Team member contribution
During the experiment, Triyana was given the task to make the red cabbage and turmeric pH indicator. Triyana was also responsible to write the discussion section in the report.
The purpose of this investigation was to determine the pH value of five common household substances by using the natural pH indicators of red cabbage and turmeric.
Natural substances such as red cabbage and turmeric can be used to determine the acidity or basicity of other substance. The household substances that were used are Vinegar, Detergent, Bicarbonate Soda, Lemon Juice and Ammonia. Lemon juice and Vinegar are acids and have the pH value of 2.3 and 2.9 respectively. ...view middle of the document...
Table 1: The pH and colour change range of red cabbage pH indicator
pH 2 4 6 8 10 12
Colour Red Purple Violet Blue Blue-Green Greenish Yellow
Source: Helmenstine, n.d, ‘Red Cabbage pH Indicator’, in About.com Guide, accessed 12 October 2010, from < http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm>
This can be seen from the experiment that the acidic substances such as vinegar and lemon juice turned light pink and darker pink respectively after they were added with red cabbage juice. The alkaline substances such as detergent turned into light violet, bicarbonate soda light blue and ammonia light green.
According to GNI (2010), Turmeric contains up to 3% curcumin which as a polyphenol and known as C.I. 75300 or Natural Yellow 3. Similar to the pigment in red cabbage, the colour of curcumin can be altered in response to changes in its hydrogen and hydroxide concentration. The turmeric indicator changes colour between roughly a pH of 7.4 and 8.6. If turmeric is exposed to neutral or acidic substances (those with a pH of less than 7.4) it will retain its yellow colouration. However, if turmeric is exposed to more alkaline substances (those with a pH greater than 8.6) it becomes a dark pink/red (Australia’s National Science and Technology Centre, 2009). Based on the experiment conducted, substance ammonia which is alkaline and has a pH of 11.5 turned dark brownish red when turmeric pH indicator added. Bicarbonate soda which is also an alkaline...