PURPOSE
To reinforce knowledge of the parts of an atom (electrons, protons, neutrons) and their relationships. Use and limitations of a model. Isotopes (add or subtract a neutron) and ions (add or subtract an electron).
NOTES
Each student builds a model of one or more atoms using the periodic table, cotton balls, pipe cleaners and beads. You need 55 each or neutrons, protons and electrons to build atomic numbers 1-10. If a class of 20 builds two of each so that each child can build one atom, you'll need 125 of each subatomic particle to allow for spares. You'll also need 25 support pipe cleaners and 100 pipe cleaners for the electron shells. Use tacky glue (20 oz) or some other fast-drying glue. Ordinary Elmer's doesn't dry fast enough and the nucleus tends to fall apart since the kids move it around before it's dry.
You'll also need string or yarn (10 yards) and paper clips (20) if you want to hang the atoms from the ceiling. Stapling the index cards around the string or pipe cleaner works well but you can also glue or tape them.
Have the kids familiar with the periodic table and the parts of atoms. You can even have them select their elements and complete steps 1 and 2 in a separate period. If you do this, assembling the atoms should be done in a single period.
Emphasize following the steps. They are the easiest, surest way of building the model plus, it is good training for the following chemical experiments where following the instructions is essential. Reading the lab as a class just before assembly can reinforce this.
PURPOSE
To review terminology and the relations between different atomic objects.
ANSWERS
add or subtract an electron = ion
add or subtract an neutron = isotope
C12 and C14 are an example. C14 is used for dating of
archeological discoveries.
add or subtract an proton = new element
an element is defined by how many protons it has (the
atomic number)
add another atom = molecule
if the atom is of the same type as the original = element
if the atom is of a different type as the original = compound
PURPOSE
To model atomic weight and see that it is just the weight of one atom relative to another. To understand the difference between atomic (relative) weight and the actual weight of an atom. Weighing, multiplication & division, unit conversion.
NOTES
We will use different sized nuts (as in nuts and bolts) to simulate atoms. We will compute the "atomic weight" of the larger nuts relative to the arbitrarily selected smallest nut.
The periodic table was originally based on H, later changed to O and currently is based on the most commonly occurring isotope of carbon, C12. The atomic weight represents the average of the
weights of the naturally occurring isotopes and hence the slight deviations from whole numbers.
The rule used is simply:
PURPOSE
To give the kids some practice reading the periodic table and to familiarize them with what they're made of. Also, decimal addition, graphing.
NOTES
Most kids know that we are made mostly of water but the first question is about elements in the body, not molecules.
PURPOSE
To reinforce than molecules are always moving and that they move faster as their temperature increases.
NOTES
Rinse, dry and save all equipment when done.
When you put food color in water, it would just sit there if nothing in the water were moving. When we use hot water, the food color mixes faster because the molecules are moving faster.
Be sure to remind the kids to not bump or stir their beakers or the food color will mix into the water due to this physical disturbance.
This is the first "chemistry experiment" so it is a good time to review measurement technique and the need to rinse equipment between and after use.
Accurate measurement of the volume of solids requires that the solid be level in the measuring spoon or cup. Use a plastic straw or stir stick for leveling.
Accurate measurement of the volume of liquids requires that the cup be placed on a flat surface (desk top) and that the kids get their eyes level with the top of the liquid when making the measurement.
Be sure to rinse stir sticks, measuring cups, etc. after each use and especially before using them for a second substance!
Also, remind the kids that they should always explain their answers even if they are not explicitly asked for an explanation.
Note the hypothesis and conclusion both "answer" the same question; the hypothesis gives your prediction before the experiment and the conclusion answers the question based on what you observed.
PURPOSE
To observe the effects of surface tension.
NOTES
Rinse, dry and save all equipment when done.
Use soap and oil in plastic squeeze bottles to make it easy to add only one drop.
Pepper floats on water. When you put a drop of oil on the water, the pepper moves aside and the oil flattens out and floats. The oil doesn't flatten beyond a certain point because it's surface tension holds it together.
When you add a drop of dish detergent, it also floats on the surface of the water. But it spreads out much thinner than oil and therefore takes up more surface area. Like the oil, it pushes the pepper aside.
If you now sprinkle more pepper on top of the soap, the soap wets the pepper, making it heavier so that it sinks.
The hardest part for the kids will be to stop after each step and document their observations as they go. It's important that they also resist temptation and only add single drops of oil and soap.
If the kids want to experiment on their own, have them complete the lab first, the experiment. Have them write down what they do and the results so they are experimenting, not playing.
PURPOSE
To develop a better understanding of why some materials absorb water. A chance to use a microscope. Measurement of length. Sample preparation.
NOTES
Warning: most of the kids will never have used a microscope and they are fascinating. You might want to give the kids the microscopes to use for a half hour or so the day before so they have a chance to explore. Perhaps then the next day they can concentrate on the experiment.
They can pick their own paper samples; each team can use different ones if they like. Some types of paper are:
paper towels
newspaper
notebook paper
construction paper
glossy magazine paper
In general, paper that looks the "fluffiest" will absorb most quickly.
PURPOSE
To review density of solids and liquids. Deduction. To learn proper technique to pour liquids.
NOTES
The mystery liquids are:
Dark corn syrup (brown)
Dish washing detergent (blue or green)
Water with food coloring (green or blue)
Vegetable oil
Teach the kids how to pour two chemicals together: hold a stick inside the jar with its tip touching the inside wall of the jar. Pour the liquid on the stick. If you pour slowly, the liquid will run down the stick and then down the side of the jar.
Remind the kids to never pour extra chemicals back in the bottle. Throw them away.
For jars, use disposable water bottles with the tops cut off. These are plastic (unbreakable), clear, and have a small diameter so they require less of the liquids to make a thick layer.
Although none of these chemicals are particularly harmful, stress the importance of safety: never taste or touch an unknown chemical and smell them very carefully.
To clean the jars, dump out half of the contents leaving the detergent and corn syrup in the bottom. Swirl the liquid briskly and the detergent will clean out the corn syrup. Rinse the jar well.
Rinse and save the "small objects" so they're there for the next class.
PURPOSE
To see that different substances evaporate at different rates. Reinforces measurement of liquids (see note earlier) both in a measuring cup and in the jars. Arithmetic using dates.
NOTES
Each team fills 3 identical jars with 3 liquids: rubbing alcohol, water, liquid soap and observes over a day or two how they evaporate. You need 1/8 cup per team of each liquid so, for a class of 20, you need 3 cups (24 oz) of each to allow for some extra.
Be sure the kids rinse the jars well when they are done. I don't use oil because it is so messy to clean up well.
PURPOSE
To reinforce the difference between mixtures and chemical reactions, suspensions and solutions.
NOTES
Rinse everything well when done.
Baking soda forms a solution although it may take a few minutes to dissolve completely.
Flour forms a suspension which will precipitate out fairly quickly.
Baking powder undergoes a reasonably dramatic chemical reaction which results in a gas and a suspension.
PURPOSE
To use the physical properties of solids to separate them.
NOTES
Rubbing the plastic stir stick in your hair charges it with static electricity. It then attracts the pepper more so than the salt because the pepper particles tend to be lighter weight than the salt. You will probably pick up some salt, too.
The experiment is designed so that the iron filings do not touch the magnet. It's a bit tedious to get them off.
Save all of the substances the kids separate and mix them back together for another class. You'll need to add some extra salt because this is not recovered. It could be if we took the time to evaporate off the water.
Remind the kids how to fold a filter paper (in quarters). You don't need a funnel, just hold the paper over the beaker.
AUGMENT
Use magnifiers to look at the solids before mixing them. Then let them look at what they've separated to see how pure it is. Let them evaporate a little of the salt water on a microscope slide to see that they can recover the salt.
PURPOSE
To open up the possibility that not every substance is a solid, liquid or gas.
NOTES
Don't rinse slime down the sink except for what's left on the kids' hands. Run the water for a few minutes after so it doesn't set up in the drains. Throw away any equipment that touches the slime.
You have to measure the components very carefully to get the slime affect.
Warning: Play alert. This stuff is great fun. You might want to warn your class before hand to try to exhibit some self control.
If they play with the slime long enough, it will undergo yet another change - it will dry out and get crumbly.
PURPOSE
To become acquainted with this fundamental physical law which forms the basis of understanding chemical reactions. To see chemical reactions, state changes.
NOTES
Seal the bags well. Remind the kids to be gentle so they don't tear the plastic bags. Have paper towels handy in case someone breaks their bag.
Two or three scales should be enough because each team will need the only briefly and will need them at different times.
PURPOSE
To see that some chemical reactions give off heat (exothermic) and some require heat (endothermic). To see that some reactions are fast and some are slow. Use of a control. Distinction between qualitative and quantitative observations. Measurement of volume and temperature.
NOTES
Handle the thermometers carefully. They are glass and will break if bent or stepped on. Also, the glass tube can slide in its holder resulting in an incorrect reading. The kids should make sure that the bulb is in the hole in the backing. Another way is to cross-calibrate the two thermometers against each other. They should be reading the same room temperature. Remind the kids not to hold the bulb of the thermometer or they will be taking their own temperature.
This experiment uses disposable equipment so that no plaster is washed down the sink. The salt mixture can be washed down the sink.
This experiment will take an hour to allow time for the plaster to cure although most of that time the kids can be working on something else while they are waiting. The plaster is made first intentionally to reduce the overall waiting time.
Emphasize that this is road salt, not table salt (NaCl) and must not be tasted.
The plaster is a slow reaction that gives off heat (exothermic). The salt is a fast reaction that needs heat (endothermic) and so chills its surroundings (like a chemical ice pack).
Making electricity uses exothermic reactions such as nuclear fission in which U235 splits into two lighter element, giving off lots
of energy in the process. It also gives off two neutrons which react with other U235 to keep the reaction going (a chain
reaction, see next experiment).
PURPOSE
To become acquainted with a chain reaction. To model nuclear fission of U235.
NOTES
See notes for previous experiment.
The most prevalent, naturally occurring isotope of uranium is U238.
Both chain reactions take the same amount of time: the time it takes 4 dominoes to tip each other sequentially. However, if each domino tipped gives off the same amount of energy, it's clear that the second arrangement gives off far more energy in the same amount of time - it is more powerful.
Warning: play alert. The kids will want to play with the dominoes.
AUGMENT
Have the kids figure out the pattern to the number of dominoes in each row (factors of 2).
PURPOSE
To see that photosynthesis is a chemical reaction.
NOTES
Tipping the jar/pan combination over works pretty reliably; however, you may want to ask the teams to wait until you can watch to tip the jar. This may reduce silliness and increase the probability of success (decrease the chance of mess).
You can use tree leaves, plant leaves in place of lettuce leaves as long as the leaves are freshly picked.
The plant (leaf) has everything it needs for photosynthesis - at least for a day or two. Little gas bubbles should form on the leaf. This is the oxygen given off by the plant.
This experiment has to sit for a day or two. Don't let it go longer or the leaves start to rot.
Copyright 1996, D.M.Candelora. All rights reserved. Reproduction for educational use is encouraged.