DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.
DrDAQ is used here as a pH meter with the addition of a pH probe to measure the pH level over the entire pH scale of a range of common drinks.
Recently dentists have begun warning about the dangers of drinking acidic drinks. Teenagers, they suggest, who drink large amounts of fizzy ‘pop’ drinks suffer from tooth erosion whereby the enamel covering of the tooth is dissolved by the acid in the drink. Athletes are also at risk from drinking sports drinks.
The recommended ‘safe’ level for the pH of drinks is 5.5, anything below this can promote tooth erosion.
This experiment looks at the relative pH values of different drinks and can be used to determine whether a particular drink is ‘safe’ according to the above criteria. It can also be used as a good introduction to further studies into tooth decay and enamel stripping.
It is suitable for ages 14+ and requires some knowledge of the pH measurement.
A selection of common drinks - we used:
Here is a table showing the pH of some common substances for reference.
Before starting the experiment, make a table listing drinks that you will test and indicate what you expect the pH of each drink to be.
Create your table as shown below:
|Liquid||Expected pH||Recorded pH|
Gently agitate the pH probe in each liquid for a minute or two while the pH reading settles then record the reading in the table and move onto the next liquid.
NOTE: Take care to thoroughly clean the pH probe in a large container of water between each liquid to reduce cross-contamination of the liquids.
When you have tested all your available drinks, plot the results on a bar graph with each bar showing the expected value and recorded value for each liquid.
The formula for pH is: pH = –log[H+]
Q1. With respect to the results you have obtained, can you make any predictions about the likely pH values of the foods and drinks we consume ?
Q2. Find the pH of a solution whose [H+] is 9.5E-8 M
Q3. Calculate the [H+] of a solution with a pH of 5.45