Topic 3 - chemical change Flashcards
What is an acid?
A substance with a pH less than 7
What ions do acids form in water?
H+ ions
What is an alkali?
A base that is soluble in water. pH more than 7
What ions do alkalis form in water?
OH- ions (Hydroxide ions)
What is the pH of a neutral solution?
pH 7
What is an indicator?
A dye that changes colour depending on whether it’s above or below a certain pH.
Explain the effect of acidic, neutral and alkaline solutions on litmus
Red in acidic, purple in neutral, blue in alkaline
Explain the effect of acidic, neutral and alkaline solutions on methyl orange.
Red in acidic, yellow in neutral and alkaline solutions
Explain the effect of acidic, neutral and alkaline solutions on phenolphthalein
Colourless in acidic and neutral solutions, pink in alkaline
What’s the effect of increasing the concentration of hydrogen ions in an acidic solution?
The solution becomes more acidic so the pH decreases
What’s the effect of increasing the concentration of hydroxide ions in an alkaline solution?
The pH increases so becomes a stronger alkaline.
What happens to the pH of a solution when hydrogen ion concentration is increased?
As hydrogen ion concentration increases by a factor of 10, the pH of the solution decreases by 1
What does concentrated mean for an acid?
An acid with a large number of acid molecules compared to the volume of water
What does dilute mean for an acid?
An acid with a small number of acid molecules compared to the volume of water.
What are strong acids?
Acids that ionise almost completely in water ie. a large proportion of the acid molecules dissociate to release H+ ions.