10/19/2011 Objective: Understand pH and concentration Design a lab procedure Warm-Up: You have two test tubes. Each has 10 mL of hydrogen peroxide solution. In Test Tube 1, there is 8mL of H2O and 2mL of hydrogen peroxide. In Test Tube 2, there is 5mL of H2O and 5mL of hydrogen peroxide. Which test tube has a higher concentration of hydrogen peroxide?

Looking Ahead Enzyme lab on Monday Lab Report Due Thursday Quiz on Friday, October 28 Energy and Enzymes County Quarterly Exam: November 2nd

Concentration

Concentration If you have 20 mL of a solution that is made up of 15 mL water and 5 mL bleach, this would be a 25% bleach solution. (volume bleach)/(total volume) = %bleach (5 mL)/(20 mL) = 25% If you have a 50 mL solution that is 20 mL water and 30 mL hydrogen peroxide, what is the percent hydrogen peroxide in this solution?

pH: Measuring Acidity 0-6 is acidic 8-14 is alkaline (basic) 7 is neutral As pH decreases, acidity increases As pH increases, alkalinity increases It is a logarithmic scale This means that something with pH of 2 is 10x more acidic than something with pH 3

Writing a Procedure Your lab group will create a procedure to address the question: “How do temperature, pH, and substrate concentration affect enzyme activity?” You will perform this procedure on Monday Keep in mind that you will be constrained by time, so your procedure might not be ideal You can address this in your lab report!

The Reaction: H2O2  H2O + O2 This is the conversion of hydrogen peroxide to water and oxygen The enzyme that catalyzes this reaction is called catalase What’s the substrate? What’s the product?

For the lab… For this particular reaction, the product is a gas To make any claims about enzyme activity, we’ll need to look at how much gas is produced You may create a qualitative scale for this if you’d like You might also think about measuring the column of bubbles

Example… You might use the following scale, or something similar: 0=no reaction 1=small bubble formation 2=bubbling fast 3= foaming

Measuring Bubbles….

Supplies? You will be provided with the enzyme, catalase, and the substrate, hydrogen peroxide, as well as any other chemicals/solutions you think you’ll need You also have access to all of the lab equipment we’ve used so far this year… Glassware (beakers, test tubes, graduated cylinders, etc.), hot plates, droppers, thermometers…

Your Task Write up a procedure that will allow you to gather data to address the question: “How do temperature, pH, and substrate concentration affect enzyme activity?” Include materials, step-by-step, and data tables Each person in your group should have a copy