Kia Ora
In science we were testing the pH scale colours, and we were adding in sodium hydroxide to create the pH scale colours. We started off at red, which was just sulfuric acid. To make red we added Universal indicator, which went red. When the sulfuric acid and Universal indicator went red, it was showing that the solution was an acid with a pH of 1. At this point there was lots more H+ ions than OH- ions, and the solution was a strong acid.
As we added a little bit of sodium hydroxide (NaOH) the colour started to change to orange. As it was changing to orange the pH scale was changing, as there was more base going into the acid. Adding base into the acid, and it turning orange meant that the solution was as acid, but a weak acid as the pH scale was 3. At this point there is still more H+ ions than OH- ions , but not as many more as it was at pH 1.
As we added more sodium hydroxide the solution changed colour to yellow. This meant that the solution was a weak acid, as it was heading closer to neutral. The pH scale was about 5 here, meaning that there was a little more H+ ions than OH- ions.
As we add more sodium hydroxide the solution becomes green. As it changed to green the pH scale is 7, which is neutral so not a base or an acid. At this point there is the same amount of H+ions and OH- ions which is why the solution is neutral.
When we add more sodium hydroxide the neutral turns into a weak base. This colour is blue, and the pH scale is 9. At this point there is less H+ ions than OH- ions , but there isn’t very many less. At this point there is a little more base in the solution then acid.
The last small amount of sodium hydroxide was added into our solution, and the solution turned violet, which is the lase colour. This means that it is a strong base, and it cannot get much stronger. The pH scale at this point is 14, and there is many more OH- ions than H+ ions.