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Elementary Science Education

Bernard Nebel

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  • in reply to: Sundial at the Equator #8294

    Bernard Nebel
    Keymaster

    Yes, quite so. It will be interesting to observe how, over the period of the equinox, the noon shadow (what there is of it) will shift from north to south, or vis versa.

    In the whole process, don’t let kids loose track of basic phenomenon–the shift is due to the Earth maintaining the same degree and direction of tilt as it orbits the sun.

    in reply to: Sundial at the Equator #8292

    Bernard Nebel
    Keymaster

    You are quite right. A traditional sundial will not work at the equator. During the summer months (spring equinox to fall equinox) the arc of the sun’s path will go to the north of you making shadows fall to the south and the opposite during the winter months. However, you can still make a modified sundial. Mount a pole vertically in the ground (or straw vertically on poster board). Each day its shadow will start as long to the west, gradually shorten to zero when the sun is directly overhead at solar noon, then gradually lengthen to the west. You can calibrate the length of shadow with cross lines for each hour. These hour lines should remain consistent throughout the year, although the sun will proceed to make a low arc south and north of directly overhead.

    This will not permit the determination of north as described in the text. However, a line from the tip of the first morning shadow to the tip of the last evening shadow will be an almost perfect east-west line. A perpendicular line, of course, will be north and south. Thanks for the question. Please ask further.

    in reply to: 2 Questions about burning wood & matter vs mass #8269

    Bernard Nebel
    Keymaster

    Thank you for your questions. They show good thinking.

    Why can’t we “un-burn” a piece of wood?

    Reese is quite right in his thinking. The formula for any chemical reaction can be written backwards as well as forwards, making it theoretically possible. Specifically the chemical reaction for burning wood (mostly cellulose) is:
    C6H12O6 + 6O2 —–> 6H2O + 6CO2 + release of energy
    The reverse (unburning) is:
    6H2O + 6CO2 + input of energy —-> C6H12O6 + 6O2 and is theoretically possible. In fact, plants do this with the aid of light energy. It is called photosynthesis.
    However, distinguish theoretical possibility from practical feasibility. Plants accomplish the unburning of wood (photosynthesis) through a dozen or more individual chemical steps driven by energy from light. To have it happen on one big step as occurs in the burning is what is impossible.

    Its a little like smashing a dinner plate on the floor. You can see the smashing apart occurs with one bang. You can see that the pieces might go back together to “unbreak” the plate. Then you might do so by carefully picking up each piece and fitting and glueing them back together. What remains impossible is having them go back together in one “bang.” Thus we say that the breaking of a plate (and unburning wood) are irreversible.

    Is there conservation of mass as well as conservation of matter?

    Yes! (But don’t confuse mass and weight.) Since each particle (atom) of matter has a certain mass and atoms remain the same, mass will also remain the same. Seeing this in practical way is what is difficult. Note from the above equation for burning wood, the major products are carbon dioxide and water (vapor) which go off in the air. (They retain their mass although weighing them is impractical.) A very small portion of the log ends up as ash. To prove that mass (in terms of weight) remains constant, you would have to burn the wood plus sufficient oxygen in a totally sealed container so that the water vapor and carbon dioxide are held in. (Scientists have done this.) It is found that the total mass and weight
    does not change.

    Please question more as you wish.

    in reply to: Help for Explaining Weightlessness #8262

    Bernard Nebel
    Keymaster
    in reply to: Help for Explaining Weightlessness #8261

    Bernard Nebel
    Keymaster

    This sounds fine. Plus, you illustrate an important aspect of learning. When you can take a concept and explain it your own words, it shows you have really mastered it. Nice work. However, I would make an adjustment to your line, ” The sensation of weightlessness does not mean you dont weigh anything at all.” This is where we should switch from speaking of weight to speaking of mass. That is, a scale will read different weights depending on gravity–zero in a state of free fall. But you and anything else remains constant. We speak of that “weight” that remains constant as mass and measure it in kilograms. That is, a mass of 10 kilograms will remain 10 kilograms regardless of any force of gravity including zero force.

    Thank you for your question. Please ask further.

    in reply to: Question about heat energy release #8256

    Bernard Nebel
    Keymaster

    There is nothing like experimental data to get at the truth.
    You have discovered an error in the text. The baking soda-vinegar reaction is endergonic. That is, heat from the environment is sufficient to drive the reaction. As heat from the environment goes into the reaction, the temperature falls.
    Congratulations and thank you for exposing this error in the text.

    in reply to: Living or Biological Clarification #8213

    Bernard Nebel
    Keymaster

    Sorry to harp on what you already know well, Cindy. I try to compose answers that speak to others in the group. I hope more will join in and comment or ask questions. I would love to see this group generate more questions and discussion.

    in reply to: Living or Biological Clarification #8211

    Bernard Nebel
    Keymaster

    Regarding your first question, everything human-made starts with from something biological (add) or NATURAL EARTH categories (or both). A tin can, for example is from natural earth materials–iron ore. (How much work sheet stuff you have your son do is up to you. If he enjoys it, fine; If he doesn’t like it, go easy on it. We don’t want him to get the feeling that science is too much forced dull work.

    To round out the concept, introduce the word “resources”. Everything human-made demands starting with certain resources–biological and or natural earth.

    Regarding your second question. I would let it go for the time being and move on to Lesson C-1. There you will develop concepts of energy and forms of energy, which are very different from any form of matter. Then you can come back to fire and the sun. What we witness here is heat and light, i.e., forms of energy.

    The concept you are heading toward is that we have two things: matter (biological and natural earth) and energy, which makes everything go, work, or change. Energy becomes a required resource for everything we do/make in addition to the material resources.

    Please don’t expect that learning should occur in specific steps that kids can check off on a worksheet. The vastness of everything out there is bound to cause confusion and missunderstandings. The real learning occurs as you recognize and accept the confusion and struggle with sorting it out and correcting the misunderstandings. You are on the right track by asking questions. Please keep at it.

    in reply to: Living or Biological Clarification #8202

    Bernard Nebel
    Keymaster

    Thank you for your question. I think your son (for age almost 5) is expressing remarkably good knowledge and understanding. A perfectly logical argument can be made for paper being biological as it is made from from trees. It is quite arbitrary that we move it into the human-made category to express the role that humans played in producing it. Recognizing that everything human-made starts with resources from biological and/or natural earth categories should be a major point of this lesson.

    I don’t know if this helps. Please ask further as you like.

    in reply to: Living or Biological Clarification #8201

    Bernard Nebel
    Keymaster

    Thank you for your question. I think your son (for age almost 5) is expressing remarkably good knowledge and understanding. A perfectly logical argument can be made for paper being biological as it is made from from trees. It is quite arbitrary that we move it into the human-made category to express the role that humans played in producing it. Recognizing that everything human-made starts with resources from biological and/or natural earth categories should be a major point of this lesson.

    I don’t know if this helps. Please ask further as you like.

    in reply to: Question about microscopes #8136

    Bernard Nebel
    Keymaster

    Hello Sherrie,
    Kids should have plenty of experience with pocket magnifiers before proceeding to a microscope. Then, the general type of microscope you want is shown here:

    https://www.amscope.com/student-microscopes/elementary-k-8/40x-1000x-student-compound-microscope-home-school-science.html

    You may wish to go up from here and get a mechanical stage and diaphragm condenser for better control of light, and other features as you may desire. Of course you will need slides, coverglasses, etc.

    Please ask further questions as you wish.

    in reply to: Creation of the Grand Canyon video #7773

    Bernard Nebel
    Keymaster

    Thank you for bringing this to my attention. I have replaced it with another video. Enjoy.

    in reply to: PRINTABLE ILLUSTRATED ENERGY & ACTION CARDS FOR PART 1 #7538

    Bernard Nebel
    Keymaster

    Thank you very much, “stoker”. This is a nice addition.

    in reply to: Starting Vol. 2 soon–what type/brand of microscope? #7263

    Bernard Nebel
    Keymaster

    The Brock microscope is the one microscope that I DO NOT recommend. Focusing is very tricky. Then, when you wish to go from scanning to higher power you must disassemble, screw in the higher power lens, and refocus. Refocusing under the higher power is almost impossible.

    Therefore, go with the three-lens, par focal, standard student scope, an example of which may be seen at
    https://www.amazon.com/AmScope-M150C-I-40X-1000X-Biological-Microscope/dp/B00AM5XB5O/ref=sr_1_3?ie=UTF8&qid=1538751948&sr=8-3&keywords=microscope

    They are actually less expensive than the Brock.

    in reply to: Weightlessness during space travel? #7247

    Bernard Nebel
    Keymaster

    That’s a good question. I’ve had to think about it too. In answer, I changed the question to, “What do you need to feel gravity, i.e., have a feeling of weight?” My reasoning: You need to be on a platform (something to stand or sit on) that is holding its position within a gravitational field. An airplane is holding its up/down position within the earth’s gravitational field, forward motion notwithstanding. Therefore, aboard the airplane you experience gravity much as you do on earth. Either that or you must be accelerating or decelerating so you feel the inertial force, which is indistinguishable from gravity.

    Now, assume you have blasted off on a straight line mission to Mars. After gaining required speed, engines have been turned off; hence, you are neither accelerating nor decelerating so you feel no force from that. Nor is your rocket ship holding a position within a gravitational field. It may be traveling at great speed in a straight line, but it is not moving or holding a position counter to any gravitational field. Therefore, despite its straight line of travel, it and you in it are in a state of free fall within whatever gravitational field(s) are present. Therefore, you would feel weightless. Please ask further or give an alternative argument.

Viewing 15 posts - 1 through 15 (of 48 total)