NEUTRAL

Chemical reaction to make... Use a neutralisation Chemical reaction to make... ? UNKNOWN DISCOVER

Mixing a strong acid and a strong base What happens when a strong acid and a strong base are mixed? ? Mixing an acid and a base causes a chemical change. This chemical change is called a chemical reaction. How do you know this chemical reaction has taken place?

1. Measure 5 cm3 hydrochloric acid (1 1. Measure 5 cm3 hydrochloric acid (1.0MHCl) pour into evaporating dish – test pH using 2 drops of universal indicator solution, note down observation and pH 2. Rinse the measuring cylinder with distilled water. Measure 5 cm3 sodium hydroxide (1.0MNaOH) – test pH using 2 drops of universal indicator solution, note down observation and pH. 3. Add NaOH to evaporating dish with the acid. 4. Gently mix the solutions with the stirring rod for 1 minute What is the pH and color after mixing? 5. Place the evaporating dish on the gauze. Light the Bunsen burner. Make sure the Bunsen burner is directly below the evaporating dish. 6. Heat very gently until all the liquid has evaporated. The hot liquid may ‘spit’. How can you do this safely? 7. When all the liquid has evaporated, turn off the Bunsen burner. Be careful not to touch any of the equipment, WHY? What is left? 8. Add 2 drops of universal indicator liquid to the substance. What color did it turn? and what is the pH?

Colour of universal indicator Results/Observation Chemicals to test Colour of universal indicator pH Hydrochloric acid Sodium hydroxide Solution obtain from mixing acid and base Substance from step 8

Neutralisation is a very clean process… We take an acid and base… And just get a salt and water. Let the water evaporate and we’ll just be left with the crystallised salt… …as long as we start with just the right amount of acid and base so neither is left over.

Definition A neutralisation reaction between a strong acid and a strong base is where the acid reacts with the base to produce a neutral solution of a salt and water. sodium hydroxide pH 14 neutralisation sodium chloride pH 7 hydrochloric acid pH 1

All these will neutralise an acid Type of compound Contain React with acids to give Metal Hydroxides Metal Oxides Metal Carbonates OH- water + a salt O2- water + a salt CO32- water + a salt + CO2

Uses of sodium chloride salt Sodium chloride is used: As table salt. To preserve meat and vegetables.

SUMMARY Acids Bases Red Neutralization Purple 1 14 Water Salt Green React with Bases Change universal indicator to Change universal indicator to By Red Neutralization Purple Which represent a pH value of To produce Which represent a pH value of 1 14 Water Salt Which is use for Change universal indicator to Change universal indicator to Green Preservation Green Which represent a pH value of Which represent a pH value of 7 7

Evaluation Question 1: a. Name the acid reactant in your experiment. 1mrk b. Name the base reactant in your experiment. 1mrk Question 2: a. Explain what neutralisation means. 3mrks b. State the neutral products you have ended up with? 2mrks Question 3: a. Besides bases, state another chemical that can neutralize an acid? 1mrk b. State the products from this reaction? 3mrks

Evaluation Question 4: a. What did you observe about the colour after mixing the acid with the base? What does this tell you about the solution? 2mrks b. When 2 drops of universal indicator was added to the substance in step 8, what did you observe about the colour of the indicator? What does this tell you about the substance made? 2mrks c. State two uses of sodium chloride salt. 2mrks

Answers Neutralisation Question 1: a. Name the acid reactant in your experiment. Hydrochloric acid b. Name the base reactant in your experiment. Sodium hydroxide Question 2: a. Explain what neutralisation means. Neutralisation is the chemical reaction that takes place when an acid reacts with a base. New chemicals are made which are neutral. b. State the neutral products you have ended up with? sodium chloride water Question 3 a. Besides bases, state another chemical that can neutralize an acid? b. State the products from this reaction? Metal Carbonate Salt, water and carbon dioxide gas.

Answers Neutralisation Question 4 a. What did you observe about the colour after mixing the acid with the base? What does this tell you about the solution? b. When 2 drops of universal indicator was added to the substance what did you observe about the colour of the indicator? What does this tell you about the substance made? The solution/substance went green, meaning that there was no base or acid left over, just the neutral products. c. State two uses of sodium chloride salt. Sodium chloride is used as table salt and to preserve meat and vegetables.