The pH scale
The Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline. scale measures the Corrosive substance which has a pH lower than 7. Acidity is caused by a high concentration of hydrogen ions. or A base which is soluble in water. of a Mixture formed by a solute and a solvent..
| pH | Meaning |
| \(\textless\)7 | acidic |
| = 7 | neutral |
| \(\textgreater\) 7 | alkaline |
| pH | \(\textless\)7 |
|---|---|
| Meaning | acidic |
| pH | = 7 |
|---|---|
| Meaning | neutral |
| pH | \(\textgreater\) 7 |
|---|---|
| Meaning | alkaline |
The pH of a solution can be estimated using A chemical solution that produces many different colour changes corresponding to different pH levels. and a colour chart, or measured using a pH meter.
Learn more on the pH scale in this podcast.
Listen to the full series on 大象传媒 Sounds.
Using an indicator
- dip a clean glass rod into the solution
- transfer one drop of solution to a piece of universal indicator paper on a white tile
- wait 30 seconds for the colour to develop, then match the colour to the colour chart
Using a pH meter
The pH of a solution can be measured using a pH meter:
- wash the pH probe with distilled water
- put the end of the probe into the solution
- record the reading on the pH meter
The pH meter may need calibrating first. This is done by adjusting the reading to match the pH of a buffer solution, a solution with a known pH.