Glacial Heat – Teaching Supersaturated and Supercooled Solutions

Glacial Heat

Glacial Heat

What’s Happening?

Inside the Glacial Heat exists a supersaturated and super-cooled (below its freezing point) solution of sodium acetate and water.This supersaturated solution was created by mixing the salt (sodium acetate) in hot water. Hot liquid will dissolve more salt than a cold one. When this solution is cooled slowly, the salt stays in solution.

CH3COONa.3H2O + Heat -> CH3COO-(aq) + Na+(aq)+3H2O
(Solid) (Liquid)
A small, stainless steel, metal chip provides the “spark”. When the chip is squeezed, a small, single, solid salt molecule is created. This is the seed ,on which, the other salt crystals begin to form. The normal freezing point for sodium acetate is 130 degrees F (54 degrees C). The reaction occurs quickly, with heat being released and the liquid becomes solid (freezes). The heat being released is equal to the freezing point of the solution (54 degrees C). The sodium acetate (a salt) dissolving and freezing in the water is an example of a physical change.

 

How do I Teach With Glacial Heat?

Discuss physical and chemical properties:

Physical properties are observable (color, size, luster and smell) and also include characteristics, such as, freezing point, melting point, malleability, conductivity, volume, mass, weight and length.

Chemical properties are only observable during a chemical reaction and can include flammability or the ability to rust. In each of these examples, a new compound has been formed.

Discuss physical and chemical changes:

Physical changes include ice melting, molding clay, water evaporating, a coke freezing and sugar dissolving in water. In these examples, no chemical changes have occurred and the changes can be reversed.

Chemical changes include metal rusting, lighting a match, milk souring and the stomach digesting food. These changes are not easily reversed. The presence of light, color change, odor, gas production, heat or sound can indicate that a chemical change has taken place.

The Glacial Heat can be boiled (melted) for 7-10 minutes and reused over and over again.

Teaching the Carbon Cycle

The carbon cycle is the process by which carbon enters and exits the earth’s atmosphere. Carbon, in the form of carbon dioxide, and along with other gases, acts as a warming layer for Earth. Without this layer of gases, the Earth would be too cold to sustain life. There are many carbon cycle models and carbon cycle demonstration kits available to assist in the explanation of this process. Below is a basic explanation of the carbon cycle.

The Carbon Cycle

Carbon is released into the environment in many ways. Animals and plants respire, releasing carbon dioxide into the atmosphere. Animals release solid waste products into the soil and water. Also, leaves, roots, wood and dead animals decay. Finally, the burning of fossil fuels and wood release stored carbon into the atmosphere.

The carbon that is released into the environment, is used by many plants and animals. This is the part of the carbon cycle that removes carbon from the atmosphere. Plants and algae take in carbon dioxide during photosynthesis. Many sea creatures take in carbon when making shells and bones. When these animals die and sink to the ocean floor, this carbon is stored for some time.

The Ocean’s Role

The majority of photosynthesis occurs in the oceans by algae and phytoplankton. Also, due to the large surface area of the oceans , carbon dioxide diffuses in and out in an attempt to equalize.

Owl Pellets and Owl Digestion

owlDissecting owl pellets is a fun and educational method of analyzing predator/prey relationships and for learning basic dissection techniques.

What is an Owl Pellet?

An owl pellet is the portion of an owl’s prey that has not been digested. Owl’s swallow their prey whole (they don’t have teeth to chew) and the feather’s, fur, bones and other undigestible parts are regurgitated by the owl.

How Does the Owl Pellet Form?

When the prey is swallowed, it travels through the esophagus and into the first part of the stomach, the proventriculus. Unlike other birds, the owl does not have a crop to store the food. As a result, the prey enters directly into the digestive tract. This part of the stomach has enzymes and acids (like our stomachs) to aid in digestion. From the proventriculus, the food travels to the second part of the stomach, the gizzard. The gizzard is a muscular organ that grinds the food and “filters” undigestible parts from traveling into the intestines.

The pellet is formed from the hair, bones or feathers that are left in the gizzard. The pellet will take several hours to form and several more before it is regurgitated. The owl cannot eat again until this pellet is expelled.

Does the Regurgitation of the Pellet Benefit the Owl?

Yes. Many scientists believe that this regurgitation of the pellet keeps the upper digestive tract clean.

Hydrolysis – The Splitting of Water

See the Oxygen molecules bubble and the indicator turn pink

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?)

Gram Staining Bacteria

grain staining bacteriaBacteria 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.