(Last of two parts)

LAST WEEK, we looked at three fun math activities that are applied to real-life situations.
This week, two of my students in the psychology class, Learning Processes in Math and Science, discuss ways to make science concepts come alive.

Sink or float: Density

Shellah Marie Tabayoyong-Cruz, who teaches chemistry at Marist School in Marikina City, says the concept of density is hard for students to grasp. Students tend to equate density with its formula and unable to apply concepts to real life. Cruz offers a simple demonstration:

Place on the desk two of the students? favorite beverages?diet and regular Coke. Put two covered containers beside them?one with water and the other with rubbing alcohol.

Ask the students: What will happen to regular Coke if poured into the container with water? With alcohol? How about diet Coke? Write your predictions.

After students have made their predictions, perform the demonstration. Students soon see that diet Coke floats in water while regular Coke sinks. Ask why.

Both drinks sink in alcohol. Why? (Diet Coke has less density than water, while regular Coke has more density. Both beverages are denser than alcohol.)

Use other materials (paper clips, magnets, rubber ball, and so on) and repeat the procedure. Once students see what things float or sink, they will better understand density.

Students can also be encouraged to note the positions of objects in the water and to use rulers to measure their position. Ask the students if size or shape affects whether an object will float or sink. How about the type of liquid?

Applications of density are numerous. For example, the Philippines is hit by typhoons regularly. Ask the students: Suppose you are living in an area near a creek or coastal region, which is easily flooded. How can you apply the concept of density in preparing for a storm or a flood?

Extend the concept of density to liquids floating or sinking in liquids. For instance, how can an oil spill in the sea be cleaned up?

Skin deep

Beethoven Amper, who teaches at the Malinta National High School in Bulacan, says a biology and chemistry topic, such as skin and the processes it undergoes, can be made interesting for students by linking it to?what else??beauty.

Start by describing what skin is. Skin is the outer covering of the body, reflecting mood, health, race, and even personal hygiene. The Filipino word kutis derives from the Latin cutis. Skin is the largest organ of the human body. Made up of multiple layers of tissue, it guards the underlying muscles, bones, ligaments and internal organs.

List the functions of skin. Because it interfaces with the environment, skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, and synthesis of vitamin D.

Ask students about their skin care regimen, and discuss why proper skin care is essential. Hygiene is important because unclean skin favors the development of pathogens. Dead cells that continually slough off the epidermis mix with secretions of sweat and oil glands. Dust on the skin form a dirty layer on the surface.
If not washed off, these mixtures of secretions, dirt and dead skin are decomposed by bacteria, producing a foul smell. The functions of the skin are disturbed when it is dirty, and dirty skin is prone to infections.

Introduce applied chemistry into the discussion by studying samples of cleansers and cosmetics. Cosmetics should be used carefully because they may cause allergic reactions.

Take oily skin, typified by shininess, blemishes and pimples. Oily skin is treated by removing excess surface sebum (a naturally healthy skin lubricant) without completely removing skin lipids. Clean oily skin with a cleanser of pH 4.5 to 5.5, since the skin?s pH value is about 5.4. Gel cleansers work best on oily skin, since they contain little natural oils, and no waxes or other agents. Moisturizer may be included in a hydroxyl acid product to counteract a cleanser?s drying effects.

Oily skin is not bad, as it is less prone to wrinkling and other signs of aging. Why? Oil helps to keep needed moisture locked into the epidermis.

Finally, ask students how they can achieve rosy pink skin. The important concept here is blood. About 98.5 percent of the oxygen in a sample of blood from a healthy human (who is at sea level) is chemically combined with hemoglobin. The hemoglobin molecule is the primary transporter of oxygen. If oxygen supply is inadequate, the body has to produce more blood to obtain more oxygen. Thus, the number of red corpuscles double, giving blood a much redder color. This color intensity is reflected by the skin, thus rosy skin is acquired.

A case in point is the Igorot who lives in high-altitude locations like Baguio, where the air is thinner and oxygen lesser in volume compared to low-lying areas like Metro Manila. The Igorot has rosy complexion (without the help of cosmetics).

Tourists who stay in Baguio for a lengthy period of time manifest the same skin tone transformation. Though some people say the cold climate is responsible for such lovely skin, emphasize to the students it is the reaction of the blood to thin oxygen that produces this effect.

E-mail the author at blessbook@yahoo.com.