Handle acid with care!

Some everyday things that contain acids

In fact, we even have acid in our stomach!!!

What properties do acids have in common? Sharp and sour taste. Corrosive pH less than 7

What is the meaning of acids? An acid is a substance that produces ___________ when it dissolve in water. hydrogen ions,H+

Acids only produce hydrogen ions in water. without water water Acids only produce hydrogen ions in water. Acids only show the properties of acids when they are dissolved in water.

This is because acids ionise in water. add water It is the hydrogen ions which are responsible for acidic properties.

HCl H2SO4 HNO3 H+ and Cl- H+ and SO42- H+ and NO3- Common acids: Formula: Ions produced: Hydrochloric acid HCl H+ and Cl- Sulphuric acid H2SO4 H+ and SO42- Nitric acid HNO3 H+ and NO3-

What is the pH Scale? A scale which measures the degree of acidity or alkalinity of an aqueous solution. Ranges from 0 – 14.

pH of some common substances: 1 2 3 4 5 6 7 8 9 10 11 12 13 pH = 14 pH = 0 Increasing Acidity Alkalinity Neutral HCL Lemon Juice , Vinegar Orange Juice Acid Rain Urine Soft drink, Black Coffee “Pure water” Ammonia Sea water Baking Soda Soap Detergent Sodium hydroxide

Solutions of pH less than 7 is acidic. 1 2 3 4 5 6 7 8 9 10 11 12 13 pH = 14 pH = 0 Solutions of pH less than 7 is acidic. The smaller the pH, the more acidic. HCl Soft drink Solution of pH 7 is neutral “Pure water” Solutions of pH greater than 7 is alkaline. The bigger the pH, the more alkaline. Detergent Sodium hydroxide

Indicator –is a chemical compound that is added in small amounts to a solution so that the pH (acidity or basicity) of the solution can be determined visually. Common pH indicators: Universal Indicator Litmus paper Phenolphthalein Methyl orange Different colours are observed in solutions depending whether it is:- acidic alkaline.

Type of Reactions of Acids: reacts with 1. Metals 3. Metal Oxides And Hydroxides (Neutralisation) 2. Carbonates

Summary (a) Acid and Metal metal + acid  salt + hydrogen (b) Acid and Carbonate carbonate + acid  salt + water + carbon dioxide (c) Acid and Metal Oxide/ Hydroxide (Neutralisation) acid + base  salt + water

Not done yet! So,what are the common alkalis used in our daily life?

Some everyday things that contain alkali

Perming solutions contain alkali which makes hair curly

What properties do bases have in common? pH >7 Bitter taste. Soapy feeling to the skin.

What is the meaning of bases? solution of hydroxide ions, OH-are produced when bases dissolve in water. NaOH  Na+ + OH- Ca(OH)2  Ca2+ + 2OH –

Bases reactions BASES 1. Acids 2. Ammonium (Neutralisation) Salts reacts with 1. Acids (Neutralisation) 2. Ammonium Salts

1. Neutralisation reaction Bases reacts with an acid to produce a salt and water ACID + BASE --> SALT + WATER HCl + NaOH -----> NaCl + H2O

Importance of pH: pH of soil pH of tank pH of food

pH & Agriculture pH of soil Excess acid in the soil can be neutralised by adding calcium hydroxide (slaked lime). Farmers spread calcium hydroxide powder over their fields to neutralise acids.

The main active ingredient in household cleaning fluids. CHEMICAL NAME FORMULA DISSOLVE IN WATER FOUND IN/USED FOR Sodium hydroxide NaOH Yes Alkali pH 13 Used to make soap. Ammonia NH3 pH 10 The main active ingredient in household cleaning fluids. Calcium Ca(OH)2 Used in agriculture to neutralise acidic soils. Aluminium Al(OH)3 No Base Used in some indigestion tablets.