Chemical Changes

Question 1

Acid definition

Answer 1

Substance with pH less than 7
Forms hydrogen ions in water
Higher concentration of hydrogen ions = lower pH

Question 2

Base definition

Answer 2

Substance that reacts with acid to produce salt and water

Question 3

Alkali definition

Answer 3

Base that is soluble in water
pH is more than 7
Forms hydroxide ions in water
Higher concentration of hydroxide ions = greater pH

Question 4

indicator definition

Answer 4

dye that changes colour depending on pH of surroundings

Question 5

Litmus as an indicator

Answer 5

acidic - red
neutral - purple
alkaline - blue

Question 6

methyl orange as an indicator

Answer 6

acid - red
neutral - yellow
alkaline - yellow

Question 7

phenolphthalein as an indicator

Answer 7

acid - colourless
neutral - colourless
alkaline - pink

Question 8

dissociation definition

Answer 8

when compounds split up to make ions when dissolved

also ionisation

Question 9

strong acid definition

Answer 9

acids that ionise almost completely in water

pH 0-2

Question 10

weak acid definition

Answer 10

do not fully ionise in solution (smaller proportion of acid molecules release hydrogen ions)
pH 2-6
ionisation is reversible

Question 11

acid strength definition

Answer 11

proportion of acid molecules that ionise in water

Question 12

concentration of an acid definition

Answer 12

how much acid there is in a set volume

Question 13

how concentration affects pH

Answer 13

if concentration increase by factor of 10, pH decreases by 1

if concentration decreases by factor of 10, pH increases by 1

Question 14

salt definition

Answer 14

ionic compound formed during a neutralisation reaction

Question 15

MASH

Answer 15

Metal + Acid -> Salt -> Hydrogen

Question 16

BASHO

Answer 16

Base + Acid -> Salt + H2O

Question 17

CASHOCO

Answer 17

Carbonate + Acid -> Salt + H2O + CO2

Question 18

How to test for hydrogen

Answer 18

Hold lit splint in gas

If squeaky pop is made, hydrogen is present

Question 19

How to test for carbon dioxide

Answer 19

Bubble gas through limewater

If limewater turns cloudy, carbon dioxide is present

Question 20

sodium salts solubility

Answer 20

soluble

Question 21

potassium salts solubility

Answer 21

soluble

Question 22

ammonium salts solubility

Answer 22

soluble

Question 23

nitrate salts solubility

Answer 23

soluble

Question 24

chloride salts solubility

Answer 24

soluble except:
silver chloride
lead chloride

Question 25

sulfate salts solubility

Answer 25

soluble except:
lead sulfate
barium sulfate
calcium sulfate

Question 26

carbonate salts solubility

Answer 26

insoluble except:
sodium carbonate
potassium carbonate
ammonium carbonate

Question 27

hydroxide salts solubility

Answer 27

insoluble except:
sodium hydroxide
potassium hydroxide
ammonium hydroxide

Question 28

how to make insoluble salts w/ method

Answer 28

Pick right 2 soluble salts and react them together
Dissolve reactants and mix together in a beaker
Filter out precipitate by pouring beaker into filter paper
Swill out remaining contents in beaker using deionised water and filter
Rinse contents of filter paper with deionised water
Scrape precipitate onto fresh filter paper and leave to dry

Question 29

how to make soluble salts w/ method

Answer 29

React right acid with an insoluble base or metal
Heat acid to speed up reaction in a fuse cupboard
Add base to acid and keep adding base until there is an excess of base
Filter excess solid
Gently heat solution then leave to dry
Salt should eventually crystallise