ZERO-IN

Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ANALYZE IT

Ask students to determine the concentration of the unknown solution by using the absorbance data to create a concentration curve. Explain that scientists that perform spectrophotometric work create a concentration curve by plotting the concentration of known solutions as compared to the absorbance of unknown solutions.

Instruct students to complete the Analysis Questions in their SDRs then discuss them as a class. Use the suggested responses below to guide students’ answers.

• Study the concentration curve. What is the concentration of food coloring in the unknown sample? Approximately 2 drops of food coloring per 200 ml water.

• What do you think a transmittance graph would look like? Support your predictions. A transmission graph would be the reciprocal of the absorbance graph. There is an inverse relationship between the amount of light that is transmitted versus that which is absorbed.

GET FOCUSED

Instruct students to complete the Focus Question in their SDRs then discuss it as a class. Use the suggested response below to guide students’ answers.

• What is the relationship between the absorption and transmission of light through transparent substances? There is an inverse relationship between the amount of light that is transmitted versus that which is absorbed as light interacts with a transparent liquid. The more light that is transmitted, the less that is absorbed. As more light is absorbed, less is transmitted through the transparent medium.