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homeschoolsciencegeek

November 2016

Today’s lab came out of the HomeScientist’s chemistry manual CK01A, VIII-1:Observe the Pressure-Volume Relationship of Gases (Boyle’s Law).  I’ve tried to do this lab before with the  Boyle’s Law apparatus from Home Science Tools and have never gotten very good results (and it actually broke today) so I decided to give this other version a try.  I’m pretty sure the one from Home Science Tools just needed more oil on the syringe plunger.  Anyway, the Home Scientist’s version of this experiment uses a much smaller syringe (10mL) and you just have to lightly hold a 2L soda bottle upside down on the plunger to exert the pressure on the gas.  The syringes come with caps so you can contain the gas in the syringe.  Using the soda bottle lets you easily increase its mass by 200 gram increments just by adding 200 ml of water (density of water is 1 g/ml).

The actual experiment is relatively easy, lubricate syringe plunger (very important to do a good job on this step), find mass of empty bottle and syringe plunger, add water to bottle to get a total of 200 grams to put pressure on the gas volume in syringe, record volume of gas off syringe.  Then add 200 ml of water to bottle, find volume of gas and repeat until soda bottle is full.

The complicated part of this lab is the data analysis.  We’re recording the mass exerting a force on the gas not the pressure, so we have to calculate the pressure and add the atmospheric pressure  because its also pushing down on the syringe plunger.    I helped the younger kids in the class with these calculations and showed the older kids how to set up a spread sheet to make it easier. Then the students plotted their data,  volume as a function of pressure and found that as pressure on a gas increases (at constant temperature) the volume will decrease.

I recommended the students watch the following videos before class:

Today we got through three different lessons.  I started by reviewing atoms and how they are made of protons, neutrons and electrons.  I drew a few atoms on the white board showing how the electrons go in shells and how the atoms prefer to have 8 in the second shell.  If there is only one electron in that shell the atom would prefer to get rid of it, or if it has 7 electrons in that shell it would really like to have one more.  I drew a bunch of different atoms showing how they could share electrons and then both atoms shells would be full and you would have a molecule – covalent bonding.  Then I showed them how to draw lewis dot diagrams to show the outer or valenece electrons so we don’t have to draw an atom with the shells each time.  The students created a few lift the flap pages in their notebooks using the lewis dot diagrams from Chemistry: Compounds, Bonding & RXNs by Stephanie Elkowitz and we used pages on covalent bonds from Covalent Bonding for Interactive Notebooks by Bond with James – both of which can be bought on Teacherspayteachers.com.

The second thing we did was an electrolysis demonstration, shown above.  This is a set up that was purchased from Carolina.com by a fellow homeschooler.  You fill the test tubes with water and invert them on to the black stand so that there is no air in the test tubes.  When you hook up the wires to a 9V battery the electric current flows and breaks up the water molecules producing hydrogen and oxygen gas.  In the photo we used salt water which made for a much more exciting demonstration and you can see the test tube on the right has created quite a bit of gas, almost filling a third of the test tube and this happened in maybe a minute or two.

Lastly, I explained to the students that isotopes were atoms of the same element (same number of protons) but with different numbers of neutrons and therefore slightly different masses.  The students then played Atoms & Isotopes that I had downloaded from Elemental Science for free.  I had to print out a bunch of playing cards and dig out some pony beads but it seemed to go over well with the kids.  The way to win the game is to build all the isotopes on your card.  There’s only two different cards, Hydrogen with 3 isotopes for a quick game or Nitrogen with 2 isotopes but a lot more protons, neutrons and electrons to collect before you finish.  The kids played a couple rounds in the last 30 minutes of class.

NOVA has a great FREE app, Elements,  for iPads where you can build atoms just like in this game. You drag protons, neutrons and electrons. This feature is hidden a bit, from the main menu go to the interactive periodic table and click on the element you want to build. a window pops up with info on the that element and in the top right corner is a green button with Build on it. Click on build and then drag the particles from the bottom of the screen into the center to build the atom.  The app keeps a running tab for you on the left side of the screen.

2016-2017 Complete.

Honors Chemistry 32 – Specific Heat

Complete 2016-2017.  Students in this class were  10-13 years old.

Intro Chem 19 – Acids & Bases

Intro Chem 20 – Controlling the Products

Intro Chem 21 – Precipitate

Intro Chem 22 – Reaction rates

Intro Chem 23  – Catalysts

Intro Chem 24 – Game Day!

Intro Chem 25 – Identifying unknowns & Elements 4D

Intro Chem 26 – Acid Concentration, Color & pH

HOLLYWOOD ( and all that )

hanging out and hanging on in life and the movies (listening to great music)

Learn from Yesterday, live for today, hope for tomorrow. The important thing is not stop questioning ~Albert Einstein

graph paper diaries

because some of us need a few more lines to keep everything straight

Evan's Space

Wonders of Physics

Gas station without pumps

musings on life as a university professor

George Lakoff

George Lakoff has retired as Distinguished Professor of Cognitive Science and Linguistics at the University of California at Berkeley. He is now Director of the Center for the Neural Mind & Society (cnms.berkeley.edu).