year 9 end of years Flashcards
what is an atom?
the smallest part of an element
what is a molecule?
a substance made of more than one atom
what is an element?
one type of atom on its own or joined to another atom of the same type
what is a compound?
different types of atom joined by a chemical bond
what is a mixture?
different types of atoms or compounds that can be physically separated (no chemical bond)
what is an atomic number and what does it represent?
the atomic number represents the number of electrons which is also the number of protons - it is normally the smaller bottom - on the bottom
what is a mass number?
the mass number is the sum of protons + neutrons - it is normally the bigger number - on the top
what is an isotope?
isotopes have the same atomic number but a different mass number (same amount of protons, different amounts of neutrons)
what does RAM stand for?
Relative Atomic Mass (it can also be written as a capital A with a small r)
what is relative atomic mass?
a formula (measuring the weight in grams of the number of atoms of the element)
what is the RAM formula?
(mass number x natural abundance) + (mass number x natural abundance) divided by 100
what is a solvent?
the liquid in which a solute is dissolved
what is a solute?
a substance that is dissolved in a solution
what is a solution?
formed when the solute and solvent mix
what is a saturated solution?
a solution that has dissolved as much as it is capable of dissolving
what is simple distillation?
the solution is heated until the substance with the lowest boiling point starts to evaporate. The vapour is cooled and condenses (turns back to liquid). This liquid is then collected, leaving the rest of the solution back in the original conical flask
what is fractional distillation?
this is the same as simple distillation, but the original solution is heated by an electrical heater
what is filtration?
filter paper is placed in a funnel above a beaker, the mixture of an insoluble solid and liquid is poured through which will only allow small liquid particles to pass through as filtrate. the solid particles are left on top
what is crystallisation?
the solution is heated, allowing the solvent to evaporate to leave a saturated solution, which is then allowed to cool and solids will come out of the solution and crystals will grow
what is paper chromatography?
a pencil line is drawn on chromatography paper, and spots of ink/dye are placed on it. Paper is lowered into solvent, allowing the solvent to travel up the paper, taking some of the coloured substances with it. Different substances have different solubilities so will travel at different rates, causing the substances to spread out
how does chromatography provide information about the composition of a mixture?
it shows how the mixture is made by showing the solubility of the different substances that make the mixture
how do you figure out the Rf value?
(distance travelled by component) divided by (distance travelled by the solvent)
does the Rf value have to be between 0 and 1?
yes
‘the smaller the Rf value, the more soluble the substance is’. Is this true?
no, it’s ‘the bigger the Rf value, the more soluble the substance is’