Why are Photovoltaic Cells Black?

The dark color reduces the amount of photons reflected. Photons that are not absorbed by the panel cannot be used to produce electricity.

What are Photovoltaic Cells Made From?

Silicon is the major material in the cells. Pure silicon crystals are poor conductors of electricity. Other elements are added to the silicon, such as, phosphorus and boron. When the energy from the sun hits the cell, the electrons in the elements begin to move around. The sun causes the panel to have a positive and negative side. This electrical difference causes electrons to flow through a diode.

What Factors Affect the Production of a Solar Cell?

The factors that most affect the production of a solar cells are the angle of the panel in relation to the sun, the peak wattage, the light intensity and the hours of sun exposure.

How is Wattage (or Power) Calculated?

The formula for power is   Power=Current X Voltage. Power is measured in watts, current in amperes and voltage in volts.

The Solar Science Kit has a small motor, photovoltaic cell and disc that works well in demonstrating this in a classroom or home setting.

See the Oxygen molecules bubble and the indicator turn pink

Hydrolysis Water Splitting
Using a 9V battery, 2 electrodes and small gauge wire, you can split water into its component parts. This process is called hydrolysis. We add a small amount of salt to increase the conductivity of the water and an acid/base indicator to visualize the reaction.

The chemical formula of water is H2O. When the electrical current, produced by the battery, passes through the water,  the water will split and the two electrodes will bubble. Hydrogen will appear at the cathode and the oxygen at the anode. The acid base indicator around the cathode will turn blue (because the free OH molecules raise the pH) and the area around the anode will turn pink (because the free hydrogen molecules lower the pH).

Looking at the formula for water, there are twice as many hydrogen atoms as oxygen. When hydrolysis occurs, twice as many hydrogen bubbles will be released as oxygen. You can visually see extra bubbles at the point where hydrogen is being released.

Hydrolysis experiments can be quantitative (how much hydrogen and oxygen are released?) or qualitative (can I visually see the reaction taking place?)

Praying Mantid Eggcase

What is the difference between complete and incomplete metamorphosis in insects?

Incomplete and complete metamorphosis differ in the number of life cycle stages insects go through during their transformation from egg to adult. Complete metamorphosis has 4 life cycle stages and incomplete metamorphosis has 3 life cycle stages.

Complete Metamorphosis

Complete metamorphosis has four distinct life cycle stages: egg, larva, pupa and adult. Examples of insects that go through complete metamorphosis are butterflies, silkworms, mealworms and ladybugs. The larva can be worm-like, although you can still see the six legs. The larvae for moths and butterflies are called caterpillars. Maggots are the larval stage of flies. The larvae eat constantly and grow rapidly. A hard, protective case forms around the larva…this is the pupa stage. The pupa stage for a butterfly is called a chrysallis. The pupa stage for a moth is called a cocoon.

Incomplete Metamorphosis

Incomplete metamorphosis only has three life cycle stages: egg, nymph, adult. The nymph looks similar to, but a smaller version of, the adult. The nymph is also wingless. Examples of insects that go through incomplete metamorphosis are stinkbugs, earwigs, crickets, grasshoppers, cockroaches, ants and praying mantids.

Keep the lid over your plate to prevent contamination.

All living organisms require energy. They can get their energy from multiple sources: organic chemicals(carbon containing compounds), inorganic chemicals and light. Bacteria use organic chemicals, such as, sugars, starch, protiens and fats to grow. Bacteria are called heterotrophs.

Most bacteria grow best at normal, human body temperature (98-99 degrees F). When growing the bacteria, incubate at a temperature as close to this as possible. The bacteria will grow slower at lower temperatures.

Aseptic technique is the process of growing and transferring bacteria without contaminating the culture by touching or breathing on the sample.

Nutrient agar is a general purpose prepared media and grows many types of bacteria and fungi. If you have a specific bacteria culture, you can spread the bacteria on the plate using a sterile swab or innoculating loop. The bacteria will grow and become visible in 24-48 hrs. If you would like to determine the types of bacteria growing on a sink, chair, table or other areas, a sterile swab can be used to rub across the area you would like to test. After the sample is taken, you can transfer the bacteria to the nutrient agar plate by swiping the swab across the surface of the agar plate. After 24-48 hrs, you may find many, different looking colonies growing on the nutrient agar plate. Each type of bacteria look a little different (color, shape, size) when they grow.

Bacteria can be differentiated based on how they react to a a procedure of dying cells called Gram stain. Bacteria are divided into a group that turns purple (gram positive) and a group that turns red (gram negative). Bacteria that are gram (+) include Staphylococcs, Streptococcus, Bacillus and Micrococcus. Gram (-) bacteria include E.coli and Salmonella. The Gram staining procedure is as follows:

Gram Staining Bacteria Procedure
1.Place a drop of distilled water on a slide and, using a swab or inoculating loop, mix the bacteria with the water an smear the mixture on the slide. The mixture will appear cloudy. Using a flame, heat fix the bacteria to the slide (pass the slide through the flame a few times to “dry” the bacteria and affix it to the slide).

2. Using a dropper, add crystal violet to the slide. Let stand for 1 minute.

3. Add iodine to the slide. Let stand for 3 minutes.

4. Decolorize the sample with alcohol. Let stand for 30 seconds.

5. Counter stain the sample with safranin. Let stand 1-2 minutes. Using a dropper, rinse with distilled water.
Gram Staining Results
Gram positive bacteria will appear purple under the microscope. They have a single, thick cell wall. The crystal violet and iodine combine to attach to this wall. The decolorizer (alcohol) dehydrates the cell wall, causing the pores to close, trapping the stain inside. the safranin added in the final step, does not penetrate the wall.

Gram negative bacteria will appear red. The have a cell wall and additional thin layers of fatty sugars. The decolorizer easily penetrates these thin sugar layers, washing away the crystal violet – iodine chemical (purple color). The safranin in the last step attaches to these layers and appears red.

Crayfish are marvelous classroom organisms. They are exciting and easy to care for. Through close observation, students can learn interesting details about animal structures while developing sensitivity to the needs of living organisms.

About
Crayfish are also known as crawfish, crawdads, mudbugs, and yabbies; they resemble and are related to lobsters. Crayfish most commonly live in freshwater, only a few have the ability to survive in salt water. There are over 500 different species of crawfish in the world and more than half of them are located in North America. Specifically, Louisiana produces 90% of the world’s crayfish for consumption as food.

Care
To keep your pet crayfish comfortable you will need to keep it in a freshwater aquarium, a fish tank will work just fine. Make sure to cover any holes in the lid of the tank to keep your crayfish from escaping. Feeding your crayfish is simple; many common fish foods will work. Pet crayfish will eat shrimp pellets, vegetables, fish food, algae wafers, goldfish, and minnows. Be careful which fish, if any, you put in the aquarium with your pet crawdad because they will attack and eat fish if they feel threatened or if they appear to be an easy snack. When using a prepared food, do not overfeed. The excess food will spoil the water.

Crayfish from the wild may have mud on their swimmerettes. The crayfish need to be purged (placed in clean, dechlorinated water) to remove the mud. Depending on how much mud is present, several water changes may be necessary.

Crayfish like to have a place to hide. The crayfish will molt, shed it’s exoskeleton. During the few hours after the molt, the crayfish has a soft exoskeleton and is vulnerable to predators. The larger the crayfish grows, the longer the time is in between molts. Crayfish have gills for breathing underwater, but can also breathe air.

What is a Geode Rock Formation
Geodes are a great way to view and learn about the formation of rocks. They occur in sedimentary as well as some volcanic rocks too. These geological rock formations are most commonly limestone on the outside, while the inside is hollow and full of quartz crystals. If there is no air pocket in the formation it is called a nodule instead of a geode.

How Do Geodes Form?

A geode starts off as a bubble or a void left by an animal burrow, tree root, or something else. Water is trapped inside of the void, which contains silica precipitation that has other minerals or elements present in it such as calcite, iron or manganese. The basic crystals of a geode are made of quartz (silicon dioxide) and are colored based on the contents of the surrounding soil.  Over thousands of years different layers of silica precipitation cool and create different layers of crystals. There is no way to tell what is on the inside of a geode without cracking it open. You can view the process of cracking open a geode below.