It¡¦s a natural treat loved by people around the world. For a lot of moviegoers, a night out at the cinema wouldn¡¦t be the same without it. Many adults and kids also delight in making it at home to snack on. After all, it¡¦s hard not to love a food that explodes . But why exactly does popcorn blow up and turn into something delicious?
In fact, the science behind popcorn is fairly simple. With popcorn, there are three main factors at work. Firstly, the kernel, or seed, of popcorn contains a small amount of water, along with a large amount of starch. Secondly, the outer shell of the kernel, which is called the hull, is strong and traps water inside it. Thirdly, when heated enough, the water expands into steam. This steam makes the starch softer. It also produces pressure inside the kernel. Since the steam cannot escape from the hull, it eventually explodes. When that happens, the kernel basically turns inside out.
Does all corn act this way? No, the corn that people commonly eat is a variety known as sweet corn. No matter how long someone leaves sweet corn on a barbecue or in an oven, it won¡¦t burst into little puffs. The popcorn people eat comes from a variety of corn that is itself called popcorn. Another interesting fact about popcorn is related to the reason that it makes a bang when it pops. It was once thought that the sound came from the kernel breaking. However, scientists discovered it is actually due to the sudden release of water vapor from the kernel. In other words, this swift change in air pressure produces the popping sound.
1. What is the second paragraph mainly about?
(A) How and where popcorn is grown.
(B) Why popcorn bursts open when heated.
(C) The history behind a popular snack food.
(D) Why popcorn is so popular around the world.
2. According to the passage, which part of the kernel prevents steam from flowing out?
(A) A (B) B (C) C (D) D
3. Four students are in a group discussion. Which of the following statements is correct?
(A) ¡§In addition to popcorn, sweet corn can also pop.¡¨
(B) ¡§The corn kernel is mainly composed of the seed, starch, and flakes.¡¨
(C) ¡§Many people enjoy eating popcorn while watching movies.¡¨
(D) ¡§Sweet corn also makes a popping sound when fried in hot oil.¡¨