Category Archives: Chemistry

Week 39 – You Made It!

Welcome to Week 39!  You made it!  This will be a year we will all remember. It has been my great pleasure getting to know you this school year and teaching you about science.  You are welcome to turn in any work from 4th quarter (Unit 4, beginning with Week 30) until noon on Friday, June 19.  If you revise an assignment and would like it re-graded, please also re-share the link.

Before you head off into your bright future, please complete the Week 39 Attendance Check-In.  Finally, please consider watching the videos below and use what you learn to re-make our community, our country, and our world for the better.

Week 38 – Properties of Light

Some of our deepest scientific insights have come from the most basic of questions.  For our last lesson of the week, we will dig into the question:  What is light?

The short answer to the first question (what is light?) is that light is what we experience as a narrow band of waves of specific wavelengths within the visible part of the electromagnetic spectrum.  A particle of light is called a photon.  Visible photons (light) have properties of both a particle and a wave.  Photons travel in waves, and waves can be described mathematically by measuring wavelength, amplitude, period, frequency, and speed.

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To visualize the parts of a wave, let’s bring in Bill Nye the Science Guy:

Thank’s Bill Nye!  Here’s what we learned:

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In the vacuum of space, nothing moves faster than light.  In fact, we can say the speed of light is the cosmic speed limit.  In a vacuum (like space), light travels at 300 million meters per second (3.0 x 108 m/s).  Because this number does not change, it is a constant and is assigned the letter c (c = speed of light).  Side note: Thanks to Albert Einstein, you’ve probably heard of the equation E = mc2. In words, the equation says that energy (E) is equal to mass (m) times the speed of light (c) squared.  You already knew that c = speed of light!

Ever wondered how long it takes for light from the Sun to reach Earth?  Click here to work through the math and find out!

To complete our study of the properties of light, we need to introduce Planck’s constant (h):

Next, let’s revisit the parts of a wave and make some connections:

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The notes above introduce Planck’s constant, h, which has units of Joule • seconds.  Planck’s constant (h) relates a photon’s energy (E) and frequency (f).  Frequency is defined as the number of complete waves that pass through a point in one second.  The faster a light wave is traveling (greatest speed, measured in meters per second, m/s), the higher the frequency (f, waves/second).  Therefore, the faster a light wave is traveling, the higher the energy (E) of the wave.  Energy has units of Joule • meters.  Waves with the shortest wavelengths (λ) have the highest frequency (f) and therefore have the greatest energy (E).

If you followed all that (and I have no doubt you did!) you are ready for an introduction to Quantum Mechanics.  Enjoy!

Return to Week 38 – Light and Color and continue working.

Week 38 – Star Spectra

We’ve reached the end our our learning this school year.  Appropriate, perhaps, that we end where we began: in the stars.  Way back in Unit 1, you learned that stars fuse lighter elements like hydrogen and helium to form heavier elements up through iron.  Elements with more protons than iron are created when stars go supernova. Plants and animals (yep – humans are animals) are made of star stuff – we are quite literally the product of exploding stars.

We also conducted flame tests, showing that metal cations are responsible for producing specific colors of flame when ionic compounds are burned.  Now we understand that our perception of color is a result of photoreceptors in our eyes being capable of detecting specific wavelengths of electromagnetic radiation.  When those receptors are activated, they send information to our brain which then decodes the signal into our perception of light and color.

When we look up at the stars, we are looking back in time, as it takes time for light to travel from its source to our eyes here on Earth.  The more distant the object, the further back in time we see.  It’s not too hard to imagine there might be organisms billions of light-years away that witnessed the supernova (singular) or supernovae (plural) that launched the atoms within you and me toward our remote location within the Milky Way galaxy.  The force of gravity eventually caused those atoms to coalesce to form our Sun and the planets that orbit it, including the Earth.  After 4.5 billion years, here we are, studying the stars:

Anyone who would like to invest further in their understanding of the stars should email me for a copy of the handout that goes along with the Star Spectra Gizmo.  This activity is purely optional and available for your own personal growth.  It will not be entered in the grade book.

Return to Week 38 – Light and Color and continue working.

Week 38 – Light and Color

Welcome to Week 38!  For our final lesson of the 2019-20 school year, you will be exploring the connection between light and color.  Whether you are taking physics or any of our other science electives next year, this lesson will be a great preview.  Let’s get to it!

  1. Week 38 Attendance Check-In (required by 10am 6/12)
  2. Properties of Light
  3. Electromagnetic Spectrum
  4. Star Spectra
  5. NPR’s Student Podcast Challenge: Meatless Mondays

That’s it!  No new assignments this week (spoiler alert: no new assignments next week either).  Please make sure you have everything turned in by June 19.  It has been my absolute pleasure teaching you chemistry this year.  What a year to remember!

Remember, you can email me any time.  Office hours for Science are Tuesdays from 11am-12pm and Thursdays from 1pm-2pm.  Check your student Gmail for Zoom instructions.

Week 38 – How long does light from the Sun take to reach Earth?

Our live are largely built around the rising and setting of the Sun in the sky each day.  Our biology is intimately connected to this via our circadian rhythms:

Have you ever wondered what would happen if the Sun just suddenly blinked out of existence?  When would you know?  Turns out, it takes time for light to travel from the Sun to the Earth.  We’ve just learned that light travels at a constant speed, c, in a vacuum like outer space.  We know that c = 3.0 x 108 m/s.  To calculate how long it takes light to travel from the Sun to Earth, we need to know the distance between the two.  While the orbit of Earth around the Sun is not a perfect circle, on average the Earth is about 93 million miles (mi) from the Sun.  Time for some math!

Have: c = 3.0 x 108 m/s and distance = 93 x 106 mi

Want: Time it takes light to travel from the Sun to Earth

Need: Connection between meters (m) and miles (mi)

Another quick Google search tells us there are 1609.34 meters in 1 mile.  We are in business!

Calculation: (93 x 106 mi) x (1609.34 m / 1 mi) x (1 s / 3.0 x 108 m) = 499 s

Analysis: It takes about 499 seconds for light to travel from the Sun to the Earth!  Divide 499 by 60 and that gives us about 8.3 minutes.  So if the Sun blinked out right now, at this very instant, we wouldn’t know until 8.3 minutes from now.  The Sun is our nearest star, and it still takes 8.3 light-minutes for its light to reach us.

The second closest star to Earth is called Alpha Centauri.  Alpha Centauri is actually a triple star system (three stars in orbit around each other) located approximately 4.37 light-years from Earth.  Traveling at the speed of light, c, it would take 4.37 years to reach Alpha Centauri.  How many miles away is that?

4.37 light-years x (365 days / 1 year) x (24 hours / 1 day) x (60 minutes / 1 hour) x (60 seconds / 1 minute) x (3.0 x 108 meters / second) x (1 mile / 1609.34 meters) = 2.57 x 1013 miles, or 25.7 trillion miles away!

That’s a long way!  It also means that if you look at Alpha Centauri in a telescope (or just look in the right part of the night sky), you are actually seeing light that left the star system 4.37 years ago.  You are literally looking back in time!  In fact, every time you look up in the night sky, you are looking back in time.

If traveling 4.37 years at the speed of light seems like a long time, don’t despair.  The distance from Earth to the nearest planet outside our solar system is a bit less.  Discovered in 2016, the planet Proxima Centauri b orbits Alpha Centauri and is “only” about 4.2 light-years from Earth.

Last week, MIT Technology Review announced the likely discovery of an Earth-like planet around a Sun-like star. (To be more accurate, and to give you a sense of how the scientific process works, the exoplanet was observed, the findings were written up into a scientific article and submitted to the scientific journal Astronomy & Astrophysics on October 16, 2019, and after successfully completing the peer-review process, the article was accepted for publication on May 3, 2020 and then published by the journal on June 4, 2020.  Here is the link to the published article.)  The exoplanet is named KOI-456.04 and is 3,140 light-years from Earth.  

While humanity hasn’t yet engineered a solution for how to accelerate a large spacecraft to near the speed of light, the video below introduces some important concepts regarding near light-speed travel.

Finally, if you think a bit more about the idea that looking at the stars is like looking back in time, the same hold true for Earth.  An alien pointing a telescope at Earth would be looking back in time at Earth as it was when the light left Earth.  If the alien is currently 65 million light-years from Earth, then the light they are observing today through their telescope left Earth 65 million years ago.  Is there a sufficiently powerful telescope that would allow the alien to actually see dinosaurs on Earth?  So glad you asked!

Return to Week 38 – Properties of Light and continue working.

Week 38 – Electromagnetic Spectrum

When we think about light, we think about what can be seen.  If you’ve ever looked through a prism, you understand that white light is actually a collection of all the colors of the rainbow.  The visible spectrum consists of all of the light that we can see with our eyes.  Let’s go back to the rainbow.  The acronym ROYGBIV is a helpful way of remember the colors of the rainbow in “order” where R=red, followed by Orange, Yellow, Green, Blue, Indigo, and Violet.  It turns out that red light has a wavelength range of 620-750 nanometers (nm), while violet light has a wavelength range of 380-450 nm.  Remember, the shorter the wavelength, the greater the energy.  Therefore, because violet light has a shorter wavelength than red light, violet light is higher energy than red light.  We have specialized photoreceptor cells in our eyes that are excited by specific wavelengths of light.  When white light strikes an object, some wavelengths of light are absorbed by the object while other wavelengths are reflected. The color of an object is actually the wavelength of light that object does not absorb!  When reflected light is detected by our eyes, we see color.

Now for the really interesting part: visible light only comprises a small part of the larger electromagnetic spectrum.  The shortest wavelength of electromagnetic radiation is on the scale of 10-12 cm (smaller than the diameter of an atom).  Remember, the shorter the wavelength, the greater the energy.  Photons with the shortest wavelength are called gamma rays and they are powerful enough to shred DNA.  We learned about gamma (γ) rays earlier in the school year during our study of nuclear decay (Lesson 15).  Viewing the night sky with gamma ray detectors gives us a very different perspective about the structure of space compared to looking with our eyes.

At the other end of the electromagnetic spectrum are the radio waves, with wavelengths on the scale of 104 cm (the height of the Statue of Liberty).  Radio waves are emitted by stars and planets and can be detected with radio telescopes.  When the night sky is scanned using a radio telescope, we once again see structures in space that are invisible to our eyes.

To learn more about the visible spectrum, gamma rays, radio waves, and all the rest of the electromagnetic spectrum, visit NASA’s Tour of the Electromagnetic Spectrum and prepare to be amazed with the richness of the Universe!

Return to Week 38 – Light and Color and continue working.

Week 37 – Acids and Bases

Welcome to Week 37!  This week, we will tackle the topic of acids and bases.

Last week was the latest in a long string of really tough weeks for our country.  Rather than try making a light-hearted video introduction, I am simply asking you to visit the Future Voter registration page on the Washington Secretary of State website.  You can register to vote as early as age 16, and then you will be able to vote once you turn 18.  Vote for the country you want and vote in every single election.  While you are waiting to turn 18, remember that every dollar you spend is also a vote in support of wherever your money was spent.  Be intentional with who you choose to give your money to.  Your vote is your voice – scream!

  1. Week 37 Attendance Check-In (required by 10am 6/5)
  2. [H+] and pH (pH Concepts Google Form assignment)
  3. pH Indicators (pH Analysis Gizmo)
  4. pH Lab@Home (optional bonus credit lab)

You did it!  Just to make sure, here’s a checklist of items you must complete this week by Sunday, June 7 at 11:59pm:

  • Week 37 Attendance Check-In (school district requirement)
  • pH Concepts (worth +10 assignment points)
  • pH Analysis Gizmo (worth +20 assignment points)
  • Optional pH lab (worth +40 bonus lab points)

Remember, you can email me any time.  Office hours for Science are Tuesdays from 11am-12pm and Thursdays from 1pm-2pm.  Check your student Gmail for Zoom instructions.

Don’t forget to complete the Week 37 Bonus Credit Opportunity!  For a complete list of all of the bonus credit opportunities, bonus assignments, and bonus lab reports offered during distance learning, click here.

Week 37 – pH Lab@Home

If you have access to some red cabbage and a few household solutions, you have what it takes to prepare the cabbage juice indicator shown in both Tyler DeWitt’s “magic trick” and Mr. Swart’s Week 36 introduction video.  Either way, earn up to 40 bonus points in the lab portion of your grade by documenting your efforts to:

  1. Prepare red cabbage indicator
  2. Observe after adding baking soda to the indicator
  3. Observe after adding an acid to the indicator
  4. Observe after adding a base to the indicator
  5. Observe after adding an acid to the indicator, followed by baking soda
  6. Observe after adding a base to the indicator, followed by baking soda

To earn the full bonus credit, document all of your work as a lab report and share it with Mr. Swart at david.swart@g.highlineschools.org.  Before you begin, review the Week 34-35 bonus credit lab report post and recall what happens when you mix baking soda and vinegar (an acid) – it gets messy!  That post includes videos, lab report requirements, and lab report templates you are welcome to use as appropriate.  Have fun!

Return to Week 37 – Acids and Bases and continue working.

Week 37 – [H+] and pH

The words acid, base, and neutral are all familiar.  By now in your schooling you have probably learned that water is a neutral substance, lemon juice is an acid, and bleach is a base.  You may have been introduced to the pH scale where you learned that water has a pH of 7, while acids have a pH of between 0 and less than 7 and bases have a pH of greater than 7 up to 14.  In fact, the pH of lemon juice is around 2.0, while the pH of bleach is around 12.6.  Lemon juice is a fairly strong acid, while bleach is a strong base.  Your blood has a pH of 7.4, making it slightly basic.

So what exactly makes something an acid or base?  Why are some acids and bases stronger than others?  Click the image below (or just click here) and read all about the relationship between hydrogen ion (H+) concentration and pH.

Acids-and-Alkalis-The-pH-Scale

Next, watch the video below from Mr. Anderson at Bozeman Science:

 

Finally, complete the pH Concepts Google Form assignment and show what you know about acids, bases, and pH.  When finished, return to Week 37 – Acids and Bases and continue working.

Week 37 – pH Indicators

To determine whether a solution is an acid, neutral, or a base, we need a tool.  In the lab, we can use a pH probe to obtain a quantitative pH value (an actual number).  Back in the day, we used pH strips to estimate the pH of different solutions.  Some strips are more sensitive than others, but the common theme is the strips rely on the user matching the color of the strip to a color chart which then estimates the pH.

At home (or in high school classrooms with limited funding) we can create a colorimetric indicator using cabbage! Colorimetric pH indicators provide us with a semi-quantitative measurement of pH.  By comparing the color of the indicator to a scale showing the color at a known pH, we can estimate the pH visually.  Color alone would be a qualitative data point (a description) while matching the color to a number provides us with a quantitative data point (an actual number).

To be fair, scientists use laboratory-grade colorimetric indicators in the lab all the time, and then use machines called spectrophotometers to quantitatively determine the optical density of the light passing through…remember the ELISA post from last week?

If you watched the Week 36 Intro video, you will soon realize that it also introduced you to this part of our lesson.  Prepare to be dazzled by the wizardry that is red cabbage juice indicator:

What is the actual chemistry behind red cabbage juice indicator?  Click the picture below and find out:

Making-a-Red-Cabbage-pH-Indicator

You now have what you need to complete the pH Analysis Gizmo.  The Gizmo was sent as a PDF attachment on Monday morning at around 8:00 am to the Week 37 – Chemistry Lesson email.

Anticipated answers to the question, “How do I turn in the Gizmo?”

  • If you have access to a printer, print the Gizmo and then:
    • Scan and email your completed work to Mr. Swart
    • Send pictures of your completed work Mr. Swart
    • Insert pictures of your completed work into a Google Doc and share with Mr. Swart.
  • If you do not have access to a printer:
    • Write answers on a piece of paper and then see above.
    • Write answers in a Google Doc and then see above.
    • Add comments to the PDF and share with Mr. Swart
    • This is 2020 – get creative!

Extend your learning!  For more on acid-base indicators, read Lesson 117 in the online textbook.  Note: this is not an assignment and you are not required to turn in any work related to lesson 117.

Return to Week 37 – Acids and Bases and continue working.