## Compressed Air as a Force

July 31, 2009

by: Norman Barstow

When the National Research Council produced the National Science Standards in 1995, they did so without including sets of lesson plans nor did they design them as part of a standard curriculum package. They were written to be used as goals for our students’ achievement in science.

In my classroom I always used the National Standards when designing my lessons, and they were always clearly represented in the objectives I set for my students. I have found that the topics of Force and Motion, as well as Air, (as part of a weather unit), can be easily taught using balloons to demonstrate the concepts of each. I have designed two different lesson activities that can be used to meet the following standards.

National Science Standards
Content Standards: K-4
Physical Science; Content Standards

• An object’s motion can be described by tracing and measuring its position over time.
• The position and motion of objects can be changed by pulling or pushing. The size of the change is related to the strength of the push or pull.

National Science Standards
Content Standards: 5-8

• The motion of an object can be described by its position, direction of motion and speed.
• An object that is not being subjected to a force will continue to move at a constant speed in a straight line.
• If more than one force acts on an object along a straight line, then the forces will reinforce or cancel one another, depending on the their direction and magnitude. Unbalanced forces will cause changes in the speed or direction of an object’s motion.
• Energy is transferred in many ways.

Balloon Rockets
In a recent workshop I attended, which presented a module on Air and Weather, ‘Balloon Rockets’ was an activity used to show that compressed air can exert pressure to propel a balloon rocket.

The activity used a straw threaded through fishing line, which was stretched across the room. A ziplock bag was then attached to the straw, and the inflated oblong balloons were launched by placing them into the open bag. The force produced by the balloon propelled the straw along the fishing line.

I noticed that the balloons tended to make the bag move from side to side, thus decreasing the distance traveled. We tried the activity again using balloons directly attached to the straw with masking tape. The oblong balloon traveled much farther than the ziplock bag attempt. Next, I introduced the Educational Innovations Rocket Balloons. What a difference, both in distance traveled and speed. The Rocket Balloons release the compressed air steadily from the opening of the balloon to the weighted tip thereby pushing the straw farther along the fishing line.

Balloon powered car

Another recent discovery I made in my basement was a compressed air (balloon powered) car that I saved from an NSTA workshop I had once attended. The ‘car’ was built with a piece of cardboard as the frame and an axle system made using a wooden skewer inside a drinking straw. The ‘wheels’ were bottle caps and the ‘engine’ was a straw with a balloon attached.

While the oblong and/or round balloons worked fine, I wanted to try the EI Rocket Balloon. I had to modify the ‘car’ to account for the increased length and mass of the rocket balloon. The new chassis was now 4 X 14 inches, and I moved the wheels accordingly for this ‘super sized’ car. Again, the difference increased significantly in both distance and speed.

In addition to meeting the above National Standards, these are perfect experiments for elementary and middle school students on manipulating variables and testing hypotheses using the scientific method.

## Slime, Gak, and other Gross Science

July 24, 2009

by: Tami O’Connor

Let’s face it, kids of every age love gooey substances! The year is never complete until you have made at least one version of slime. Depending upon your grade level, the topic you’re teaching, your classroom budget, and the time you have available, there are a number of options open to you.

One of my favorite “recipes” is the ever popular Elmer’s Glue Gak. Aside from the fact that it’s easy to make, it’s rare that you wouldn’t have most of the essential ingredients at your fingertips.

You will need equal parts of Elmer’s glue-all and water. I tend to use two cups side by side and pour about 1/4 cup of glue in one and an equal amount of water in the other. Students can easily judge if the two liquids are equal without messing around with measuring cups. Pour the water into the glue and stir well. At this point, you can add food coloring, or better yet, phosphorescent powder so your gak will glow in the dark. If you’re using food coloring, only 4 or 5 drops are necessary.

In a separate cup you will need to mix hot water and Borax (sodium tetraborate) until you have a saturated solution. 20 Mule Team Borax can usually be found in your grocery store in the laundry aisle. I explain to my students that the water is saturated when the powder no longer dissolves in it. Evidence that you have a saturated solution is when the powder remains on the bottom of the beaker or glass even after the liquid is stirred well.

While mixing the glue mixture, slowly add the Borax solution. Students will immediately find that the glue mixture begins to clump and turn from a liquid to more of a putty-like solid. This is because the sodium tetraborate is a cross linking agent that hydrogen-bonds with the long polymer molecules found in the Elmer’s glue.

Another favorite gooey activity is slime making…. For this, I always use polyvinyl alcohol. I love using the hot water soluble Polyvinyl Alcohol Bags commonly used in hospital laundry rooms. Typically, these bags are used to place soiled linens within them reducing the chance that a hospital worker will come into contact with contaminants. When the bag, filled with sheets etc. is thrown in the washing machine, the hot water dissolves the bag exposing the linens to the water and detergent. When the water leaves the washing machine, so does the dissolved PVA.

To make the slime, dissolve the PVA bags in hot water (the appropriate amount is in the directions), and then slowly stir in the same Borax solution used to make Gak. The basic difference between slime and Gak is textural and color. Gak is opaque while slime is more transparent, and slime tends to be a little thinner and less putty-like. As with Gak, slime can be colored by using a couple of drops of food coloring before adding the Borax solution.

For those teachers who have less time to spare, Educational Innovations carries a Classroom Slime Kit that has everything you need premixed. All you have to do is combine the PVA solution and Borax solution and voila… instant slime!

Finally, the gross fluid that behaves like a liquid and a solid; Oobleck! When allowed to sit in its container, Ooblek behaves like a liquid. As soon as pressure is applied, this non-newtonian fluid behaves like a solid. It can be rolled into a ball, but then as soon as you stop rolling, it “melts” in your hands! Kids love experimenting with this material!

Oobleck is easily made by using 2 parts cornstarch to one part water. If you are planning to color your Oobleck, it’s easiest to color the water you add to the cornstarch. Finally, if you are working with younger children, the perfect literature connection is Dr. Suess’s Bartholomew and the Oobleck.

Clean-up for any of the gooey mixtures is fairly simple. A warm soapy sponge should clean most flat surfaces. It’s a good idea to keep any of the polymers away from clothing or carpeting, especially if you use food coloring. With the exception of the Borax solution, I would avoid putting anything else down the drain, but putting them in the garbage can should be fine… Be sure there is a plastic liner in the can or you will not be the custodian’s favorite teacher!

## High School Density

July 22, 2009

by: Ron Perkins

Whether teaching general science, chemistry or physics, one of the first experiments I assigned was to determine the density of a metal using a set of different sized cylinders of aluminum in a tray.

Each Student:

• Determined both the mass and volume of a single assigned sample.
• Recorded their data point on a large classroom Mass vs. Volume Graph.
• Participated in a class discussion on: determining volume by different methods; drawing a straight line through the data points (including the origin); and calculating the slope of the line (rise over run)

Ron’s suggestions:
1. The set of aluminum cylinders (DEN-102) or PVC (DEN-120) are ideal beginning sets. The brass set (DEN-110) is interesting as one can determine the percentage of brass and zinc from the density using a CRC Handbook. The Polypropylene set (DEN-132) is interesting because the specimens float.

2. The Density Mystery Set (DEN-202) uses the element of surprise to teach students to trust their data. The set is made of two different black polymers, each with its own density. When the data is plotted, two different straight lines are produced, each with its own slope or density. Typically students will assume that the material is all the same and start questioning their own measurements. About half of the samples sink in salt water and half float

3. Our most popular set provides samples of 12 different substances (DEN-212). Also popular are the cubes of 6 metals (DEN-220). Once students have mastered mass and volume measurements, they find it interesting to be able to identify a substance by determining its density.

Advantages of using our Density Kits:

• Students learn that the density depends upon the ratio of mass to volume and not upon size of the sample.
• Students observe that some methods for determining volume are more accurate than others.
• Students discover that the slope of the “best” straight line usually gives a more accurate density value than calculating from a single piece of data.
• The teacher can immediately tell from the data points if a student needs help in measuring.
• The teacher can quickly see if all of the samples have been returned at the end of class.

## Ants

July 3, 2009

by: George Kerr

Now is the perfect time of year to use the ants from out on the playground, campus fields, or any location near your classroom for some serious experimentation! First, have your students google information about ants and the roles they play within their colony. Then use your media center/school library to supplement their research . After you’re comfortable that your students have learned enough about ants to give them the background they need to begin to make educated guesses about ant behavior, take your students to an ant hill and circle out along where the forage ants are walking.

Since ants are social insects, your students should easily see the work being done that was described in your research. Guards are guarding the entrance to the nest, builders are hauling pebbles and grains of sand, nurse maids are hauling trash, and foraging ants are hunting and dragging food back to the colony.

This is a perfect opportunity to demonstrate how ants communicate using pheromones. Trap a few ants by the entrance, and watch as the alarm spreads outward like a rock in a pond. All ants will stop what they are doing and turn to the task of defense. They will eventually calm down if the danger is restricted to that minor disturbance. When they do, using the white spray paint the P.E. teacher uses to make the foul lines on the playground, spray-paint all the ants near the nest, and ask your students to count the white ants.

Your students should record the number of white ants on a data table. Ask students to meet you before school, during lunch, and after school for the next few days to count the white ants they see. Science data collection is that kind of a chore. Then have your students use the data to tell a story. Use student observations and guesses to create testable events. For example, many of your students will declare that the paint killed most of the ants causing a low population of white ants the next day. Test this hypothesis in a classroom lab.

One way to do so is to point out that research indicates that ants change jobs every four days or so. By painting the foraging ants it’s easy to see if one ends up on guard duty. The idea is to have students test what they read.

The final chapter should indicate that if students see only a few white ants in the days following the painting, it’s likely that the nest is a large one. If a large number of white ants is present shortly after, it’s likely that the nest is fairly small.

So how does an ant farm enter the lesson? Well thats the best part. It keeps the population biology lesson alive all year. Parents come to visit the classroom and students tell them all about Ant Day or Ant Week all year.

Though it is difficult to paint the ants in a classroom ant farm, having an ant farm on hand allows your students to observe the varied jobs in the colony and provides hours of learning and enjoyment for your students. Educational Innovations carries the AntWorks ant farm. The clear gel provides all the nutrients your ants need to survive for months, and best yet, you never have to feed or water these ants. Everything is self contained.

Oh, one more thing…I am from Nevada, we have no fire ants in the northern part of the state. Our red ants are great to work with. It’s best to consider the safety factors in your location before going outside to collect your ants. The ant farm from Educational Innovations has a coupon that will deliver nice ants to your classroom if you are unable or unwilling to collect your own…