pH Scale & Indicators
What pH number represents a neutral solution?
7
Acids taste ______ and alkalis feel ______.
Sour, slippery (soapy)
Which acid is found in vinegar?
Acetic acid
What are the products of acid + alkali reaction?
Salt and water
What should you always wear when handling acids or alkalis?
Safety goggles and gloves
What color does universal indicator turn in a strong acid?
Red
What element is found in all acids?
Hydrogen
Which weak acid is found in citrus fruits?
Citric acid
What type of reaction happens between an acid and an alkali?
Neutralisation
What does the “corrosive” hazard symbol mean?
It can burn skin or damage materials
What pH range represents a weak alkali?
8 to 10
Give two examples of alkalis.
Sodium hydroxide, potassium hydroxide, calcium hydroxide
Which acid is present in fizzy drinks?
Carbonic acid
Write the word equation for hydrochloric acid and sodium hydroxide.
Hydrochloric acid + sodium hydroxide → sodium chloride + water
What does the “toxic” symbol with a skull mean?
The substance can cause serious harm or death if swallowed or inhaled
What color does litmus paper turn in acid and in alkali?
Red in acid, blue in alkali
How can you identify an acid using litmus paper?
It turns blue litmus red
Name one alkali used in toothpaste.
Calcium carbonate or sodium bicarbonate
How does adding lime (calcium hydroxide) help acidic soil?
It neutralises the acid and makes the soil suitable for plants
Why is it important to read hazard labels on chemical bottles?
They warn users of potential dangers and how to handle chemicals safely
Why does the universal indicator show many different colors instead of just two?
It measures a full pH range from strong acids to strong alkalis
Why can strong alkalis be as dangerous as strong acids?
They are corrosive and can burn skin or materials
Why are alkalis used in oven cleaners and drain cleaners?
They dissolve grease and remove organic dirt effectively
In antacid tablets, which reaction occurs in the stomach?
The alkali in the tablet neutralises excess stomach acid
Explain what could happen if you mix strong acids and alkalis carelessly.
A violent reaction can occur, producing heat and splashes that cause burns