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Chemistry Review (化学復習、自分用)
お久しぶりです。いきなりですが僕はインターに通っています。今回は学期末テストが近づいてると言うことで自分用に科学の復習をさせてもらいます(自分勝手ですみません)。一部は日本語訳をつけました。念の為言っておきますが内容は簡単ですw。今回は物理変化と科学変化(Physical Change and Chemical Change)についてです。最後まで読んでくださいとは言いません(なぜならつまらないからですw)。
Physical Change and Chemical Change (物理変化と科学変化)
Physical Change - Reversible, no new substances are formed
ex). Change of state (状態変化)
Chemical Change - Irreversible, new substances are formed
ex). Cooking, Metal rusting, Paper burning
More about chemical change - Chemical change takes place when atoms (原子) of chemical substances break apart (分離)and rearrange(再配置) to form new substances.
State symbol
l→liquid(液体), s→solid(個体), g→gas(ガス), aq→aqueous (substances that are dissolved in water, 水成?)
Word equation - Word equation is a shorthand way of writing a chemical reaction
Reactants→Product
イメージとしてはreactantsが材料、productが出来上がった製品
ex).
The word equation for hydrogen reacting with water is
Hydrogen (水素)+oxygen(酸素)=water
In this case, hydrogen and oxygen are the reactants and water is the product.
Zinc(亜鉛)+copper oxide(酸化銅)=zinc oxide(酸化亜鉛)+copper(銅)
In this case, zinc and copper oxide is the reactants and zinc oxide and copper are the products.
Causes of chemical change
1. Heat
2. Light
3. Mixing substances
4. Electricity
(紛らわしくなってしまうかもしれないので先に言っておきます。上の4つは科学変化の原因でこれから説明する燃焼などは1.heatの種類です)
Changes cause by heat
1. Combustion (is a scientific word for burning, 燃焼)
In combustion, a substance burns react with oxygen to produce heat and light energy
Burning fuel
-Fuel (燃料)
-Petrol(ガソリン), wood(木), methane gas(メタン), ethanol(エタノール) are an example of fuels.
-Most fuels contain the elements carbon and hydrogen.
Combustion of methane (メタンの燃焼)
-Natural gas, methane
-Word equation for the combustion of methane
methane + oxygen = carbon dioxide + water
メタン+酸素=二酸化炭素+水
Complete combustion and incomplete combustion (完全燃焼と不完全燃焼)
-In complete combustion, a fuel burns in a sufficient amount of oxygen. Products are Carbon dioxide and Water.
- In an incomplete combustion, a fuel burns in insufficient amount of oxygen. Carbon monoxide (一酸化炭素)and/or soot (すす)and water are formed.
-the orange part of a fire is incomplete combustion.
-the blue part of a fire is complete combustion.
- Flame of bunsen burner with air -hole opened is a complete combustion because there are plenty of oxygen taken in from the air-hole
- Flame of bunsen burner with are-hole closed is an incomplete combustion because there is a shortage of oxygen taken in from the air-hole
- ブンゼンバーナーの穴が閉じている時は不完全燃焼、開いているときは完全燃焼
2. Thermal Decomposition (熱分解)
- One substance breaks down into two or more simpler substances
ex).
Sugar→Carbon + water vapor
砂糖→炭素+水蒸気
Calcium carbonate → carbon dioxide +calcium oxide
炭酸カルシウム→二酸化炭素+酸化カルシウム
3. Combination
- Combination is also known as synthesis reaction.
- Chemical reaction in which two or more substances combine to form a new compound.
Examples of combination
1. Elements react together to form compunds
(a) magnesium + oxygen → magnesium oxide
(b) hydrogen + oxygen → water
2. Compounds react together to form a new compound
(a) Calcium oxide + water → calcium hydroxide
Summary
Heat
1. Combustion (complete combustion, inpomplete combustion)
2. Thermal Decomposition
3. Combination
Chemical Changes caused by Light
Photosynthesis (光合成)
- Carbon dioxide + water → glucose + oxygen
- 6CO2 + 6H2O → C6H12O6 + 6O2
Film photography
- Black and white photographic film contains silver bromide coating which is sensitive to light.
- When it is exposed to light, silver bromide(臭化銀) decompose into silver, which produces the dark area on the film
-The stronger the light, the darker the area on the film.
- Silver bromide (ArBr) → Silver (Ag) + Bromine (Br、臭素)
Chemical Changes caused by mixing substances
- Chemical changes can occur when we mix two or more substances together
- Zinc + dilute hydrochloric acid = hydrogen
- Sulfuric acid + sugar = carbon
- Baking soda + vinegar = carbon dioxide
Chemical Changes caused by electricity
Electrolysis
- Decomposing a substance into simpler substances by using electricity.
- Sodium Chloride → Sodium + Chlorine
- Aluminum oxide → alumium +oxygen
Decomposition of water (水分解)
- Water decomposes into oxygen gas and hydrogen gas when electricity passes through it.
- Hydrogen gas is in the negative electrode, oxygen gas is in the positive electrode (水素は陰極、酸素は陽極)
Test for gasses (気体の確かめ方)
Hydrogen: a lighted splint extinguishes with a ‘pop’ sound
Ammonia: Moist/damp red litmus paper turns blue
Carbon dioxide: Pass the gas into limewater (石灰水): turns limewater milky or gives a white precipitate in limewater, Ca(OH)2 水酸化カルシウム
Oxygen: a glowing splint rekindles or relights
Test for water
1. Cobalt chloride test paper (塩化コバルト紙): it turns from blue (dry) to pink (wet)
2. Dry copper sulfate: it turns from white to blue when water is added
以上で全てです。最後まで読んでくださりありがとうございます。最後の方は少し雑になってしまいました。読んでくれている方がいるかどうかわかりませんが、ありがとうございました。
また次の記事でお会いしましょう。
お城君
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