TOPIC 4 - Chemical Changes Flashcards
What is the PH scale?
A measure of how acidic or alkaline a solution is.
The lower the PH of a solution, the more…
Acidic it is.
The higher the PH of a solution, the more…
Alkaline it is.
What does a neutral substance have a PH of?
- E.g. Pure water.
What is an indicator?
A dye that changes colour depending on whether it’s above or below a certain PH.
What are wide range indicators?
Substances that gradually change colour as PH changes.
How can you measure PH electronically?
You put a PH probe attached to a PH meter and put it in the solution so the PH will be shown as a number - it is more accurate than an indicator.
What happens when acids dissolve in water?
They form solutions with a PH of less than 7.
What are Alkalis?
Bases that dissolve in water to form solutions with a PH greater than 7.
What do acids form in water?
H+ ions.
What do Alkalis form in water?
OH- ions.
What is the reaction between acids and bases called?
Neutralisation.
What is the product of neutralisation reactions?
7 - they are NEUTRALised.
Give the word equation for a neutralisation:
Acid + base —> salt + water.
What colour are acids under the PH Scale?
Red.
