When peanuts are dropped into a glass of beer, they sink to the bottom before floating up and “dancing” in the glass. Scientists investigated this process in a study involving the alcoholic drink beer. The research helped them understand mineral extraction (提炼) or magma (岩浆) in the layer of Earth called the crust.
Brazilian researcher Luiz Pereira told the media that he first had the idea when passing through Argentina’s capital Buenos Aires to learn Spanish. It was common for barkeepers to take a few peanuts and drop them into beers. Because the peanuts are denser (密度大的) than the beer, they first sink to the bottom of the glass. Then each peanut becomes what is called a “nucleation site”. Hundreds of tiny bubbles (气泡) of CO2 form on their surface. The bubbles act as floatation devices that carry the peanuts upward. The bubbles prefer to form on the peanuts rather than on the glass. When the bubbles reach the surface, they burst. The peanuts sink again before newly formed bubbles send the peanuts up again. Like a dance movement, the peanuts continue sinking and floating until the CO2 runs out, or someone drinks the beer.
In the experiments, the team of researchers examined how peanuts acted in the “beer-gas-peanut system”. They found the larger the “contact angle” between the curve of an individual bubble and the surface of the peanut, the more likely it will grow. But it cannot grow too much—less than 1.3 millimeters across is best.
Pereira said he hoped that by deeply researching this simple system, we could understand a system that would be useful for industry or explaining natural processes. For example, the floatation process is similar to the one used to separate iron from ore. Air is added into a mixture in which a mineral, such as iron, will rise because bubbles attach themselves more easily to it, while other minerals sink to the bottom. The same process can also explain why volcano scientists find that the mineral magnetite rises to higher layers in Earth’s crust than expected.
【小题1】When did Luiz Pereira first notice peanuts dancing in a glass of beer?| A．Early in his childhood. | B．During one of his experiments. |
| C．On his way to study abroad. | D．When he first threw peanuts into a glass of beer. |
| A．Their special surface. | B．The bubbles on their surface. |
| C．Their reaction with the beer. | D．The bubbles existing at the bottom of the bottle. |
| A．Its feature. | B．Its principle. | C．Its process. | D．Its significance. |
| A．Why Peanuts “Dance” When Dropped in Beer |
| B．Brazilian Researchers Found Peanuts Dropped in Beer |
| C．The Function of CO2 in Beer |
| D．The Principle in Mineral Extraction |
