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Fichas por lauyuentong99, actualizado hace más de 1 año
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Creado por lauyuentong99
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| Pregunta | Respuesta |
| The Group 1 elements | 1.They are metals and they conduct electricity and are shiny when freshly cut 2.Softer than most other metals and cut be easily cut with a knife 3.Low melting points than most other metals 4.Have low densities than most other metals 5.Have exciting reactions with water. As they react , they zoom around on the surface of water 6.From top to bottom of group 1 : melting and boiling point decrease , density decrease and the reactions with water get more vigorous. |
| The Group 2 elements | 1.Have electrons in their outermost shell. 2.Their similar electron arrangements give the elements similar properties. 3.From top to bottom of group 1 : the reactions of the elements with water get more vigorous , the reactions of the elements with acids get more vigorous. |
| The Group 7 elements | 1.They are non-metals and do not conduct electricity and are poor conductors of heat. 2.Fluorine ,chlorine .bromine and iodine destroy bacteria. They are Halogens. 3.Low melting and boiling points because they exist as molecules. 4.A strong force holds two atoms of the molecule together, the forces between a molecule and its neighbours are weak and easy and easy to separate the molecules of chlorine in the liquid state to form a gas. 5.From top to bottom of group 7 : melting point and boiling point increase , the reactions with iron get less vigorous. |
| Periodic trends | 1.The horizontal rows of the periodic table are called periods . 2.From left to right of periods 1 and 2 : melting points increase for the first four elements and melting points of the other elements in the periods are lower. |
| Energy changes in chemical reactions | 1.Kerosene, woods and gas are fuels. Fuels release useful heat when they burn . Burning reactions release heat. 2.Exothermic reactions is reactions the release ,or give out heat 3.Endothermic reactions is some changes take in heat from the surroundings. 4.Melting and evaporation are endothermic. 5.Melting - its particles use the energy to leave their places in the pattern of solid ice and start moving around , in and out of each other. 6.Evaporation -the particles of a liquid take in heat from surroundings , they use energy to leave the liquid. 7.All chemical reactions and changes od state involve energy changes. |
| Choosing fuels | 1.Ethanol ,hydrogen and diesel are fuels. A fuel is a substance that releases useful heat when it burns . Burning fuels reactions are exothermic. 2.The products of combustion are the substances made when a fuel burns. Hydrogen has only one combustion product- water. Ethanol produces CO2 and water on burning . When diesel burns, the main products are carbon dioxide and water. 3.Carbon dioxide is a greenhouse gas. In the atmosphere , it causes climate change. 4.Diesel is a mixture of compounds. Its compounds made up of carbon and hydrogen. 5.Diesel is separated from crude oil. Crude oil was formed over million of years from dead-sea animals. It is a non-renewable resources. 6.Hydrogen fuels is made from mathane.it is formed from animal waste and on rubbish dumps and it is a renewable. 7.Ethanol fuels is made from plants. It is renewable. 8.Diesel and ethanol are liquid at 20 degree celsuis and convenient to transport and store and hydrogen is gas at 20 degree celsius and difficult to store and transport and it is must be stored away from flames and sparks |
| Calculating food energy | 1.The greater the temperature increase of the water, the more energy a food or fuel has released as heat. But temperature is not the same as heat. 2.The equation for the energy transferred to the water as heat is : 3.H = M x C x T 4.H = heat , M = mass , C= heat capacity and T = temperature |
| the reactions of metals with oxygen | 1.Some metals burn in air . 2.On burning, metals react with oxygen to make metal oxides . 3.The burning reactions of sodium and magnesium are very vigorous. |
| The reactions of metals with water | 1.Some metals react with water to make hydrogen and a metal oxide or hydroxide. 2.Potassium ,sodium ,lithium and calcium react most vigorously with water 3.Gold ,silver and copper do not react with cold water. 4.Metals that react with water form two products : an oxide or hydroxide and hydrogen 5.The metals that react with oxygen also react with water ( vigirously) 6.Metals that do not react with water are very useful |
| The reactions of metals with acids | 1.Many metals react with dilute acids to make salts and hydrogen gas. 2.Magnesium and zinc react vigorously with dilute acids. 3.Copper and gold do not react with dilute acids. |
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