chemistry

• what is a molecule 


  a molecule is a substance that contains two or more atoms held together
• what is the change of an electron

  negative 1 or -1
• name the particles that are found in the nucleus of an atom

  protons and neutrons
• why do atoms have a neutral charge

  because they have the same number of posotive protons an negative electrons so the charges cancel out
• what is a mixture 


  a mixture is a group of different eliments or compounds which are not chemicley bonded together
• what is the charge of a neutron

  neutral or 0
• what is the overall charge of an atom

  neutral or 0

  (if an atom does have a positive or negative charge- it's not an atom its an ion)
• what does the mass number of an atom tell you

  the total number of protons + neutrons the atom has
• do compounds have the same properties as the atoms they're made from

  no, they have different properties
• what is the charge of a proton

  positive 1 or +1

  (you can remember it as P for Proton and P for Positive)
• what is a compound

  a compound is a substance formed from two or more eliments where the atoms of each are in fixed positions/ proportions and are held together by chemical bonds
• what does the atomic number of an atom tell you

  the number of protons the atom has.

  (it allso tells you the number of electrons it has but only if it is a neutral atom - if the atom has a charge it's an ion and the atomic number wont tell you the number of electrons)
• what is the relative mass of a proton

  1
• How can you use the atomic number and mass number of a given atom to work out how many neutrons it has 


  number of neutrons= mass number - atomic number
• what is the relative mass of an electron

  in exams you can say 0,1/2000 or negligible
• what is the relative mass of a neutron

  1
• what is diffution 


  diffution is the gradual movement of particles from places where there are lots of them (high consentration) to places where there are fewer of them (low consentration)
• true or false 


  true- most of the solvents you'll come across will be liquids
• what is a solution

  a mixture is a solute and a solvent that doesn't separate out
• what is the relative charge of a neutron? what is its relative mass?

  a neutron's relative charge is 0. remember, neutrons are neutral. the relative mass of a neutron is 1
• true or falce? most of the mass of an atom is located in the nucleus

  true. electrons have a tiny mass (virtually none at all)
• what is it meant by the term Isotopes

  Isotopes are different atomic forms of the same eliment which have the same number of protons but different numbers of neutrons
• in chemistry what is the definition of a pure substance

  a pure substance is completely made up of a single element or compound
• what is it meant by the term element

  an eliment is a substance that consists of only one type of atom (i.e. all its atoms have the same atomic number)
• true or falce? mixtures can be separated out by physical methods

  true. there are no chemical bonds between the diferent parts of a mixture, so they can be separated out physically
• when can filtration be used to separate a mixture

  filtration can be used when you have a mixture of an insoluble solid and a liquid
• when is crystallisation used to separate a mixture

  crystallisation is used to separate a soluble solid from a solution
• true or falce? water is always used as a solvent in paper chromatography

  false- the solvent used depends on what is being tested. you need a solvent that will dissolve the compounds you are investigating
• why should you put a lid on the container during a paper chromatography experiment

  a lid helps it to stop from evaporating
• in paper chromatography, what is a chromatogram

  a pattern of spots formed as a result of separating a mixture using paper chromatography
• true or falce? a pure substance produces two spots during paper chromatography 


  falce - a pure substance isent separated by paper chromatography - it moves as one spot
• in fractional distilation where is the hottest point of the fractionalising column

  the bottom of the fractionalising column is the hottest
• true or false? simple distillation can be used to separate a mixture of substances whith very diferent boiling points

  true. if the substances in the mixture have very similar boiling points, however, fractional distillation could be used instead