Mark Bryant, age 10, of Rogers, Arkansas, for his question:
What causes soft drinks to fizz?
They made the first soft drinks about 200 years ago. They made them with soda type chemicals and when the bottles were opened they went off with a loud pop. Nowadays, we do not use soda to make our soft drinks. And when you open a bottle for a refreshing drink, the fizz behaves itself. But for old times sake, we still call it soda pop.
The first fizz water was made by the earth. Sometimes rainwater is trapped below ground in rocks that are still hot from ancient volcanos. The hot water dissolves soda type chemicals from the rocks. So long as it stays below, under the pressure of heavy rocks, the dissolved minerals remain invisible.
But when this mineral water escapes to the surface, the pressure is released. Its dissolved chemicals become bubbles of gas and we get a bubbling spring. Some of these mineral springs are thought to be good for what ails you and people travel for miles to drink the bubbly water. Around 1772, the English scientist John Priestly set about copying nature's soda pop.
He used nature's own recipe, more or less, and dissolved soda type chemicals under pressure. Nowadays, instead of soda we dissolve carbon dioxide gas. The separate molecules of gas disappear when they are forced into the water under several hundred pounds of pressure. So long as the bottle is sealed with an air tight cap, the gaseous molecules stay dissolved in the mixture.
But great changes occur when we take the cap off the bottle, or open a can of soft drink. The pressure is removed. There is nothing to keep the carbon dioxide gas dissolved in the liquid. And it wastes no time in escaping. The gaseous molecules gather in bubbles and the bubbles fizz up to, the surface there they rise higher and the carbon dioxide mingles with the other gases of the air.
It is still possible to make soda pop by compressing soda into soft drinks. But carbon dioxide gas happens to be more convenient and also less likely to be harmful. True, it does us no good, but in small quantities it does us no serious harm. The bubbles of carbon dioxide in soft drinks disappear right after they tingle your tongue.
Carbon oxide also works to make our bread tasty and digestible. They re created by yeast cells that form alcohol and bubbles of carbon dioxide. In the hot oven, the alcohol disappears. And the gassy bubbles leave light spongy holes in the bread.
When your grandparents were children, a soft drink was a rare treat. Nowadays, we are told that too many soda pops tend to cause tooth decay, especially when the soft drinks contain a lot of sickly sweet sugar. Maybe grandma's mother had the right idea and soft drinks should be saved for special treats.