Time taken for the milk to Turn Solid through different concentrations of rennin

Aim: To test what the effect of concentrations of hydrochloric acid has on a mixture of rennin and milk’s reaction rate.

Hypothesis: As the hydrochloric acid becomes more concentrated, the mixture of rennin and milk will have a faster reaction rate.

Variables:
Independent- Concentration of hydrochloric acid
Dependent- Reaction rate of rennin and milk
Controlled- Amount of milk, amount of hydrochloric acid, surface area, Type of Milk (Skim, Full, Soy)

Materials:
• 5 Beakers (50mls)
• Rennin Tablet
• 500mls Milk (full cream)
• Papeete (5)
• Hydrochloric Acid (20mls)
• Distilled Water
• Paper Towel
• Timers (5)

Method:
1. Pour 20mls of distilled into a beaker.
2. Place Rennin tablet in the distilled water and wait for it to dissolve completely.
3. After the rennin tablet has dissolved, put 1ml of rennin into each Papeete.
4. Add 30mL of milk into each of the 5 beakers
5. Make the following concentrations of hydrochloric acid: 1.0, 0.75, 0.5, 0.25, 0.0
6. Add 1mL of the rennin mixture with to each of the 5 beakers.
7. Add the 5 different concentrations of acid to the 5 beakers of milk along with the rennin and start your timers.
8. Note the time it takes for the milk to turn solid. (or there abouts if time does not allow)

Changes that occurred during the dissolving of the rennin tablet:
• The water turned a milky colour.
• It took roughly 6 minutes to dissolve.

Results:
1.0 – 8.31 minutes
0.75 – 8.23 minutes
0.5 – 7.58 minutes
0.25 – 8.01 minutes
0.0 – 20+ minutes

Discussion:
When conducting this experiment some of the results that came back had a surprising outcome, according to the data we collected, the rate that the milk hardens relies on how strong the acid is. Too weak, and it takes too long and too strong and the time also increases. The optimum acid concentration was at 0.65, as we only recorded 0.5 and 0.75 either side of the optimum point; this was where the line of best fit showed. The experiment that we conducted is reliable as there is nothing that could have changed if we conducted it again. Some possible random errors that could’ve occurred during this experiment are a miss measurement of rennin or hydrochloric acid that would trip the whole experiment. Some possible systematic errors occurring are that the Papeete was taking an air bubble and not moving liquid around it and thus giving a false reading of measurement, a timer may have low batteries and running faster or slower than usual, a beaker may have a chip on the inside therefore giving a lesser reading. The improvements we could’ve made to our experiment are; leaving a longer waiting time for the rennin, milk and acid mixture to properly turn solid, making more acid dilutions so that we have more data to use in our report and graph, we could’ve done it the experiment more than once to see if our results repeated and to eliminate errors in information received from the practical.

Conclusion:
My hypothesis: As the hydrochloric acid becomes more concentrated, the mixture of rennin and milk will have a faster reaction rate.
This was somewhat supported in saying that the reaction became quicker the more concentrated the acid was, but as it became further concentrated, beyond 0.7, it began to slow down the reaction. So I did not state in my hypothesis that the reaction would slow down due to the increased concentration of acid.