Matter - P1

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  • Created on: 06-04-17 09:35
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  • Matter - P1
    • The History of the Atom
      • John Dalton 1800s
        • Proposed that all matter is composed of small, indivisible objects which he called atoms
        • Dalton concluded that atoms combined to form compounds
        • Built upon Ancient Greeks Democritus and Leucippus' ideas
      • J J Thompson 1897
        • Found out that atoms weren't solid spheres
          • Tiny negative electrons could be stuck in the positive spheres like 'plums in a pudding,' and the 'Plum Pudding Model' (or the 'Thomson model') was born
        • Thomson discovered that electrons can be removed from atoms
          • His measurements of charge and mass showed that an atom must contain smaller, negatively charged particles - ELECTRONS!
        • His measurements of charge and mass showed that an atom must contain smaller, negatively charged particles - ELECTRONS!
        • Tiny negative electrons could be stuck in the positive spheres like 'plums in a pudding,' and the 'Plum Pudding Model' (or the 'Thomson model') was born
      • Ernest Rutherford, Hans Geiger and Ernest Marsden 1909
        • Conducted the famous gold foil experiment
          • They fired positively charged alpha particles at an extremely thin sheet of gold
          • From the Plum Pudding Model, they expected the particles to pass straight through the gold sheet or only be slightly deflected
            • Most of the particles did go straight through the gold sheet but some were deflected more than they had expected and even deflected back the way they had come - something the Plum Pudding Model couldn't explain
              • They fired positively charged alpha particles at an extremely thin sheet of gold
              • Rutherford came up with the theory of the nuclear atom
                • In his model, most of the mass of an atom is concentrated in a tiny, positively charged nucleus at the centre
                  • This nucleus is surrounded by a 'cloud' of negative electrons - most of the atom is empty space
                    • Scientists then realised that electrons in a 'cloud' around the nucleus of an atom would be attracted to the nucleus, causing the atom to collapse
        • Rutherford came up with the theory of the nuclear atom
          • In his model, most of the mass of an atom is concentrated in a tiny, positively charged nucleus at the centre
            • This nucleus is surrounded by a 'cloud' of negative electrons - most of the atom is empty space
              • Scientists then realised that electrons in a 'cloud' around the nucleus of an atom would be attracted to the nucleus, causing the atom to collapse
      • Niels Bohr
        • Built upon Rutherford's model and solved the 'collapsing of the atom'
          • Proposed a new model where electrons are in shells and suggested that electrons can only exist in these shells and that each shell has a fixed energy
          • His theory is the closest to the modern day model of the atom
      • Atomic Structure
        • Basic Structure
          • The atom is a positively charged nucleus surrounded by negatively charged electrons
          • The nucleus contains positively charged protons and neutral neutrons which gives it an overall positive change
            • The atom is a positively charged nucleus surrounded by negatively charged electrons
          • Protons
            • Positively charged
            • Same size as a Neutron:    1 x 10^-15m
            • Found in the nucleus
          • Neutrons
            • Found in the nucleus
            • Same size as a Proton:      1 x 10^-15m
            • Neutral charge
          • Electrons
            • Found in the electron shells
            • Negatively charged
            • 1 x 10^-16m
          • Size of an atom: 10^-10m
      • Density (D)
        • Mass per Unit Volume
        • Measured in: g/cm³ or kg/m³
        • Useful Equations
          • D = M ÷ V
          • M = D x V
          • V = M ÷ D
        • A measure of how tightly packed and how heavy the molecules in an object are
        • The density of an object determines whether it floats or sinks. High density sinks, low density floats
        • Mass (M)
          • Measured in kg
          • Measure the mass of something using weighing scales
        • Volume (V)
          • Measured in m³
          • 1 cubic cm (cm³ or cc) = 1 ml
          • Cube            = w x l x h
          • Cylinder        = (Pir²) x h
          • Sphere         = 4/3 Pir³
          • Eureka (Archimedes) Can
            • Used to measure the volume of irregular objects
            • If the object floats, you cannot use this method
            • 1. Fill the eureka can with water up to just under the spout
              • 2. Place a measuring cylinder under the spout then gently lower the object into the can. The displaced water will start to come out of the spout
                • 3. Measure the volume of water collected in the measuring cylinder.This is the volume of the object
      • The Particle Theory
        • States of Matter
          • Solid
            • Strong forces of attraction hold the particles close together in a fixed, regular arrangement
            • The particles don't have much energy in their kinetic energy stores so they can only vibrate about their fixed positions
            • Melting does not dramatically alter volume because particles stay approximately same distance apart
            • HIgh density
          • Liquid
            • The forces of attraction between the particles are weaker. The particles are close together but can move past each other and form irregular arrangements
            • The particles have more energy in their kinetic stores than the particles in a solid - they move in random directions at low speeds
            • High density
            • Water is less dense as a solid than as a liquid
            • Evaporation increases volume dramatically because spacing between particles significantly increases
          • Gas
            • There are almost no forces of attraction between the particles
            • Particles have more energy in their kinetic energy stores than those in liquids and are free to move - travel in random directions at high speeds
            • Condensing decreases volume significantly because particle spacing dramatically decreases
            • Low density
            • The Pressure of Gases
              • As gas particles move about, they collide with each other and any objects in their way. When they collide with something, they exert a force on it
                • All these collisions cause a net force on the inside surface of the container. The force acting per unit on the area is pressue
              • Increased
                • The gas particles have more energy therefore they move and vibrate faster and the collisions become harder and more frequent
                • When the temperature is increased, the pressure also increases
                  • The gas particles have more energy therefore they move and vibrate faster and the collisions become harder and more frequent
              • Decreased
                • The gas particles  have less energy therefore they move and vibrate slower and the collisions are less hard and less frequent
                  • When the temperature is decreased, the pressure also decreases
                    • Decreased
                      • The gas particles  have less energy therefore they move and vibrate slower and the collisions are less hard and less frequent
                        • When the temperature is decreased, the pressure also decreases
            • The mass of a substance isn't affected when it changes state
          • There are three states of matter: solid, liquid and gas
          • The particles of a substance in each state are the same - only the arrangement and energy of the particles are different
          • If you reverse a change of state, the particles go back to how they were before, so physical changes are different from chemical reactions]
          • The energy in a substance's thermal energy store (Internal Energy) is held by its particles in their kinetic energy stores
          • When you heat a liquid, the extra energy passes into the particles' kietic energy stores, making them move faster. When the particles have enough energy to overcome their attraction, gas bubbles form in the liquid and it starts to boil
          • When you heat a solid, the extra energy makes the particles vibrate faster until the forces between them are partly overcome and the particles start to move around and the solid starts to melt
        • Specific Heat Capacity and Specific Latent Heat
          • Specific Latent Heat (L)
            • The energy needed to change the state of 1kg of a material
            • Measured in J/kg
            • Energy (J) = Mass (kg) x Specific Latent Heat (J/kg)
            • Of fusion: The specific latent heat for melting or freezing
            • Of vaporisation: The specific Latent Heat for boiling or condensing
          • Specific Heat Capacity (SHC)
            • The energy required to heat up 1kg of a material by 1°C
            • The larger the SHC the more energy it takes to heat up
            • Energy (J) = SHC (J/kg°C) x Mass (kg) x Temperature Change (°C)
            • Measured in J/kg°C

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