatively depression melting points and humid points.

Covalent Bonding � small unproblematic molecules

For strongly bonded 3D networks east.g.

(i) an ionically bonded lattice of ions (ionic bonding ),

(ii) a covalently bonded lattice of atoms (covalent bonding � giant covalent structures ),

(iii) and a metal lattice of ions and free outer electrons (thouetallic bonding ),

the structures are much stronger in a continuous way because of the continuous chemical bonding throughout the structure.

Consequently, much greater energies are required to melt or vaporise the cloth.

This is why they have so much higher melting points and humid points.

Substance formula Type of bonding, construction and attractive forces operating Melting point M (Kelvin) = ^oC + 273 Energy needed to cook substance Boiling point Grand (Kelvin) = ^oC + 273 Energy needed to eddy substance

methane CH_iv small covalent molecule � very weak intermolecular forces 91K/�182^oC 0.94kJ/mol 112K/�161^oC 8.2kJ/mol

ethanol ('alcohol') C_twoH_fiveOH larger covalent molecule than methane, greater, only still weak intermolecular forces 156K/�117^oC iv.6kJ/mol 352K/79^oC 43.5kJ/mol

sodium chloride Na⁺Cl^� ionic lattice, very strong 3D ionic bonding due to attraction between (+) and (�) ions 1074K/801^oC 29 kJ/mol 1740K/1467^oC 171 kJ/mol

iron Atomic number 26 stiff 3D bonding by allure of metal ions (+) with free outer electrons (�) 1808K/1535^oC 15.4kJ/mol 3023K/2750^oC 351kJ/mol

silicon dioxide (silica) SiO_ii giant covalent structure, stiff continuous 3D bond network 1883K/1610^oC 46.4kJ/mol 2503K/2230^oC 439kJ/mol

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3. Dissolving solids, solutions and miscible/immiscible liquids

3a. WHAT HAPPENS TO PARTICLES WHEN A SOLID DISSOLVES IN A LIQUID SOLVENT?

What do the words SOLVENT, SOLUTE and SOLUTION mean?
When a solid (the solute) dissolves in a liquid (the solvent) the resulting mixture is called a solution.
- In general: solute + solvent ==> solution

3b. WHAT HAPPENS TO PARTICLES WHEN TWO LIQUIDS COMPLETELY MIX WITH EACH OTHER?

WHAT DOES THE Give-and-take MISCIBLE MEAN?

Using the particle model to explain miscible liquids.

If ii liquids completely mix in terms of their particles, they are called miscible liquids because they fully deliquesce in each other. This is shown in the diagram beneath where the particles completely mix and move at random. The process can be reversed by fractional distillation.

3c. WHAT HAPPENS TO PARTICLES WHEN 2 LIQUIDS DO NOT MIX WITH EACH OTHER?

WHAT DOES THE Discussion IMMISCIBLE MEAN?

WHY Exercise THE LIQUIDS Not MIX?
Using the particle model to explain immiscible liquids.
If the two liquids exercise NOT mix, they form two separate layers and are known equally immiscible liquids, illustrated in the diagram below where the lower purple liquid will exist more than dumbo than the upper layer of the greenish liquid.
- Y'all can separate these two liquids using a separating funnel.
- The reason for this is that the interaction between the molecules of one of the liquids lonely is stronger than the interaction between the two dissimilar molecules of the different liquids.
- For example, the strength of attraction between water molecules is much greater than either oil�oil molecules or oil�water molecules, so two split up layers class because the h2o molecules, in terms of energy alter, are favoured by 'sticking together'.

3d. How a separating funnel is used

one. The mixture is put in the separating funnel with the stopper on and the tap closed and the layers left to settle out.

two. The stopper is removed, and the tap is opened so that you tin carefully run the lower grey layer off first into a beaker.

three. The tap is then airtight again, leaving behind the upper xanthous layer liquid, so separating the two immiscible liquids.

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State changes: 2a evaporation and boiling, 2b condensation, 2c distillation, 2d melting, 2e freezing, 2f cooling and heating curves and relative energy changes, 2g sublimation * 3. Dissolving, solutions. miscible/immiscible liquids Boiling * point * Brownian motility * Changes of land * Condensing * Cooling curve * Diffusion * Dissolving * Evaporation * Freezing * point * Gas particle picture * Heating curve * Liquid particle picture * Melting * indicate * miscible/immiscible liquids * Backdrop of gases * Backdrop of liquids * Properties of solids * solutions * sublimation * Solid particle picture * GCSE/IGCSE multiple option QUIZ on states of affair gases liquids solids practise revision questions Revision notes on particle models and properties of gases, liquids and solids KS4 Science GCSE/IGCSE/O level Chemistry Data on particle models and properties of gases, liquids and solids for revising for AQA GCSE Science, Edexcel Scientific discipline chemical science IGCSE Chemistry notes on particle models and properties of gases, liquids and solids OCR 21st Century Science, OCR Gateway Science notes on particle models and properties of gases, liquids and solids WJEC gcse science chemistry notes on particle models and properties of gases, liquids and solids CIE O Level chemical science CIE IGCSE chemistry notes on particle models and properties of gases, liquids and solids CCEA/CEA gcse science chemistry (revise courses equal to US grade eight, class 9 grade 10) scientific discipline chemical science courses revision guides caption chemical equations for particle models and properties of gases, liquids and solids educational videos on particle models and properties of gases, liquids and solids guidebooks for revising particle models and properties of gases, liquids and solids textbooks on particle models and properties of gases, liquids and solids state changes & particle model for AQA AS chemical science, state changes & particle model for Edexcel A level Every bit chemistry, state changes & particle model for A level OCR Equally chemistry A, state changes & particle model for OCR Salters AS chemistry B, state changes & particle model for AQA A level chemistry, state changes & particle model for A level Edexcel A level chemistry, country changes & particle model for OCR A level chemistry A, state changes & particle model for A level OCR Salters A level chemistry B country changes & particle model for US Honours course xi form 12 land changes & particle model for pre-university chemistry courses pre-university A level revision notes for state changes & particle model A level guide notes on state changes & particle model for schools colleges academies scientific discipline course tutors images pictures diagrams for state changes & particle model A level chemistry revision notes on state changes & particle model for revising module topics notes to aid on understanding of state changes & particle model university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships Usa United states of america class 11 grade xi AQA A level chemical science notes on state changes & particle model Edexcel A level chemistry notes on state changes & particle model for OCR A level chemistry notes WJEC A level chemistry notes on state changes & particle model CCEA/CEA A level chemistry notes on state changes & particle model for university entrance examinations draw some limitations of the particle model for gases, liquids and solids

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What Happens To The Entropy Of A Sample Of Matter When It Changes State From A Solid To A Liquid?

2e. Freezing (liquid to solid)

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2 h. More on the latent estrus changes of physical changes of state Changes of physical state i.e. gas <==> liquid <==> solid are as well accompanied by energy changes. To melt a solid, or boil/evaporate a liquid, rut energy must be absorbed or taken in from the surroundings, and so these are endothermic free energy changes. The organisation is heated to issue these changes. To condense a gas, or freeze a solid, heat free energy must be removed or given out to the surround, and then these are exothermic energy changes. The system is cooled to effect these changes. Generally speaking, the greater the forces betwixt the particles, the greater the free energy needed to effect the state change AND the higher the melting point and boiling betoken. A comparison of free energy needed to melt or boil different types of substance (This is more for avant-garde level students) The heat energy change involved in a land change can exist expressed in kJ/mol of substance for a fair comparison. In the table below ΔH_melt is the energy needed to melt ane mole of the substance (formula mass in m). ΔH _vap is the energy needed to vaporise past evaporation or boiling one mole of the substance (formula mass in m). These are the latent heats required to alter the physical land of a substance. For simple minor covalent molecules, the energy captivated by the material is relatively small to melt or vaporise the substance and the bigger the molecule the greater the inter�molecular forces. These forces are weak compared to the chemical bonds belongings atoms together in a molecule itself. Relatively low energies are needed to melt or vapourise them. These substances have relatively depression melting points and humid points. Covalent Bonding � small unproblematic molecules For strongly bonded 3D networks east.g. (i) an ionically bonded lattice of ions (ionic bonding ), (ii) a covalently bonded lattice of atoms (covalent bonding � giant covalent structures ), (iii) and a metal lattice of ions and free outer electrons (thouetallic bonding ), the structures are much stronger in a continuous way because of the continuous chemical bonding throughout the structure. Consequently, much greater energies are required to melt or vaporise the cloth. This is why they have so much higher melting points and humid points.
Substance	formula	Type of bonding, construction and attractive forces operating	Melting point M (Kelvin) = ^oC + 273	Energy needed to cook substance	Boiling point Grand (Kelvin) = ^oC + 273	Energy needed to eddy substance
methane	CH_iv	small covalent molecule � very weak intermolecular forces	91K/�182^oC	0.94kJ/mol	112K/�161^oC	8.2kJ/mol
ethanol ('alcohol')	C_twoH_fiveOH	larger covalent molecule than methane, greater, only still weak intermolecular forces	156K/�117^oC	iv.6kJ/mol	352K/79^oC	43.5kJ/mol
sodium chloride	Na⁺Cl^�	ionic lattice, very strong 3D ionic bonding due to attraction between (+) and (�) ions	1074K/801^oC	29 kJ/mol	1740K/1467^oC	171 kJ/mol
iron	Atomic number 26	stiff 3D bonding by allure of metal ions (+) with free outer electrons (�)	1808K/1535^oC	15.4kJ/mol	3023K/2750^oC	351kJ/mol
silicon dioxide (silica)	SiO_ii	giant covalent structure, stiff continuous 3D bond network	1883K/1610^oC	46.4kJ/mol	2503K/2230^oC	439kJ/mol