1. Indicators were identified with the observation that the colour of some flowers depends on soil composition
Students learn to:
* Classify common substances as acidic, basic or neutral
The most common method to test whether a substance is acidic, basic, or neutral is with litmus paper. As the litmus paper makes contact with a substance, its colour changes. If the litmus turns red, the substance is acidic. If the litmus turns yellow, it is neutral and if the litmus turns blue, it is basic.
* Identify that indicators such as litmus, phenolphthalein, methyl orange and bromothymol blue can be used to determine the acidic or basic nature of a material over a range, and that range is identified by change in indicator colour
Indicators such as litmus, phenolphthalein, methyl orange and bromothymol blue can be used to determine the acidic or basic nature of a material over a range, and that range is identified by change in indicator colour.
* Litmus: Red = Acidic, Yellow = Neutral, Blue = Basic
* Methyl Orange: Red – pH <2.9, Orange – pH >4.0
* Bromothymol blue: Yellow – pH <6.0, Blue – pH = 7.10, Dark Blue – pH >7.2
* Phenolphthalein : Colourless –pH <8.3, Fuchsia – pH >10
* Identify and describe some everyday uses of indicators including the testing of soil acidity/basicity
Acid-base indicators can be used for a variety of uses such as:
* Chemical research
* Testing the acidity of water
* Testing the acidity of soil
Chemical research:
In chemical laboratories, acid-base indicators are used to test whether a substance is acidic, basic or neutral and to monitor the change in acidity during volumetric analysis when an acid is used to neutralize a base.
Testing the acidity of water:
Indicators can be used to monitor the pH of water. The most useful indicator is the universal indicator. As the universal indicator is dropped into the water, a colour change occurs. If the colour changes...