4. Chemical changes (pH scale and neutralisation of acids and bases) Flashcards
What is the pH scale, from 0 to 14, a measure of?
How acidic or alkaline a solution is
What does pH < 7 mean for the solution?
The solution is acidic
What does pH > 7 mean for the solution?
The solution is alkaline
What does a neutral substance have a pH of?
7
Give examples of neutral substances?
- Water
- Milk
- Cooking oil
What can be used to measure the pH of something?
- Universal indicator
- pH probe
What is an indicator?
A dye that changes colour depending on whether it’s above or below a certain pH
How does a universal indicator work?
- The universal indicator will change to a colour that is represents the pH of the solution
How does a pH probe work?
- A pH probe attached to a pH meter measures pH electronically
- The probe is placed in the solution you are measuring and the pH is given on a digital display as a numerical value
Which is more accurate, a pH probe or universal indicator?
pH probe
What is an acid?
a substance that forms aqueous solutions with a pH of less than 7
What is a base?
A substance with a pH greater than 7
What is an alkali?
A base that dissolves in water to form a solution with a pH greater than 7
What is the reaction between an acid and base called?
neutralisation reaction
When an acid neutralises a base, what pH are the products?
pH 7 - neutral
