Identifying Acids and Bases

Observations:
Table 1: Colour Change with Indicators for a Strong Acid, a Strong Base, and Water
Materials
pH paper
Red litmus Blue
Phenolphthalein Bromothymol
(colour and paper (red litmus
(colourless or blue number) or blue) paper (red pink)
(colour?)
or blue)
HCl
Light
Red:
Blue: turns Colourless
It turns orange #3 stayed red red orange (acidic)
(acidic)
NaOH
Dark blue: Red: turns Blue: stays Bright pink
Coulour, blue
#13
blue blue (basic)
(basic)
water
Green #7
Red:
Blue:
Colourless
Colour, blue stayed red stayed blue
(neutral)
(neutral)

Table 2: Colour Change with Indicators and Household Products
Materials
pH paper
Red litmus Blue
Phenolphthalein
paper litmus paper
Milk of
Dark green Red: turns Blue: stays Pink magnesium #10 blue blue
(basic)
(basic)
Seven up
Light
Red: stays Blue: turns Colourless orange #3 red red (acidic)
(acidic)
Borax
Green #10 Red: turns Blue: stays Pink blue blue
(basic)
(basic)
Vinegar
Light
Red: stays Blue: turns Colourless orange #3 red red (acidic)
(acidic)
Lemon juice Dark
Red: stays Blue: turns Colourless orange #2 red red (acidic)
(acidic)
Skim milk
Yellow #6 Red: stays Blue: turns Colourless red red
(acidic)
(acidic)

Bromothymol blue Colour, dark blue Colour, yellow Colour, blue

Colour, yellow Colour, yellow Colour, dark green Discussion:
1.What is the purpose of an indicator? [ 2 marks]
The purpose of an indicator is to identify whether a substance is acidic, basic, or neutral. Indicators can tell how basic or acidic a substance is on a scale of 0 to 14. The lower the number the more acidic the substance is and the higher the number the more basic the substance is. Indicators are very useful for finding and adjusting the pH level of substances. 2.What is meant by a "positive test"? [2 marks]
A positive test means that the substance in which