1. STATES OF MATTER GCSE EDEXCEL CHEMISTRY Explanation


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States of matter
Introduction : Kinetic particle theory 

The kinetic particle theory explains the properties of the different states of matter. 
The particles in solids, liquids and gases have different amounts of energy. 

They are arranged differently and move in different ways.








2.1​ ​Describe​ ​the​ ​arrangement,​ ​movement​ ​and​ ​the​ ​relative​ ​energy​ ​of particles​
 ​in​ ​each​ ​of​ ​the​ ​three​ ​states​ ​of​ ​matter:​ ​solid,​ ​liquid​ ​and​ ​gas


The​ ​three​ ​states​ ​of​ ​matter​ ​are​ ​solid,​ ​liquid​ ​and​ ​gas

They can be represented by a simple model where particles are represented 
by small solid spheres
  • solids- particles have a regular arrangement and are close together
  • liquids- particles have a random arrangement and are close together 
  • gases- particles have a random arrangement and are spread apart


Which state a material is in depends on 
how strong the  forces of attraction are between the particles of the material 
(the atoms, ions  or molecules). 
The strength of forces between particles is determined by:  
ƒ the material (the structure of the substance and  the type of bonds holding 
the particles together),  
ƒ the temperature,  
ƒ the pressure. 



Comparison Table of particle arrangement and movement in the 3 states
The table below summarizes the arrangement and movement of the particles
 in solids, liquids and gases, and shows simple diagrams for the arrangement 
of the particles.





Solids
The table shows some of the properties of solids and why they are like this.


In solids, there are strong forces of attraction between particles. These forces  hold the particles close together in fixed positions to form a very regular  lattice arrangement.  The particles in a solid don’t have much energy, so they don’t move from their  positions. Because of this, all solids keep a definite shape and volume. The  particles vibrate about their positions, and as the temperature increases, the  particles vibrate more. This is why solids expand slightly when heated. 



Liquids
The table shows some of the properties of liquids and why they are like this.

Liquids  In liquids, there are weak forces of attraction between the particles.  The particles are randomly arranged and are free to move past each other, but  they tend to stick closely together. Liquids have a definite volume but don’t  keep a definite shape, and will flow to fill the bottom of a container — see  Figure 3.  The particles in a liquid are constantly moving with random motion. The  hotter the liquid gets, the faster the particles move. This causes liquids to  expand slightly when heated. The particles of a substance in the liquid state  will have more energy than when the substance is in the solid state, but less  energy than when the substance is in the gas state. 
Gases

The table shows some of the properties of gases and why they are like this.



In gases, the forces of attraction between the particles are very weak. The gas  particles are free to move, and do so constantly with random motion.  They travel in straight lines, until they collide with another particle or with the  walls of the container. When a gas molecule hits the walls of the container, it  exerts a pressure on the walls.  The particles are very far apart, so much so that most of a gas is actually  empty space. Gases don’t keep a definite shape or volume and will always  fill any container. The hotter a gas gets, the faster the particles move and the  harder and more frequently they hit the walls of the container. This causes the  pressure of the gas to increase, or, if the container isn’t sealed the volume of  the gas will increase. For any given substance, in the gas state its particles will  have more energy than in the solid state or the liquid state.
  • Summary 





2.2​ ​Recall​ ​the​ ​names​ ​used​ ​for​ ​the​ ​inter conversions​ ​between​ ​the​ ​three​ ​states of​ ​matter,​ ​recognizing​ ​that​ ​these​ ​are​ ​physical​ ​changes:​ ​contrasted​ ​with chemical​ ​reactions​ ​that​ ​result​ ​in​ ​chemical​ ​changes




    • Melting​ ​and​ ​freezing​ ​take​ ​place​ ​at​ ​the​ ​melting​ ​point
      o solid​ ​→​ ​liquid:​ ​melting
      o liquid​ ​→​ ​solid:​ ​freezing

      Boiling​ ​and​ ​condensing​ ​take​ ​place​ ​at​ ​the​ ​boiling​ ​point

      o liquid​ ​→​ ​gas:​ ​boiling
      o gas​ ​→​ ​liquid:​ ​condensing


      ●  State​ ​changes​ ​(melting,​ ​boiling,​ ​freezing​ ​and​ ​condensing)​ ​are​ ​physical​ ​changes​ ​– they​ ​involve​ ​the​ ​forces​ ​between​ ​the​ ​particles​ ​of​ ​the​ ​substances​ ​but​ ​the​ ​particles themselves​ ​don’t​ ​change.​​​​​​​



    • ●  Chemical​ ​changes​ ​are​ ​where​ ​a​ ​new​ ​product​ ​has​ ​been​ ​formed




    • 2.3​ ​Explain​ ​the​ ​changes​ ​in​ ​arrangement,​ ​movement​ ​and​ ​energy​ ​of​ ​particles during​ ​these​ ​interconversions
      • Particle​ ​theory​ ​can​ ​help​ ​to​ ​explain​ ​melting,​ ​boiling,​ ​freezing​ ​and​ ​condensing...
      o The​ ​amount​ ​of​ ​energy​ ​needed​ ​to​ ​change​ ​state​ ​from​ ​solid​ ​to​ ​liquid​ ​and from​ ​liquid​ ​to​ ​gas​ ​depends​ ​on​ ​the​ ​strength​ ​of​ ​the​ ​forces​ ​between​ ​the
      particles​ ​of​ ​the​ ​substance.
      o The​ ​nature​ ​of​ ​the​ ​particles​ ​involved​ ​depends​ ​on​ ​the​ ​type​ ​of​ ​bonding​ ​and the​ ​structure​ ​of​ ​the​ ​substance.
      o The​ ​stronger​ ​the​ ​forces​ ​between​ ​the​ ​particles​ ​the​ ​higher​ ​the​ ​melting point​ ​and​ ​boiling​ ​point​ ​of​ ​the​ ​substance.
      • When substances are heated, the particles absorb thermal energy which is converted into kinetic energy. 
      • Heating a solid causes its particles to vibrate more and as the temperature increases, they vibrate so much that the solid expands until the structure breaks and the solid melts.
      • On further heating, the now liquid substance expands more and some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate.
      • When the b.p. temperature is reached, all the particles gain enough energy to escape and the liquids boils.
      • While changing state, the temperature of the substance remains the same as the heat energy is rapidly converted into kinetic energy. This is called latent heat.
      Melting
      • Melting is when a solid changes into a liquid.
      • Requires heat energy which transforms into kinetic energy, allowing the particles to move.
      • Occurs at a specific temperature known as the melting point (m.p.) which is unique to each pure solid.
      Boiling
      • Boiling is when a liquid changes into a gas.
      • Requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid.
      • Occurs at a specific temperature known as the boiling point (b.p.) which is unique to each pure liquid.
      Freezing
      • Freezing is when a liquid changes into a solid.
      • This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same. Water for example freezes and melts at 0ºC.
      • Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance.
      Evaporation
      • When a liquid changes into a gas. Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the b.p. of the liquid.
      • The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate.
      • No heat is required and evaporation occurs over a range of temperatures.
      Condensation
      • When a gas changes into a liquid, usually on cooling. When a gas is cooled its particles lose energy and when they bump into each other, they lack energy to bounce away again, instead grouping together to form a liquid. 
      • No energy is required for condensation to occur and it takes place over a range of temperatures.
      Sublimation
      • When a solid changes directly into a gas.
      • This happens to only a few solids such as iodine or solid carbon dioxide.
      • The reverse reaction also happens and is also called sublimation (sometimes called deposition or desublimation).
      • Sublimation occurs at a specific temperature which is unique for a pure substance.
        2.4​ ​Predict​ ​the​ ​physical​ ​state​ ​of​ ​a​ ​substance​ ​under​ ​specified​ ​conditions, given​ ​suitable​ ​data

        • ○  at​ ​temperatures​ ​below​ ​the​ ​melting​ ​point,​ ​the​ ​substance​ ​will​ ​be​ ​solid
        • ○  at​ ​temperatures​ ​above​ ​the​ ​melting​ ​point​ ​but​ ​below​ ​the​ ​boiling​ ​point,​ ​the substance​ ​will​ ​be​ ​liquid
        • ○  at​ ​temperatures​ ​above​ ​the​ ​boiling​ ​point,​ ​the​ ​substance​ ​will​ ​be​ ​a​ ​gas



        ● if​ ​you​ ​are​ ​given​ ​the​ ​melting​ ​point​ ​and​ ​boiling​ ​point​ ​of​ ​a​ ​substance: The physical state of a substance under certain conditions can be predicted from a given set of data.


      • Normally you are given melting and boiling point data for a substance and asked to predict its physical state in specified conditions.

      • At temperatures below the melting point:
      The substance is will be in the solid state
      • At temperatures above the melting point:
        The substance will be in the liquid state
          • At temperatures above the boiling point:
          The substance will be in the gaseous state.






            • A boils at temperatures above -173ºC so at -1501 ºC A is a gas.
            • B melts at 1736ºC so at 50ºC it is a solid.
            • C melts at 1105ºC and boils at 1450ºC so at 1400ºC it is a liquid. 
            • D melts at 650ºC so at 400ºC it is a solid.


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            GCSE EDEXCEL - MIXTURES SEPARATION AND PURIFYING


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