Physical Science - MiniLab 1

 

“Each  man is a tool in his own hands.  Our greatest satisfaction doesn’t come from the rewards of our work, but from the working itself; and our greatest responsibility is to sharpen, and improve the tool that is ourselves so as to make it capable of tackling bigger jobs.”
                                                                                  by Gordon R. Dickson

 Instructions:   This experiment is designed to be completed at home.  As homework, neatly summarize all your information on notebook paper (front only).  Answer all questions (with complete sentences) as well.  You may wish to make drawings to complement your observations.   Return all the equipment in the ziplock bag, dry and clean, with your write-up next class period.  Be sure your name is at the top of the paper (please include class period as well).

 

 1. Cohesion and Adhesion

          Find the tiny piece of clear plastic in the ziplock bag.  Place it over the typewritten instructions on this page.  Obtain a small amount of water in a small cup.  Use the plastic dropper (called a transfer pipet)   to add 1 drop on top of the plastic.  Draw the shape of the convex droplet.  What effect does the water droplet cause as you look at the typeface beneath the plastic?    Try adding another drop of water to make your droplet larger.  What happens to the magnification?   The drop is acting as a lens.  What does a greater curvature of the droplet cause?  Is the water more attracted to itself (cohesion) or more attracted to the plastic film (adhesion)?

 Bonus:  How could you calibrate the dropper used?  What techniques worked to allow constant volume drops?  Why will the dropper not work if there is a small hole in the bulb?  Design an experiment to test your calibration ideas.

            Bonus:  Cut a clean straw in half.  Extend one half into a cup of water vertically.  Holding the second straw at right angles to top of the first straw, blow through the horizontal straw (hint: the end of the horizontal straw and the top of the vertical straw must be touching).  Can you get water to move up the vertical straw and be expelled out, away from you?  What happens to the water as it is expelled?  What scientific principles are involved?  Make a scaled drawing, with measurements, of your final straw-setup. 

 2. Coins and Graphing

          Obtain a penny, nickel, dime, and quarter.  Clean and dry each coin.  Again using the cup of water and plastic pipet, see how many drops you can place on each coin without them spilling off.    Remember to hold the pipet vertically and eliminate air bubbles (to have consistent drops).  Record these numbers.  You should repeat each coin three times to get an average.

          Using the diameter of each coin (found on the chalkboard), calculate the number of drops per square centimeter for each coin  (i.e.,  # drops/cm²).  If you were given the area of a half-dollar, how would you calculate the number of drops it would hold?  What factors might cause this prediction to be incorrect?

Bonus:  Try graphing the number of drops versus area of coin.  Draw a straight line through the data points.  Will this help you determine the drops that a half-dollar might hold?  What problems are encountered if you use soap on the coin before adding the drops (or touch the coin with the oils on your fingers)?  What shape did the water take on top of the coin?  Can you draw the shape?

 

3. Dissolving

          Fill a clear glass with water.  Allow the water to sit for a few minutes (why).  Slowly add a few small salt particles.  Try to observe how they dissolve.  If rock salt (or any large salt piece) is available add it to the water slowly and record observations.  Place some of the salt in a spoon and add a drop of water on top of it (what does the convex water droplet do to the salt crystal?).  Try switching to sugar and determine if there are differences.  What effect would hot or cold water have on the rate of dissolving?  From Earth Science what determines the size of the salt crystal as it is formed in nature?

 

4.  Mirrors

          Hold a clean spoon about 25 cm (10 inches) away from your face.  Look into the concave surface.  You should see a rough image of your face.  Describe the image (i.e., upright, inverted, reversed left to right, enlarged, etc.)  Now flip the spoon and look at the convex surface and describe the image of your face.  Next move the concave and convex surface closer to and farther away from your face.  Describe your facial image each time (be sure to include a complete description; i.e., concave, farther away = …).  Try flipping the spoon handle up and seeing if it makes any difference.

 

5.  Flight

          Do a simple internet search for uncommon paper airplane designs.  Prepare instructions for folding the airplane (must be done by you).  Test fly it and record what you think would be the important flight data.  Discuss how you could turn this into a research project.  What would be your dependent and independent variables?  What variables would you control?  Can you develop a simple hypothesis to test?

 

Concurrent student work:

1)  review my website:  www.sciencebyjones.com

2)  print out lab safety rules and math review sections found in the PDF files menu  (second option on left side of main menu).  If you have trouble printing these out let me know and I will get you copies.