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### States of Matter

1. LEARNING OUTCOMES  State evidence in support of the particulate nature of matter  Explain the differences between the three states of matter in terms of the arrangement of particles STATES OF MATTER Chapter 1
2.  Matter can exist in 3 states: solid, liquid and gas.  For example, water can exist as:  ice (solid state),  water (liquid state) and  steam or water vapour (gaseous state). STATES OF MATTER Chapter 1 States of Matter
3. States of Matter  The state in which a substance exists depends mainly on its temperature and pressure.  For example, iron is a solid at room temperature and pressure; but at around 1500 oC, it becomes a liquid.  Similarly, oxygen is a gas at room temperature and pressure, but at –183 oC, it is a liquid. STATES OF MATTER Chapter 1
4. Chapter 1 STATES OF MATTER Diffusion  Diffusion is the spontaneous movement of particles of a substance from a region of higher concentration to a region of lower concentration.  Diffusion occurs in all states of matter.  For solids, diffusion can be shown by placing a block of gold and a block of lead together. Some gold atoms will be found in the lead block and some lead atoms will be found in the gold block after a few years.
5. Chapter 1 STATES OF MATTER For liquids, diffusion can be shown by placing a drop of ink or a crystal of purple potassium manganate(Vll) into a beaker of water. Diffusion After some time, a uniform purple colour is seen throughout the beaker.
6. For gases, diffusion can be shown by setting up the apparatus shown below. 1.Soak a piece of swab with concentrated hydrochloric acid and insert it into one end of the glass tube. 2. Soak another piece of cotton swab with concentrated ammonia solution and insert it into the other end of the glass tube. 3. Seal both ends of the glass tube with rubber bungs and leave the tube horizontal. 4. After a few minutes, a white disc of ammonium chloride is formed. Diffusion STATES OF MATTER Chapter 1
7. Rate of diffusion  The speed of diffusion is fastest in gases followed by liquids and very slowly in solids.  The rate of diffusion increases with temperature.  At higher temperatures, the particles have higher kinetic energy and hence move faster and diffuse at a faster rate. At O oC At 2O oC The Three States of Matter Chapter 3
8. Rate of diffusion  The rate of diffusion also depends on the relative molecular mass of the particles.  Heavier particles will diffuse at a slower rate than lighter particles.  The rate of diffusion of a gas is inversely proportional to the square root of its relative molecular mass. The Three States of Matter Chapter 3
9. Chapter 1 STATES OF MATTER Osmosis Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane. It is a special type of diffusion carried out by plants to obtain water and mineral salts from the soil.
10. Differences between solids, liquids and gases A solid has a fixed shape and a fixed volume. A solid cannot be compressed. A liquid has a fixed volume but no fixed shape. A liquid cannot be compressed. A gas has neither fixed shape nor volume. A gas can be easily compressed. STATES OF MATTER Chapter 1
11. Differences in properties Solid Liquid Gas Particles are close together, but not tightly packed. Particles are very far apart. Particles are packed closely together in an orderly pattern. Solid particles can only vibrate in fixed positions but cannot move away from each other. Liquid particles can vibrate and move freely throughout the liquid. Gas particles can vibrate and move very freely and randomly in all directions. STATES OF MATTER Chapter 1
12. The Particle Theory  According to this theory, the particles in matter are in a state of constant motion due to their kinetic energy.  Gas particles of a substance have more kinetic energy than liquid particles, while liquid particles have more kinetic energy than solid particles.  Hence, gas particles can move much more freely and quickly than liquid particles, which in turn, can move more freely than solid particles.  Matter can be converted from one state to another by changing the amount of energy of the particles. If a matter gains heat energy, the particles will move faster and further apart, thus changing from a more orderly state to a more disorderly state.  Conversely, if heat energy is removed from a matter, the particles will slow down and move closer together, thus resulting in a more orderly state. STATES OF MATTER Chapter 1
13. Melting  Melting is the change from a solid to a liquid.  The temperature at which a solid melts is called its melting point.  A pure substance has a fixed melting point. E.g. The melting point of ice is 0 oC. Solid Liquid melting STATES OF MATTER Chapter 1
14. Melting point graph  During melting, heat energy is absorbed by the solid.  The temperature remains constant during melting because the heat absorbed is used to overcome the forces of attraction between the solid particles instead of using it to raise its temperature.  A melting point graph can be plotted for a solid which undergoes heating, and its melting point can be determined from the graph. Temperature/oC Melting point  solid state solid + liquid Liquid state Melting point graph STATES OF MATTER Chapter 1
15. Freezing  Freezing is the change from a liquid to a solid. It is the reverse of melting.  The temperature at which a liquid freezes is called its freezing point.  For most pure substances, the freezing point is the same as the melting point. E.g. The melting point of ice and the freezing point of water are both 0 oC. SolidLiquid freezing STATES OF MATTER Chapter 1
16. Freezing point graph  During freezing, heat energy is released (given out) by the liquid particles as they slow down and move closer together to take up the orderly positions of a solid.  The temperature remains constant during freezing because the heat given out compensates for the loss of heat to the surroundings.  A freezing point graph (or cooling curve) can be plotted, and the freezing point of the liquid can be determined from the graph. Temperature/oC Freezing point  solid statesolid + liquid Liquid state Freezing point graph STATES OF MATTER Chapter 1
17. Boiling  Boiling is the change from a liquid to a gas or vapour.  The temperature at which a liquid boils is called its boiling point.  A pure substance has a fixed boiling point. E.g. The boiling point of water is 100 oC under normal atmospheric pressure. Liquid boiling Gas STATES OF MATTER Chapter 1
18. Boiling point graph  During boiling, heat energy is absorbed by the liquid particles to change into a gas.  The heat energy absorbed is used to overcome the forces of attraction between the liquid particles and to increase their kinetic energy until they have sufficient energy to escape from the liquid.  The temperature of a liquid remains constant during boiling as the heat energy absorbed is used to increase the kinetic energy of the particles and not to raise its temperature. Boiling point  Liquid state Liquid + gas Gaseous state Boiling point graph STATES OF MATTER Chapter 1
19. Chapter 1 STATES OF MATTER Evaporation  Evaporation is the change from liquid into gas without boiling. E.g. A drop of ethanol or perfume evaporates at room temperature.  Evaporation occurs below its boiling point.  Evaporation only takes place at the surface of a liquid.  Evaporation takes place slowly.  Evaporation produces a cooling effect because heat energy is absorbed from the surroundings.
20. Condensation  Condensation is the change from a gas to a liquid. It is the reverse of boiling.  Heat energy is released (given out) during condensation as the gas particles slow down and move closer together to become a liquid.  The temperature of a substance remains constant during condensation since the heat given out compensates for the loss of heat to the surroundings. STATES OF MATTER Chapter 1
21. Sublimation  Sublimation is the change from a solid directly into a gas without melting.  For example, iodine crystals sublime into purple iodine vapour when heated. Solid Gas Iodine vapour Solid iodine Sublimation  Other examples of solids which sublime are dry ice, ammonium chloride and naphthalene. STATES OF MATTER Chapter 1
22. Summary Liquid Gas Solid Melting (energy absorbed) Freezing (energy released) STATES OF MATTER Chapter 1
23. Quick check 1 1. State whether heat energy is absorbed or released in each of the following processes: (a) melting, (b) boiling, (c) freezing, (d) condensation 2. State whether the speed of the particles increases or decreases during: (a) melting, (b) condensation, (c) boiling, (d) freezing 3. The information below gives the melting points and boiling points of four substances: Substance Melting point (oC) Boiling point (oC) W −123 −150 X −59 247 Y 98 597 Z 20 125 (a) For each substance, state whether it is a solid, a liquid or a gas at room temperature and pressure. (b) In which substance are the particles furthest apart at −60 oC? Solution Chapter 1 STATES OF MATTER
24. Solution to Quick check 1 1. (a) melting – heat absorbed, (b) boiling – heat absorbed, (c) freezing – heat released, (d) condensation – heat released 2. (a) melting – increases, (b) condensation – decreases, (c) boiling – increases, (d) freezing – decreases 3. Substance Melting point (oC) Boiling point (oC) W −123 −150 X −59 247 Y 98 597 Z 20 125 (a) W: gas, X: liquid, Y: solid, Z: liquid (b) W Return STATES OF MATTER Chapter 1
25. References  Chemistry for CSEC Examinations by Mike Taylor and Tania Chung  Longman Chemistry for CSEC by Jim Clark and Ray Oliver 25
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