Bonding and Structure

• strong attractive forces between the particles in a substance make its melting and boiling point high. This is because more energy is needed to overcome these forces
• you can work out the state of a substance at room temperature or any other temperatures using its melting and boiling points
• when a substance melts, attractive forces between the solid particles are broken as the particles break away from the solid lattice and become liquid particles. The temperature remains constant until all these bonds are broken
• When a liquid build the particles overcome the attractive forces between the liquid particles to become a gas. The temperature stays constant at the boiling point until all these attractive forces are overcome
• The state of a substance at room temperature and pressure can be shown in a symbol equation by using the state symbol for the substance
• The state symbols are (s) for solids; (l) for liquids and (g) for gases. The extra symbol (aq) is for substances dissolved in water to give an aqueous solution
• The three states of matter can be represented by a simple model. This particle model can help to explain melting, boiling, freezing and condensing. The limitations:

  • The model assumes that the particles are spheres
  • Many particles are not spheres, e.g. polymers
  • In the model there are no forces between the particles, which is not correct!

  
• Which state matter could be described as having a fixed volume but no fixed shape?

  Liquid
• If a substance has a low melting point, what can you say about the forces of attraction between its particles?

  They are weak