SCIENCE NETWORK NEWS

Vol. 1, #2, February 6, 1989 CIRCE, College of Education, UIUC

OPTIONS ON THE SCIENCE NETWORK You may request a specific type of answer when you use the Science Network. You may request any combination of the following:

We are anxiously awaiting your questions! Whenever possible, we will honor your request for a specific type of answer. Sometimes we may only be able to answer a question in a certain way (i.e., the answer may require a diagram). Occasionally, a question may be asked that we are unable to answer. These
possibilities are illustrated in the following questions.

QUESTIONS TEACHER EDUCATION STUDENTS ASKED ABOUT AIR PRESSURE These questions arose in an elementary science methods class taught by Bernadine Stake at UIUC. The students were trying to explain why a balloon they had inflated and let go flew all over the room.

Q1: Is the denseness of air the same on the inside and the outside of the balloon?

Q2: If not, is the air inside the balloon or outside the balloon more dense?

Al & 2: The air inside an inflated balloon would be more dense than the air outside because of the added pressure of the stretched balloon. (This should become clearer in the answers to related questions below.)

Questions that need pictures sent through the mail to help answer them.

Q3: Some people think the elasticity of the balloon pushes the air out rather than the density. What do you say to that?
A3: Words like "elasticity", "density," "gravity" & "pressure" are often used as explanatory terms without further explanation of how air acts on things. T hose words take on a semi-magical qualify. so people wonder when to use each word to act their answer marked right. In developing processes of science, the idea is not to try to memorize words, but to think for yourself. One way of teaching about air pressure is to draw a picture showing how the air inside and outside an inflated balloon work. Then describe your picture to another person using words that make sense to both of you.

First draw a balloon with lots of dots inside, and make dots all around it outside that are less dense (i.e., spread out more). Now, you can think about the inside air pressing against the balloon harder than the outside air does. It's like two people pushing against opposite sides of a door. One is pushing harder than the other one, but the door doesn't move because it has a spring that is trying to close it.
Now draw another balloon without dots, and think what would happen if you could get your fist inside (like putting your hand in a tight rubber glove) the rubber of the balloon would press against your hand all over. Draw arrows pressing inward all around the inside of the balloon. They represent the forces pushing against the trapped air when you blow up the balloon in the first place. Something else is also pushing inwards. That is the whole atmosphere outside the balloon. Draw more arrows outside also pushing inward, to represent the atmosphere. What is holding back ail those inward forces? The force of the compressed air inside, pushing outwards. So draw arrows from the center outwards, but the outward arrows need to be as long as both kinds of inward arrows (you may have to erase and redraw the first two arrows). The more densely compressed air inside is holding off both the stretched balloon and the atmospheric pressure. Again, that's pushing out in all directions. Now you can call those three kinds of arrows what you will, or just point to them.

Responses to unanswerable questions:

Q7: What is the whole concept of air pressure?

A7: I don't know the whole concept of air pressure! I personally don't like to pretend to know the whole of anything, although sometimes I might sound like I think I do. Scientists often act as though they know all about certain things, like air pressure, but the history of science keeps showing that there is more to learn. Just yesterday, I read in a book by Nobel Prize winner, Ilya Prigogine, that Newtonian mechanics (i.e., gravitational force, acceleration, and all that) which I studied for years, and which Einstein is supposed to have overthrown is not dead. New discoveries are being made that enable us to use

Newton's theory in new ways.--JE

GETTING MORE OUT OF A UNIT: AN EXAMPLE FROM THE ORLANDO PARK CURRICULUM When working on a science unit, teachers often question whether the students are learning the concepts they should be. For example, some Orlando Park teachers were curious about an activity in the second grade "Wheels" unit, making and racing tinker-toy cars. The children equipped cars with all kinds of accessories, but the cars didn't run very far or very straight. T he race went down a ramp, across the floor, and fizzled. Often, an activity Hat is supposed to be educational for children isn't. This brings up a question about learning science processes and concepts. Do children learn to value the processes they are using if they don't get any good ideas (about how to make cars that run better) out of those processes? In cases like this, you ma y want to ask how to improve the activity, or what concepts the children should be learning. You can encourage the children themselves to ask their own questions if they didn't seem to enjoy the unit. How might we respond to this unit?

In the case of the tinkertoy cars, we might suggest that better running cars, and clearer concepts of wheels, could be developed if the four red swivels in each box (so obviously intended to mount the four big red wheels were not used. Instead, there are two ways to use two long axles instead of four short ones (the swivels). Both methods line up the wheels better, and leave less friction, than with the swivels. (1) The two long axles could an, in bearings mounted on the car with over-sized holes; or (2) they could be mounted so they don't turn but have wheels placed on them which have over-sized holes (bearings in the wheels). Typically, a box will have four wooden wheels of two different sizes which have over-sized holes, and two yellow plastic cylinders with slightly over-sized holes. Some compromises with appearance and even some extra work enlarging holes (with a rat-tailed file) may be needed. The performance reported by one teacher using such modifications was that the cars ran ten squares or more along the floor because of the one or two squares they ran when swivels were used.

There is an additional reason for doing away with the swivels. The swivels conceal the axles and the bearings, and learning about them is just as important as learning about wheels. We think the children will be much happier because they find out about bearing friction, wheel alignment, and the two kiwis of axles. You don't have to tell them these ideas; if they can be shown a car which embodies them and performs better, they will learn these ideas themselves by modifying their own car accordingly.

If you are worried that your pupils are not doing well because they don't think of such things themselves, we think you should do something about it. It may be that they are not used to using toys except as replicas of things. We'd love to hear from a teacher who has taught such a unit and has something else to say about it. Similarly, raise any questions about your experiences with children's reactions to any units. We'll try to respond, and we may ask your permission to put your message in the newsletter.

POSSIBLE QUESTIONS RELATING TO A SCIENCE LESSON
Fifth grade students using Orlando Park curriculum unit "Clean Up your Act: Water: Not So Clean and Pure" learn about water pollution and methods of removing pollution froth water. Since students test for phosphates in water in this activity, they might ask what phosphates are, how phosphates get into lakes ant rivers, or why phosphates are "bad" to have in water. How would we respond?

QI. What are phosphates?
A I. Phosphates are chemicals made from the mineral phosphorous (which comes from rocks) plus hydrogen and oxygen. They are used in fertilizers and to make detergents work better.

Q2. How do phosphates get into lakes and rivers?
A2. Phosphates get into lakes and rivers from rain water which picks up fertilizer chemicals when it runs over fields and into drainage ditches and streams. They also enter lakes and rivers from sewage, and from water used when washing clothes with detergents containing phosphates.

Q3. Why are phosphates "bad" to have in water?
A3. Phosphates act as fertilizers, so a lot of algae grows in lakes and rivers where there are extra phosphates. This algae coals beaches and the surface of the water with a scum, so it is unpleasant to boat on or swim in a lake with phosphate pollution. When the algae dies (for instance, during winter), bacteria in the water go to work to make it rot. The rotting algae produce gases which slink and are sometimes poisonous. Also, the bacteria use up the oxygen dissolved be the water, killing deep water fish like trout and whitefish.

Related Information:
Other chemicals get into water in much the same way as phosphates. Some of these chemicals, such as nitrates, are harmful to drink. Nitrates (like phosphates) commonly enter streams and lakes from water running off fertilized fields. Nitrates (like phosphates) are also harmful because they contributed to algae growth. Last summer, a park where people living in Champaign-Urbana like to go for picnics and for fishing and boating had to be closed because the hake there was coated with a very poisonous type of algae.