The Collision Theory Gizmo refers to the theory that gives a chance for you to experiment with a few factors that affect the rate at which reactants are transformed into products in a chemical reaction. For those who are going to take a test, you are advised to check out the Collision Theory Gizmo answer below so that you can learn and get a decent result. Keep in mind that the correct answers are in bold.
Prior Knowledge Questions
- 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? The hot water
- Suppose you held a lighted match to a solid bunk of wood and another match to a pile of wood shavings. Which form of wood will catch fire more easily? Wood shavings
- 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.
- Click Play. What do you see? Reactant A just bounced off reactant B. No products formed.
Activity A: Temperature
Question: How does temperature affect the rate of a chemical reaction?
- Observe: Select the ANIMATION tab. View the animation with No catalyst selected. What do you see? Reactants collide and reaction happens; products form.
When two reactant molecules meet, they form a temporary structure called an activated complex. The activated complex breaks up into the product molecules.
- Observe: Return to the CONTROLs pane. Set the Temperature to 0 °C and the Simulation speed to its maximum setting. Click Play
A. Describe the motions of the molecules. Reactant B “shakes” or “vibrates”. Reactant A makes around and bounces of each other or reactant
B. Now set the Temperature to 200 °C. How does increasing the temperature affect the motions of the molecules? Increasing temp makes “A” moves faster
C. What do you notice about the chemical reaction at the higher temperature? Reaction takes place faster
- Interpret: Select the GRAPH tab. Click the zoom out button (-) until you can see the whole graph. What does this graph show? Reaction concentration: Product concentration
- Predict: How do you think temperature will affect the rate of a chemical reaction? Temp increase means the reaction rate increases kinetic energy in the reactants to go up and collision to increase
- 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.
Repeat the experiment at different temperatures to complete the table. (Note: To get exact times, you can refer to the TABLE tab.)
- 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.)
- Analyze: What do your results indicate? As temp rises the reaction time lowers
- 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 molecules heat up and move faster. Kinetic energy increases
- 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 reactants need to have enough energy in order to burn heating the paper allows the collision frequency to rise
Activity B: Surface area and concentration
Question: How do surface area and concentration affect reaction rates?
- 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 reactant A to collide more with reactant B which forms products
- Predict: How do you think increasing the surface area will affect the rate of the reaction? Will increase the rate of reaction. More reactant B for reactant A to collide with
- 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.
- Analyze: What do you results indicate? Increasing surface area dramatically increases reaction rate
- Explain: Why does the reaction proceed more quickly when the surface area is increased? More surface area means more places and areas for reactant A to collide with reactant B
- Observe: Click Reset. Move the Reactant concentration slider back and forth. What do you notice? Reactants increase and decrease
- Predict: How will increasing the reactant concentration affect the rate of the reaction? Why? Increasing reactant concentration allows more reactants to collide, collision frequency increases
- 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.
- 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 aout for 2.0 mol/L?
Mean for 0.4 mol/L: 207 seconds Mean for 2.0 mol/L: 53 seconds
- Analyze: What do these results indicate? Increasing reactant concentration increases reaction rate collision frequency increases
- 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 temp, reactant concentration, and surface area
Activity C: Catalysts
Question: How do catalysts affect the rate of a chemical reaction?
- Observe: Select the ANIMATION tab. Select With catalyst, and observe.
A. What do you see? Catalyst causes the reactants to attract to each other and reaction happens faster
B. Why do you think the shape of a catalyst is important? Reactants collide on specific angle and the catalyst itself is not used in reaction
Many catalysts have a special shape that allows them to bind to specific reactant molecules.
- Predict: How do you think catalysts will affect the rate of a chemical reaction? Speed up reaction while decreasing the activation energy
- 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.
- Analyze: What do your results indicate? Adding a catalyst increases the reaction rate significantly. Reaction happens faster. Catalyst decreases activation energy
- 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? Very 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? Reaction finishes before 10 minutes
C. Why do you think the catalysts allowed the chemical reaction to take place at 0 °C? Catalyst provide a short pathway for reaction while temp was 0 °C. Activation energy decreases but stays at 0 °C
- Draw conclusions: What is the usefulness of catalysts? Allows reaction to happen at any temp
- 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? Protein wouldn’t break down and be used. Would build up in stomach and restrict other prods from breaking down