C3 science

Mind Map by Katie., updated more than 1 year ago
Created by Katie. almost 5 years ago


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C3 science
1 Atoms have a nucleus which is positively charged, and electrons which are negatively charged.
1.1 Atoms can form bonds to make molecules or compounds. It's the electrons that are involved in making bonds. Sometimes an atom loses or gains one or more electrons and this gives it a charge (positive if it loses an electron and negative is it gains one.)
1.1.1 Charged atoms are known as ions. If a positive ion meets negative ion they'll be attracted to one another and join together. The other main type of bond is called a covalent bond. When non-metal atoms combine together they form covalent bonds by sharing pairs of electrons. Because the bond is a shared pair, no atom loses electrons.
2 Combustion is an exothermic reaction -- heat's given out. The best example of an exothermic reaction is burning fuels. In an endothermic reaction, heat is taken out. Endothermic reactions are less common and less easy to spot. One example is thermal decomposition.
2.1 Energy must always be supplied to break bonds, and energy is always released when bonds form.
3 Reactions happen is particles collide. So if you increase the number of collisions, the reaction happens more quickly.
3.1 Increasing the temperature means the particles are going faster and have more energy. This means they will have more collisions, therefore the reaction will happen faster.
3.2 Increasing the concentration (or pressure) means the particles and more crowded together. More collisions will happen.
3.3 More surface area means other particles can get to it more easily. If one of the reactants is a solid then breaking it up into smaller pieces will increase its surface area. This means the particles around it will have more area to work on so the frequency of collisions will increase.
3.4 A catalyst increase the number of successful collisions. A catalyst is a substance which increases the speed of a reaction, without being chemically changed or used up in the reaction. Catalysts tend to be very fussy about which reactions they catalyst though -- you can't just stick any old catalyst in a reaction and expect it to work.
4 In the periodic table, the elements all have two number. The bigger one is the relative atomic mass.
4.1 To figure out the relative formula mass, all your need to do is add all the relative atomic masses together.
4.1.1 In a chemical reaction, mass is always conserved. During a chemical reaction no atoms are destroyed and no atoms are created. This means there are the same number and types of atoms on each side of a reaction equation.
5 A lot of reactions make more than one product. Some of them will be useful, but others will just be a waste (e.g when you make quicklime from limestone, you also get carbon dioxide which is a waste product.
5.1 The atom economy of a reaction tells you how much of the mass of the reactants is wasted when manufacturing a chemical.
5.1.1 Atom economy = total Mr of desired products divided by total Mr of all products x 100.
5.1.2 100% atom economy means that all the atoms in the reactants have been turned into useful (desired) products. The higher the atom economy the 'greener' the process.
6 The predicted yield of a reaction can be calculated from the balanced reaction equation. Percentage yield is given by the formula: Percentage yield = actual yield (grams) divided by predicted yield (grams) x 100.
6.1 Percentage yield is always somewhere between 0 and 100%. 100% yield means that you got all the product you expected to get. 0% yield means that no reactants were converted into product (no product at all was made.) Industrial processes want as high a percentage yield as possible to reduce waste and reduce cost.
6.2 You never get 100% yield because some product or reactant will always get lost along the way. This depends on what sort of reaction it is and what apparatus is being used. Things that can go wrong are: Evaporation, filtration, and transferring liquids.
7 Batch production only operates at certain times. Batch production is often the most cost-effective way to produce small quantities of different drugs to order because it's flexible, start-ip cost are relatively low, it's labour intensive and it can be tricky to keep the same quality from batch to batch.
7.1 Continuous production runs all the time. The haber process for making ammonia uses continuous production because the production never stops, so you don't waste time emptying the reactor and setting it up again. It runs automatically, and the quality of the product is very consistent.
8 Diamond is used in jewellery and cutting tools. They're lustrous (sparkly) and colourless. Each carbon of atom forms four covalent bonds in a very rigid giant covalent structures. These take a lot of energy to break and give diamond a very high melting point. It doesn't conduct electricity because it had no free electrons or ions.
8.1 Graphite makes the lead of your pencil. It's black but still kind of shiny. Each carbon atom only forms three covalent bonds, creating sheets of carbon atoms which are free to slide over each other.The layers are held together weakly so they are slippery. Graphite has a high melting point and they can conduct electrons.
8.1.1 Fullerenes are molecules of carbon, shaped like closed tubes or hollow balls. Fullerenes can be used to cage other molecules as the structure forms around another atom or molecule. Nanotubes have a huge surface area, so they could help make great industrial catalysts.
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