The LCCC Science in Motion Program would like to share free, online educational science activities that can be used by teachers, students, and parents to help continue learning during the coronavirus pandemic. We have created scaffolded science activities that can be used to help engage and entertain students in elementary through high school grades using household materials. Our first module is focused on Rocket Science, using straws, soda bottle rockets, and computer simulations that the whole family can work on together and enjoy. These modules are being shared with the public through our LCCC Canvas Course site and the individual files can be downloaded from https://lccc.instructure.com/courses/5456/modules
We also have a wide variety of lab experiments with actual lab data, that you can share with your students to analyze the results and draw conclusions about the scientific principles involved. Many of these labs also have short video presentations on youtube or other sources that accompany the experiments to explain the methodology and equipment used during the lab. If needed, we can create new videos that demonstrate the lab techniques and instruments used, such as spectrophotometers for colored solutions, burets for titrations, or sensor carts for collision studies, that you can use with your students. You may also request either an equipment loan to use with your students during in-person classes or for you to demonstrate during Zoom meetings. Check out what we offer at https://www.lccc.edu/academics/science-and-engineering/science-in-motion/labs-equipment
Stay safe. Keep Healthy.
Mark and Krys
Vernier Experiments and Sample Data Library
To assist you as you quickly move from the classroom or laboratory setting to online teaching, Vernier Software & Technology is offering the Vernier Experiments and Sample Data Library—a library of over 80 experiments with sample data files covering many subjects that you can distribute to your students at home. Students won’t actually conduct the experiment themselves, but they can follow along with the written procedure and access sample data. Students can then perform their own analysis of the sample data using our free Graphical Analysis™ 4 app and answer questions based on their results. More information about this free resource can be found at Free Sample Data Library
While we strongly advocate for hands-on science when possible, we understand that many schools are in a situation where it is not possible at this time. We hope you and your students find this option helpful. Additional experiments will be made available soon.
Instructions for Teachers
- Download and peruse the library of available experiments. Note that each experiment consists of two or more files. These files include
- Student handout
Each experiment has one Word file. This file includes the experiment instructions and is meant to be distributed to students. The file can be opened in Word or uploaded into Google Drive and converted to a Google Doc. You can edit the instructions before sending the file to your students if you wish, or distribute as is.
- Sample data files
Each experiment has one or more Graphical Analysis 4 files (file extension of .ambl). To open and use these files, you and your students will need to install our free data-collection and analysis app, Graphical Analysis 4, on your devices. Graphical Analysis 4 is available for WindowsⓇ, macOSⓇ, Chrome OS™, iPadOSⓇ, iOS, and Android™.
- Send your students the files for the experiment(s) of your choice. Ask them to read the written instructions as if they were conducting the experiment themselves but complete the data analysis and questions using the sample data provided.
Tips for Teaching with Vernier Sample Data Files
- Note that the student handouts, as written, are designed for an in-person classroom or laboratory environment. We encourage you to read through the Word files prior to sending them to your students, as you may wish to edit to improve their online-learning experience.
- Some experiments require multiple sample data files. The file naming convention will make this clear (e.g., “PEP 23 Magnetic Field – Current Data” and “PEP 23 Magnetic Field – Distance Data”). If you choose to use one of these experiments, make sure the students are given access to all necessary files.
- The Vernier Video Training Library has quite a few videos, some of which might be useful to you or your students to visualize how an experiment is set up or how a sensor works.
- Answers to the analysis questions are not being provided in an effort to keep them from circulating freely and being found by students. If you need assistance with an answer, email email@example.com using your school email address so we can verify your identity.
Click on the links below to download experiments and sample data files.
Elementary and Middle School High School and College
General Science Biology Chemistry Physics
Free Subscriptions to Vernier Graphical Analysis Pro App
The Lehigh Carbon Community College Science in Motion Program has purchased a subscription for the Vernier Graphical Analysis Pro App
, which covers all science teachers and their students from our supported schools until the end of June, 2021. It allows instructors to demonstrate a Vernier lab with GA Pro on their computer via Zoom or Canvas during an online session, and students can connect via WiFi to simultaneously view and receive the collected data (along with any saved data sets) on their own devices that are also running the GA Pro App. Students will then have the ability to perform statistical and/or graphical analysis of the data to help them interpret the results and draw conclusions. Vernier also has a sample library of other experiments, with saved data and many with videos of the set up and procedures, that can be accessed with the GA Pro App from their website at https://www.vernier.com/remote-learning/sample-data-library/
If you want to preview how the GA Pro can be used as a stand-alone App to work with more than 40 sample experiments in biology, chemistry, physics, and middle school science, check out the Graphical Analysis Pro Part 1
To preview how the GA Pro App can be used to explore over 300 additional experiments from the Vernier remote learning sample data library, check out the Graphical Analysis Pro Part 2
In order to request access to either the GA Pro License Key or Teacher Notes
for any of the Vernier experiments that we offer at the Lehigh Carbon Community Science in Motion Program, please visit our website listed below and complete a request form
Free Pivot Interactives Subscriptions Available from Vernier
Pivot Interactives is a powerful supplement to hands‑on experimentation, allowing students to vary experimental parameters one at a time to view results from a set of many slow-motion recordings of the same experiment. Students make measurements and analyze their data directly within the online environment to "discover" scientific principles. There are lessons for biology, chemistry, and physics for middle through high school students. Go to https://www.vernier.com/remote-learning/
to explore the videos and lessons that are available. To access the free resources being offered and select the 30-day free trial for an unlimited number of students during the trial period, click on the link Pivot Interactives Free Trial
. The Lehigh Carbon Community College Science in Motion Program has also purchased a site license to allow up to 30 subscriptions per teacher that can be shared between students in all of their classes. Submit a request form at a request form
to get your Pivot subscriptions.
Teachers can assign a lesson to their students to complete during group work or as individual assignments. Focus questions guide student thinking and analysis and tools are provided to prepare data tables, calculations and graphs. Students can create their own account at www.pivotinteractives.com and they need to enter the Class Key code provided by their instructor.
Free Trial of Video Analysis App Available from Vernier
The Vernier Video Analysis app allows students to use their mobile devices in the laboratory or out in the field to make a video with recorded motion, mark data points to track the object in motion, and set the scale of the video. This app brings video analysis to all of your students regardless of the device – even Chromebooks. Go to https://www.vernier.com/remote-learning/
to explore the free resources and lessons that are available. To access the free resources being offered and select the free trial for everyone in a single school building until the end of June 2020, click on the link Vernier Video Analysis Free Trial
2021 AP Exam Information and Review Materials
AP Online Course Schedule
Attention ALL AP Teachers!!!
Teachers and students can keep working toward college credit and placement with free, live AP review lessons, delivered by AP teachers from across the country. These courses:
- Are optional, mobile-friendly, and can be used alongside any work the teacher may assign.
- Will be available on-demand, so you can access them any time.
- Will focus on reviewing the skills and concepts from the first 75% of the course. There will also be some supplementary lessons including topics from the final 25% of the course.
To access the live classes and recordings, visit the AP YouTube channel. For more details about your exams, visit https://lccc.instructure.com/courses/5456/modules
Annotated Websites with Science Activities
The Steve Spengler Science website has commercial lab kits available for simple science activities, but also has about 50 at-home experiments that are trending and are being offered for free during this stay-at-home period. Below are two activities that can be used to build a simple motor or create a density column using sugar solutions.
World's Simplest Motor: https://www.stevespanglerscience.com/lab/experiments/worlds-simplest-motor-version-1/
An electric motor is a machine that converts electrical energy into motion. These machines can come in all sizes and are often used everyday. The simple principle is that an electrical current in a wire moves through a magnetic field producing a force which spins the wire. Here you can make a simple motor using items found at home!
Density is a measurement of how much "stuff" or mass is within a given area. This concept can be easily understood by using sugar, water and some food coloring. By mixing varying amounts of sugar into water each glass of water will have a different mass. This experiment uses that to prove the density of each sample based on the mass contained in them.
Flinn Scientific is offering access to over 50 free at-home experiments, many of which utilize common household materials. (Flinn also sells lab kits that include the necessary supplies to conduct the experiments.) The activities are organized by subject area and grade level. Detailed instructions and Teacher's Notes are provided for each activity and can be downloaded at https://www.flinnsci.com/athomescience/at-home-activities/
ZOO CAMs: Explore zoo’s from Alaska to Atlanta and all around the world right from your living room.
Alaskan Zoo Polar Bear Camera
provides video of the zoo’s polar bear though out the day and night. The website also has detailed species descriptions and pictures of each of their animals.
Atlanta Zoo Panda Cam
provides vide footage of their panda bear as well as educational readings about other species in the zoo.
offers information about each of the animals in their zoo. Students can start by viewing the animals alphabetically, by classification or by habitat.
Arizona Science Center
provides fun and easy science activities to do right from your home. Supplies is minimal and the instructions are detailed. Some activities include making a constellation viewer, making a lava lamp and even creating snowflake crystals. Helpful videos are also provided as well as scientific articles.
National Ocean Service
has an educational page “Just for Kids”. This page offers games, coloring pages, puzzles, videos and learning activities. Students can learn about efforts being used to protect oceans such as oil spill prevention and how oil behaves in water. Games include building a climate-resilient city, multiple water life challenges and pollution solution games.
PA Dept. of Conservation and Natural Resources
With all of us working, teaching, and learning from home and all State Park & Forestry programs canceled for March & April, here are our curated options for online learning, outside activities, and more.
- Need activities and lessons for your at-home students? We have you covered (see below).
- Encourage your students to explore their own backyard as a classroom- Ideas from Project Learning Tree (PLT)
- Take a walk in your local park! Ask you students to check out their local state or community park and use it as a learning space. Here are activities from Project Learning Tree (PLT) to make it more meaningful.
- Go for a hike! Introduce your students (& their parents) to their local PA State Park. They can find their local PA State Park here.
- Try bird watching! Have your students record backyard birds (through April) with Project FeederWatch
- Teach a kid to fish! In response to virus concerns, the Statewide Opening Day of trout season will take place on April 18, but non-trout waters can be fished prior to 4/18/20. All those age 16+ must have a fishing license. Go here to get yours. FYI- To reduce unnecessary travel and social contact amid health concerns, PFBC Commission Executive Director Tim Schaeffer signed an emergency order that allows anglers and boaters to display their fishing license, launch permit, or boat registration digitally on a phone or other mobile device as proof of possession. First time fishing? Check out PFBC's "Fishing Fundamentals."
- Free! Environmental Education activities from Project Learning Tree (PLT)!
- Are your students able to start a garden or plant seeds in a pot? Even one seed pack can lead to tons of learning investigations. Learn more here (includes lesson plans).
- Encourage your students to work with their family to make their home greener (from PLT)
- Learn outside! Utilize these amazing, printable nature activity and information sheets from the NY Department of Environmental Conservation
- Have you tried Yogarate yet? It is the brainchild of Ron Shuali, M,Ed. that combines yoga, karate, Reiki, and other martial arts to improve health, behavior management, and relaxation. Ron is offering >25 different Yogarate videos for free to engage and educate your students (from YouTube).
- Here is a HUGE list of educational companies offering FREE remote learning & teaching resources to Educators. It has grown so large that it has been moved from a Google Form to the web- http://www.amazingeducationalresources.com/ This list includes free access to Kahoot Premium for the rest of the school year!
- Do you teach high school students about watersheds? Utilize DCNR's Watershed Education website. Check out tons of watershed-related resources here. Consider utilizing our Watershed Education pre-assignments (This section). All of these free lessons are suitable for high school and college students.
- Teach about the vital importance of clean water, water conservation, & hand washing! Free to download from Project WET's Clean and Conserve Education Program! This program includes:
- Project WET's Clean & Conserve Activity Guide which is a 40-page Activity Guide for Educators which contains 5 water conservation and hygiene lessons, as well as introductory material, a glossary, and information about Ecolab & Project WET.
- Clean and Conserve Water Activity booklet
- Clean and Conserve Water Science Project Guide
- Water for You & Me Children's storybook
- and more!
- Project WET's WASH (Water, Sanitation, and Hygiene) trainings give access to materials on hand-washing and health for free! Available at www.projectwet.org/wash
- Turn screen time into learning time with FREE online water games for kids in grades 3-6. Ask your students to check out the Project WET Foundation's https://www.discoverwater.org/ .
- Over 30 FREE virtual field trips! Tour museums, visit the San Diego zoo, watch animal behavior up close with hidden cameras, explore Mars on a rover, and more. It's the next best thing to being there!
- Want to observe wildlife up close and be able to study their behavior? Check out live wildlife cameras! There are 1000’s of cameras worldwide. Here are the best just in PA . Here are some of the best from the US and Canada. Everyone needs at least one good bat cam as well.
- Use your student's backyard for science inquiry. Micro-nature is an excellent way for your students to “claim” a little piece of the outdoors, get to know it intimately through observation, and repeat visits by focusing deeply into one contained spot, as large as 1’ X by 1’ in area, or as small as a square inch.
- This is a great list of at-home learning ideas from a seasoned Teacher. Check out this really good, practical list.
- Remote education resources from Project WILD https://www.fishwildlife.org/projectwild/remote-wild (to get the most out of the activities listed, you will need a current copy of the Project WILD K-12 Curriculum & Activity Guide. This guide can only be obtained by attending an in-person training).
- Earth Day turns 50 years old this year! Sadly, most Earth Day (4/22/20) events will be cancelled this year. Teach your students about the history of Earth Day & what they can do here.
Play Games to Learn Computer Science
You can continue to learn at home while schools are closed. Try out fun computer science tutorials, watch videos about computer science concepts, and even build your own projects! This site https://studio.code.org/courses
a free K-12 curriculum with a wide variety of activities that help students learn how to write code and understand how computer programs operate. Learn while playing Minecraft or Angry Birds, or have a Dance Party with a group of animated friends.
Code.org® is a nonprofit dedicated to expanding access to computer science in schools and increasing participation by women and underrepresented youth. Our vision is that every student in every school has the opportunity to learn computer science
, just like biology, chemistry or algebra. Code.org provides the leading curriculum for K-12 computer science in the largest school districts in the United States and Code.org also organizes the annual Hour of Code
campaign which has engaged more than 15% of all students in the world. Code.org is supported by generous donors including Amazon, Facebook, Google, the Infosys Foundation, Microsoft, and many more
NASA STEM Engagement Activities
NASA has created fun STEM activities for students to do at home, which can be accessed by clicking on the link www.nasa.gov/stem-at-home-for-students-k-4.html
. These include projects to build, puzzles to solve, images to color, books to read, and more. Topics are presented in a clear concise manner, including Humans in Space, the Solar System and Beyond, Space Technology, Earth images and videos from space, and more. Enjoy the spectacular, out-of this-world views from the Hubble telescope, unmanned explorers, and manned spacecraft!
Soda Bottle Experiments
Recycling plastic 2 liter soda bottles to become vessels for science experiments is an inexpensive way to explore such topics as ecosystems and rocket science. The website http://bottlebiology.org/ has detailed instructions for creating terrariums/aquariums to study decomposition of organic materials, the fermentation process, and the interactions between terrestrial and aquatic environments. Click on the site above to find detailed design instructions and measureable data used to study changes that occur over time.
It Really is Rocket Science
Introduction: The design, construction, testing and launching of soda bottle rockets provides students with a learning experience that is guaranteed to capture their interest. Students must originate their own design, gather their own materials, build, test and make improvements in order to make their rocket fly successfully. Students can apply Newton’s Laws of Motion to launch their homemade creations into the air in a single bound using pressurized water, traveling well over one hundred meters.
Rocket Design and Construction: Students are challenged to design and build a rocket using a 2-L plastic soda bottle and water pressure as the engine that will travel the greatest distance without tumbling out of control. They will be given a few days to gather materials before construction begins. Do not use metal, glass, hard plastics, spikes, rocks or other hard objects as materials because they would create a dangerous projectile. Rockets will be built in class with allowances for making refinements at home. Fins and nose cone can be duct taped or glued onto the bottles. The fins add stability and the nose cone helps to reduce drag caused by air friction during flight. (A parachute could be added under the nose cone.) The LCCC Science in Motion Program has a triple bottle rocket launcher that can be used to pressurize and fly the rockets that your students design. As a preliminary activity, complete the POGIL lesson on Projectile Motion.
Projectile Motion Simulation
In order to get an understanding of projectile motion and the variables that describe the flight path of the soda bottle rockets, students can access an online simulation of a cannon shooting a pumpkin, a human, or other objects into the air with the goal of hitting a target.
Complete the following POGIL activity to gain an understanding about what variables can affect projectile motion.
- Launch the Lab activity. Notice that there are multiple variables that can be changed, such as the Initial Speed, mass, and diameter of the object that is fired from the cannon. Fire the Cannonball and notice its flight path and where it lands. Notice that the cannonball misses the target when using the default setting.
- Try changing the mass of the cannonball. Explain if this will help to hit the target. Click the eraser.
- Try changing the diameter of the cannonball. Explain if this will help to hit the target. Erase.
- The Earth’s gravity is normally 9.81 m/s2, so do not change it. Check the box to create air resistance against the cannonball. Explain how the mass and diameter of an object determines the effect of air resistance on the height and distance the projectile travels.
- Click the reset button . Move the target location so that it is centered at a distance of 25.0 m from the cannon. Now adjust only the angle of the cannon to try to hit the middle of the target. Explain how the angle of the cannon effects the height and distance the projectile travels.
- Click the reset button . Move the target location so that it is centered at a distance of 20.0 m from the cannon. Now adjust only the Initial Speed of the cannonball to try to hit the middle of the target. Explain how the Initial Speed of the projectile effects the height and distance that it travels.
- Click the reset button . Raise the platform that the cannon rests on to a height of 10 m and set the angle of the cannon to 0º. Fire 1 shot and note where the cannonball lands. Now, without changing the position of the cannon, adjust any of the other variables to try to hit the target in 2 attempts or less. Summarize what combination of variable settings resulted in a bulls-eye.
Suggested Activities from the LCCC SIM ClassVR Provider
The Tierney Professional Development team
is focused on supporting student learning beyond the four walls of the classroom. Due to the developments of COVID-19 (coronavirus), and the recommendations of various health organizations, many states have determined they will be closing schools and are requesting that schools develop distance learning plans. Many schools are providing plans specific to their students, but we understand some families are looking for additional resources to keep the students engaged in additional learning opportunities.
The sites in this list below allow you to create accounts as a parent to help support your child’s learning. Please keep in mind that you are responsible for reading and determining if the terms of service for a given tool align with your personal comfort level in using these digital tools.
Khan Academy Kids
Prodigy - Math Game
Epic! - Kids’ Books and Videos
Scholastic Learn at Home
- Grades: PreK-6+
- Subjects: Variety, with a focus on reading
- Get set up as a parent
- Parent support and guidance may be necessary for some activities
- 3 Free Weeks of Maker Stations
- Each challenge includes instructions using materials around the house, QR code video resources, and a student recording sheet.
- Parent support and supervision may be necessary for some activities
- From Teach Outside the Box Facebook Page
Public Library Books
- Web-based and App-based
- Ages: Grades 4-8, but my 2nd grader can do it with my assistance
- Subjects: Variety, with focus on Coding
- Accounts are not necessary when you access via the Curriculum Page
Little Sports YouTube Channel
- Cloud Library
- Ages: All ages
- Subject: Variety
- Using your public library card - download ebooks and audiobooks
- Web and App based
- Ages: 4+
- Subject: Fitness (Physical Education)
- Exercise and movement videos, 9- 21 minutes in length
College Board Advanced Placement Exams
Taking the AP Exams
College Board surveyed 18,000 AP students to see if they still wanted the opportunity to test this year. Their answer: a resounding yes.
Free resources will be available through exam day to help you get ready. While we encourage you to wait until closer to the test to decide, any student registered for an exam can cancel at no charge.
For the 2020-21 exam administration only:
- We’re developing secure 45-minute online free-response exams for each course.
- The exam content will focus on what most schools were able to complete by early March.
- You’ll be able to take your exams on any device you have access to—computer, tablet, or smartphone. You’ll also have the option to write your responses by hand and submit a photo.
- Colleges support this solution and are committed to ensuring that AP students receive the credit they have worked to earn. For decades, colleges have accepted a shortened AP Exam for college credit when groups of students have experienced emergencies.
- We know that not all students have access to the internet or a device. We’re working on solutions to help students get what they need to show their best work. If you need mobile tools or connectivity or know someone who does, you can reach us directly to let us know.
The exams will be secure. We’re using a variety of digital security tools, including plagiarism detection software.
Free AP Review Classes
Beginning on Wednesday, March 25, you can attend free, live AP review courses, delivered by AP teachers from across the country. These courses:
- Are optional, mobile-friendly, and can be used alongside any work your teacher may give you.
- Will be available on-demand, so you can access them any time.
- Will focus on reviewing the skills and concepts from the first 75% of the course. There will also be some supplementary lessons including topics from the final 25% of the course.
To access the live classes and recordings, visit the AP YouTube channel or find your course schedule below. We’ll be adding more courses soon.
Download the daily schedule for 32 courses (.pdf/151 KB).
Mark Case AP Chemistry Mock Exam Reading Webinar 3/19/20
On March 19, 2020, I worked with Maureen McGrail from the Advanced Placement Teacher Investment Program (AP-TIP IN), which is part of the University of Notre Dame’s outreach program, to record a 2 ½ hour webinar focused on a Mock Exam Reading using the 2013 Practice Multiple-Choice and 2019 Free-Response portions of the AP Chemistry Exam. This webinar was designed to offer insight into how the actual exam is designed and scored and what resources teachers can use to help students improve their performance on the actual AP Exam (originally) scheduled to be held in May.
You can access the video of this webinar from my google drive using the link below:
Errata & Clarifications
During the process of recording this webinar, I tried to be as thorough and accurate as possible, but after watching and listening to the video, there are a few errors in statements that I made, which I feel need some clarification.
Each item is referenced by the time stamp periods when they occurred, using the hour:minute:second format.
00:46:50 to 00:48:31 The Nernst Equation can be used to predict voltages of electrochemical cells when they are at non-standard conditions, Ecell, by comparing them to the voltages derived from the standard reduction potential values, Eºcell.
The value of the reaction quotient, Q, is dependent on the concentrations of the products divided by those of the reactants in the half-cells. Under standard conditions of 25ºC, 1 M aqueous solutions, 1 atm partial pressure of gases, Q, has a value of 1. When Q = 1, the value of lnQ = 0, which makes Ecell = Eºcell.
When Q > 1, the value of lnQ is a positive value, which makes Ecell < Eºcell.
When Q < 1, the value of lnQ is a negative value, which makes the Ecell >Eºcell.
In the video, I initially stated that Q has a value of 1 under standard conditions, but then I misstated that Q = 0 and then lnQ = 0 at standard conditions, which is incorrect.
00:51:10 to 00:52:05 While discussing the different assigned values for constants used in formulas on the AP Constants & Equations Pages, I stated that the value for the speed of light, c, is 3 x 108 m/s, and attributed that speed to the light “particles”, when I should have said “photons of light”. Although, quantum physicists might argue that both are correct.
00:58:10 to 00:58:50 For the rubric to score Question 1 (c) on the Powerpoint, the common errors/misconceptions list includes a rounding error when changing 0.0897 moles to 0.08 moles in the intermediate work. I incorrectly stated that the student would not earn the point due to a significant figure error, but this was not the question that was scored based on using correct significant figures. This rounding is actually a math error, when the student would truncate the 0.0897 moles to 0.08 moles. If they rounded up to 0.09 moles, that would be a correct answer. Rule of thumb: Don’t round off intermediate answers, only the final answer.
00:58:50 to 01:00:05 Additional Scoring Guideline - If the student incorrectly determines the molarity of the urea solution in Part 1 (c) to be greater than 19.8 at 20.ºC, then they must identify the reaction as being exothermic in Part 1 (d) and use a similar justification in order to earn a point based on consistency with their previous answer.
01:02:20 to 01:02:30 Inadvertently stated that the “temperature” is placed in the Styrfoam cup, when I meant to say “thermometer”.
01:21:55 to 01:22:15 While describing the effective nuclear force, Zeff , of the oxygen atom compared to the oxide ion, I incorrectly determined their values. Both the oxygen atom and oxide ion have 8 protons in the nucleus and 2 electrons in the first occupied shell. Therefore, their Zeff values both equal +6, calculated from 8 protons – 2 inner-shell electrons. When the oxide ion gains two more valence electrons, the extra electrons create more repulsion of the outer-shell electrons and cause the oxide ion to increase in size. This increase in size causes the Coulombic attraction between the protons and the valence electrons to decrease.
01:23:01 to 01:24:10 Similarly, when a sodium atom loses 1 valence electron to form the Na1+ ion, the ion now has only 2 occupied main energy shells, compared to the sodium atom that has 3 occupied main energy shells. This causes the effective nuclear force, Zeff , of the atom to be 11p – 10e- = 1+ and the ion is 11p – 2e- = 11+. This large increase in the Zeff and the loss of an occupied main energy level causes the Coulombic forces of the ion to increase greatly, as compared to those of the sodium atom.
01:40:18 to 01:41:35 I eluded to the relationship between Kc and Kp when using either the concentration or gas pressure to calculate the equilibrium constant in Question 2 (e). The equation that used to be included on the AP Exam Formulas Sheet is written as:
Kp = Kc (RT)∆n, where Kp is the equilibrium constant based on the partial pressure of the gases, Kc is the equilibrium constant based on the molarity of the gases, R is the ideal gas law constant, T is Kelvin temperature, and ∆n is the #molesproduct - molesreactant. In this case, the moles of reactants and products are equal, which makes the Kp = Kc. So, either format is an acceptable answer. The symbol PBrCl is used to express the partial pressure of the gas and (PBrCl)2 encloses the pressure in ( ) when solving for Kp. [ ] are used to express molarities when solving for Kc.
02:00:25 to 02:03:00 Although my explanation seemed logical to me for Question 2 (h) as to why Na2CO3 would not be suitable to make a buffer with a pH of 6, I could not swear to it that the AP reader who was given the pleasure of evaluating my paper would agree. In order to add some clarity, let me write some more…. something we tell our students to never do on the exam. (Rule of thumb: Know when to fold them and stop writing.)
A buffer works by having about the same concentrations of both the acid/conjugate base pair that can neutralize either small amounts of added base or acid. This buffer zone occurs during an acid-base titration when ½ of the amount of titrant needed to reach the equivalence point has been added to the other reactant. For a weak acid, the pH value at this ½ equivalence point will equal the pKa value, which should be equal to 6.
When the carbonate and hydrogen carbonate ions are present in equal concentrations in a buffer, the [OH-] = Kb = 2.1 x 10-4.
Since the [H+] [OH-] = Kw, the [H-] = 1 x 10-14 / 2.1 x 10-4 = 4.8 x 10-11.
The pKa = - log [H-] = - log (4.8 x 10-11) = 10.3 Therefore, the Na2CO3 could not be used to make a buffer with a pH of 6, since its buffer would be closer to a pH of 10.
You could estimate these values by considering only the 10x powers of the variables in this problem to obtain an answer close enough for government work.
[H-] = Kw / [OH-] = 10-14 M / 10-4 M = 10-10 M
pH = - log [H-] = - log (10-10) = 10, which is nowhere near pH of 6.