Invitation to Inquiry
Experiment 1 Invitation to Inquiry
Measurements of variables involved in some physical relationship will often yield a straight line, and this relationship is said to be direct, or linear. There are more types of relationships between variables, and most can be identified as producing one of five basic shapes of graphs. These are identified, left to right, as no relationship, linear, inverse, square, and square root.
Data that yields a straight line has a linear relationship and can be described algebraically by the slope-intercept form of an equation, y = mx + b where m is the slope and b is the y intercept. If a graph results in one of the three curves, data can be manipulated to produce a straight-line graph. For example, a graph of the pressure changes of a confined gas that occurs with changes in volume might produce a graph that looks like this:
Since this curve is an inverse relationship, the plot is redone as P vs. 1/V. The graph now looks like this:
As you can see, it now has a straight line that can be described by the slope-intercept equation to describe Boyle’s law.
After giving the possibilities some thought, look for relationships that might result in something other than a direct relationship. Make measurements, graph your data, then decide which of the five shapes the graph resembles. If the data results in one of the curves, try manipulating the data to generate a straight-line graph. For example, obtain a toy dart gun and dart. Vary the weight of the dart by taping small masses to the dart, then measure the height the dart is propelled. What is the relationship between the weight of a dart and the height it is propelled? What is the shape of a graph comparing the weight and height and what does this mean about the relationship?
What other relationships can you find in the lab, outside, or between any two variables in everyday occurrences? Can you find an example of each of the five shapes of graphs?
Experiment 2 Invitation to InquiryIf you have popped a batch of popcorn, you know that a given batch of kernels might pop into big and fluffy popcorn. But another batch might not be big and fluffy and some of the kernels might not pop. Popcorn pops because each kernel contains moisture that vaporizes into steam, expanding rapidly and causing the kernel to explode, or pop. Here are some questions you might want to consider investigating to find out more about popcorn: Does the ratio of water to kernel mass influence the final fluffy size of popped corn? (Hint: measure mass of kernel before before and after popping). Is there an optimum ratio of water to kernel mass for making bigger popped kernels? Is the size of the popped kernels influenced by how rapidly or how slowly you heat the kernels? Can you influence the size of popped kernels by drying or adding moisture to the unpopped kernels? Is a different ratio of moisture to kernel mass better for use in a microwave that in convention corn popper? Perhaps you can think of more questions about popcorn.
Experiment 3 Invitation to Inquiry
Have you ever seen an entire stage covered with dominoes lined up, one after another and winding around into interesting patterns? The entertainer tips over one domino, which falls into another, which falls into the one next to it... and on until in a short time all the dominoes have fallen over.
How far apart should the dominoes be spaced for maximum speed? Is it possible to vary this speed by changing the spacing? One domino causes a falling row to continue falling by hitting its neighbor, so the limit to how far apart the dominoes are spaced must be the length of a domino. The other limit would be zero space between two adjacent dominoes, so the limits to the spacing between two adjacent dominoes must be somewhere between zero and one domino length. Thus it would be convenient to record spaces between dominoes as a ratio of domino lengths, that is, the space between dominoes in cm divided by the length of one domino in cm.
If you accept this invitation, you will need to determine how you plan to space the dominoes as well as how many dominoes are needed to measure the speed. By making a graph and doing some calculations, can you predict how many dominoes would be needed--and at what spacing--to make a row that takes exactly 2 minutes to fall?
Experiment 4 Invitation to Inquiry
Find out how well you can predict the motion of falling objects. First, select some objects such as a rubber ball, a sheet of notebook paper, and a large metal paper clip. Predict, then study the detail of each object falling independently... for example, what happens to each as they fall? Then compare the motion of the objects side by side. Is it possible to cause them to fall together, at the same time?
Here are the five basic shapes of graphs that are produced by different types of relationships between variables. What variables are involved in falling objects? What are the relationships between them? If any of the graphs you produce have the shapes of one or more of the curves, what can be done to make it into a straight line?
Use measurements to construct a graph or graphs that show what is going on between the variables involved in falling objects. Then use the graph to show how to place three or four objects on a long cord. Attach them so when the cord is hung from a high place, then dropped, the objects make a constant plop, plop, plop sound when they hit the ground.
Experiment 5 Invitation to Inquiry
What is the acceleration of a pendulum bob as it swings back and forth? One way to find out is to measure acceleration just as Galileo did hundreds of years ago. Galileo found that you could "slow" the acceleration of a falling object by making them "fall" at an angle, that is, fall down an inclined plane. One way to measure the acceleration of a pendulum bob is to set up an inclined plane so a rolling ball "falls" down the board at the same angle as it "falls" as a pendulum.
First, obtain a ramp or board about two meters long. Measure down from the top about 20 cm and draw a zero line. Place tape marks at 25 cm, 50 cm, 100 cm, and 150 cm down from the zero line. Use a pencil to hold the ball at the zero line then pull it away quickly to release the ball. Place a wooden block or some other stop at the bottom to keep the ball from rolling off the ramp. Figure out a procedure for using a stopwatch to calculate the acceleration of the ball at each of the marks while a ball is rolling down the ramp. Should the acceleration change as the ball rolls downhill?
Second, move the ramp so the angle is about the same as a model pendulum you have set up. Adjust the ramp so the ball takes about the same time to roll down the ramp as the pendulum bob does to swing from its high to low point. This comparison will take care of friction losses on the ramp. What is the acceleration of the ball? Can you find a pattern to changes in acceleration and changes in ramp angle? Finally, set up an Experiment to compare the findings of the pendulum Experiment with the acceleration of various weight balls rolling down an incline plane. What did you expect to find?
Experiment 6 Invitation to Inquiry
In this investigation you studied a relationship between the velocity of a moving ball and the distance it travels when rolled off a table. Why not consider the height from which the ball is released and the distance it travels before it hits the floor? First, move the ramp so the end of the track is parallel to the table top and the ball shoots off the track horizontally. This might require a curved ramp, depending on your setup. Move the apparatus so that the end of the track is flush with the edge of the table (see diagram below). Again use a sheet of carbon paper on a sheet of white paper so the ball will leave a mark you can measure. Release the ball from at least 6 different heights, where height is the measure of how far you raise the ball above the flat portion of the track. For each height measure the horizontal distance which the ball traveled. Graph your results, then do what you need in order to straighten out at a curve if one is obtained. What do your findings mean about the distance and height relationship; what is the relationship?
Experiment 7 Invitation to Inquiry
1. Design a demonstration of Newton's second law of motion using a student on ice skates (or roller blades) and a spring scale. The student on skates or roller blades should hold the hook on one end of the scale while you pull the hook on the other end, pulling with a sufficient force to exactly maintain a constant force. Calculate the acceleration by using the equation F = ma, then measure the acceleration a second way by marking distances and measuring the change of velocity.
2. Repeat the demonstration with a more massive student on ice skates or roller blades. Compare the difference, if any, needed to maintain a constant force on a more massive moving object.
3. Make a velocity vs. time graph for the application of a constant force on the first student, and another graph for the more massive student. What characteristic of the graph changes?
4. Using any everyday materials you wish, design a demonstration to prove that a moving object with zero net force moves at a constant velocity.
5. For the demonstration in Invitation 1 (constant force) and the demonstration in Invitation 4 (zero force) sketch three graphs to predict (a) force vs. time; (b) acceleration vs. time; and, (c) force vs. acceleration. Do several demonstrations to show your six predictions are correct.
Experiment 8 Invitation to Inquiry
How are momentum changes and collision forces related? A rubber ball, a ball of modeling clay, and a super ball all exert forces, and all undergo a momentum change when they strike the floor or a wall. Do they all exert the same force if they have the same momentum? Do they all undergo the same momentum change? Set up a demonstration of a pendulum with a rubber ball, ball of modeling clay, and a super ball as a bob. If all have the same mass, will all move a wooden block over the same distance if released from the same height? Or, is it necessary to adjust the height to see the same results? Note the clay might stick to the block, the super ball will bounce back at almost the same speed, and the rubber ball will be somewhere between sticking and bouncing back with the same speed. Make your predictions, then take a survey of your classmates about their predictions. Can anyone give an explanation for their predictions in terms of Newton's second law of motion, momentum, and the force exerted by moving objects? Do the demonstration to find answers to this question.
Experiment 9 Invitation to Inquiry
As you may have noticed, a moving bicycle is more stable than a stationary one and it may be difficult to stay upright on the bike when stopped. Investigate the relationship between torque and spinning with a bicycle wheel mounted on an axle. Find a way to measure the torque needed to change the axis of rotation, say from a vertical to a horizontal direction. Compare the torque needed to do this for a slowly spinning wheel as compared to a rapidly spinning one. Also compare any differences observed when you apply the torque quickly in a fast flip as compared to application of torque slowly in a slow flip. What relationships were found?
Experiment 10 Invitation to Inquiry
1. Did you ever try to figure out which is a cooked egg and which is a raw one without breaking the shell? One way to accomplish this is by spinning the eggs on a plate, and the well-cooked one will continue to spin while the uncooked egg will rock back and forth. The yolk is heavier than the white, but why would an uncooked egg spin more slowly? Use your understanding of centripetal force to develop some ideas about why eggs should behave this way, then design a demonstration or Experiment to test your idea.
2. Experiment with some things that rotate, such as rolling cylinders. Roll large, small, solid, hollow, and various combinations of large and solid cylinders, small and solid cylinders down an incline. Predict ahead of time which will reach the bottom of the incline first. Then test your predictions.
3. A hollow and solid cylinder of the same size do not have the same weight. If you roll the two cylinders down an incline slope together, side by side, the solid cylinder should win. Yet if you attach strings of equal lengths to make pendulums from the same hollow and solid cylinders, then you will find that they swing together, side by side. Is this true? Experiment to find out, then be prepared to explain your findings.
4. Explore relationships between mass distance from an axis and how hard it is to set an object into rotational motion. Consider using a baton with some kind of movable masses that can be fixed to the baton different distances from the axis of rotation. A large wooden dowel rod and lumps of clay might be a good Experimental alternative to a baton.
Experiment 11 Invitation to Inquiry
1. Explain why a ball of clay sinks, but when shaped into a boat, it floats. Experiment with a ball of clay and container of water to find which shape of clay will hold the most "cargo."
2. Try to float an egg in a glass with a measured amount of fresh water. Keeping track of how much you use, add salt to the water, stirring, until the egg floats. Calculate the density of the egg from the salt and water measurements. Then calculate the density of the egg by weighing and finding the volume by water displacement.
3. Make a hydrometer by adding modeling clay to the bottom of a plastic soda straw until it floats upright. Mark the water level for when the hydrometer is floating in distilled water, then compare to the level in other liquids. Visit a service station or shop where antifreeze and car batteries are checked. Find out how specific gravity is used to make these tests.
Experiment 12 Invitation to Inquiry
Make a Cartesian diver by putting a little water in a small test tube, then inverting it in an almost filled, small-mouth bottle of water. Adjust the water inside the small tube so it just floats, then place a rubber stopper in the bottle. Pressure on the bottle will cause the inverted tube to sink because pressure compresses the air inside the little tube, allowing in more water which increases its weight. If you can find a flat (flask-shaped) bottle, you can adjust the tube so pushing on the flat sides makes it sink and stay down, but pushing the other way makes it rise again. Use the diver to quantify some volume and pressure relationships.
Experiment 13 Invitation to Inquiry
You may have seen a person use a bare hand to break a board with a Karate chop. The person hits the 3/4 inch (1.9 cm) board with a quick movement, transferring enough kinetic energy to break the board. How much kinetic energy is needed to break the board? You can find this if you know how much work is needed to break it. Obtain a 15 by 30 cm pine board, cut so the grain is parallel to the shorter side. Figure out a way to hang weights around the center of the board as you measure how much the board bends under the increasing weight. When it breaks, you will have the force needed and the distance the force moved the board, so you will be able to calculate the work done. Working backward from the work needed, you will be able to find the kinetic energy you need to transfer to break the board.
Experiment 14 Invitation to Inquiry
- How would changing the area of contact between the block and board affect (a) the mk and (b) the ms ? Make your prediction below, then Experiment with the one of its smaller surfaces of the block to test your prediction.
- What would happen to the frictional force and the coefficient of friction if the board is raised at one end? What happens to the frictional force and the coefficient of friction as the angle is increased more and more?
Experiment 15 Invitation to Inquiry
Using the same spring and set-up of this Experiment, adjust the total mass on the spring to 500 g. Pull the spring down 5 cm and release it. Measure its period by timing 5 to 10 oscillations or cycles. Divide the total time by the number of cycles to find the average period. The equation for the period of a spring is
where p = 3.1416, m = mass, and k = the spring constant. Use this equation to determine the spring constant k, then compare it to the value found from the spring elongation graph in the Experiment.
Experiment 16 Invitation to Inquiry
- Wash an aluminum pop can, leaving a small amount of water in the can. Use tongs to hold the can over a heat source until the water boils, and you can see steam condensing in the air at the opening. Immediately invert the can part way in a container of cool water. Explain what happens in terms of Charles' law, Boyle's law, and a molecular point of view.
- Place the ends of a one meter metal rod on two wood blocks and secure one end to its block. Place a pin through a tagboard pointer under the free end. The metal rod should be able to move back and forth, turning the pin as it moves. Explain what happens to the pointer as the metal rod is heated, then cooled.
- Boil a small amount of water in a clean 500 mL flask, then apply a round balloon over the mouth before the flask cools. Place a rubber band, doubled if necessary, around balloon on the neck of the flask. Explain what happens to the balloon as the flask is heated or cooled without using the terms "drawn in" or "suck."
Experiment 17 Invitation to Inquiry
The sketch below is of a termometro lento, an interesting device first named by Galileo Galilei (1564-1642). It is a "floating glass bulb" thermometer and the name means "slow thermometer." This thermometer is "slow" because it depend on density changes that occur with changes in the temperature. In general, the density of a liquid increases with decreases in temperature and this increases the buoyancy of the liquid. All of the bulbs have different masses of liquids in same-volume bulbs, so each bulb has its own density. When the temperature of the liquid in this thermometer rises, it becomes less dense and the bulbs will sink slowly one by one, according to their density. In the same way, the bulbs are buoyed up as the temperature decreases. The temperature is read by the lowest floating bulb (see sketch below). The density of each bulb has been calibrated in a temperature-stabilized bath, and this temperature is marked on the bulb.
Is the termometro lento drawn below in a cool or warm environment? What would you need to know to build such a thermometer? How much would you need to vary the mass in each bulb to create a thermometer with a two degree Fahrenheit scale?
Experiment 18 Invitation to Inquiry
Predict what will happen if you heat a brass, glass, and iron ball to 100° C and place them on a sheet of paraffin. Test your prediction, then explain how this could happen.
Experiment 19 Invitation to Inquiry
Make a charge detector. Spray two grains of puffed rice or wheat with a very thin layer of aluminum paint. Use a needle and thread to suspend the grains from a stopper or cork. Use this charge detector to investigate charged plastic rods, combs, glass rods, and other items.
Experiment 20 Invitation to Inquiry
Obtain a lemon and roll it a few times on the table top. Make two parallel slits very close together in the lemon and insert a clean strip of magnesium in one slit and a clean strip of copper in the other slit. The strips can be very close but must not touch each other. Use alligator clips and see if you can run a small motor or bulb with this cell. Try the two metals in orange juice, a potato, apples, soft drinks, and other substance. Try two different metals. How long can you run a clock or some other device? Which substance is best for running a clock or bulb? Which two metals?
Experiment 21 Invitation to Inquiry
Make a model of a way to wire a circuit in two rooms. Arrange bulbs and switches so a person walking into one side of a room can turn on the lights, then turn on the lights in a second room so the lights in the first room turn off at the same time.
Experiment 22 Invitation to Inquiry
The carbon resistors that are used as standard sources of resistance in electrical circuits are marked with a code of colored bands. Here is the code for the colors:
| Black = 0 | Green = 5 | |||||
| Brown = 1 | Blue = 6 | |||||
| Red = 2 | Violet = 7 | |||||
| Orange = 3 | Gray = 8 | |||||
| Yellow = 4 | White = 9 |
The value of the resistor is AB X 10C ± D where no D band means ± 20%, silver means ± 10%, and gold means ± 5%. The band placement is shown above. As an example, consider bands of red, yellow, red, and silver on a resistor. This means 24 X 102 ± 10% ohms, or 2400 ± 240 W.
Obtain 5 or 6 resistors and a meter to measure the Experimental resistance of each. Read the code to determine the accepted value, then find the Experimental error as described in the Appendix. What could account for Experimental errors, if any?
Experiment 23 Invitation to Inquiry
Is it possible to produce electricity in an extension cord that is not plugged into a circuit? Hook a 50 ft extension cord to a galvanometer and move it as a jump rope, cutting the magnetic field lines around the earth. Figure out how you are going to attach the cord to the galvanometer and how you are going to move it across the earth's magnetic field lines. Can you think of any practical uses for "jump-rope electricity?"
Experiment 24 Invitation to Inquiry
Will one electromagnet attract or repel another electromagnet when there is a current in both coils? Test this idea with an Experiment after recording your prediction.
Experiment 25 Invitation to Inquiry
Investigate the "Donald Duck effect" that takes place when one breathes helium. Your voice is normally produced by a stream of air flowing between the vibrating vocal chords in the larynx. The sound of your voice is also determined by the configuration of your throat, mouth, and nasal cavities. Sound waves bouncing back and forth in a cavity will interfere constructively, making standing waves known as the resonance frequencies. The cavities in the vocal tract have such resonances, and a resonance frequency will be strongly transmitted, while other frequencies will be damped.
But what happens when one breathes helium? Does your voice change to that of a high-pitched Donald Duck because helium is a low density gas? This is an invitation to investigate why the pitch of a person's voice changes. Will certain mixtures of helium and oxygen produce different effects? Warning: This is an invitation to work out the theory behind the "Donald Duck effect." Any Experimental verifications must be approved ahead of time and then supervised by your instructor.
Experiment 26 Invitation to Inquiry
For any sound, there is a relationship between v, f, and l. For any sound produced in a closed air column there is also a relationship between the temperature, l and the length of the shortest air column at which resonance occurs. Therefore, it should be possible to calibrate a closed air column, making marks on the side of the tube so you can use it as a thermometer. How can you make a sound-resonance thermometer that will show the present temperature?
Experiment 27 Invitation to Inquiry
Trace the travel of light rays through a convex lens, a concave lens, and a triangular prism. What are the factors that determine how much the light ray is bent in each lens?
Experiment 28 Invitation to Inquiry
In many communities the recycling of aluminum, paper, and plastics is started by first segregating items made of these materials from the rest of the trash. A major problem in recycling plastics is the many different types of plastics that exist, all with different chemical and physical properties. Some of these materials are more desirable for recycling than others, so they must be sorted. One way of sorting plastics is to read the code that might be stamped on the bottom. Here are some letter and number codes from some common plastic items. The number usually appears inside the recycling arrow logo: 2 (HDPE) milk jugs, bleach and detergent bottles; 1 (PETE) soft-drink bottles; 5 (PP) catsup bottles, yogurt cups; 6 (PS) transparent plastic drinking cups, CD boxes, and; 4 (LDPE) plastic squeeze bottles. Can you find a way to separate mixture of pieces of plastic from each of these 5 groups by taking advantage of the differences in chemical or physical properties? Consider cutting pieces of plastic from each of the group and finding important properties that could be used in a separation scheme.
Experiment 29 Invitation to Inquiry
Are the laboratory results obtained always what you expect? If not, what is the meaning of unexpected results? Measure exactly 50 mL water into a 100 mL graduate cylinder. Carefully measure 50 mL of ethyl alcohol (pure as possible) into another graduated cylinder. Place both graduated cylinders on a balance and record the mass. Slowly pour the alcohol into the water. Note the combined volume and the total mass. Were the findings expected? What could possibly explain this?
Experiment 30 Invitation to Inquiry
Oxygen gas was collected in this laboratory investigation by bubbling the gas through water. Does much of the gas dissolve in water during the process? If so, is the temperature of the water important in determining how much gas dissolves in the water? You can test these relationships by setting up an Experiment with Alka-Seltzerâ tablets. Set up a flask on a sensitive balance, with two tables wrapped in a tissue, then lodged inside the neck of the flask. Record the weight, then gently push the tissue so it falls into the water. The difference in mass will be a result of carbon dioxide leaving the flask. Compare how much carbon dioxide is dissolved in water of different temperatures. Should you expect the same dissolving rate for oxygen?
Experiment 31 Invitation to Inquiry
Use some small gauge wire, a flashlight battery, and a flashlight bulb and holder to set up your own portable conduction tester. Test a variety of materials to find which are conductors and which are nonconductors. Generalize what categories of materials are conductors and what categories seem to be nonconductors.
Experiment 32 Invitation to Inquiry
Epson salts is the common name for magnesium sulfate heptahydrate, which contains water. The water is released when a sample of epson salts is heated. Most drug store chains have their own generic brand of epson salts. Do the different brands have the same proportion of water? Using the procedures of this lab investigation, you should be able to Experimentally very if all brands of Epson Salts have the same proportion of water. Test several different brands of Epson salts, then report your findings to your class.
Experiment 33 Invitation to Inquiry
Make a plan for using the fewest number of steps possible in an Experimental study to place six metals (Mg, Zn, Fe, Sn, Cu, and Al) in an activity series from highest to lowest. Describe the procedure you would use for determining the position of a Ni salt in this series.
Experiment 34 Invitation to Inquiry
Salinity is a measure of the amount of salts dissolved in 1 kg of solution. For example, if 1 kg of seawater were evaporated, 965 g of water would leave and 35 g of salt would remain. This is a salinity of 35 parts per thousand, or 35
Measuring, then evaporating the water from a kilogram sample of water would be time consuming. To save time, design a way to measure salinity from conductivity. Construct a conductivity table for salt solutions of known concentrations, then use the table to check the salinity of a sample of sea water. You could also consider measuring the density of seawater by constructing a calibrated hydrometer.Experiment 35 Invitation to Inquiry
Foods naturally contain enzymes, biochemical compounds that originate in plants and animals. Cooking changes enzymes, and the purpose of blanching, or steaming food shortly before freezing is intended to destroy enzymes. One of the enzymes in foods is a catalysts that will speed the decomposition of hydrogen. You can design a home Experiment to use hydrogen peroxide (3% solution) to test fresh, blanched, and cooked crushed food (or juices from the foods) for the catalyst enzymes. If you can find a way to quantify the measurements, perhaps you can come up with specific recommendations about how hot the food should be heated, and for how long.
Temperature is one of the more important factors that influence the rate of a chemical reaction. You can use a "light stick" or "light tube" to study how temperature can influence a chemical reaction. Light sticks and tubes are devices that glow in the dark and have become very popular on July 4th, Halloween, and other times why people might be outside after sunset. They work from a chemical reaction that is similar to the chemical reaction that produces light in a firefly. Design a home Experiment that uses light sticks to find out the effect of temperature on the brightness of light and how long the device will continue providing light. Perhaps you will be able to show by Experimental evidence that use at a particular temperature produces the most light for the longest period of time.
Experiment 36 Invitation to Inquiry
What factor is most important in determining the rate of the chemical reaction? For example, is temperature, surface area, agitation, or concentration of reactants most important in determining how fast a reaction takes place? Or perhaps they are all equally important? Design your own Experiment to answer these questions. Use Alka-Seltzerâ tablets that you will dissolve in water, and design an Experiment to find the best way to increase the dissolving rate.
How can you measure the dissolving rate of Alka-Seltzerâ in water? Consider collecting the gas given off by water displacement, using a stop watch to determine rate. See laboratory Experiments in this manual concerned with oxygen and/or hydrogen for an Experimental setup on collecting a gas by water displacement.
Of those listed--temperature, surface area, agitation, or concentration--which of the factors tested were important in determining the rate of the a reaction?
Experiment 37 Invitation to Inquiry
Washing soda, borax, or trisodium phosphate are often added to laundry products to soften the wash water. Add a small amount of each to 5 mL of tap water, then measure the hardness with the soap-drop method. Is one of the softening chemicals more effective than the others?
Is there a practical way to obtain pure water from a hard water source? Design, use, and evaluate an apparatus for purifying water--by boiling, freezing, filtering, precipitation of dissolved minerals--or by any means you can imagine. Evaluate your technique in terms of usefulness and effectiveness.
Experiment 38 Invitation to Inquiry
There are many common things that can be used as acid and base indicators. For example, from foods you could try boiled purple cabbage juice, grape juice, blackberry juice, ordinary tea, and others, and from the office supply store certain construction papers might show color changes. To test foods, try soaking strips of filter paper in juices or solutions, then allowing it to dry completely. Materials such as construction paper can be tested directly. Plan tests to find what color each indicator will appear when exposed to solutions of acids or bases, and test other materials, too. Show how your collections of indicators will identify the pH from a wide range of possibilities.
Think of some way to measure the "strength" of an acid or a base without using an indicator. Taking proper precautions, do Experiments to compare several methods of measuring strength.
Experiment 39 Invitation to Inquiry
Cobalt chloride is often used to test for the presence of water since it undergoes a reversible color change when exposed to moisture or humidity. For example, cobalt chloride is sometimes included with silica gel pellets to indicate when the gel has absorbed moisture. Experiment with cobalt chloride dried on filter paper strips. Find out if the color change is sensitive enough to water vapor and temperature to be used as an indicator of the relative humidity.
Experiment 40 Invitation to Inquiry
Ionizing radiation is understood to be potentially harmful if certain doses are exceeded. How much radiation do you acquire from the background where you live, from your lifestyle, and from medical procedures? Investigate radiation from cosmic sources, the sun, from television sets, from time spent in jet airplanes, and from dental or other X-ray machines. What are other sources of ionizing radiation in your community? How difficult is it to find relevant information and make recommendations? Does any agency monitor the amount of radiation that people receive? What are the problems and issues with such monitoring?
Experiment 41 Invitation to Inquiry
Investigate the crystal structure of some of the large samples. Consider, for example, measuring the angles between the faces, comparing how the crystal transmits light, and other measurements that would help you interpret the structure in terms of atoms or molecules. Does the structure provide any information about the conditions necessary for growing large and well-formed crystals? Or are the same conditions needed for all crystals? Are there any upper limits on the size of a crystal?
Experiment 43 Invitation to Inquiry
Survey the use of rocks used in building construction in your community. Compare the type of rocks that are used for building interiors and those that are used for building exteriors. Are any trends apparent for buildings constructed in the past and those build in more recent times? If so, are there reasons (cost, shipping, other limitations) underlying a trend or it simply a matter style?
Experiment 44 Invitation to Inquiry
There are several ways to find your latitude by measurement. First, determine your latitude by measuring the angle of the North Star above the horizon. Second, determine your latitude by measuring the angle between a vertical stick and a line to the noonday sun on the spring equinox (March 21) or the autumnal equinox (September 23). For the North Star, consider making two measurements 12 hours apart and averaging the two. Why do these two different methods tell you your latitude? Is one more in "agreement" with the stated latitude for your location?
Experiment 45 Invitation to Inquiry
Design an Experiment to study the effect of the diameter of a lens on the image formed. Do the Experiment.
Use plane (flat), concave, and convex mirrors to find when you can see:
- an enlarged image.
- a reduced image.
- an image of the same size.
- an image that appears upright.
- an image that appears inverted.
- an image that appears upright, then inverted after some adjustment.
What generalizations can you make to inform someone how to make the various images with mirrors?
click here to post your own inquiry
