States of Matter

• Chemistry is the study of the structure and behaviour of

  matter.
• Matter has both mass and volume.
• A Greek philosopher called Democritus developed the

  idea that matter consisted of particles.
• Atoms are the building blocks of matter.
• The particulate theory of matter states that all matter is made of particles.
• The particulate theory of matter helps us to explain both the physical

  properties of matter and also the differences between the three states of matter.
• The particulate theory of matter has four main ideas:

  . all matter is made of particles

  . the particles are in constant, random motion

  . there are spaces between the particles

  . there are forces of attraction between the particles.
• Some physical phenomena that the particulate theory of matter explains are density, temperature, pressure, scent and surface tension.
• . The three states of matter that are

  the most common are the solid, liquid and gaseous states.
• The difference between these states lies in the energy and arrangement of the particles.
• Particles in the solid state have the least amount of energy, they simply

  vibrate in their fixed position and they are packed closely together.
• Particles in the liquid state have medium amounts of energy, they move about slowly and they have small spaces between them.
• Particles in the gaseous state have the greatest amount of energy, they move about rapidly and they have large spaces between them.
• The energy of the particles is directly related to the temperature of the

  particles and matter can change from one physical state to another by

  changing its temperature.
• Phase change occurs because increasing the temperature of a substance increases the kinetic energy of the particles in the substance. The greater the kinetic energy the particles possess, the faster they move.
• Increasing the temperature of a solid causes the particles to vibrate more vigorously until eventually some of the particles gain enough energy to break free from their positions and become part of the liquid phase.
• If the temperature continues to increase, the particles will continue to gain energy and eventually some of the particles in the liquid will be able to escape from the surface of the liquid and enter the gas phase.
• When all the particles in a sample of matter have gained sufficient energy to be able to escape from their fixed positions, then the entire sample will be converted into gas (the gaseous phase).
• A physical change occurs when the form of the substance is changed without changing its chemical composition.

  Example: water as a solid, ice, has exactly the same chemical particles as water in the liquid state and as water in the gaseous state, water vapour.
• Diffusion and osmosis which we can perform to provide evidence for the particulate theory of matter.
• Diffusion occurs because particles of matter are in constant motion and will move from a region of higher concentration to one of lower concentration.
• Osmosis is the movement of water molecules through a differentially permeable membrane from a region with a lot of water molecules to a region with fewer water molecules.
• A differentially permeable membrane is a membrane that allows some

  substances to pass through but not others.
• Two practical uses of osmosis are pest control and preserving foods.
• Physical properties are characteristics that can be observed or measured without changing the chemical composition of a substance.
• Shape, volume, density, compressibility, solubility, melting

  point and boiling point are all examples of physical properties.
• The different physical properties of the three states can be explained by the particulate theory of matter.
• We can use the arrangement of particles in the three states of matter to

  explain the physical properties of the different states.
• Solids have a fixed shape because their particles are arranged in a regular way and they are unable to move out of their fixed positions.
• Solids have a fixed volume and are very difficult to compress because

  their particles are packed very closely together and cannot be pushed

  any closer together.
• Liquids flow because their particles are able to move past each other.
• Liquids can be compressed slightly because their particles have small

  spaces between them enabling them to be pushed closer together.
• Gases take the shape and volume of the container they are in because

  their particles move freely and rapidly. They have only weak forces of

  attraction between them, therefore they spread out to fill any available

  space.
• Gases are easy to compress because their particles have large spaces

  between them, therefore they can be pushed closer together.
• Study Table

  
• Matter can be changed from one state to another by heating or cooling.
• A change of state is caused by a change in temperature and

  consequently a change in the kinetic energy of the particles.
• When a solid is heated, the particles gain kinetic energy and begin to vibrate more vigorously. Eventually the particles are able to overcome the strong forces of attraction between them and they move more freely and further apart forming a liquid.
• When a liquid is heated, the particles gain kinetic energy and move faster.

  Some of the particles near the surface of the liquid have enough kinetic

  energy to overcome the forces of attraction between them and are able to leave the liquid and become a vapour.
• When a liquid is heated its temperature eventually reaches a certain point where it starts to boil. At this point the liquid particles have gained enough kinetic energy and started to move fast enough to change into a gas both within the liquid and at its surface.