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Gases

Gases. The Air and Oxygen. The Composition of Air. How to measure the percentage of oxygen in air. This is one of the experiments to measure the percentage of oxygen in air One syringe should be filled with 100 centimetres cubed of air and the other should have no air in it

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Gases

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  1. Gases The Air and Oxygen

  2. The Composition of Air

  3. How to measure the percentage of oxygen in air • This is one of the experiments to measure the percentage of oxygen in air • One syringe should be filled with 100 centimetres cubed of air and the other should have no air in it • The apparatus is heated and air is pushed several times over the copper • The apparatus is cooled and all gas is pushed into the syringe that previously was the only one with air in • There is a decrease in the air, which is the amount of oxygen in the air

  4. Hydrogen peroxide is poured into the flask, onto a catalyst called manganese dioxide • A catalyst is a substance that changes the speed of a chemical reaction, but is not used up in the reaction itself • The oxygen formed is collected over water as it is only slightly soluble in water Equation: 2H2O2 => 2H2O + O2 Manganese dioxide is not in the equation because it is a catalyst. Sometimes, it is put above the arrow in a chemical equation https://www.youtube.com/watch?v=oZV3u1bbJqg Preparing oxygen Diagram:

  5. Examining the properties of oxygen 1. Litmus and oxygen Place pieces of moist red and blue litmus paper into a jar or test tube of oxygen gas. There is no change in colour, indicating that oxygen is a neutral gas. 2. Wooden splint and oxygen Light a wooden splint and place it in the oxygen. It burns more vigorously. Shake it so that it is just glowing and then place it back in the jar. The splint will relight. This indicates that oxygen supports combustion. This means that substances which burn in air burn more vigorously in oxygen.

  6. Properties of Oxygen *Reacts with most elements to form oxides: For example, magnesium reacts with oxygen to form magnesium oxide and carbon reacts with oxygen to form carbon dioxide.

  7. Uses of Oxygen 1. Breathing Oxygen stored in cylinders is used to support breathing. For example, patients in hospital and mountain climbers use oxygen for this purpose. 2. Burning and welding Acetylene is a gas that burns in air, but burns much more fiercely in oxygen to produce a very hot flame of about 3000°C. This flame is hot enough to cut through and weld metals. 3. Space rockets Rockets carry both oxygen (as there is no oxygen in space) and hydrogen (fuel). They carry two tanks, one containing the fuel and the other containing liquid oxygen.

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