chemistry p1

• the mass of electrons is very small - almost 0, so its not included in the mass number of an atom
• isotopes are atoms of the same element with the same number of protons but a different number of neutrons
• how to work out relative atomic mass from isotope abundances:

  (% of isotope 1 x mass of isotope 1)

  +

  (% of iso2 x mass of iso2)

  divided by 100
• the three separation techniques are distillation, crystallisation and filtration
• filtration is used to separate insoluble solids from a solvent
• distillation is used to seperate liquids that have different boiling points
• crystallisation is used to separate solutes from their solvents
• when an alkali metal is added to water it forms a metal hydroxide and hydrogen
• the word equation for burning magnesium in oxygen is magnesium + oxygen -> magnesium oxide + heat
• a solution is a homogenous mixture where one substance has dissolved into another
• Alkali Metals React with Water

  2Na + 2H2O → 2NaOH + H2
• Alkali Metals React with Acids

  Metal + Acid → Salt + Hydrogen
• Magnesium Reacts with Hydrochloric Acid

  Mg + 2HCl → MgCl2 + H2
• What is the product of the reaction between Magnesium and Hydrochloric Acid?

  Magnesium Chloride and hydrogen
• potassium is more reactive than lithium as its outer electron is further away from the nucleus and therefore easier to be lost
• ionic compounds can conduct electricity as a liquid but not as a solid as in a solid the electrons are stuck in a lattice shape and therefore unable to move and carry charges
• the transition metals are good conductors of thermal and electrical energy because they have delocalised electrons
• compared with the alkali metals, transition elements have much higher melting points
• transition metals are stronger and more dense than alkali metals, but less reactive
• many transition metals are catalysts for chemical reactions
• one nanometre is 1 x 10^-9 metres
• depending on their size, particles can be called nanoparticles, fine particles or coarse particles
• particulate matter


  particles in the air, such as pollen or dust
• a micrometre is 1 x 10^-6 metres
• nanoparticles have diametres between 1 and 100nm
• fine particles have diametres between 100 and 2500 nm
• coarse particles have diametres between 2500 and 100000nm (10um)
• coarse particles are often called dust
• nanoparticles are more reactive as they have a higher surface area to volume ratio, so more atoms are at the surface
• nanoparticles are used in skincare or deoderant as they are absorbed deeper into the skin
• nanoparticles are used in suncreams as they are more effective at blocking the suns rays than normal particles
• in medicine,

  buckminster fullerenes are used to deliver drugs in the body

  coatings of nanoparticles on wounds helps protect against bacteria
• nanotubes are used in computers, or to strengthen materials for sports equipment
• the large surface area of nanoparticles makes them very effective as catalysts
• nanoparticles have risks as they have unpredictable effects on cells and breathing them in could cause lung damage
• if nanoparticles enter the environment this could cause damage to the aquatic life
• the yield of a chemical process is how much you actually make
• a reaction that has a high percentage yield means it's efficient because most of what was reacted produced the desired product
• a reaction with a low percentage yield means its not so efficient because there were many side reactions which wasted some of the starting material
• percentage yield = (actual mass of product / maximum theoretical mass of product) x 100