Day 2.31 Heating Mg Ribbon

Mon. Mar 17, 2014

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Chemistry students heated magnesium ribbon in a crucible today.  By measuring the mass of the magnesium ribbon before heating and after we will make some predictions about what the reaction.  We will also use the data to determine the percent composition of the product as well as the empirical formula.  I believe using lab data to enforce the importance of mass and mole relationships is vital to student understanding.

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Day 2.27 CAM Challenge

Tues. Mar 11, 2014

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Physics students were given a variety of challenges today.  One was to drop a marble from a designated height so that it would land in the cart approaching on the ground below.  As you can see above this group did quite well.

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Day 2.26 Lens Lab Data – Call for Help

Thurs. Mar 6, 2014

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Physics 2 students were given the freedom to investigate anything they felt compelled to using a light source, converging lens, and viewing screen.  Some groups choose to measure the distance from the light to lens and compare to the distance from the lens to image.  This was good, and the data modeled the Lens Equation  (1/do + 1/di = 1/f ) perfectly!

The above group (and one other one) choose to measure the distance from light to lens vs. the size (height) of the image produced.  The board above shows their data.  The raw data shows an inverse relationship.  So we decided to graph y vs. 1/x, this straightened the data out, so good, right?  Now comes the tough part.  What is the data modeling for us?  Here is where we are stuck.  One thing to keep in mind the focal length of the lens used is 15.0 cm.  (BTW, the other group used the same focal length lens and ended up with similar data.)

do = (14.67cm^2)(hi) + 14.91 cm

From what I can figure the y-intercept is the focal length of the lens, because you would get a image of size 0cm if the light was at the focal length of the lens.  BUT, what is the slope indicating?  What is with the units of cm^2?  Is it a coincidence that this number is also close to the focal length, or is it something significant?  What are we missing here.  Any and all help will be appreciated.  Please comment below or tweet me @MrBWysocki.

Thanks for the help!

Posted in Light, Modeling, Physics | 3 Comments

Day 2.25 Turning Mass to Moles for the 1st Time!

Wed. Mar 5, 2014

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Late last week chemistry 1 students reacted zinc metal with hydrochloric acid.  After another long weekend we dried and massed the product, zinc chloride yesterday.  Today groups analyzed their data by figuring out how much zinc was reacted, zinc chloride was produced, and chlorine was in the product.

The challenge then came in as to how to analyze the ratio of atoms being used in the reaction, and not the masses.  Through some discussion students realized they could use the unit of moles to “count” the atoms.  But how?  I came back to the idea of relative masses and the masses listed on the periodic table.  We decided that if 1 atom of Zn has a mass of 65.38 amu and 1 atom of Cl has a mass of 35.45, why couldn’t 1 MOLE of Zn have a mass of 65.38 GRAMS, and 1 MOLE of Cl have a mass of 35.45 GRAMS!  As long as we are comparing equal numbers of particles the mass ratios should be the same!

This is where we left off today, and tomorrow we will be able to analyze the mole ratio for the Zn and Cl and be able to write an empirical formula for the Zinc Chloride compound.

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Day 2.24 Using v vs. t Graphs to Quantitatively Analyze Accelerated Motion

Tues. Mar 4, 2014

 

 

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This isn’t the best picture to show it, but we quizzed on using quantitatively accurate v vs. t graphs to analyze accelerated motion.  We have not derived any of the standard kinematic motion mathematical models.  With the exception of defining acceleration as change in velocity over a change in time.  All problem solving is being done with the understanding that the slope of a v vs. t graph is the acceleration and the area under the graphed line is the displacement.  From here it is just using simple algebra and/or some basic geometry.

I much prefer this approach over the standard plug and chug of equations.  I feel the students get a much better sense of what they are solving for and how to relate the actual motion of an object to the numbers we are solving for.

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Day 2.23 Modeling Real Image Formation

Fri. Feb 28, 2014

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Physics 2 students have already seen real images with their eyes, but were now given the task to model the light from the object as it is treated by a converging lens.  Each group placed the object in a different place in respect to the lens.  Group D decided that since the light rays leave the lens parallel to each other no image will be formed.  The next step is to move the object inside the focal point and figure out what happens then.

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Day 2.22 Empirical Formula Lab

 

 

 

 

 

 

 

Thurs. Feb 27, 2014

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Chemistry groups began the process of figuring out the empirical formula of Zinc Chloride today.  Groups started with a known amount of solid zinc, and then reacted it with hydrochloric acid.  The reaction was then placed on a hot plate until the liquid was boiled away.  The solid zinc chloride remains in the beaker.  Groups will finalize the drying and check the mass of the product tomorrow.

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