Last Saturday, two of my 11th grade students – Catolo and João – a chemistry teacher, and I attended the regional science fair in Chimoio. Eighteen secondary schools from Mozambique's southern and central regions – Sofala, Manica, Tete, Gaza and Inhambane provinces – attended the fair to put their best science students' work on display. The fair, which is facilitated by Peace Corps volunteers, took place in Chimoio, the provincial capital of Manica.
Catolo presented an experiment that we had done together: The effect of using salt on the cooking of beans. He demonstrated that significant amounts of salt in the water used to boil beans slows the cooking process. Everyone in our community knows this: Agua doce (fresh or “sweet” water) cooks beans more quickly than agua salgada (salty water). Because the pumps and wells where we live give very salty water, we make a point of going to the pumps and wells that give the least salty water when we want to cook beans. However, Catolo was able to explain that increased concentrations of salt in the water decrease the movement of water by osmosis. In his first experiment, he made beans in three pots, one with fresh water, another with salty water, and another with very salty water. When he accidentally didn't add enough water, he saw that the beans in the fresh water burned – the water all having entered the beans – while the water that remained in the other pots corresponded to the amount of salt that was left.
João, who every day helps his dad bake bread for a neighborhood market, presented an experiment that he developed on the effects of sugar and salt on bread size. He added combinations of sugar and salt to his bread dough and then, when the bread was baked, checked the volume of the bread. The addition of small amounts of sugar, he showed, increases bread volume because the yeast uses it to form more carbon dioxide, which makes the bread expand. Salt, however, had the opposite effect. He wondered if perhaps some of the salt entered the yeast instead of sugar, and lessening the amount of carbon dioxide produced. Or, he thought, maybe salt affects the chemical composition of the bread dough so that it does not hold carbon dioxide as well.
A Peace Corps volunteer teaches João to use a microscope, at the regional science fair.A number of local science-oriented companies – a local greenhouse, an HIV-testing service, a tobacco plantation - were invited to the fair and setup booths to explain some of the science behind their work. A table of microscopes and prepared slides were setup for students to use. There were games and a raffle. Didinho, the host of a children's show on the national TV station TVM, oversaw the ceremonies. A jury made up of local doctors and scientists judged students' work. Didinho gave out awards.
Best of all: After the ceremonies, we all took a field trip to a local cheese and yogurt factory, where the students were given a tour, and we all enjoyed some delicious dairy.
