2a Flashcards
(24 cards)
whats the mass number?
number of protons and neutrons
whats the atomic number?
number of electrons
what is a compound?
two or more compounds that are chemically bonded
what is an isotope?
a different form of the same element which have the same number of protons but a different number of electrons
what is ionic bonding?
where atoms lose or gain electrons to form ions which are strongly bonded to each other
what are the properties of ionic compounds?
- high melting/boiling points
- carry an electric current
- dissolve in water
what type of ion do the elements in group 1 form?
positive ions
what type of ion do the elements in group 7 form?
negative ions
what is covalent bonding?
where atoms share electrons with each other so that they both have full outer shells
what are the two types of covalent substances?
simple molecular and giant covalent
3 examples of simple molecular substances
chlorine, oxygen and water
3 examples of giant covalent structures
diamond, graphite and silicon
why are alloys harder than pure metals?
because they have different sized atoms, making it more difficult for them to slide over each other
what is a ‘smart’ material?
a metel alloy that changes shape and then returns to its original shape when heated
what are nanoparticles?
really tiny particles that contain a few hundred atoms
what is using nanoparticles known as?
nanoscience
what is the difference between thermosoftening and thermosetting plastic?
thermosoftening- individual chains of polymers held together by weak intermolecular forces
thermosetting- strong intermolecular forces between the polymer chains called cross link, they hold the chains firmly together.
what is relative atomic mass?
the relative atomic mass (Ar) is the same as the mass number of the element
what is the relative formula mass?
all the relative atomic masses added together.
what is the relative formula mass of a substance known as?
Moles
number of moles=
mass in grams/ relative formula mass
what three factors can reduce the percentage yield of a reaction?
- the reaction is revisable, therefore the reactants will never be completely converted
- when you filter a liquid, you remove solid particles, you will lose a bit or liquid or solid
- there many be unexpected reactions which use up the reactants.
explain how paper chromatography can be used to analyse the dyes used in a brown sweet
- extract the colour and put with a solvent (water, ethanol, salt)
- put spots of the coloured solution on the pencil baseline on the filter paper
- roll up the sheet and put it in a beaker with the solvent
- the solvent will seep up the paper, taking the dye with it
- different dyes form spots in different spaces
how does gas chromatography work?
gas chromatography can separate out a mixture of compounds and help to identify the substances present.
