Question

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

Explanation:

Measure the diffusion spot diameter

Using the Diffusion Rate Calculation knowledge point

• The blue diffusion circle on the centimeter ruler starts at \(0\text{ cm}\) and extends to \(8\text{ cm}\).
• Therefore, the diameter of the diffusion spot is:

$$ d = 8\text{ cm} = 80\text{ mm} $$

Calculate the average diffusion rate

Using the Diffusion Rate Calculation knowledge point

• The elapsed time is \(15\text{ minutes}\), which is converted to hours:

$$ t = \frac{15\text{ min}}{60\text{ min/h}} = 0.25\text{ h} $$

• The average diffusion rate \(R\) in \(\text{mm/h}\) is calculated by dividing the diameter by the time:

$$ R = \frac{80\text{ mm}}{0.25\text{ h}} = 320\text{ mm/h} $$

Answer:

• Diffusion spot diameter: \(80\text{ mm}\) (or \(8\text{ cm}\))
• Average diffusion rate: \(320\text{ mm/h}\)