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Sunday Science

歡迎閱讀《週日科學版》！我們每週日都要為你介紹可以在家中進行的有趣科學實驗。你可以在《科學日誌》中記錄自己做了哪些活動，這樣就可以將所學的紀錄下來，比較這些結果，也許還可以利用它們來設計新的實驗！先看一下《科學日誌》的點子再開始吧。展開實驗之前，記得要獲得大人許可喔！

Sunday, Jan 20, 2008,Page 14

照片︰michael kearney PHOTO: MICHAEL KEARNEY, TAIPEI TIMES

Temperature’s effect on molecular speed

溫度對分子速度的影響

In this experiment we’re going to find out if temperature affects the speed of molecules in water.

What you will need: Six clear glasses

Food coloring

Water (cold, room temperature and hot)

Salt

A spoon

►Fill two glasses with cold water, two with water that is about room temperature and two with very hot water. You can use ice or a freezer to get cold water, but when you’re doing the experiment, none of the water should be frozen. Be careful not to burn yourself with the hot water!

►Put about a teaspoon of salt into three of the glasses (one of each temperature). Stir.

►Wait a few minutes for the water you just stirred to stop moving. It’s important for the next step that the water in each glass is absolutely still.

►Add two drops of food coloring to each of the glasses. Observe the way the food coloring moves through the water.(MICHAEL KEARNEY, STAFF WRITER)

在本實驗中，我們要來查明溫度是否會影響水中分子的速度。

所需材料︰

六個乾淨的玻璃杯

食用色素

水（冰水、溫水和熱水）

鹽

一個湯匙

►裝兩杯冰水、兩杯室溫下的水，和兩杯非常燙的熱水；你可以用冰塊或冰庫製成冰水，但在進行實驗時，不能用結冰的水；用熱水的時候要小心別燙傷自己！

►在三杯水中（三種溫度各一）各加入一茶匙鹽巴，然後攪拌。

►等個幾分鐘，等你剛剛攪拌的水都靜止下來；杯中的水需完全靜止後才能進行下一個步驟。

►在六杯水中都各自加入兩滴食用色素，觀察食用色素在水中運動的情形。（翻譯︰袁星塵）

TODAY'S WORDS 今日單字 1. molecule n. 分子 (fen1 zi3) 2. frozen adj. 結冰的 (jie2 bing1 de5) 3. kinetic energy n. 動能 (dong4 neng2) 4. disperse v.t./v.i. 散開 (san4 kai1) 5. container n. 容器 (rong2 qi4) 6. irrigate v.t./v.i. 灌溉 (guan4 gai4) 7. crop n. 作物 (zuo4 wu4) 8. turn over v. phr. 翻轉 (fan1 zhuan3)

What's the science? 科學原理 Increasing the heat of water increases its kinetic energy. An increase in kinetic energy causes the water molecules to move more quickly. You can see the effects of this by watching the food coloring. The hotter the water is, the more quickly the food coloring disperses throughout it. Adding salt to the water makes it denser. In the samples with salt, you should notice that the food coloring takes longer to sink to the bottom of the container. This is like if you try to float in freshwater and saltwater (like the sea) — you’ll be able to float longer in saltwater because it’s denser. 增加水的溫度會增加它的動能，動能增加後，水中分子會更快速地活動，你可以透過食用色素觀察到此作用；水愈熱，色素在水中散播得愈快。 在水中加入鹽巴使得水的密度增加，在加了鹽巴的樣本中，你會發現色素需要更多時間才會沉到杯子底部；這就像你試著浮在淡水和鹽水（例如海水）中─你在鹽水中可以漂浮得更久，因為它的密度更高。

Bonus 你知道嗎 Cold water is denser than warm water. Usually cold water sinks to the bottom of a body of water. But in the past, cold water in the Dead Sea sat on top of warmer water underneath. This is because the water underneath was saltwater, and the upper layer of water, which came from rivers, was fresh. But as people used more and more of the rivers’ water to irrigate their crops, less freshwater reached the sea. Finally, in the winter of 1978 to 1979, the sea turned over and saltwater reached the top! 冷水的密度比溫水高，因此冷水通常會沉到下方，但是過去的死海冷水卻盤據在較暖的水上方，這是由於下方的暖水是鹽水，而上層的水是來自河川的淡水；隨著人們利用更多河裡的水來灌溉農作物，流入海中的河水減少，最後在一九七八年到一九七九年間的冬天，死海的海水翻轉，鹽水就漂到了上方！

Science Journal 科學日誌 What do you know about water? How about molecules? How does temperature affect the movement of molecules? How does adding salt change the experiment? Does adding salt change the density of the water? 你對水了解多少？分子呢？溫度會如何影響分子的運動？加入鹽巴會對實驗產生什麼影響？加入鹽巴會改變水的密度嗎？

Further ideas 進階點子 What happens if you add food coloring immediately after you finish stirring the water? What happens if you change the amount of salt you add? Don’t forget to record your observations in your Science Journal. 若你在攪拌後立刻加入食用色素，會發生什麼事？若你改變鹽巴的添加量，會有什麼變化？別忘了在《科學日誌》裡記下你的觀察。

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