Name: ______Block: ______Date: ______

Collision Theory/Enzyme Gizmo (adapted from http://www.explorelearning.com)

Warm-up Questions (Do these BEFORE using the Gizmo.)

1.  Define the following terms (in your own words):

Product ______

Reactant ______

Catalyst ______

______

Enzyme ______

2.  Suppose you added a spoonful of sugar to hot water and another to ice-cold water. Which type of water will cause the sugar to dissolve more quickly?______

Gizmo Warm-up

A chemical reaction causes the chemical compositions of substances to change. Reactants are substances that enter into a reaction, and products are substances produced by the reaction. The Collision Theory Gizmo™ allows you to experiment with several factors that affect the rate at which reactants are transformed into products in a chemical reaction.

You will need blue, green, and orange markers or colored pencils for the first part of this activity.

1.  Look at the key at the bottom of the SIMULATION pane. In the space below, draw the two reactants and two products of this chemical reaction (using the same colors that are used in the simulation).

Reactants: Products:

2.  Click Play (). Watch for about 30 seconds and then describe what you observed.

______

______

______

Part A: How does temperature affect the rate of a chemical reaction?

·  Click Reset ().

·  Check that the Reactant concentration is set to 1.0 mol/L, the Catalyst concentration is set to 0.00 mol/L, and the Surface area is Minimum.

1.  Select the ANIMATION tab. View the animation with No catalyst selected.

What do you see? ______

______

______

When two reactant molecules meet, they form a temporary structure called an activated complex. The activated complex breaks up into the product molecules.

2.  Return to the CONTROLS tab. Set the Temperature to 0 °C and the Simulation speed to its maximum setting. Click Play.

A.  Describe the motions of the molecules. ______

______

B.  Now set the Temperature to 200 °C. How does increasing the temperature affect the motions of the molecules? ______

C.  What do you notice about the chemical reaction at the higher temperature? ______

______

3.  Select the GRAPH tab. Click the zoom out button () until you can see the whole graph. What does this graph show? Explain in detail. ______

______

______

4.  How do you think temperature will affect the rate of a chemical reaction? ______

______

______

Gather data: Click Reset. A useful way to compare reaction rates is to record the time required for half of the reactants to react, called the “half life” of the reaction. With the Temperature set to 200 °C, click Play. Click Pause () when the number of reactant molecules is 10. Repeat the experiment at 150 °C, 100 °C, and 50 °C. Record the half-life time in the first space of the table below. (Note: To get exact times, you can refer to the TABLE tab.)

200 °C / 150 °C / 100 °C / 50 °C
Half-life Time

5.  Analyze: What do your results indicate about the effect of temperature on half-life time? ______

______

______

Part B: How do catalysts affect the rate of a chemical reaction?

A catalyst is a substance that helps a chemical reaction to proceed more quickly. The catalyst molecules are not changed by the reaction and can be reused over and over again.

1.  Select the ANIMATION tab. Select With catalyst, and observe.

A.  What do you see? ______

______

B.  Why do you think the shape of a catalyst is important? ______

______

______

Many catalysts have a special shape that allows them to bind to specific reactant molecules.

2.  How do you think catalysts will affect the rate of a chemical reaction? ______

______

3.  On the CONTROLS pane, set the Reactant concentration to 2.0 mol/L, the Surface area to Maximum, and the Temperature to 50 °C. Measure the half life time for each given catalyst concentration. Click Pause () when the number of reactant molecules is 20.

Trial / Reaction Half life at each Catalyst concentration
0.00 mol/L / 0.05 mol/L / 0.10 mol/L / 0.15 mol/L
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4.  What do your results indicate about the effects of catalysts on reaction time? ______

5.  Select RESET. Set the Catalyst concentration to 0.00 mol/L and the Temperature to 0 °C. Click Play, wait for 10 minutes of simulated time, and click Pause.

A.  What happens? ______

B.  Click Reset, set the Catalyst concentration to 0.25 mol/L, and click Play. After 10 simulated minutes, click Pause. Record the number of reactants ______& products ______

Explain what happened.______

______

C.  Why do you think the catalysts allowed the chemical reaction to take place at 0 °C?

______

______

______

6.  What is the usefulness of catalysts? ______

______

______

7.  Most of the chemical reactions inside your body rely on protein catalysts called enzymes to take place. For example, the enzyme pepsin helps to break down protein molecules in your stomach. What might happen if your stomach stopped producing pepsin?

______

______

______

8.  The rate of enzyme activity is affected by certain factors. List two of these factors and explain how they affect the rate of enzymatic activity.

______

Enzyme-Controlled Reactions Virtual Lab

Go to the following website http://tinyurl.com/32f3as4 Chapter 6: Chemistry in Biology Virtual Labs

- Click Enzyme-Controlled Reactions

In this investigation you will determine the effect of substrate concentration and pH on the initial rate of an enzyme catalyzed reaction.

You will explore the following question: What are ideal conditions for optimal enzyme activity?

1.  Read the information in the text box to the left of the simulation.

2.  Read and follow the procedures for the lab simulation. Don’t forget to click the TV first!

3.  You can adjust pH by clicking the up and down arrows under each test tube in the virtual lab. You will test enzyme activity at pH 3, 5, 7, 9, and 11

4.  Change the pH so that all the test tubes have a pH of 3. Now add the substrate to each tube. Record your results in the data table.

5.  Repeat step 4, changing the pH each time (pH 5, 7, 9, and 11).

Data Table 1: Initial Enzyme Reaction Rates
Substrate
Amount / Initial Reaction Rate
(# Molecules x 106/min) / Average of Molecules
(per substrate amount)
pH 3 / pH 5 / pH 7 / pH 9 / pH 11
0.5 g
1.0 g
2.0 g
4.0 g
8.0 g
Average of Molecules
(per pH level)

Create two line graphs using the averages from the above chart.

Title: ______

Analysis Questions

1.  Which amount of substrate produced the most molecules? ______

2.  Which amount of substrate produced the least amount of molecules? ______

3.  Which amount of substrate resulted in amounts of product that were the same? ______

4.  Which pH level was the most ideal to turn the substrate into molecules? ______

5.  What was the temperature for each trial? ______

6.  Do you think your results would have been different if you increased the temperature? Explain. ______

7.  Do you think your results would have been different if you decreased the temperature? Explain. ______

8.  At what place does the substrate bind to the enzyme in order for the enzyme to work? (Hint: Play the movie by clicking on the TV for this info). ______

9.  After analyzing your data, what conclusion can you come to about the substrate amount and enzyme activity? ______

10.  After analyzing your data, what conclusion can you come to about the pH and enzyme activity? ______

11.  Do all enzymes function best at the same pH? Explain. ______

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