Name: ___________________ ( ) Class: 2A Acid and Alkali Name: ___________________ ( ) Class: 2A

Acid rain Acidic gases dissolve with water droplets in clouds 2 Acidic gases dissolve with water droplets in clouds 3 Water droplets falls as acid rain 1 Acidic gases such as sulfur dioxide and oxides of nitrogen released into the air

Acid Rain Effects: Acidification of soil, ocean and sea Soil becomes acidic and affects growth of plants Sea creatures affected as sea and ocean becomes acidic Corrode buildings made of metal and calcium carbonate Loss of heritage buildings

Colour of universal indicator pH pH is a measurement of solution to determine if it is acid, alkali or neutral. Teacher’s demo with Universal indicator: Solution Colour of universal indicator pH Acid Alkali Water Use a colour chart for pH column

Acid and Alkali Place a piece of blue litmus paper and red litmus paper on a clean filter paper. Using dropper 1, place a drop of hydrochloric acid on both strips of litmus papers. Record your observation: Blue litmus paper: ________________ Red litmus paper: ________________

Acid and Alkali Place a piece of blue litmus paper and red litmus paper on a clean filter paper. Using dropper 2, place a drop of sodium hydroxide on both strips of litmus papers. Record your observation: Blue litmus paper: ________________ Red litmus paper: ________________

Acid and alkali pH 1-6: _________ pH 7: _________ pH 8-14: _________

Acid and alkali Universal indicator Litmus paper test 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acid Neutral Alkali Turn ______ litmus paper ______ Turn ______ litmus paper ______ Litmus paper test

Scenario Imagine you are an environmental consultant. Farmer Bob has a farm which has been experiencing poor plant growth over the past 2 years. He decided to consult you regarding this.

Identify problem You have been provided Sample X, a sample of the soil from the farm. Conduct necessary tests to determine the problem. Sample X: 2M HCl

Identify problem Place a piece of blue litmus paper and red litmus paper on a clean tile. Using dropper 3, place a drop of Sample X on both strips of litmus papers. Record your observation: Blue litmus paper: ________________ Red litmus paper: ________________ Conclusion: The soil is * acidic/alkali (circle the correct answer)

Recommendation Farmer Bob should add alkali solution to gradually increase the pH of the soil to pH 7. This process is called neutralisation.

Neutralisation Using a syringe, add 1 ml of soil sample X into a test tube. Put 2 drops of Universal indicator. (Colour of Universal indicator: __________) Shake the test tube. Using dropper 2, add sodium hydroxide drop by drop until it changes colour. Shake the test tube after every drop. After it changes colour, allow it to stand for 2-3 minutes. X: 2M HCl 2M NaOH

Neutralisation Results: No of drops needed: ____ Observation: Universal indicator changes colour from ______ to ______. After a few minutes, it changes colour to ______. Conclusion: Soil sample change from _________ to _________.

Conclusion For every 1 ml of soil, Farmer Bob should add ____ drops of sodium hydroxide to neutralise the soil.