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Flashcards by ellie peng, updated more than 1 year ago
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Created by ellie peng
over 9 years ago
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| Question | Answer |
| Everyday Acids and Alkali's | Testing With Litmus and Universal indicator. the pH scale, 1= (red) very strong acid, 7= (green) neutral substance, 14= (purple) very strong alkali. acids always have a low pH eg. hydrochloric acid. alkali's have a high pH eg. sodium hydroxide. |
| Dilution | Acids and Alkali's can be made less concentrated by DILUTING them with water. when they are transported or stored, safety is very important. temperature also affects the hazards. the hotter the acid or alkali the more concentrated it is. |
| Neutralisation | ACID + ALKALI = SALT + WATER neutral substances are called salts. table salt = sodium chloride, all salts have two part names. neutralisation is when an acid and an alkali react together to form a neutral substnace. |
| Atoms | the ancient greeks had ideas about elements, but John Dalton developes the first theory about atoms - in the early 1800's. it is the smallest parat of a substance. it is a basic particle form of which all substances are built up. |
| the Atomic Stucture | Subatomic particles = protons - have a charge of +1 neutrons = a charge of 0 electrons = have a charge of -1 in a atom's structure, the nucleus has neutrons and Protons while the electrons "orbit" around them. |
| elements & the periodic table | an element is a pure substance that cannot be split up into simpler substances. each element only contains one type of atom. some elements do not exist as one single atom, they combine to form molecules. these elements are called diatomic and we represent them using a small 2 after the symbol. |
| measuring physical properties of elements | dencity measures how much mass there is in a fixed volume of material. density (g/cm3) = mass (g) /volume (cm3) finding the volume of a solid, volume of object = (volume of water + object) - (volume of water) another way is to use a displacement can |
| pure and impure substances | mixtures contain two or more different substances that are not chemically joined. pure substances contain only atoms/molecules of that one substance. if there are only small amounts of another substance they are called impurities. chromatography is a way of assessing the purity of a coloured substance |
| dissolving & solutions | a solute is the solid that is being dissolved, a solvent is the liquid the solute is dissolving in adn a solution is the liquid that is formed. a saturated solution is when it contains all the solute it can hold. dissolving can be reversed. 10g of solute + 100g of solvent = 110g of solution. |
| solutions 2 | concentration tells us how much solute has dissolved in a solvent. it is measured in g/dm3. liquids can also mix together, thy are called miscible. eg. alcohol and water. some liquids will not mix eg. oil and water.the concentration of liquids is measured in cm3/dm3. |
| factors affecting solubility | solubility is a physical property. it is a measure of how soluble a substance is, it measures how much of a solute/gas can dissolve in a fixed volume of solvent. |
| separating mixtures | separation methods: filtering, chromatography, evaporation, distillation, magnetism, freezing, melting and fractional distillation. freezing is when you have two different liquids that freeze at different temperatures eg. water and ethanol. melting is when you have two solids with different melting points. |
| separating mixtures 2 | filtration is used to separate insoluble solids from liquids. sand can be separated from a mixture of sand and water. evaporation is used to separate a soluble solid from the liquid it was dissolved in. distillation is used when you want to separate and collect the liquid solvent. it is to separate to liquids. |
| the particle model | the three states of matter are solids, liquids and gases. expansion is when... a solid is heated, it gains more energy. this make the particles vibrate faster and they move further apart. the solid expands. |
| solids | solids have a fixed shape and size. the particles are very close together and are held in place by strong bonds. the particles cannot move around, they can only vibrate. |
| liquids | they do not have a fixed shape but they do have a fixed volume. the particles are close together, and most of the particles touch each other. the particles can move around. a liquid flows and takes the shape of the container. |
| gases | gases do not have a fixed shape or volume. the particles move around all the time and spread out. this is why a gas fills all the spaces it can get to. a gas can be compressed into a very small space - this pushes the particles close together. |
| changing state | evaporation is different to boiling, in evaporation only the particles at the surface are involved but in boiling all of it involved |
| diffusion | moving particles will spread out if they have space to move into. this is called diffusion. particles move from a strongly concentrated area to areas where there are fewer of them. gases diffuse easily. liquids can also diffuse. diffusion in a liquid usally happens slowly. |
| gas pressure | as gas particles move around they hit objects, this is known as gas pressure. the faster the gas particles move, the more force they exert, so the greater the pressure is. the hotter the gas, the more energy its particles have and the harder they hit the container. |
| air pressure | air pressure is caused by air particles moving around. it acts in all directions. if the pressure is greater on one side, the unbalanced can make the object collapse. if you remove the air from the inside of a can, the can will collapse. |
| density | density measures how concentrated teh mass of an object is. if an object has its mass spread over a large volume, its density will be low. if all the mass is concentrated in a small space, its density will be high. a object will float if its density is less than the density of the liquid it is in. some types of wood are less dense than water so they will float. |
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