Chemistry- Topic 3 Chemical Changes (Acids+ Alkalis) Summer Term Y9

what pH is acid

7 and under

what pH is alkali

7 and above

what pH is neutral

pH 7

Acid Indicators

• Red in UNIVERSAL

• Red in LITMUS

• Red in METHYL ORANGE

• Colourless in PHENOLPHALEIN

Alkali Indicators

• Purple in UNIVERSAL

• Blue in LITMUS

• Yellow in METHYL ORANGE

• Pink in PHENOLPHALIEN

Acids in solution produce…

Hydrogen ions (H⁺)

• hydrochloric acid - HCl

• sulfuric acid

• Nitric acid

Alkalis in solution produce…

hydroxide ions (OH^-)

• sodium hydroxide

• potassium hydroxide

what do stronger acids have

a higher concentration of hydrogen ions

are alkalis soluble

alkalis are soluble bases

neutralisation reaction

a reaction between and acid and a base

Acid / Alkali Neutralisation Reaction

reaction when hydrogen ions from the acid react with hydroxide ions from the alkali to form water

Base

-all metal oxides are bases

-soluble bases are alkali (but not all bases are alkali)

salt

when hydrogen ions are replaced by positive ions (cations)

CORE PRACTICAL - Investigating Neutralisation

calcium hydroxide+ hydrochloric acid → calcium chloride + water

• 0.3 g calcium hydroxide is continually added to 50 ml of hydrochloric acid and the pH is tested

• there will be a sudden change around neutral (7)

Acid + Metal

Acid + Metal → Salt + Hydrogen

test for hydrogen

light a splint over and there will be a squeaky pop if present

Acid + Metal Carbonate

Acid + Metal Carbonate → Salt + water + carbon dioxide

test for carbon dioxide

by bubbling it through lime juice which will turn cloudy if present

CORE PRACTICAL - Preparing Copper Sulfate

sulfuric acid + copper (ll) oxide → copper (ll) sulfate + water

• a water bath is used to speed up reaction between acid and base