今日化學: 鹽的化學
The Chemistry of Salt explains and illustrates the molecular structure of sodium chloride (NaCl) crystals; the structure and symmetry of crystal lattices; and why one crystalline solid, salt, melts another, ice.
科學教師及實習教師專業成長
2011/12/06
教學時機：2011年12月10日月全食
2011年12月10日的月全食是很好的教學時機，觀測時間非常恰當，台灣月食時間預測如下：
半影食開始：19:31:54月球與地球半影第一次接觸，必須使用望遠鏡來觀測。
月偏食開始：20:45:24 月球與地球本影第一次接觸，肉眼可見月亮東邊變暗。
月全食開始：22:05:42 月球已完全進入地球本影中，肉眼可見月亮呈現紅色。
月全食結束：22:58:00 月球正要開始離開地球本影，肉眼可見月亮西邊生光。
本影食結束：00:18:18月球正好完全離開地球本影，肉眼可見月亮完全復圓。
半影食結束：01:31:42月球正好完全離開地球半影，必須使用望遠鏡來觀測。
錯過這次的月全食，下一次在台灣要能見到完整的月全食過程是在2018年的1月31日，而最近一次可以看到不完整的月全食(月出帶食)則是在2014年10月8日。
2011/12/10 月全食相關資料：
NASA預測資料：
http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2011Dec10T.pdf
台北天文台完整資料：
http://tamweb.tam.gov.tw/bew/TW/content.asp?mtype=c9&idx=266
台北天文台月全食動畫與新聞資料下載：
http://tamweb.tam.gov.tw/bew/TW/content.asp?mtype=c9&idx=272
月全食成因動畫：
http://csep10.phys.utk.edu/astr161/lect/time/lunar_anim.html
http://www.teachersdomain.org/asset/psu10phy_vid_eclipser/
月全食教學海報下載：
http://tamweb.tam.gov.tw/bew/TW/content.asp?mtype=c9&idx=273
2011/11/22
透鏡成像：免費模擬軟體--光學透鏡 (Optical Lenses)
一套好用的透鏡成像模擬軟體，最重要的是：它免費!
只要到下列網址下載：
http://download.cnet.com/Optical-Lenses/3000-2054_4-75416337.html?tag=mncol;7
然後按照指示安裝即可。操作時只要以滑鼠左鍵移動物體，則光線及像會跟著移動，很方便老師做解說。
老師可以用來教：
1.成像作圖；
2.歸納物距與像距、像的大小、和像的性質之間的關係。
你還想到可以教什麼嗎? 你想可以如何用在教學上?
不過要注意提醒學生，物體發出(反射)的光線不是只有那幾條，也不是只有那一點。
只要到下列網址下載：
http://download.cnet.com/Optical-Lenses/3000-2054_4-75416337.html?tag=mncol;7
然後按照指示安裝即可。操作時只要以滑鼠左鍵移動物體，則光線及像會跟著移動，很方便老師做解說。
老師可以用來教：
1.成像作圖；
2.歸納物距與像距、像的大小、和像的性質之間的關係。
你還想到可以教什麼嗎? 你想可以如何用在教學上?
不過要注意提醒學生，物體發出(反射)的光線不是只有那幾條，也不是只有那一點。
靜力平衡: 萬夫莫敵--力的挑戰 (One Man Army: Strength Challenge)
Discovery的"萬夫莫敵(One man army)"競技節目，有一個項目(影片06:56起)很適合用來教靜力平衡。可以先說明比賽規則，請學生想出贏取比賽的方法，然後看影片，再請學生畫力圖分析得勝的原因。裡面牽涉到共點三力平衡、共線二力平衡、及合力概念。
2011/07/20
通往宇宙之窗：美國地球科學教師協會提供的教學資源網站
美國地球科學教師協會(The National Earth Science Teachers Association, NESTA) 開放「通往宇宙之窗(Windows to the Universe)」新網站，提供K-12地球與太空科學教育者教學資源。
「通往宇宙之窗(Windows to the Universe)」網站包含9000頁以上的內容，以及上百個測試過的教學活動，可供教師隨時運用於教學。
美國教師學會(NSTA)也提供「變遷中的地球行星(Our Changing Planet」系列教學活動設計12單元，配合優美動人的「NBC學習(NBC Learn)」影片，是進行環境教育，探討環境及氣候變遷教學的寶庫。
- 通往宇宙之窗(Windows to the Universe)網址:
http://www.windows2universe.org/
- 變遷中的地球行星(Our Changing Planet)網址：
http://www.windows2universe.org/earth/changing_planet/changing_planet.html
2011/04/23
今日化學：分子結構、特性
Chemistry Now: Molecule Structure, Properties
美國科學基金會(NSF)、美國科學教師協會(NSTA)及美國國家廣播公司(NBC)合作，為化學年製作了一系列教學單元，名為「今日化學(Chemistry Now)」，每周推出一單元，預計製作31單元。內容涵蓋日常生活中的化學，包含了21世界的先進化學。以下是第三單元：「鏡」分子--香芹酮("Mirror" Molecule: Carvone)。
旁白：
"Mirror" Molecule: Carvone
Spearmint. Caraway. Dill.
A chewing gum flavor. A seed in rye bread. And an herb in pickles. Wouldnt seem they have anything in common, but they do. Reduce spearmint, caraway seed and dill to their essential oils and a sizable percentage of all three turn out to be made up of the same molecule: carvone.
How can you explain one molecule being responsible for distinctly different smells and tastes? With two hands, a mirror, a lightbulb and a pair of gloves.
Start with the basics: Carvones chemical formula tells you what its made of: 10 atoms of Carbon, 14 atoms of Hydrogen, and 1 atom of Oxygen. Just as important as how many atoms of what elements make up a molecule is how those atoms are bonded together and in what configuration, or structure.
We think of molecules, when and if we think of molecules, as having only one set structure. This is H2O, for example not this, or this. But a molecule like Carvone can have slightly different arrangements of their atoms and still be the same molecule like a girl who has different looks depending on how she parts her hair, or the way she wears a sweater. As long as how she rearranges her hair and clothes doesnt add or take away anything, shes still the same girl in the same outfit.
The carvone molecule has two slightly different looks or, as theyre called, stereoisomers: this one and this one. Stereoisomers are three-dimensional, but its easier to understand these two by looking at a standard two-dimensional drawing of their structures. Notice anything? The two are mirror images of each other. Some structures, like, say, a lightbulb, are the same in mirror image or side by side. But carvone stereoisomers are like a pair of hands: A hand and its mirror reflection will exactly match but hands arent the same side by side, or superimposed.
Actually, carvone stereoisomers are like left and right hands even down to their names: This one is R-carvone the R stands for the Latin word meaning right. The structure of this gives spearmint its taste and smell. Its mirror opposite is S-carvone the S stands for the Latin word meaning left. The way this one is arranged is what gives caraway its flavor and aroma and dill, too. In pure form, the two flavors are almost the same.
This kind of left-handed/right-handed molecule is called chiral. Carvone has chirality, terms, not coincidentally, from a Greek word meaning hand. The Greek word for nose is rhinous, yes, as in rhinocerous. which is the way well segue into this next part on how your nose and tongue work to distinguish the difference between the smells and tastes of spearmint or caraway or dill through specialized receptors that interact with molecules in very specific ways.
Think of some receptors as structured like baseball mitts specifically designed to pick up molecules with structures like baseballs but not footballs which have their own receivers. These receptors are so highly specialized that they interact distinctively with molecules that differ only in very small ways, like their handedness, almost as if some receptors are like right-handed gloves able to pick up only the R-carvone molecules, recognize them, and send a message to the brain saying Its spearmint!
And as if S-carvones only fit into left-handed glove receptors, who recognize them and tell the brain: Its caraway! or Its dill!
There you go: a handy explanation of carvone.
學習單
國中：Molecules, Isomers, and Our World
高中：Introduction to Enantiomers and Handedness
《上一單元：吉士堡化學--乳酪 ‖ 下一單元：化學鍵》
進一步參考資料
1. NBC Learn- Chemistry now
2. NSTA Blog
旁白：
"Mirror" Molecule: Carvone
Spearmint. Caraway. Dill.
A chewing gum flavor. A seed in rye bread. And an herb in pickles. Wouldnt seem they have anything in common, but they do. Reduce spearmint, caraway seed and dill to their essential oils and a sizable percentage of all three turn out to be made up of the same molecule: carvone.
How can you explain one molecule being responsible for distinctly different smells and tastes? With two hands, a mirror, a lightbulb and a pair of gloves.
Start with the basics: Carvones chemical formula tells you what its made of: 10 atoms of Carbon, 14 atoms of Hydrogen, and 1 atom of Oxygen. Just as important as how many atoms of what elements make up a molecule is how those atoms are bonded together and in what configuration, or structure.
We think of molecules, when and if we think of molecules, as having only one set structure. This is H2O, for example not this, or this. But a molecule like Carvone can have slightly different arrangements of their atoms and still be the same molecule like a girl who has different looks depending on how she parts her hair, or the way she wears a sweater. As long as how she rearranges her hair and clothes doesnt add or take away anything, shes still the same girl in the same outfit.
The carvone molecule has two slightly different looks or, as theyre called, stereoisomers: this one and this one. Stereoisomers are three-dimensional, but its easier to understand these two by looking at a standard two-dimensional drawing of their structures. Notice anything? The two are mirror images of each other. Some structures, like, say, a lightbulb, are the same in mirror image or side by side. But carvone stereoisomers are like a pair of hands: A hand and its mirror reflection will exactly match but hands arent the same side by side, or superimposed.
Actually, carvone stereoisomers are like left and right hands even down to their names: This one is R-carvone the R stands for the Latin word meaning right. The structure of this gives spearmint its taste and smell. Its mirror opposite is S-carvone the S stands for the Latin word meaning left. The way this one is arranged is what gives caraway its flavor and aroma and dill, too. In pure form, the two flavors are almost the same.
This kind of left-handed/right-handed molecule is called chiral. Carvone has chirality, terms, not coincidentally, from a Greek word meaning hand. The Greek word for nose is rhinous, yes, as in rhinocerous. which is the way well segue into this next part on how your nose and tongue work to distinguish the difference between the smells and tastes of spearmint or caraway or dill through specialized receptors that interact with molecules in very specific ways.
Think of some receptors as structured like baseball mitts specifically designed to pick up molecules with structures like baseballs but not footballs which have their own receivers. These receptors are so highly specialized that they interact distinctively with molecules that differ only in very small ways, like their handedness, almost as if some receptors are like right-handed gloves able to pick up only the R-carvone molecules, recognize them, and send a message to the brain saying Its spearmint!
And as if S-carvones only fit into left-handed glove receptors, who recognize them and tell the brain: Its caraway! or Its dill!
There you go: a handy explanation of carvone.
學習單
國中：Molecules, Isomers, and Our World
高中：Introduction to Enantiomers and Handedness
《上一單元：吉士堡化學--乳酪 ‖ 下一單元：化學鍵》
進一步參考資料
1. NBC Learn- Chemistry now
2. NSTA Blog
今日化學 ：吉士堡化學—乳酪
Chemistry Now : Cheeseburger Chemistry—Cheese
美國科學基金會(NSF)、美國科學教師協會(NSTA)及美國國家廣播公司(NBC)合作，為化學年製作了一系列教學單元，名為「今日化學(Chemistry Now)」，每周推出一單元，預計製作31單元。內容涵蓋日常生活中的化學，包含了21世界的先進化學。以下是第二單元：吉士堡化學--乳酪(Chemistry of Cheeseburger--Cheeses)。
旁白：
The Chemistry of Cheese
AL ROKER, reporting:
You cant have a cheeseburger without it: cheese. Cheddar, Swiss, Mozzarella, Blue, Monterrey jack, Pepperjack. To keep the chemistry more basic, we wont deal here with whats called American or processed cheese.
Cheese is an ancient food, dating back some 4,000 years to when humans first domesticated goats, sheep, yaks and other mammals for meat and milk: the sole basic ingredient in cheese, then and today.
JULIE YU, The Exploratorium: Cheese is a very concentrated form of milk with the water removed.
ROKER: Turning milk into cheese involves a change in a substance from one common state of matter to another, in this case, from liquid to solid. Some of these changes can be physical those are changes that are reversible, like freezing water into a solid ice cube: it can melt into water again.
When a change involves a chemical reaction, it generally cant be reversed and turning liquid milk to solid cheese is a good example: the cheese can never go back to being milk again. Heres why:
YU: Were going to make the worlds simplest cheese.
ROKER: Julie Yu, a scientist at The Exploratorium in San Francisco whos funded by The National Science Foundation, starts with milk.
YU: Milk is composed of proteins, fats, sugars and water. The process of making cheese is somehow removing that water so that youre left with the concentrated mass of the proteins and fats.
ROKER: Thats not so easy. Milk is an emulsion: uncounted illions of globular protein molecules and droplets of fat are suspended in the liquid. How to separate those from the water, and concentrate them? Think of panning for gold. If the gold was in the form of tiny individual flecks, itd be impossible to pan out; itd just flow through any strainer with the water. The gold has to be in clumps, nuggets, to be sifted out. So how do you get the fats and proteins in liquid milk to form little nuggets so they can be separated from the water?
YU: Cheesemaking relies on changing the structure of the proteins that are in milk because in order to separate out the proteins from the water in our milk, we need to change their form.
ROKER: Its called denaturing, which is pretty much what it sounds like: changing the natural structure or qualities of something.
YU: Proteins are typically folded up in a three-dimensional structure. When theyre denatured, they relax into a long chain. And so those chains can tangle together and become enmeshed and they solidify in a way that you are able to strain them from the milk. In general, there are three ways to denature proteins: one is to introduce heat, one is to introduce high salt, and one is to introduce acid.
ROKER: Like the citric acid in lemon juice.
YU: Were going to use lemon juice today. The proteins are normally in tight little balls. The acid is going to relax them. And theyre going to coagulate, theyre going to stick together in this nice gooey mess. And were going to strain that out and that will give us the cheese.
Im going to pour this through a strainer that I have lined with some cheesecloth. And thats going to keep the solids behind, which we now call the curds. And the liquid, which we would call the whey, is going into this bowl.
ROKER: Yes, curds and whey, what Little Miss Muffet was eating, as she sat on whatever a tuffet is, before unexpected arachnid proximity prompted flight.
YU: Once we strain out all of the whey it firms up into this nice ball of fresh cheese. There are some fresh cheeses that are made this way, just by simply adding acid. But the majority of cheeses are made in another way. They use a bacteria and an enzyme in order to coagulate their proteins.
ROKER: An enzyme called rennet, which cheesemakers can buy in tablet form.
YU: Rennet is an enzyme thats actually in the stomach lining of most animals. Its made to digest milk proteins. Rennet further breaks down the proteins and creates this nice gooey mesh and gives you cheeses of different textures.
ROKER: Rennet may explain how those ancient ancestors of ours made the first cheese.
YU: Its possible that someone had a pouch made out of animal stomach and was holding milk inside of that. Any enzymes present in the stomach would break down the milk and when they poured out their milk they would have been surprised to find curds and whey.
ROKER: Today cheeses come in a global array - at least 670 different kinds are listed in a leading cheese database. Chemistry is the reason all those different textures and flavors develop during cheese processing and aging: fermentation, oxidation, dehydration, bacterial and mold growth. Theyre all chemical reactions. So, there you are: a basic explanation of the chemical processes that turn liquid milk into solid cheese and turn a hamburger into a cheeseburger.
學習單
國中：Blowing up balloons with yeast
高中：Kitchen Mystery
《上一單元：水的化學 ‖ 下一單元：分子結構》
進一步參考資料
1. NBC Learn- Chemistry now
2. NSTA Blog
旁白：
The Chemistry of Cheese
AL ROKER, reporting:
You cant have a cheeseburger without it: cheese. Cheddar, Swiss, Mozzarella, Blue, Monterrey jack, Pepperjack. To keep the chemistry more basic, we wont deal here with whats called American or processed cheese.
Cheese is an ancient food, dating back some 4,000 years to when humans first domesticated goats, sheep, yaks and other mammals for meat and milk: the sole basic ingredient in cheese, then and today.
JULIE YU, The Exploratorium: Cheese is a very concentrated form of milk with the water removed.
ROKER: Turning milk into cheese involves a change in a substance from one common state of matter to another, in this case, from liquid to solid. Some of these changes can be physical those are changes that are reversible, like freezing water into a solid ice cube: it can melt into water again.
When a change involves a chemical reaction, it generally cant be reversed and turning liquid milk to solid cheese is a good example: the cheese can never go back to being milk again. Heres why:
YU: Were going to make the worlds simplest cheese.
ROKER: Julie Yu, a scientist at The Exploratorium in San Francisco whos funded by The National Science Foundation, starts with milk.
YU: Milk is composed of proteins, fats, sugars and water. The process of making cheese is somehow removing that water so that youre left with the concentrated mass of the proteins and fats.
ROKER: Thats not so easy. Milk is an emulsion: uncounted illions of globular protein molecules and droplets of fat are suspended in the liquid. How to separate those from the water, and concentrate them? Think of panning for gold. If the gold was in the form of tiny individual flecks, itd be impossible to pan out; itd just flow through any strainer with the water. The gold has to be in clumps, nuggets, to be sifted out. So how do you get the fats and proteins in liquid milk to form little nuggets so they can be separated from the water?
YU: Cheesemaking relies on changing the structure of the proteins that are in milk because in order to separate out the proteins from the water in our milk, we need to change their form.
ROKER: Its called denaturing, which is pretty much what it sounds like: changing the natural structure or qualities of something.
YU: Proteins are typically folded up in a three-dimensional structure. When theyre denatured, they relax into a long chain. And so those chains can tangle together and become enmeshed and they solidify in a way that you are able to strain them from the milk. In general, there are three ways to denature proteins: one is to introduce heat, one is to introduce high salt, and one is to introduce acid.
ROKER: Like the citric acid in lemon juice.
YU: Were going to use lemon juice today. The proteins are normally in tight little balls. The acid is going to relax them. And theyre going to coagulate, theyre going to stick together in this nice gooey mess. And were going to strain that out and that will give us the cheese.
Im going to pour this through a strainer that I have lined with some cheesecloth. And thats going to keep the solids behind, which we now call the curds. And the liquid, which we would call the whey, is going into this bowl.
ROKER: Yes, curds and whey, what Little Miss Muffet was eating, as she sat on whatever a tuffet is, before unexpected arachnid proximity prompted flight.
YU: Once we strain out all of the whey it firms up into this nice ball of fresh cheese. There are some fresh cheeses that are made this way, just by simply adding acid. But the majority of cheeses are made in another way. They use a bacteria and an enzyme in order to coagulate their proteins.
ROKER: An enzyme called rennet, which cheesemakers can buy in tablet form.
YU: Rennet is an enzyme thats actually in the stomach lining of most animals. Its made to digest milk proteins. Rennet further breaks down the proteins and creates this nice gooey mesh and gives you cheeses of different textures.
ROKER: Rennet may explain how those ancient ancestors of ours made the first cheese.
YU: Its possible that someone had a pouch made out of animal stomach and was holding milk inside of that. Any enzymes present in the stomach would break down the milk and when they poured out their milk they would have been surprised to find curds and whey.
ROKER: Today cheeses come in a global array - at least 670 different kinds are listed in a leading cheese database. Chemistry is the reason all those different textures and flavors develop during cheese processing and aging: fermentation, oxidation, dehydration, bacterial and mold growth. Theyre all chemical reactions. So, there you are: a basic explanation of the chemical processes that turn liquid milk into solid cheese and turn a hamburger into a cheeseburger.
學習單
國中：Blowing up balloons with yeast
高中：Kitchen Mystery
《上一單元：水的化學 ‖ 下一單元：分子結構》
進一步參考資料
1. NBC Learn- Chemistry now
2. NSTA Blog
訂閱：
文章 (Atom)