Handboiler

Educational Innovations’ website teachersource.com sells tons of unique science related items. One of those items is the handboiler. When you wrap your hand around the base the colored liquid (probably alcohol) heats up and moves up to the top where it eventually bubbles. My guess is that the molecules of the liquid speed up causing them to move up. When you let go the liquid eventually cools and goes back down via gravity. You can make the liquid go down faster by grabbing the top with your hand. I do this demo with student volunteers. We make observations and they hypothesize what is causing it. We also record who is able to send the liquid up the fastest.

Precautions: Don’t squeeze the handboiler. It can break easily.

Video Demo: Flame Tests

Every chemical has its unique characteristic properties. These properties can include hardness, density, melting point, boiling point, color, taste, texture etc. No matter what sample you have of a pure substance they will display its characteristic properties. This is how a an unknown chemical can be identified. The properties of the unknown chemical can be compared to the properties of known chemicals. In this activity there are 3 unknown chemicals (X, Y, and Z) that are to be identified based on 5 properties: color, boiling point, melting point, density, and color when burned. This is a simple and quick lab activity. The handout has the density, boiling point, and melting point filled in already. The students must observe the color and the color when burned–a flame test. Slide 1 shows the materials needed for the activity (the 3 chemicals are copper sulfate, strontium chloride, and lithium chloride). Slide 2 shows the Bunsen burner flame with the typical blue color. Slide 3 shows the inoculating loop collecting some of chemical Y. When the different chemicals are put in the flame, they burn at different colors (Slide 4 shows copper sulfate’s green flame, and slide 5 shows lithium chloride’s red flame).

Tips: Make sure students are careful to not contaminate the tubes and to thoroughly clean loop before testing each chemical.

Safety: Make sure students wear goggles, and know how to properly use a Bunsen burner safely.

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This is a variation on the flame test lab. Instead of using a Bunsen burner, a denatured alcohol flame is used (the best results is achieved by using methanol). Put a spoonful of strontium chloride into a Pyrex petri dish (this glass can take the heat, any other non Pyrex glass will break). Put about 2-3 spoonfuls of denatured alcohol into the dish. Swirl around to mix. Carefully light the alcohol on fire. You will probably need to swirl it so that the strontium chloride will burn and produce the red flame (lower left image). Try this with other salts and compounds that are safe to burn and will give color (like copper sulfate–lower right image).

Precautions: ONLY TEACHER DEMO! Be sure to use only Pyrex petri dish. The dish will get very hot! Don’t let water hit it right away. Be sure to blow flame out.

Video Demo: Muscle Pair

Seventh graders in the state of California are required to learn how bones move. Of course bones move because skeletal muscles are attached to bones, and when they contract, they make a bone move in one direction. Muscle work in pairs and when one muscle contracts, the other relaxes. Below are two video demos that show students how the biceps/triceps muscle pair works together to move the radius/ulna.

The first video is a model of how the biceps/triceps muscle pair works. In the model the radius/ulna and the humerus are represented by meter sticks. The meter sticks meet at a point which represents the joint (in this case a hinge joint). A joint is where two bones meet. The muscles in the video are represented by white irrigation tubing. The tubing is attached to each bone via duct tape. The duct tape represents a tendon. Tendons are connective tissue that connects muscles to bone. When the irrigation tubing (muscle) contracts, gets shorter, it moves the radius/ulna in a certain direction. When one muscle contracts, the other muscle relaxes.

The second video demonstrates the triceps/biceps muscle pair at work in a chicken wing. The video demonstrates how to dissect the chicken wing and then what happens to the radius/ulna when the biceps contract and then when the triceps contract. If students do the chicken wing dissection, make sure that proper washing and disposal precautions are taken so as to prevent biocontamination. If anyone is interested in a student worksheet email me at sciencefix@gmail.com and put “chicken wing dissection handout” in the subject line. I will then send you a copy.

Video Demo: Grain Silo Explosion

BubbleShare: Share photos - Easy Photo Sharing This is a very popular demo in science classes around the country. You need a coffee can with lid, candle, and irrigation tubing (slide 1). You can use cake flour, corn starch, or lycopodium powder. Put some of the substance into a petri dish. Light a match and place the flame next to the substance. The substance will brown but it won’t ignite. Place the substance into the coffee can next to the tube (use a drill to make a hole near the bottom of the can so the tube can fit). Light a candle (the best kind are the flat votive kind) and place it opposite the hole (slide 2). Put the lid on the can and make sure it is snugly fit. Take in a deep breath, then place the tube into your mouth and exhale a big breath. An small explosion will happen causing the lid to fly off. This demo demonstrates that for a substance to ignite it needs oxygen. When the substance is packed together there isn’t enough oxygen that surrounds the particles and ignition can’t occur. By blowing into the can the substance spreads apart, increasing the surface area, causing the ignition and the reaction happens very quickly.

Precautions: Wear goggles. Try this demo ahead of time to make sure it works safely. Make sure students are at a safe distance.

Solar System Scale Model Tour

When students learn about the Solar System they have a difficult time visualizing or comprehending what the distances are like between the planets and the sizes of the planets and the Sun. Most textbooks show pictures of the planet on one scale and the distances between the planets on another scale. They never have them to the same scale. The reason why is that the Solar System is huge! There are a ton of Solar System scale model lessons on the web. One of the best is the half mile long model. In this model the following represent the planets (see slide show): Mercury, Mars, and Pluto = head of pin, Earth and Mars = peppercorn, Jupiter = rubber ball, Saturn = hazelnut, Uranus and Neptune = peanut, Sun = volleyball. I glued these items (except the volleyball) to paper plates. I then made a flag for each planet out of wooden dowels and construction paper. I then inserted the flags through the middle of the paper plates and set the combination into a PE cone (see slide show). The distance between the planets are on the teacher handout (students have a separate handout). I have my students record into a lab composition book a journal of their tour. They answer questions before, during and after the tour. They are pretty amazed by the size of the model (see slide show). You need to have a pretty straight stretch of street (see slide show) to use, that isn’t too busy. I give my principal notice ahead of time and I also bring a first aid kit.

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