Energy ( 能量 )

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What is Energy

• Energy Is the Ability to Do Work.( 完成工作的能力 )

• Energy causes things to happen around us.

• When a car drives by, it is being powered by gasoline, a type of stored energy.

• The food we eat contains energy. We use that energy to work and play.

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• Energy can be found in a number of different forms. It can be chemical energy ( 化學能 ), electrical energy ( 電能 ), heat (thermal energy)( 熱能 ), light (radiant energy)( 光能 ), mechanical energy( 機械能 ), and nuclear energy ( 核能 ).

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• Energy makes everything happen and can be divided into two types:

• Stored energy is called potential energy ( 潛能 ).

• Moving energy is called kinetic energy ( 動能 ).

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How Do We Measure Energy?

• One of the basic measuring blocks is called a Btu. This stands for British thermal unit ( 英國熱量單位 ) and was invented by, of course, the English.

• Btu is the amount of heat energy it takes to raise the temperature of one pound of water by one degree Fahrenheit, at sea level. ( 將一英磅重的水溫增加一度所需的熱量就是一個 Btu)

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• One Btu equals about one blue-tip kitchen match. ( 一個 Btu等於一根火柴燃燒的熱量 )

• One thousand Btus roughly equals: One average candy bar or 4/5 of a peanut butter and jelly sandwich.

• It takes about 2,000 Btus to make a pot of coffee. ( 加熱一壺咖啡需 2,000 Btus)

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• Energy also can be measured in joules ( 焦耳 ). Joules sounds exactly like the word jewels, as in diamonds and emeralds ( 綠寶石 ). A thousand joules is equal to a British thermal unit.

• 1,000 joules = 1 Btu

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• The term "joule" is named after an English scientist James Prescott Joule who lived from 1818 to 1889. He discovered that heat is a type of energy. ( 焦耳先生發現熱就是一種能量 )

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• One joule is the amount of energy needed to lift something weighing one pound to a height of nine inches. So, if you lifted a five-pound sack of sugar from the floor to the top of a counter (27 inches), you would use about 15 joules of energy. ( 一焦耳的能量等於將一英磅重的物品提高九英吋高度所需的熱量 )

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• Around the world, scientists measure energy in joules rather than Btus. It's much like people around the world using the metric system ( 公制 ) of meters and kilograms, instead of the English system of feet and pounds.

• Like in the metric system, you can have kilojoules -- "kilo" means 1,000.

1,000 joules = 1 kilojoule = 1 Btu

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• A piece of buttered toast contains about 315 kilojoules (315,000 joules) of energy. With that energy you could:

• Jog ( 慢跑 ) for 6 minutes

• Bicycle for 10 minutes

• Walk briskly ( 迅速地 ) for 15 minutes

• Sleep for 1-1/2 hours

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• Run a car for 7 seconds at 80 kilometers per hour (about 50 miles per hour)

• Light a 60-watt light bulb for 1-1/2 hours

• Or lift that sack of sugar from the floor to the counter 21,000 times!

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Changing Energy

• Energy can be transformed into another sort of energy. But it cannot be created AND it cannot be destroyed ( 能量不滅定律 ). Energy has always existed in one form or another. ( 能量的形式會改變但是總量不變 )

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• Stored energy in a flashlight's ( 手電筒 ) batteries becomes light energy when the flashlight is turned on. 10123804

• Food is stored energy. It is stored as a chemical with potential energy. When your body uses that stored energy to do work, it becomes kinetic energy. ( 以飲食為例 )

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• If you overeat, the energy in food is not "burned" but is stored as potential energy in fat cells. ( 當飲食過量，多餘的能量儲存於脂肪細胞作為潛能 )

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• When you talk on the phone, your voice is transformed into electrical energy, which passes over wires (or is transmitted through the air). The phone on the other end changes the electrical energy into sound energy through the speaker. ( 以打電話為例 )

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• A car uses stored chemical energy in gasoline to move. The engine changes the chemical energy into heat and kinetic energy to power the car. ( 以汽車為例 )

• A toaster changes electrical energy into heat and light energy. (If you look into the toaster, you'll see the glowing wires.) ( 烤麵包機 )

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Food Energy

• Energy changes form at each step in the food chain. Take an ear of corn as an example.

• Sunlight is taken in by the leaves on the corn stalk and transformed through photosynthesis ( 光合作用 ).

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• The plant takes in sunlight and combines it with carbon dioxide ( 二氧化碳 ) from the air and water and minerals ( 礦物質 ) from the ground.

• The plant grows tall and creates the ears of corn - its seeds ( 種子 ). The energy of the sunlight is stored in the leaves and inside the corn kernels ( 顆粒 ). The corn kernels are full of energy stored as sugars and starch ( 澱粉 ).

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• The corn is harvested and is fed to chickens and other animals. The chickens use the stored energy in the corn on the cob ( 玉米穗軸 ) to grow and to move. Some energy is stored in the animal in its muscle tissue ( 肌肉組織 ) (protein，蛋白質 ) and in the fat ( 脂肪 ).

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• You then eat the chicken's meat and fat and convert that stored energy into energy in your own body.

• As your body uses the energy from the chicken, you breathe ( 吸 ) in oxygen and exhale ( 呼 ) carbon dioxide. That carbon dioxide is then used by other plants to grow.

• So, it's a big circle! #10183804

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Heat Energy

• Heat is a form of energy. We use it for a lot of things, like warming our homes and cooking our food.

Heat energy moves in three ways:

• Conduction ( 傳導 )

• Convection ( 對流 )

• Radiation ( 幅射 )

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Conduction ( 傳導 )

• Conduction occurs when energy is passed directly from one item to another. If you stirred a pan of soup on the stove with a metal spoon, the spoon will heat up. The heat is being conducted from the hot area of the soup to the colder area of spoon. ( 能量直接由一個物體傳至另一個物體就是傳導 )

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Convection ( 對流 )

• Convection is the movement of gases ( 氣體 ) or liquids ( 液體 ) from a cooler spot to a warmer spot. If a soup pan is made of glass, we could see the movement of convection currents in the pan. The warmer soup moves up from the heated area at the bottom of the pan to the top where it is cooler.

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• The cooler soup then moves to take the warmer soup's place. The movement is in a circular pattern within the pan. ( 氣體或液體由低溫處移至高溫處就是對流 )

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• The wind we feel outside is often the result of convection currents. You can understand this by the winds you feel near an ocean. Warm air is lighter than cold air and so it rises. During the daytime, cool air over water moves to replace the air rising up as the land warms the air over it.

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• During the nighttime, the directions change -- the surface of the water is sometimes warmer and the land is cooler. ( 以風的移動為例，由於暖空氣上升，日間風由海吹向陸地 ( 較暖 ) ，晚間則因海水含熱量而相反 )

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Radiation ( 幅射 )

• Radiation is the final form of movement of heat energy. The sun‘s light and heat cannot reach us by conduction or convection because space is almost completely empty. There is nothing to transfer the energy from the sun to the earth. ( 幅射是能量不藉媒介物的傳送 )

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• The sun's rays travel in straight lines called heat rays. When it moves that way, it is called radiation.

• When sunlight hits the earth, its radiation is absorbed ( 吸收 ) or reflected ( 反射 ). Darker surfaces absorb more of the radiation and lighter surfaces reflect the radiation. So you would be cooler if you wear light or white clothes in the summer.

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Energy Star

• The EPA Energy Star label ( 能量之星 ) first began appearing on a few computer monitors back in 1992. Today the Energy Star -- a certification of money-saving energy efficiency and earth-saving environmental "greenness"

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nuclear energy

• Matter ( 質量 ) can be changed into energy. The world's most famous scientist, Albert Einstein, created the mathematical formula that explains this. It is:

• E = m c2

• This equation says:

E [energy] equals m [mass] times c2

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• [c stands for the velocity or the speed of light ( 光速 ). c2 means c times c, or the speed of light raised to the second power -- or c-squared.]

• This equation is the key to unlock atomic energy ( 原子能 ) and also create atomic bombs ( 原子彈 ).

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• The ancient Greeks said the smallest part of nature is an atom. But they did not know 2,000 years ago about nature's even smaller parts.

• Atoms are made up of smaller particles -- a nucleus ( 原子核 ) of protons ( 質子 ) and neutrons ( 中子 ), surrounded by electrons ( 電子 ) which swirl ( 旋轉 ) around the nucleus much like the earth revolves ( 公轉 ) around the sun.

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Nuclear Fission (分裂 )

• An atom's nucleus can be split apart. When this is done, a tremendous amount of energy is released. The energy is both heat and light energy. Einstein said that a very small amount of matter contains a very LARGE amount of energy.

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• This energy, when let out slowly, can be harnessed ( 利用 ) to generate electricity. When it is let out all at once, it can make a tremendous explosion in an atomic bomb.1026/3804

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• The word fission means to split apart. Inside the reactor of an atomic power plant, uranium ( 鈾 ) atoms are split apart in a controlled chain reaction.

• In a chain reaction, particles released by the splitting of the atom go off and strike other uranium atoms splitting those.

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• Those particles given off split still other atoms in a chain reaction. In nuclear power plants ( 核電廠 ), control rods are used to keep the splitting regulated so it doesn't go too fast.

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• If the reaction is not controlled, you could have an atomic bomb. But in atomic bombs, almost pure pieces of the element Uranium-235 or Plutonium ( 鈽， 94Pu239), of a precise mass and shape, must be brought together and held together, with great force. These conditions are not present in a nuclear reactor ( 反應爐 ). 10253902

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Nuclear Fusion ( 融合 )

• Another form of nuclear energy is called fusion. Fusion means joining smaller nuclei (the plural of nucleus) to make a larger nucleus. The sun uses nuclear fusion of hydrogen ( 氫 ) atoms into helium ( 氦 ) atoms. This gives off heat and light and other radiation.

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• Two types of hydrogen atoms, deuterium ( 氘 ,重氫 ) and tritium ( 氚 , 超重氫 ), combine to make a helium atom and an extra particle called a neutron.

Thanks to the University of California, Berkeley for the picture. ###