Elementary students generally like science. They are still involved in a love of magic and much of what their teachers do seems like magic, but it’s better — it’s real. Wise elementary science teachers keep science relevant and involve students in show-and-tell activities and give them lots of things to see.
Science Become more Abstract in Middle School
That standardized test scores drop in middle school has been observed for decades. Several reasons for the decline have been theorized. One of the most commonly discussed reasons for a drop in learning as measured by standardized tests in that middle school students are beginning to change physically and emotionally. Part of the problem is that science tends to begin to focus more on abstractions.
Teachers can’t do anything about student physiology, but they can remove some of the mystery from more complex concepts and give students examples that students can use to grasp the atomic realm. Science begins to emphasize things that students cannot see, and seeing is believing for many children and adults. Science teachers need to be armed with lessons and examples to get past abstractions and difficult concepts.
Science Textbooks can be Misleading
Science texts are notorious for demonstrating the atom as a solar system of particles. The model is suitable for elementary school, but middle school students are ready for something closer to reality. As seen in texts, there is often little difference between the sizes and distances of objects. The truth is that one cannot put a scale model of an atom in a textbook. Models help.
Some Comparative Examples of Atomic Sizes
True descriptions and behaviors of atoms are the best described with quantum theory. Atomic particles and atoms themselves exhibit some spooky properties that are best left out of middle school science. Although it is often worth mentioning that atoms cannot be seen. What we know of atoms depends on how they interact with each other and quantum theory, which is too creepy for middle school students.
- Hydrogen/basketball atom model. If a proton is represented by a basketball — the teacher can hold up a basketball for demonstration purposes — the an electron will be about the size of a period in their textbooks and be located about 20 miles from the proton. The Internet provides some attempts at scale models.
- Earth/basketball model. If the Earth were the size of a basketball, atoms would be about the side of baseballs.
- Gold atomic model. A gold nucleus is larger than a hydrogen nucleus. If one makes a scale model of a gold atom with the nucleus represented by a circle one foot in diameter, the nearest electron would be as large as a bold period and 3.3 miles away from the nucleus.
- Neutron mass vs. proton mass vs. electron mass. A neutron is the most massive of the three particles by a small amount, being approximately 1,842 times the mass of an electron. A proton is almost as massive as a neutron at 1,837 electron masses. Diameters of the particles are not appropriate for comparisons due to quantum issues.
- Football field/hydrogen model. Use a large professional football stadium to mentally construct a model for a simple hydrogen atom. Imagine a ping-pong ball sitting alone in the middle of the field on the 50 yard line. Its lone electron would be an invisible speck somewhere near the back row of the upper deck. One never knows where the electron is, only where it is most likely to be in its electron cloud — a quantum issue.
Teachers Take Care to Clarify the Concept of Physical Models
Middle schools students don’t need to be confused by quantum theory — it is counterintuitive and confuses college physics students, but teachers need to understand it. It is mentioned here so that teachers will stress the difficulty in truly comprehending what atoms are really like. The solar system model of the atom is physical model that allows people to discuss atoms using familiar objects. The actual atom bears no real resemblance to a solar system, but the model is easier to manipulate mentally.
The models above are physical models that introduce the reality of the emptiness of the atom, which is over 99% empty space. Rutherford discovered this property of atoms in his famous gold foil experiment. To make matters more confusing, atoms don’t touch each other due to the negative charges of the electrons. They can be infinitesimally close, but they don’t touch.
People don’t feel atoms of water pouring over their hands, but rather they feel the electromagnetic forces of the atoms and the properties of the molecules — e.g., heat due to rapid molecular movement being transferred by electromagnetic forces. Knives don’t cut by touching, but because electromagnetic forces push matter apart.
Examples and discussions of the ideas above tend to draw comments of amazement and disbelief, but they stimulate interest — especially the idea of atoms not touching. The important thing is that they help keep attention and enhance participation. Models are essential to teaching science and moving students toward more complex ideas. Teachers must emphasize that models are used to help understand what cannot be clearly described — atomic behavior rather than actual appearance dictates the use of models.
Source:
- Asimov, Isaac. Atom. New York: Penguin Books, 1992.
- “Quantum Theory,” Thebigview.com. (Accessed October 12, 2011)
Harvey Craft - I am a retired educator with diverse experience. I read anything science, education, and history. I write to share what I learn.
