Dry ice is a remarkable substance with many versatile uses. It might look like a simple block of white-colored ice, but this could not be further from the truth. While regular ice is the solid form of water or H2O, dry ice is the solid state of carbon dioxide or CO2. Temperatures must be incredibly low to freeze carbon dioxide gas into a solid form. This unique property makes dry ice ideal for tasks such as flash-freezing produce, keeping foods cold during transit and even removing moles from people’s skin.
One of the most notable physical characteristics of dry ice is its ability to sublime. Sublimation is a phenomenon in which a substance transforms from a solid state directly into a gaseous state without becoming a liquid. In the case of dry ice, this occurs at the frigid temperature of -78.5°C. If carbon dioxide falls below this point, it transforms into dry ice. Conversely, when it is above this temperature, it transforms into CO2 gas. Due to its extremely low temperature, dry ice can be dangerous to handle and can cause severe skin burns if touched without proper protection.
When dry ice is combined with water, it produces an interesting reaction. If you place it in a bucket of water, the carbon dioxide will react with the water and produce gas bubbles. As the gas bubbles reach the water’s surface, they create a thick fog because of the extremely cold temperature of the dry ice. The fog is much denser than the surrounding air, so it normally sinks to the ground, creating an eerie sensation. Therefore, dry ice is the perfect addition to any haunted house.
Photo: Shutterstock 照片：Shutterstock
乾冰是一種用途廣泛的奇特物質。它可能看起來純粹像一塊白色冰塊，但事實卻相差甚遠。一般的冰是水（H2O）的固態，而乾冰則是二氧化碳（CO2）的固態。要將二氧化碳氣體凍結成固態，溫度必須極低。這種獨特的性質使乾冰成為速凍農產品、在運輸過程中保持食品低溫，甚至是去除人們皮膚上的痣等任務的理想選擇。
乾冰最顯著的物理特性之一是其昇華能力。昇華是一種物質在不變成液態的情況下，從固態直接轉化為氣態的現象。就乾冰而言，這種現象發生在攝氏 -78.5°C 度的寒冷溫度下。如果二氧化碳的溫度低於此，它就會變成乾冰。相反地，當高於這個溫度時，二氧化碳就會轉化為二氧化碳氣體。由於溫度極低，乾冰的處理可能會非常危險，接觸乾冰時若沒有適當的保護措施，可能會導致皮膚有嚴重的冰灼傷。
當乾冰與水結合時，會產生一種有趣的反應。如果把乾冰放在一桶水中，二氧化碳就會與水發生反應、產生氣泡。當氣泡到達水面時，由於乾冰的溫度極低，因此會產生濃霧。這種霧的密度比周圍的空氣要大，所以通常會下沉到地面，產生一種陰森恐怖的感覺。因此，乾冰是任何鬼屋的完美附加元素。
Photo: Shutterstock 照片：Shutterstock
What Did You Learn?
1. What happens in the process of sublimation?
(A) A gas becomes a solid.
Photo: Shutterstock 照片：Shutterstock
(B) A solid becomes a liquid.
(C) A solid becomes a gas.
(D) A liquid becomes a gas.
2. Gina is working on a report about dry ice. Which of the following pieces of information is NOT correct?
(A) Dry ice is the name for CO2 in its solid state.”
(B) “If not handled properly, dry ice can pose safety risks.”
(C) “Dry ice can be used in various ways, even in the medical field.”
(D) “When the temperature drops below -78.5°C, CO2 becomes gaseous.”
3. Why does dry ice form a dense fog when it is blended with water?
(A) The dry ice turns into a solid ice block.
(B) The dry ice causes the water to dissolve, forming water vapor.
(C) The temperature of the water is far colder than that of the carbon dioxide.
(D) The combination creates cold CO2 bubbles that turn into fog on the water’s surface.
答案：
1. (C)
2. (D)
3. (D)
Words in Use
1. versatile a. 多用途的
This makeup kit is so versatile that it is the only one you will ever need.
這個化妝箱用途相當廣泛，所以你只要這一只就夠了。
2. property n. 特性
One property of diamonds is hardness.
堅硬是鑽石的一項特性。
3. produce n. 農產品
The farmer transports his produce to the market in the city every day.
那名農夫每天將自己的農產品運到城裡的市場去。
4. transit n. 運輸，運送
The package was well wrapped to prevent damage in transit.
這個包裹被包得好好的以避免在運送途中受損。
5. characteristic n. 特性，特徵
The new chemical has unusual characteristics.
這種新的化學物質有不尋常的特性。
Practical Phrases
1. sth could not be further from the truth
某事與事實完全相反；某事與實際狀況大相逕庭
It looked as if everything was fine with Scott’s family on the surface, but this could not be further from the truth.
史考特的家庭表面上一切都很好，但實際狀況卻是大相逕庭。
2. transform from A into B 從 A 轉變成B
The witch transformed from an old lady into a beautiful maiden. 那個女巫從老太太變成了美麗的少女。
3. react with... 與……產生化學反應
When certain chemicals react with each other, they can produce dangerous results.
當某些化學物質相互反應時，它們可能產生危險的結果。
聽文章朗讀及講解: https://ivy.pse.is/455bfu
本文出自常春藤解析英語雜誌: www.ivy.com.tw
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