Particles - C1
- Created on: 07-04-17 08:54
View mindmap
- Particles C1
- States of Matter
- Solids
- Strong forces of attraction between particles making them touch
- Definite shape and volume
- Regular lattice arrangement of particles
- Do not flow because the particles cannot move from place to place
- Cannot be compressed because the particles touch and have no space to move into
- Particles vibrate about their fixed positions - when heated, solids expand slightly due to the increase in energy
- Heat to become a liquid
- Liquids
- Keep the same volume
- Flow to take the shape of their container because the particles are free to move round each other
- Cannot be compressed because the particles are touching and have no space to move into - like a solid
- Irregular arrangement
- There is a force of attraction between the particles but it is weaker than that of a solid
- Particles vibrate as they constantly move randomly - when heated, liquids expand slightly due to the increase in energy
- Cool to become a solid
- Heat to become a gas
- Gases
- An extremely weak force of attraction between the particles making them free to move
- Travel in straight lines and only interact when particles collide
- Flow to take the shape of their container because the particles can move quickly in all directions
- Can be compressed because the particles are far apart and have space to move into
- No definite shape or volume
- Exert a pressure on objects they collide with
- Particles vibrate as they constantly move randomly - when heated, gas particles move faster and either expand, or their pressure increases
- Cool to become a liquid
- Limitations of the Particle Model
- In reality, the particles are not solid or spherical - they're atoms, ions or molecules
- Doesn't show the size of the particles or the space between them
- Doesn't show the forces between the particles
- Physical and Chemical Changes
- When a substance changes state,it's a physical change because no new substances are made
- Physical changes are easily reversible by heating or cooling
- During a chemical reaction, bonds between atoms break and the atoms from the reactants rearrange themselves to form the products
- Chemical changes are often hard to reverse
- Solids
- The History of the Atom
- John Dalton 1800s
- Described atoms as solid spheres and said that different spheres made up different elements
- J J Thomson 1897
- Concluded from his experiments that atoms weren't solid spheres
- HIs measurements of charge and mass showed that an atom contained negatively charged particles - electrons
- His new theory was known as the 'plum pudding model'
- Ernest Rutherford, Hans Geiger and Ernest Marsden 1909
- Conducted the famous gold foil experiment where they fired positively charged alpha particles at an extremely thin sheet of gold
- Rutherford came up with the nuclear atom theory where there is a positively charged nucleus at the centre, surrounded by a 'cloud' of negative electrons - most of the atom is empty space
- Niels Bohr
- Scientists discovered that Rutherford's theory would cause the atom to collapse
- Bohr proposed a new model where all the electrons are contained in shells
- He suggested that electrons can only exist in shells and each shell has a fixed energy
- The Bohr model is the closest to our currently accepted version of the atom
- John Dalton 1800s
- The Atom
- Made up of positively charged protons, neutral neutrons and negatively charged electrons
- The Nucleus
- In the middle of the atom
- Contains protons and neutrons
- Positively charged
- Almost the whole mass of the atom (between 10^-23g and 10^-21g) is concentrated in the nucleus
- Compared to the overall size of the atom, the nucleus is tiny (has a radius of between 10^-15m ad 10^-14m)
- The Electrons
- Move around the nucleus in electron shells
- Negatively charged
- They're tiny but their shells cover a lot of space
- The volume of their shells determines the size of the atom - the atomic radius is 10^-10m
- Electrons have virtually no mass
- Molecules
- Made up of two or more atoms
- Can be made of the same or different elements
- Simple molecules are tiny - the bonds that form between these molecules are 10^-10m
- Atoms, Ions and Isotopes
- Mass Number = Protons + Neutrons
- Atomic Number = Number of Protons
- Relative Atomic Mass = Mass Number
- Mass Number - Atomic Number = Number of Neutrons
- Ions
- Ions form when atoms gain or lose electrons
- Negative Ions form when atoms gain electrons
- Positive Ions form when atoms lose electrons
- Isotopes
- Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons
- Isotopes have the same atomic number but different mass numbers
- If they had different atomic numbers, they'd be different elements altogether
- States of Matter
Comments
No comments have yet been made