compounds and mixtures

Question 1

what are word equations?

Answer 1

Eg - sodium + water —> sodium hydroxide + hydrogen

Question 2

what is a reactant?

Answer 2

the starting materials of a reaction

Question 3

what is a product?

Answer 3

what is made in a reaction

Question 4

what are symbol equations?

Answer 4

Eg - Na + Cl- —>NaCl

Question 5

what are pace filler diagrams?

Answer 5

drawing of what happens during a reaction

Question 6

what happens to atoms during a reaction?

Answer 6

no atoms are created or destroyed just rearranged

new substances are formed

Question 7

what is an exothermic reaction?

Answer 7

when heat is released and temperature increases during a reaction

Question 8

what is an endothermic reaction?

Answer 8

when heat is absorbed and temperature decreases during a reaction

Question 9

what is a compound?

Answer 9

a substance made up of different atoms that are chemically joined together

Question 10

what is a mixture?

Answer 10

a mixture of substances not joined together

Question 11

how do you balance an equation?

Answer 11

have the same number of atoms on each side of the arrow

remember: you cannot change the formula only add numbers in front of it

Question 12

what can be observed in a chemical reaction

Answer 12

effervescence
colour change
temperature change

Question 13

what are the state symbols?

Answer 13

(S) - solid
(L) - liquid
(G) - gas
(AQ) - aqueous

Question 14

what is an aqueous?

Answer 14

dissolved in water

Question 15

describe filtration

Answer 15

example: sand and water
sand particles are larger than water particles.
Therefore, the holes in the filter paper are big enough to let water particles through but not sand particles

Question 16

describe evaporation

Answer 16

example: salt from salty water
water boils at 100* and leaves the salt behind
evaporate half with Bunsen burner and leave the other half to evaporate itself

Question 17

describe distillation

Answer 17

example: alcohol from alcohol/water solution
water boils at 100* and alcohol boils at 78*. Alcohol boils first, it cools and condenses back to liquid and is collected over the other side and the water boils eventually

Question 18

describe chromatography

Answer 18

example: separating coloured dyes in an ink
spot of dye is placed on a pencil line drawn at the bottom of chromatography paper.
paper is placed in water
as solvent soaks up paper and colour separates out
this is because the more soluble the substance is the further it will travel up the paper

Question 19

note that…

Answer 19

if the ink is insoluble the spot will not move up the paper
in this case a different solvent must be used

if the amount of water is above the spot it will not rise it will dissolve in the water

to find the spots original colour you must submerge the whole chromatogram into the solvent so that the different inks dissolve back into the liquid and mix back together

Question 20

how do you work out the Rf in value?

Answer 20

distance travelled by the spot
_______________________
distance travelled by solvent from the starting line