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Transcript
Name: Class: Kelso High School Science Summary notes Names and Formulae Acids and pH The word ACID means sour. We often say that a sour liquid tastes acid. Examples of sour liquids that you will find in the home are vinegar, lemon juice, grapefruit juice and sour milk. You can find out if a substance is an acid or and alkali by dissolving it in water and adding an indicator. An indicator is a chemical which changes colour in different pH environments so by matching the colour of the solution to the colour chart, the pH of the substance can be found. The two most commonly used indicators are universal indicator and pH paper, which is like blotting paper with the indicator soaked into it. When acid is neutralised by an alkali, a salt if formed. Common salt, or sodium chloride is formed when hydrochloric acid and sodium hydroxide react together: Hydrochloric acid + Sodium hydroxide Sodium chloride + water HCl NaOH NaCl H20 The sodium (Na) part of the salt comes from the sodium hydroxide and the chloride (Cl) comes from the acid The tables below give the names of salts produce by some common acids and alkalis Acid Hydrochloric acid Nitric acid Salt ….. Chloride Sulphuric acid ….. Sulphate ….. nitrate Alkali Sodium hydroxide Potassium hydroxide Calcium hydroxide Salt Sodium…. Potassium…. Calcium…. Rocks Human beings have used rocks for many purposes. Examples include: Weapons Building (houses and roads, etc) Sculpture Burning Rocks can be sorted into 3 types: Igneous Igneous rocks are those that have formed when magma, (hot, liquid rock) cools and hardens. They are very hard and do not scratch easily. Examples include granite, basalt and obsidian. Sedimentary Sedimentary rocks are formed when substances like sediment and silt get carried in rivers and then are deposited where the river ends. When this happens over millions of years more and more layers of sediment build up and the grains at the bottom of the pile become squashed together. They can scratch easily. Examples include sandstone, limestone and chalk. Metamorphic This name means changed form. Sometimes existing rocks can be altered by either heat or pressure. For example mountains are formed when layer upon layer of rocks are piled on top of each other. This creates huge pressure and this pressure can change the rock. Metamorphic rocks are usually very hard and cannot usually be scratched easily. Examples include marble and slate. Revision Questions 1. Give 3 examples of uses of rock by humans. 2. Use lines to correctly match the following rock type, description and examples: 3. Rock Type Description Example Sedimentary Existing rocks altered by Granite pressure or heat Metamorphic Formed from cooled and hardened magma Igneous Grains of silt pile up at the end of a river and get squashed to form layers Chalk Marble Revision Questions – Answers 1. eg, building houses/roads/walls, statues, gravestones, burning coal, etc. You may have given other correct examples. 2. Rock Type Sedimentary Description Existing rocks altered by pressure or heat Metamorphic Formed from cooled and hardened magma Igneous Grains of silt pile up at the end of a river and get squashed to form layers Example Granite Chalk Marble Soil Soil is made up of a mixture of inorganic particles, organic matter (humus), water and air. The inorganic part of the soil includes sand, silt and clay. Sand particles are the largest and have sharp edges and feel gritty. Soils with lots of sand in them can hold lots of air but not much water. Silt particles feel smooth and powdery. Soils with lots of silt feel smooth but not sticky when they are wet. Clay particles are the smallest. Soils with lots of clay hold lots of water but not much air. The organic part of the soil is known as humus. It is made up of decaying plant and animal matter which add nutrients to the soil. Soils have different characteristics and uses depending on the mixture of sand, silt, clay and humus. Revision Questions 1. List the four parts that make up soil. 2. i) Describe what is in the inorganic part of the soil. ii) List the inorganic particles of soil in order of size starting with the largest. iii) Describe what humus is made of. 3. i) Suggest why a soil with a lot of sand is not good for growing crops. ii) Suggest why a soil with a lot of clay is not good for growing crops. iii) Suggest why a soil with very little humus is not good for growing crops Revision Questions – Answers 1. Inorganic particles, organic matter (humus), water and air. 2.i) A mixture of sand, silt and clay. ii) Sand, silt, clay. iii) Dead, decaying plant and animal remains. 3.i) It cannot hold enough water for the crop to grow. ii) It cannot hold enough air for the crop to grow. iii) It does not contain enough nutrients for the crop to grow. Minerals and metals The rocks of the earth’s crust contain metal ores from which we get all the metal we use. Metal ores are usually well mixed into rocks, but sometimes they are found pure. A pure metal ore is called a mineral. Testing for metals When a geologist is searching for metal ores he can do a quick, simple test called a flame test to identify the metal present. The ore is first ground to a powder and then dissolved in acid to release the metal. The ore and acid are then heated on a wire in a Bunsen flame and the colour of the flame identifies the metal. Element Flame colour Barium Green Calcium Orange –red Copper Blue-green Lithium Red Potassium Lilac Sodium Yellow Recognising a chemical reaction All chemical reactions produce new substances. These can be recognised by A colour change An energy change (the temperature increases) Effervescence (fizzing – the production of a gas) Precipitation (the making of a solid from liquids) Corrosion and rusting CORROSION is the changing of the surface of a metal into a compound. RUSTING is the special name given to the corrosion of iron. Rusting can only happen if OXYGEN and WATER can both get to the iron together. As air contains both oxygen and water, any iron object will rust if left outside unprotected. The brown solid which forms is a compound of iron, oxygen and water. The layer of rust is very weak and falls off the surface of the iron very readily. The iron underneath then starts to rust, until eventually the whole piece of metal corrodes. Prevention of rusting There are 4 main methods of preventing rusting Barrier methods – stopping the oxygen and water reacting the iron Cathodic – using the negative terminal of a battery Plating – coating the iron with another metal Sacrificial – another metal been forced to corrode whilst it protects the iron