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同学们,让我们先来做个简单的实验.在透明塑料袋中滴入几滴酒精,将袋挤瘪,排尽空气后用细绳把口系紧,然后放入80℃以上的热水中,稍停一会儿,你会发现什么现象?从热水中拿出塑料袋,放入冷水中,稍停一会儿,塑料袋又有什么变化?原来,当塑料袋放入热水中时,袋内的酒精从液态变成了气态,袋内气压增大,使塑料袋胀了起来;把塑料袋从热水中拿出来再放入冷水中时,袋内的酒精又从气态变成了液态,袋内气压减小,塑料袋又变瘪了.在物理学中把物质从液态变为气态的过程叫做
Students, let’s first do a simple experiment.Drink a few drops of alcohol in a transparent plastic bag, squeeze the bag squeezed, drained the air with a string to fasten the mouth, and then into the hot water above 80 ℃ In the pause for a while, you will find out what phenomenon? Take out the plastic bag from the hot water, into the cold water, stop for a while, the plastic bag and what changes? The original, when the plastic bag into the hot water, the bag The alcohol within the liquid into a gaseous state, increased pressure within the bag, plastic bags swell up; take the plastic bag out of hot water and then into the cold water, the bag of alcohol from the gas into a liquid , The pressure inside the bag decreases and the plastic bag becomes deflated again. The process of changing matter from liquid to gas in physics is called