CHEMISTRY chem skills Flashcards
Why do substances have differing melting points?
The substance has a higher/lower melting/boiling point because more energy is required to overcome the
attraction
what happens when a substance melt?
energy is needed to overcome the attractions between particles in the solid.
What does a higher melting point mean?
there is more energy needed to overcome the attraction
what does insoluble mean?
Unable to disolve
What would slow evaporation do?
large crystals gained
what is sieving and what does it do
separates different sized solids to remove smaller particles
what method separates insoluble solids from liquids?
filtration
What is needed to be done after filtration and why (2)
washing
- removes impurities
- ensures all product gets washed into filtrate
What does evaporation do?
separates soluble solids form liquids
when evaporating how do you form large crystals (2 steps)
by heating the solution to remove 2/3 of the solvent
then allowing it to slowly evaporate on a window ledge
how do you ensure its completely dry (2 ways)
- continually heat until there is a change n mass
- leave to evaporate until there is no change in mass
what does fractional distillation do
separates liquids with different boiling points from each other
name 4 parts of fractional distillation
- round bottom flask
- leibig condenser
- condenser
- thermometer
what is the residue in filtration
solid that gets stuck in the filter paper
what is the filtrate in filtration
liquid that went through the filter paper
name 5 labels of evaporation
- solvent vapour
- solution
- gauze
- evaporating basin
- heat
define an atom
smallest building blocks of everything
what is a substance made of only one type of atom
element