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7.3 Chemical Reactions (Combustion (Combustion can release so much energy…
7.3 Chemical Reactions
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Chemical reactions
The process of rearranging atoms to form new substances is known as a chemical reaction, in chemical reactions: the old substances are known as the reactants, the new substances that for are referred to as the products
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During a chemical change, old substances disappear and new substances form, this can only happen is if atoms in the old substance rearrange to form a new substance
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Combustion
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When hydrogen (H2) is heated with oxygen (O2), they react explosively to produce water vapour (hydrogen + oxygen --> water vapour)
Combustion is the term given to any chemical reaction that involves burning with oxygen to release light and heat
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The most common examples of combustion are the burning of fuels such as petrol, natural gas, coal, wood and paper
When you light a Bunsen burner, you are burning methane (CH 4 ). It reacts with oxygen (O 2 ) to form carbon dioxide (CO 2 ) and water vapour (H 2 O). (methane + oxygen gas -----> carbon dioxide + water vapour
Photosynthesis
Photosynthesis is a series of chemical reactions that uses sunlight to convert water (H20) and carbon dioxide (CO2) into oxygen (O2) and a form of sugar called glucose (C6H12O6) (carbon dioxide + water -----> oxygen + glucose)
Photosynthesis occurs only in plants because the chemical reaction requires chlorophyll ( the chemical the makes leaves green)
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Chlorophyll captures the sunlight that is required to start the chemical reaction, plants obtain the carbon dioxide they need from the air and the water they need from the soil
Plants use glucose produced during photosynthesis as food, to provide them with energy to live and grow
Respiration
Respiration involves a chemical reaction that converts oxygen and glucose into carbon dioxide and water vapour, while releasing energy (glucose + oxygen ----> carbon dioxide + water
When comparing the equation for respiration with the equation from photosynthesis you will notice that the reactants of respiration are the products from photosynthesis; respiration is the reverse of photosynthesis
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Respiration is a crucial chemical reaction that occurs in all living things because it provides the energy for them to live, grow, move and even think
When take a breathe in your provide your body with the oxygen it needs for respiration, when you eat you provide your body with the glucose it needs for respiration
Glucose and oxygen travel though your blood stream to each cell where respiration is going on constantly,
Corrosion
Rust weakens and eventually destroys anything made of iron or steel for this reason iron and steel objects must be protected by coating of paint or even oil
Galvanised iron is protected by a layer of zinc(Zn), the chemical properties of zinc cause the zinc to corrode faster than the iron and steel
Corrosion is a chemical reaction that can cause damage to metals - iron (Fe) and steel (an alloy of iron) have chemical properties that cause them to react slowly with water and the oxygen gas in the air the product is iron oxide (Fe2O3) (iron +water + oxyegn gas ----> iron oxide)