Question

laboratory simulation
phase 2: diffusion rate in water
complete the following steps:
1 add water to empty dish
2 add one crystal to dish with water using tweezers
3 wait 15 minutes
4 measure the diffusion spot diameter. record in lab data
5 calculate average diffusion rate from time zero in mm/h. record in lab data

lab data
how to measure
are you sure your measurement is correct?

media: liquid (water)
diffusion spot diameter with one crystal at 15 min (mm): 40
rate of diffusion with one crystal (mm/h): 40

media: semisolid (agar)

rate mm/h = (diameter mm / time min) x 60 min

Explanation:

Read the ruler measurement

Using the Lab Data Recording knowledge point
The ruler is placed across the purple diffusion circle in the petri dish.

• The left edge of the purple circle aligns with the \(6.0\text{ cm}\) mark.
• The right edge of the purple circle aligns with the \(14.0\text{ cm}\) mark.
• The diameter of the diffusion spot is:

$$ 14.0\text{ cm} - 6.0\text{ cm} = 8.0\text{ cm} $$

• Converting centimeters to millimeters:

$$ 8.0\text{ cm} \times 10\text{ mm/cm} = 80\text{ mm} $$

Calculate the rate of diffusion

Using the Diffusion Rate Calculation knowledge point
The formula provided in the lab interface is:

$$ \text{Rate [mm/h]} = \frac{\text{diameter [mm]}}{\text{time [min]}} \times 60\text{ [min]} $$

• Diameter = \(80\text{ mm}\)
• Time elapsed = \(15\text{ min}\)
• Calculation:

$$ \text{Rate} = \frac{80\text{ mm}}{15\text{ min}} \times 60\text{ min/h} = 80 \times 4 = 320\text{ mm/h} $$

Answer:

• Diffusion spot diameter with one crystal at 15 min (mm): <blank>80</blank>
• Rate of diffusion with one crystal (mm/h): <blank>320</blank>