Chemical Changes Flashcards
The pH scale is 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.
A neutral substance has
pH 7
What is an indicator?
An indicator is a due that changes colour depending on whether it’s about or below a certain pH
Some indicators contain
A mixture of dyes that mean they gradually change colour over a broad range of pH. These are called WIDE RANGE INDICATORS
What are wide range indicators useful for?
Estimating the pH of a solution
How can you electrically measure pH?
A pH probe attached to a pH meter can also be used to measure pH electronically
How to measure the pH of a solution using a pH probe?
The probe is placed in the solution you are measuring and the pH is given on a digital display as a numerical value meaning it’s more accurate than an indicator.
Acids and bases
Neutralise each other
An acid is a substance that
Forms aqueous solutions with a pH of less than 7. Acids form H+ ions in water.
What is a base?
A base is a substance with a pH greater than 7
What is an alkali?
An alkali is a base that dissolves in water to form a solution with a pH greater than 7. Alkalis form OH- ions in water.
Give the name and formula between acids and bases:
Neutralisation
Acid + base —> salt + water
Neutralisation between acids and alkaline:
H+(aq) + OH-(aq) —> H2O(l)
