Teaching Strategies
In my class most of the time students work in groups. I use two different types of grouping based on the requirement: i.e., ability grouping and co-operative grouping. Co-operative grouping will work better at the beginning of the concept where as ability grouping works for students to gain mastery in a topic.
Nutrition Label Analysis
How many molecules of water are required to burn a lunch meal? This activity focuses on studying the nutritive values in a meal and then to determine the number of moles and molecules of water required for the digestion of that meal. The process involves the determination of caloric values from carbohydrates, proteins, and fats separately.
For example: A student picked the following items from the existing lunch options in the school cafeteria on Monday18 - orange chicken (two servings, steamed rice (1 cup), Lo Mein Noodles (1cup), pepperoni pizza (1 serving), French fries (1 serving) along with a piece of chocolate cake. Students will research and study the nutritive labels to find the food calories for each item. This process involves a great deal of math. Therefore, this would be the stepping stone to incorporate math into chemistry, without mentioning about stoichiometry. Students identify which item in the meal is healthy and which is not based on the knowledge they gained from Eat, Drink and be Healthy book and their research. After the food caloric calculation, students will calculate the volume of water required to digest the meal from the information that an average person requires about a milliliter (mL) of fluid for every calorie burned19. The first step in the calculation of water molecules is determination of volume of fluid. For instance, the number calories obtained from the above meal is 750 calories: therefore, the volume of the fluid required, with the assumption as water is the only fluid available for our case, is 750 milliliter. Then the volume of water is converted into the mass of water using the density (density of water = 1.00 g/mL). In the third step mass of water is converted into moles of water using water molar mass. The last step is converting the number of moles of water into molecules of water.
Burning Calories20: The energy in food
This activity focuses on calculation of energy in food items using a calorimeter. All foods contain energy, but the amount of potential energy stored will vary greatly depending on the type of food. Moreover, not all of the stored energy is available to do work. When we eat food, our bodies convert the stored energy, known as calories, to chemical energy, thereby allowing us to do work. A calorie is the amount of heat (energy) required to raise the temperature of 1 gram (g) of water 1 degree Celsius (°C). The density of water is 1 gram per milliliter (1g/ml) therefore 1 g of water is equal to 1 ml of water. When we talk about caloric values of food, we refer to them as Calories (notice the capital "C"), which are actually kilocalories. There are 1000 calories in a kilocalorie (or dietary Calorie). So in reality, a food item that is listed as having 38 Calories has 38,000 calories. Calories are a way to measure the energy you get from the food you eat.
Neutralizing ability of stomach acids
The focus of this activity is on stoichiometry of acid base neutralization between stomach acid and commercially available antacids. Students are required to do research to find information on the chemistry of stomach acid and commercially available antacids. At least, it is expected that students will come up with the chemical name of stomach acid, hydrochloric acid, and its neutralization with antacid, either Tums - calcium carbonate, or milk of magnesia - magnesium hydroxide. Students then write the balanced chemical equation between the stomach acid and the antacid chosen. After students understand the concept of neutralization of stomach acid with antacid (base) to maintain the pH, students will be given a virtual lab21 as home work. This virtual lab familiarizes students through the process of acid-base titration. The following class period students will complete the titration lab - neutralizing ability of stomach acids22. At the end of lab students are required to find the post lab questions and write lab report. Approximately the entire activity will be completed in three class periods.
Gas stoichiometry and cellular respiration
The activity will begin with asking students: if we are locked in the classroom and can not go out the room, how long we can survive? The activity involves: measuring the dimensions of the classroom, subtracting the volume of the tables, lab stations, etc., determination of amounts oxygen and carbon dioxide from the room dimension and composition of air, research to learn about the cellular respiration, inhalation amount of oxygen and exhalation amount of CO 2, hazardous indoor levels CO2 etc. They are supposed find the inhalation amount of oxygen and exhalation amount of CO 2 per student and multiply with number of students to calculate indoor air quality. I estimate that this activity may take one class period.
Baking cookies
This activity will focus on limiting reactants and percent yield. Students are required to calculate the maximum number of cookies they can make from the given set of ingredients. Students are required to make a list of ingredients that were excess. Students are required to identify the ingredient that will limit the number of cookies they can bake. They are required to report these amounts in SI Units. Finally they are supposed to write the reason for making such a number of cookies (limiting reactant).
After baking cookies, students will count the number of cookies they actually could bake. Using the estimated number and the actual number students will calculate the percent yield. This activity will take one ninety minute class period.
Hopefully, by the end of these activities students will be able to understand healthy food choices, ways to avoid obesity, conversions, stoichiometry relationships, limiting reactant and percent yield.
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