DNA Analysis Gizmo Answer Key

Name: Jovan Randall Date: 02-11-2022 Student Exploration: Diffusion Directions: Follow the instructions to go through the simulation. Respond to the questions andprompts in the orange boxes. Vocabulary: absolute zero, controlled experiment, diffusion, dynamic equilibrium, Kelvin scale, kinetic energy Prior Knowledge Question (Do this BEFORE using the Gizmo .) Have you ever smelled microwave popcorn? The oddly enticing scent can fill a whole house.How do you think the smell of popcorn spreads through the air? It spreads because the popcorn aroma has diffusion, whichmakes the scent fill the entire room. Gizmo Warm-up Smells are carried by tiny particles that move through the air. The Diffusion Gizmo shows gas particles in a chamber that is divided into two regions by a partial wall. Click Play ( ) and observe. 1. Describe the motion of the gas particles. Because the gas's particles are always moving, it bounces off the walls. 2. Over time, what is happening? Due to the passage of the particles from high to low concentration, the concentrationsboth eventually balance out. This process, in which particles move from an area of high concentration (region A ) to an area of low concentration (region B ), is called diffusion . 3. Select the BAR CHART tab, and observe the chart for a few minutes. After the first 30 seconds or so, how much do the numbers of particles in each region change? The gas particles are trying to become dynamic equilibrium but there numbers arechanging from 24 to 27. When the numbers don’t change much, the particles are said to be in dynamic equilibrium . 4. Click Pause ( ), and select the GRAPH tab. What does the graph tell you about the number of particles in region A? Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

The graph shows that as the time in seconds passes, there are less particles in region A. Activity A: Temperature anddiffusion Get the Gizmo ready: ● Click Reset ( ). ● Set the Wall to 100%. Introduction: In this Gizmo, temperature is measured on the Kelvin scale . On this scale, 0 K represents absolute zero , the coldest possible temperature. Water freezes at 273.15 K (0 °C), and water boils at 373.15 K (100 °C). Question: How does temperature affect the rate of diffusion? 1. Observe: Set the temperature ( Temp. ) to 100 K, and press Play . Observe the motion of particles. Click Reset . Then set the temperature to 600 K, click Play , and observe. How does the temperature of the gas relate to the motion of the particles? The higher the temperature, the speed of the particles will increase which will move anddiffuse. The temperature of a gas is a measure of the average kinetic energy of a set of particles. Kinetic energy (KE) depends on the velocity and mass of the particles (KE = mv 2 / 2). 2. Form hypothesis: How do you think temperature will affect the rate of diffusion? If the temperature is higher, the particles will diffuse much more quickly. 3. Experiment: Click Reset . Set the Wall to 50%, x in A to 100, y in B to 0, Temp. to 100 K, and Particle mass to 15 amu (atomic mass units). Select the TABLE tab. Press Play . Click Pause when x in A first reaches 55% or below. Record this Time to reach equilibrium in the left table below. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Repeat four more times at 100 K, and then run five trials with the temperature set to 600 K. Temp = 100 K experiment Trial Time to reach equilibrium 1 255 sec 2 263 sec 3 322 sec 4 228 sec 5 224 Temp = 600 K experiment Trial Time to reach equilibrium 1 132 sec 2 99 sec 3 92 sec 4 140 sec 5 120 sec 4. Calculate: Find the average time to reach equilibrium for each experiment: A. Average time to reach equilibrium at 100 K: 69.2 sec B. Average time to reach equilibrium at 600 K: 305 sec 5. Draw conclusions: Compare the average times to reach equilibrium for each temperature. A. How did temperature affect the rate of diffusion? with an increase in energy B. Why do you think this was the case? This is because molecules have less energy atlower temperatures, which also slows downdiffusion. 6. Extend your thinking: Why do you think the experimental results were different for each trial? Since the particles are constantly moving, I believe the findings varied somewhat for eachtrial since each trial involved slightly variable particle movement times. 7. On your own: In our lives, we rarely experience temperatures that are above 373 K (100 °C) or below 273 K (0 °C). Investigate how much diffusion rates differ between these two temperatures. Describe the resultsof your experiments below. For higher temperatures, the diffusion rates are substantially higher, and for much lowertemperatures, they are much lower. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

Activity B: Rates of diffusion Get the Gizmo ready: ● Click Reset . Introduction: The Diffusion Gizmo allows you to manipulate five variables: the Wall , the number of x particles in region A , the number of y particles in region B , the temperature, and the Particle mass . Question: How do factors other than temperature affect the rate of diffusion? 1. Choose a variable: Pick a variable to investigate. Which one did you choose? Molecule size 2. Form hypothesis: How do you think this variable will affect rates of diffusion? The harder it is for a molecule to diffuse over a membrane, the bigger it is. In conclusion,the size of the molecule causes a drop in diffusion rates. 3. Set up experiment: In a controlled experiment , only one variable is manipulated, or changed. Set up your experiment so that there is just one difference between set-up A and set-up B. List the Gizmo settings youwill use for each set-up below. Set-up A Wall 40 x in A 60 y in B 0 Temp. 600 Particle mass 15 Set-up B Wall 80 x in A 60 y in B 0 Temp. 600 Particle mass 15 4. Gather data: Use the Gizmo to fill in each table. As before, the “time to reach equilibrium” isthe time it takes for the number of x particles in region A to reach 55% or lower. Set-up A Trial Time to reach equilibrium 1 120 2 61 3 86 4 73 5 47 Set-up B Trial Time to reach equilibrium 1 80 2 60 3 0 4 600 5 15 Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved

5. Calculate: Find the average time to reach equilibrium for each experiment: A. Average time to reach equilibrium for set-up A: 77.4 B. Average time to reach equilibrium for set-up B: 286.2 6. Draw conclusions: Compare the average times to reach equilibrium for each set-up. A. How did the variable you investigated affect therate of diffusion? The one with a greater surface area has a smallerwall and has a faster rate of diffusion, unlike theother one with less surface area but a larger walltakes more time. B. Why do you think this was the case? Diffusion happens more quickly if the molecule hasgreater room. 7. On your own: Investigate the remaining variables. Record all experimental results in your notes. Summarize your findings in the space below. The rate of diffusion can be influenced by a number of variables, such as molecule size,polarity, ion-changing ability, temperature, and pressure. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved