Diffusion Lab (Food Coloring in Water)

Emily K
20 August 2013
Diffusion Lab
Research Question: How does the amount of water in a beaker affect the rate at which food coloring diffuses to the bottom of the beaker?
Independent Variable: Height of water in beaker (Inches)
Dependent Variable: Rate of diffusion (seconds)
Controlled Variables: * Size of beaker * Temperature of water (23°C) * Type/color of food coloring * Person Timing * Environmental conditions
Materials:
* Beaker(well over 4 in tall) * Food coloring * Tap water(23°C) * Thermometer * Ruler * Timer/Stopwatch * Masking tape
Procedure:
1. Stand a small ruler up next to the beaker and put small pieces of tape on the beaker that coincide with the heights 1 in, 2 in, 3 in, and 4in. 2. Start by filling the beaker with water up to the 1 in increment. 3. Have a stopwatch or timer ready, and hold the food coloring over the middle of the beaker 4. Drop a single drop of food coloring into the water while simultaneously starting the timer as soon the drop touches the water. 5. Stop the timer as soon as the food coloring touches the bottom of the beaker. It is easiest to notice that when the food coloring reaches the bottom, it starts the spread outwards. 6. Record the time on the timer in a data table as the trial 1 time for 1 in. 7. Repeat this process 2 more times for the 1 in increment, to have a total of 3 trials. 8. Continue steps 2-5, except for the 2 in, 3 in, and 4 in increments, and record three trials for each height.
Data:
Quantitative- Time for food coloring to diffuse to bottom (sec) | Height/ Level of water (inches from bottom) | Trials:1 | 2 | 3 | Average time with uncertainty | 1 in | 1.8 s | 2.0 s | 1.3 s | ( 1.7 ± 0.4 ) s | 2 in | 6.4 s | 7.3 s | 5.4 s | ( 6.4 ± 1.0 ) s | 3 in | 16.2 s | 8.8 s | 13.6 s | ( 12.9 ± 3.7 ) s | 4 in | 16.5 s | 15.9 s | 19.4 s | ( 17.3 ± 1.8 ) s |

Qualitative- As the height of the water in the beaker was increased, the time it took for the food coloring to reach the bottom of the beaker also increased.
Conclusion:
The amount of water in a beaker does affect the rate at which food coloring diffuses the bottom of it. As the amount/ height of water is increased, the rate at which food coloring diffuses to the bottom also increases. Some weaknesses of the experiment are that the food coloring does not always drop into the water at the same place, and sometimes the water was not always completely settled. Also, human reaction time must be taken into account since the timer could not have perfectly started the timer at the second the drop of food coloring hit the water each time. To improve these weaknesses, there should be at least two people carrying out the experiment, a dropper and a timer. This way the dropper can concentrate on making sure the water is still and the drop of food coloring goes in the same place each time, and the timer can concentrate on starting the stopwatch right when the food coloring drop hits the water, and stopping it right when it hits the bottom.