Student Exploration: Collision Theory

Jad Name: ______________________________________ 2026/03/31 Date: ________________________ Student Exploration: Collision Theory Vocabulary: activated complex, catalyst, chemical reaction, concentration, enzyme, half-life, molecule, product, reactant, surface area Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Suppose you added a spoonful of sugar to hot water and another to ice-cold water. Which hot water type of water will cause the sugar to dissolve more quickly? _________________________ 2. Suppose you held a lighted match to a solid hunk of wood and another match to a pile of shavings wood shavings. Which form of wood will catch fire more easily? ______________________ 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. Reactants: 2. Click Play ( Products: The reactants will collide with eachother and break bonds to create products. ). What do you see? ____________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 2019 Get the Gizmo ready: Activity A: Temperature  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. Question: How does temperature affect the rate of a chemical reaction? 1. Observe: Select the ANIMATION tab. View the animation with No catalyst selected. The two reactants collide into each other, and breaking each others bonds. This lead to them joining and creating the products. 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. Observe: Return to the CONTROLS pane. Set the Temperature to 0 °C and the Simulation speed to its maximum setting. Click Play. Reactant A has constant motion, colldiing with itslef and reactant B, who A. Describe the motions of the molecules. ____________________________________ is just vibrating in place ___________________________________________________________________ B. Now set the Temperature to 200 °C. How does increasing the temperature affect They move faster and more aggresively. the motions of the molecules? ___________________________________________ C. What do you notice about the chemical reaction at the higher temperature? _______ The chemical reaction happens quicker. ___________________________________________________________________ 3. Interpret: Select the GRAPH tab. Click the zoom out button (–) until you can see the whole Concentration of reactants decreasing, and concentration of products increasing. graph. What does this graph show? ____________________________________________ _________________________________________________________________________ 4. Predict: How do you think temperature will affect the rate of a chemical reaction? ________ As temperature increases the rate of reaction increases. This is due to the rise in kinetic energy and collision frequency. _________________________________________________________________________ _________________________________________________________________________ (Activity A continued on next page) 2019 Activity A (continued from previous page) 5. 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. Record the half-life time in the first space of the table below. Trial 200 °C 150 °C 100 °C 50 °C 1 372 seconds 362 seconds 662 seconds 96 minutes 2 541 seconds 442 seconds 1622 seconds 103 minutes Mean half-life 456.5 seconds 402 seconds 1142 seconds 99.5 minutes Repeat the experiment at different temperatures to complete the table. (Note: To get exact times, you can refer to the TABLE tab.) 6. Calculate: Calculate the mean half-life for each temperature. Fill in these values above. (Hint: To get an exact mean, first convert each time to seconds by multiplying the minutes value by 60 and adding this to the seconds. To find the mean in seconds, add up the two times and divide by two. Convert the answer back to minutes and seconds.) Usually, as the temperature decreases, it takes longer to react. 7. Analyze: What do your results indicate? _________________________________________ _________________________________________________________________________ _________________________________________________________________________ 8. Draw conclusions: For two molecules to react, they must collide at just the right angle and with enough energy to break the original bonds and form new ones. Based on these facts, why does the reaction tend to go more quickly at higher temperatures? The reactants move faster and collide more frequently at high temperatures. _________________________________________________________________________ _________________________________________________________________________ 9. Apply: Paper must be heated to 234 °C to begin reacting with oxygen. This can be done by putting the paper over a flame. Why do you think the paper must be heated to start burning? _________________________________________________________________________ The molecules need enough energy to start reacting, reaching its activation energy. By increasing the frequency of collisions , it will gain more than the _________________________________________________________________________ required activation energy. _________________________________________________________________________ 2019 Get the Gizmo ready: Activity B: Surface area and concentration  Click Reset.  Check that the Catalyst concentration is set to 0.00 mol/L and the Surface area is Minimum.  Set the Temperature to 200 °C. Introduction: Reaction rates are also influenced by surface area and concentration. The surface area of a solid is a measure of how much of the solid is exposed to other substances. The concentration of a substance is a measure of how many molecules of that substance are present in a given volume. Question: How do surface area and concentration affect reaction rates? 1. Observe: Change the Surface area from Minimum to Maximum. You can imagine that a solid reactant has been dissolved in a liquid. How does this change how many Reactant B molecules are exposed to Reactant A? Allows more collisions between reactant A and reactant B. _________________________________________________________________________ 2. Predict: How do you think increasing the surface area will affect the rate of the reaction? It will increase the rate of reaction, this is due to colission theory being increased. _________________________________________________________________________ 3. Gather data: Set the Reactant concentration to 2.0 mol/L. Use the Gizmo to measure the half-life of the reaction for each surface area setting. (There will now be 20 reactant molecules left at the half-life.) Then, calculate the mean half-life for each setting. Trial Minimum surface area Maximum surface area 1 318 seconds 124 seconds 2 360 seconds 162 seconds Mean half-life 339 seconds 143 seconds The rate of reaction increases as the surface area increases. 4. Analyze: What do your results indicate? _________________________________________ _________________________________________________________________________ 5. Explain: Why does the reaction proceed more quickly when the surface area is increased? More surface area allows for more collision. _________________________________________________________________________ _________________________________________________________________________ (Activity B continued on next page) 2019 Activity B (continued from previous page) 6. Observe: Click Reset. Move the Reactant concentration slider back and forth. What do you notice? The number of reactants increase or decrease, depending on the direction. _________________________________________________________________________ 7. Predict: How will increasing the reactant concentration affect the rate of the reaction? Why? It will increase. This is due to there being more reactants to collide with, making the frequency go up. _________________________________________________________________________ _________________________________________________________________________ 8. Gather data: Make sure the Temperature is 200 °C and the Surface area is Maximum. Use the Gizmo to measure the half-life for each given reactant concentration. (Note that the number of reactant molecules changes with each concentration.) Calculate the means. Trial 0.4 mol/L 0.8 mol/L 1.2 mol/L 1.6 mol/L 2.0 mol/L 1 320 seconds 183 seconds 122 seconds 55 seconds 40 seconds 2 270 seconds 124 seconds 90 seconds 98 seconds 70 seconds Mean half-life 295 seconds 153.5 seconds 106 seconds 73.5 seconds 55 seconds 9. Compare: If possible, find the mean times for each concentration for your entire class. What is the mean class time for a concentration of 0.4 mol/L? How about for 2.0 mol/L? 295 seconds Mean for 0.4 mol/L: ______________ 55 seconds Mean for 2.0 mol/L: ______________ Higher concentration means a higher reaction rate. 10. Analyze: What do these results indicate? ________________________________________ _________________________________________________________________________ _________________________________________________________________________ 11. Apply: Hydrochloric acid reacts with the mineral calcite to produce carbon dioxide gas, water, and calcium chloride. Based on what you have learned in activity A and activity B, what are three things you could do to make the reaction occur more quickly? Increase concentration, increase surface area, and increase temperature. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 2019 Activity C: Get the Gizmo ready: Catalysts  Click Reset ( ). Introduction: A catalyst is a substance that helps a chemical reaction to proceed. The catalyst molecules are not changed by the reaction and can be reused over and over again. Question: How do catalysts affect the rate of a chemical reaction? 1. Observe: Select the ANIMATION tab. Select With catalyst, and observe. The catalyst causes reactants to collide with each other faster. A. What do you see? ____________________________________________________ ___________________________________________________________________ reactants must collide with the catalyst in order to B. Why do you think the shape of a catalyst is important? The _______________________ increase the rate of reaction. ___________________________________________________________________ ___________________________________________________________________ Many catalysts have a special shape that allows them to bind to specific reactant molecules. 2. Predict: How do you think catalysts will affect the rate of a chemical reaction? ___________ _________________________________________________________________________ Speed up the reaction. 3. Gather data: 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 for each given catalyst concentration. Calculate the means. Trial Catalyst concentration 0.00 mol/L 0.05 mol/L 0.10 mol/L 0.15 mol/L 1 1300 seconds 210 seconds 128 seconds 98 seconds 2 1040 seconds 285 seconds 116 seconds 99 seconds Mean half-life 1170 seconds 247.5 seconds 122 seconds 98.5 seconds The higher the concentration of the catalyst, the higher the rate of reaction will become. 4. Analyze: What do your results indicate? _________________________________________ _________________________________________________________________________ _________________________________________________________________________ (Activity C continued on next page) 2019 Activity C (continued from previous page) 5. Explore: 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? ______________________________________________________ The reaction is incredibly slow. B. Click Reset, set the Catalyst concentration to 0.25 mol/L, and click Play. After 10 simulated minutes, click Pause. What happens now? ________________________ Almost everything has reacted. ___________________________________________________________________ C. Why do you think the catalysts allowed the chemical reaction to take place at 0 °C? Catalysts lower the activation energy required to react. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ They allow reactions to take place faster and in almost 6. Draw conclusions: What is the usefulness of catalysts? _____________________________ any condition. _________________________________________________________________________ _________________________________________________________________________ 7. Apply: 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? _________________________________________________________________________ The protein will no longer be broken down at a fast enough rate and would have been built up in the stomach. _________________________________________________________________________ _________________________________________________________________________ 2019