Practice IB Lab- “Photo Finish”

(The lab where I help you for the last time.)

How do Different Concentrations of Bicarbonate Solution Affect the Rate of

Photosynthesis in Ivy?

• Practice Writing Lab using Elodea: used Dissolved Oxygen Probe to measure the amount of oxygen

• This lab: will use how long it takes an ivy leaf disc that has been compressed to float to the surface of a column of water (indirect measurement)

Why can you use how long it takes a leaf disc to float as an indirect measurement of photosynthesis?

Remembering photosynthesis…LIGHT DEPENDENT REACTIONS• “PHOTO”

LIGHT INDEPENDENT REACTIONS• “SYNTHESIS”

What would make the disc float?

How do Different Concentrations of Bicarbonate Solution Affect the Rate of Photosynthesis in Ivy?

• What is a rate?– Is a rate measured directly?

• What would your raw data be?

*Don’t forget to always make observations!!

Let’s look at the procedure.

LAB PROCEDURE

Why do the discs sink?

DENSITY! The spaces have been filled with solution.

IDV: 5 concentrations of bicarbonate solution

IDV levels of NaHCO3:1. 0M2. 0.1M3. 0.2M4. 0.3M5. 0.4M

• NaHCO3 is 84 g/mol• Example calculation to make 100 mL of 0.2 M NaHCO3: (0.2 mol/L)(0.1 L)(84 g/mol)

In order for you to answer the question, you need to calculate a rate.

• What 2 pieces of data have been directly collected? – What is this called in your lab write up?

• You need to collect sufficient data. How many trials minimum?• What do you do next with these trials of time & distance data?

– Step 1: – Step 2:

• Which type of processing would be considered too basic to be given Data Processing credit?

• What could you do that would take this data further (beyond rate)?– -Ex: % difference between IDV “A” (control ) and IDV “B”, IDV “C”,

etc.