Igcse chemistry notes

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Coat the metal with something to keep out air and moisture. Strong and weak acids and alkalis The higher the hydrogen ions H , the higher the acidity and the lower the pH Each pH unit means a ten-fold difference in the hydrogen ion concentration. Only separation from impurities Ores more difficult to decompose Electrolysis Method of extraction more difficult Method of extraction more expensive Increasing Reactivity Heating with a reducing agent carbon or carbon monoxide Copper, Cu Silver, Ag Gold, Au Least Reactive Extraction of zinc from zinc blende Zinc blende is mainly zinc sulphide, ZnS. An exothermic reaction has a negative value of H If the reactant takes in heat to the surrounding, it has gained energy. Some of the hydroxides are coloured. The precipitate of zinc will re-dissolve in excess of ammonia but aluminum's will not. So you must start with a metal oxide. To reduce the acidity, the soil is treated with a base like limestone or quicklime or slaked lime. What does rusting involve? Then it is left to cool and crystals of zinc sulphate start to form. Explanation: The carbon dioxide is from the reduction reaction in stage 3. In it, harmful gases are present: Water Uses of water: y y y y At home for drinking, cooking, washing things and flushing toilet waste away. Chemical bonds are forces of attraction between atoms or ions. The solution and conditions of the experiments must remain the same, only the temperature will change. Similar hand-warmers can be made using the heat given out by crystallisation of a solid from super-saturated solution Endothermic reactions are far less common than exothermic ones.

It leaves out the rest. The last two properties are chemical properties, the others are physical properties.

Igcse physics notes

There are three major chemical reactions in which all acids will take part. When the indicator turns green stop adding acid. The experiment can be repeated using the known volume of acid without adding the indicator or activated charcoal can be added to remove the indicator and then the charcoal can be filtered off. Bases include alkalis, and insoluble metal oxides, hydroxides and carbonates. They can form very long chains, and can form chains linked by one double bond or triple bond. The energy change in going from reactants to products in a chemical reaction is known as the heat of reaction. Energy changes in chemical reactions Hydrocarbon molecules contain only the elements carbon and hydrogen. The pipette delivers a fixed volume accurately. A cross is marked on a piece of paper. It boils at C 2. To break these bonds requires energy Breaking chemical bonds takes in energy from the surroundings. Things to remember about the reactivity series y The reactivity series is a list of metals in order of their drive to form positive ions. Excess zinc is removed by filtering.

The solution and conditions of the experiments must remain the same, only the temperature will change. In all three reactions, they produce a metal compound called a salt.

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Plants use carbon dioxide from the air to make sugar called glucose, in a reaction called photosynthesis. The crystal lose their shape an become a powder. When crystals can be seen forming crystallisation pointheating is stopped and solution is left to crystallise. The molten iron is tapped from the bottom.

Igcse chemistry notes xtremepapers

A known volume of alkali solution is placed in a conical flask using a pipette. Excess zinc is removed by filtering. The nitrogen is from the air blast. Rates of reaction Some reaction are fast and some are slow. Usually acidity is the problem. When ammonium salts react with alkali solutions, they produce ammonia gas. For example: When a metal is heated with a oxide of a less reactive metal, it acts as a reducing agent. Soluble All sodium, potassium, and ammonium salts All nitrates Chlorides Sluphates Sodium, potassium, and ammonium carbonates Except silver and lead chloride Except calcium, barium and lead sulphate But all other carbonates are insoluble. The calcium oxide neutralizes any acidic impurities, forming a slag that is skimmed off. The chromium is deposited by electrolysis. A catalyst works by lowering the activation energy for the reaction. Characteristic reactions of acids All acids can take part in neutralisation reactions. A graph can be plotted.

When ammonium salts react with alkali solutions, they produce ammonia gas. The particles must have enough energy for the collision to be successful in producing a reaction.

Igcse chemistry notes pdf 2018

Hydrogen peroxide HO is a colourless liquid. Acids turn litmus red Alkalis You can tell if something is alkali, by its effect on litmus. A catalyst works by lowering the activation energy for the reaction. This is endothermic process. The curve for C is steeper than for D The total volume of hydrogen at the end of both the experiments is the same. Two experiments will be conducted. The limestone reacts with the sand silica in the ore, to form calcium silicate or slag. What is rate? No reaction occurs with less reactive metals. Catalytic converter is used to reduce the polluting effect of a car exhaust fume.
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