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Honors Chemistry 31 – Nuclear Chemistry

This is one of my favorite chemistry topics since its also a topic in physics.  I pulled out an old slide show on nuclear physics, different types of nuclear reactions, fission, fusion, atomic bombs, power plants, all the good stuff.  We did the activities ‘Simulation of Nuclear Decay Using Pennies and Paper’, from the Modern Chemistry curriculum and built cloud chambers.

For the paper activity,  I precut a bunch of paper strips from colored card stock and gave each IMG_9880student two strips.  They placed the first strip on a graph to represent 100 percent of material.  Half of that will decay in one half life so they take the second strip which is the same length as the first one and cut it in half.  Tape the half strip next to the first one.  Repeat with each remaining strip until you can no longer easily cut the strip.  For this example we made the half life 1 minute, which is about the time it took to fold and cut the piece of paper to make the next bar.

IMG_9881

The other part of this activity involved putting 100 pennies heads up in a box – this represents our ‘original’ sample of material.  Students shook the covered box 5 times and then removed all the pennies that had ‘decayed’ (turned to tails).  This should be roughly half the pennies.  They then repeated the shaking and removing of ‘decayed’ pennies til they had 1 or 0 pennies left.  Every shake was considered to be a half life of 10 minutes for the purposes of graphing their data.

IMG_9892Then we get to the fun part of class, making cloud chambers.  A cloud chamber is a closed container with an isopropyl alcohol soaked felt pad inside it (near the top or sides) and black paper on the bottom.  The alcohol forms a mist inside the container becoming super saturated near the cold bottom of the container which is sitting on dry ice.  As particles zip through the mist it produces ions and the alcohol drops condense on these ions, leaving a visible trail.  There are a lot of videos on the web explaining how to make cloud chambers.  Here are the two I like, one by Jefferson Labs uses a petri dish to make a small cloud chamber and the one on ScienceFriday has instructions for using something bigger.  The petri dish one works really well but its gets fogged up and you spend a lot of time wiping it off.  I bought the dry ice and 91% isopropyl alcohol at my local grocery store. Our best cloud chamber was built from a cheap (thin and flimsy) plastic cookie (Dunkers) container from Trader Joe’s.  IMG_9917

In the photo above you can see our radioactive rock and 4 trails from particles that were emitted from the rock. You can also see the alcohol mist/rain in the container.   You don’t need a radioactive sample to put in the container, you will see trails from muons and other particles that are zipping by us all the time.   Here’s two videos from class:

I asked students to watch these videos before class:

Physics highschool class

Light and matter coverThis honors highschool physics class was taught 2015-2016

Homeschool Physics 001

Homeschool Physics 002 – metric units and measurements

Homeschool Physics 003 – Velocity

Homeschool Physics 004 – Constant Acceleration

Homeschool Physics 005 – Newton’s 2nd Law

Homeschool Physics 006 – Friction

Homeschool Physics 007 – Projectiles

Homeschool Physics 008 – Static Equilibrium

Physics 009 – Uniform Circular Motion and Black Holes.

Physics 010 – Gravity & Kepler’s Laws of Planetary Motion

Physics 011 – Conservation of Energy

Physics 012 – Hooke’s Law

Physics 013 – Conservation of Momentum

Physics 014- Rotational Motion

Physics 015 – Ideal Gas Law

Physics 016 -Vibrations

Physics 017 – Sound Waves

Physics 018 – Waves

Physics 019- Electricity

Physics 020 -Playing with Fields

Physics 021 – Relativity

Physics 022 – Electromagnetism

Physics 023 – Atoms

Physics 024 – Nuclear Physics & Spectra

Physics 025 – General Relativity

Physics 026 – Ray Optics

Physics 027 – Lens

Physics 028 – Why the sky is blue

Physics 029 – Diffraction

Physics 030 – Polarization

Physics 031 – Probability

Physics 032 – Light is a particle?

Physics 033 -Particles are Waves?

Physics 034 – Bohr Atom

Real Science Odyssey Physics Class

Here’s a list of posts from the class I taught for young kids over the summer of 2016 using Pandia Press’s Real Science Odyssey Physics level 1.

RSO Physics 01 – measurement & mass

RSO Physics 02 – Mass & Buoyancy

RSO Physics 03 – Forces

RSO Physics 04 – Momentum

RSO Physics 05 – Newton’s 3rd Law

RSO Physics 06 – Friction

RSO Physics 07 – Air

RSO Physics 08 – Light

Honors Chemistry 13 – Phase Changes

We did two labs today, generating heating and cooling curves for wax  and making ‘wet’ dry ice.  The first lab involved placing some wax in a test tube and then placing the test tube in a beaker full of water (water bath).  The beaker was heated by a hot plate or butane burner until the wax melted.  A thermometer is placed in the wax (we put a bulldog clip on the thermometer to keep it from touching the bottom of the test tube) and the test tube is removed from the heat.  Students recorded the temperature of the wax for 30 minutes at 1 minute intervals.  This data will produce a cooling curve.  They also recorded the phase of the wax, liquid or solid or combination of the two.  The temperature starts to drop pretty rapidly when removed from the hot water but as the liquid wax starts to solidify the temperature change slows down.  Once the wax has finished solidifying the temperature will start to drop again.

img_6037After collecting the cooling data, students placed the test tube of solidified wax back into a hot water bath and recorded the temperature as it heated back up.  This happens a bit quicker so students took data every 30 seconds for 5-10 minutes.  One group found their water had cooled off too much so they never full liquified their wax and the other group had their water bath a little too hot and it liquified too fast.

We were having too much fun with the dry ice in the second lab to plot the data in class so I told them to use a computer/iPad to plot their heating and cooling curve at home.

The ‘Wet’ Dry Ice lab was taken from the Modern Chemistry curriculum.  Dry ice is solid carbon dioxide and can be bought in grocery stores. Most people have never seen the liquid phase of carbon dioxide because it is a gas at our normal  conditions (1 atm of pressure and 20-30 Celsius), which is why it goes straight to the gas phase when we pull the dry ice out of the cooler.  To observe the liquid phase of dry ice we have to increase the pressure, so we cut the tip off a disposable pipette and filled the bulb half way with crushed dry ice (just put a towel over the block and bang on it with a hammer).  Fold the narrow tip of the pipette over twice and close with a bulldog clip.  Placing the pipette full of dry ice in a tank of water makes it easier to see what’s going on (no condensation)  and makes a lot of nice bubbles when it pops.

Here’s a slow motion movie of a pipette with dry ice in it.  You can see the dry ice begin to melt and then boil before the pipette starts to expand from the high pressure and eventually rupture. Once its ruptured the pressure drops and the dry ice goes back into the solid phase.

I did this using a centrifuge tube as well and just unscrewed the cap to relieve the pressure before it blew up.  This was a little easier to see the carbon dioxide go back and forth between liquid and solid as I changed the pressure. I didn’t let the pressure get high img_6043enough to blow up because I wasn’t sure how bad that would be. I was the only one to use the centrifuge tube. The little plastic pipettes just make a big splash as they rip so I didn’t fear the kids getting hurt.  We did have safety goggles on for this lab.

We also made carbon dioxide bubbles and used the gas to put out candles.

 

Here’s a great video from Flinn Scientific explaining the triple point and phase diagrams for carbon dioxide and it shows how to do this experiment in detail.

RSO Physics 08 – Light

The title is a little misleading because today’s class had nothing to do with the Real Science Odyssey Physics curriculum.  This was the last class of the summer and since most of the kids in the class already seemed to know a lot of the science we had been discussing I decided to do my light lecture for older kids.   We discussed how light is a wave and why objects appear to be a certain color. For example, a blue ball looks blue because it reflects blue light and absorbs the other colors.  I then asked why is the sky blue?  Quite a few of them knew it had something to do with the atmosphere, but couldn’t really explain it, so I showed them my big tank of science… an aquarium filled half way with water and a bit of powdered milk mixed in.  The powdered milk helps scatter the light.  You can see in the first photo the milky water looks very blue near the flash light because the particles floating in the water are predominately scattering blue light.  But if you look at the flashlight from the far end of the tank it looks orange/yellow… kind of like a sunset.  When the sun sets the light reaching our eyes has gone through a lot of atmosphere (or a lot of milky water) before we see it and all the blue light has been scattered away, leaving behind the yellow/red colors.  This is also why sunsets are more spectacular when there is a wildfire or volcano because there are more particles in the air scattering light.

After explaining polarized light with the help of some pvc (check out this link  and photo below from Scientific Exploration with Paul Doherty)  I  polarizerparllori300gave each student a set of polarizers and showed them how when they are crossed they can block out all the sunlight.  Then we put plastic forks between the crossed polarizers and you could see ‘rainbows’ of a sort in the plastic where it was stressed.  This happens because the plastic is optically active, the light is actually rotated a bit as it passes through the plastic so it can now pass through the second polarizer.

We also talked about how rainbows are formed, how our eyes work and what it means to be color blind.  There’s a great app on the iPad, ColorDeBlind,  that lets you see how the world would look if you were colorblind.  It doesn’t mean you just see black and white, it means that one set of color sensing cones isn’t as sensitive as its supposed to be.  For some that means they have trouble seeing red, so a light pink shirt may look the same as  a white shirt to them.  Below is a picture I took with the app.  The image on the left is what people with ‘normal’ vision see, and the image on the right is what a red-green color blind person might see.  Notice all the reds and greens are gone but the blue stickers on the fruit still appear very blue. This really blew the kids away.  colorblind

Physics Girl has a nice video explaining the physics of rainbows.

And the Royal Institute has a video called Light Fantastic: The Science of Color that covers a lot of these same topics.

This concludes this set of physics posts.  I did not use the whole Real Science Odyssesy Physics curriculum since I was just teaching a short summer class.   The kids I had in this class were already pretty versed in science, especially for only being 8 or 9 years old and they probably could have done with a little more meat in the curriculum.  But if your kid has never done a science class  this  curriculum would be pretty easy to implement at home.

 

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