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65 Cards in this Set
- Front
- Back
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What does the mass number tell you? What does the atomic number tell you? |
Atomic: Number of protons |
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When are compounds formed?
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e.g carbon dioxide = chemical reaction between carbon and oxygen |
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What are isotopes?
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Name a popular pair of isotopes
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Carbon-12 and carbon-14 |
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What is ionic bonding? |
Atoms lose or gain electrons to form charged particles (called ions) which are then strongly attracted to one another (because of the attraction of opposite charges) |
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What kind of structure does an ionic compound have? Describe it |
A regular lattice structure Ionic compounds always have giant ionic lattices The ions form a closely packed regular lattice arrangement There are very strong electrostatic forces of attraction between oppositely charged ions, in all directions |
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What are the similar properties of ionic compounds? |
When to ionic compounds melt, the ions are free to move and they'll carry electric current. Dissolve easily in water & will carry electric current |
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Which groups are most likely to form ions?
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6 & 7 (which are non metals) |
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What electronic structure does an ion have?
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Noble gas |
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What is the overall charge of any ionic compound? |
(positive balance out negative) |
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What is covalent bonding?
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Only share with outer shell (highest energy level) Each atom involved has to make enough covalent bonds to fill up its outer shell |
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Describe the structure of simple molecular substances
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The atoms form very strong covalent bonds to form small molecules of several atoms By contrast, the forces of attraction between these molecules are very weak Weak intermolecular forces results in low melting and boiling points as the molecules are easily parted from each other Most are gases or liquids at room temp, but can be solids Don't conduct electricity - no ions |
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Describe the structure of giant covalent substances
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Similar to giant ionic lattices but there are no charged ions Bonded to each other by strong covalent bonds Very high melting and boiling points Don't conduct electricity Main examples - diamond, graphite and silicon dioxide |
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Describe the structure of diamond
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The structure makes diamond the hardest natural substance |
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Describe the structure of graphite
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Layers are held loosely together meaning that they can be rubbed off onto paper - weak intermolecular forces Only non metal which is a good conductor of heat and electricity - each carbon atom has 1 delocalised electron |
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Describe the structure of silicon dioxide
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Sand ismade of this Each grain of sand is one giant structure of silicon and oxygen |
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What are the properties of metal
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All properties are due to the sea of free electrons Giant structure Metallic bonds involve delocalised electrons - come from outer shell of every atom in the structure Good conductors of heat and electricity Free electrons hold atoms together in a regular structure Strong forces of electrostatic attraction between the positive metal ions and the negative electrons Allow the layers of atoms to slide over each other |
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Why are alloys harder than pure metals?
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Due to the different sized atoms, the layers are distorted meaning that they cannot slide over each other and therefore the alloy cannot be bent or shaped & are harder |
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What are the four structures of substances?
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Giant ionic Simple molecular Giant covalent Giant metallic |
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Give an example of a smart material and explain its properties
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Nitinol - a "shape memory alloy" it's a metal alloy, but when cool you can bend it and twist it like rubber. When bent too far, it stays bent but if you heat it above a certain temperature, it goes back to a "remembered" shape. Handy for glasses frames - if bent, but into bowl of hot water. Used for dental braces too. |
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What is a nanoparticle?
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Roughly a few hundred atoms per nanoparticle Include fullerenes - molecules of carbon, shaped like hollow balls or closed tubes, arranged in hexagonal rings. |
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What are some uses of nanomaterials?
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-Can be used to make sensors to detect one type of molecule and nothing else. These sensors are already being used to test water purity -Nanotubes can be used to make stronger, lighter building materials -New cosmetics e.g sun tan cream, deodorant have been made using nanoparticles - don't leave white marks on skin -Nanomedicine -Lubricant coatings -Tiny electric circuits |
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What determines the properties of plastics?
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Forces between molecules |
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Thermosoftening polymers
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Forces between chains are easy to overcome - easy to melt the plastic When cools, it hardens into a new shape Can melt these plastics and remould them as many times as you like |
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Thermosetting polymers
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These hold the chains together in a solid structure Doesn't soften when heated Strong, hard and rigid |
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What will affect the properties of a polymer? |
How you make it - the starting materials and reaction conditions |
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What are the two types of polythene and what are their different conditions which they are made in? |
High density - made at a lower temperature and pressure (with a catalyst). It is far more rigid, and is used for water tanks and drain pipes. |
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What is the relative atomic mass?
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It is the same as the mass number of the element. |
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What is the relative formula mass? |
In a compound Adding up all the relative atomic masses |
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What is one mole equal to? |
The relative formula mass of a substance in grams is known as one mole of that substance |
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How do you work out the number of moles?
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Mass in g/Relative formula mass |
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How do you work out the percentage mass of an element in a compound? |
/ RFM of whole compound x 100 |
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How do you work out the empirical formula?
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Write percentages or experimental masses Divide each mass by the RAM Turn this into a ratio Put the ratio into its simplest form |
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What is the calculation for the percentage yield?
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/ predicted yield (grams) x 100 |
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Give three reasons as to why yields cannot be 100%
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Filtration Unexpected reactions |
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How do you separate artificial colours using paper chromatography?
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2 - put spots of the coloured solution on a pencil baseline on filter paper 3 - Roll up the sheet and put it in a beaker with some solvent |
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Why should you not use pen when doing paper chromatography? |
It might dissolve in the solvent |
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What are the advantages of using machines to analyse unknown substances? |
Very fast Very accurate |
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Give 3 examples of rate of reaction experiments
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Hydrochloric acid and marble chips Reaction of magnesium metal with dilute HCl The decomposition of hydrogen peroxide |
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What does the decomposition of hydrogen peroxide show? What is the ideal way to measure the rate of reaction in this experiment? What gas is given off? |
Gas syringe Oxygen |
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What does the reaction of magnesium metal with dilute HCl show? How can we measure the rate of reaction? What gas is given off? |
Effects of increased concentration Change in mass Hydrogen gas |
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What does the reaction of hydrochloric acid and marble chips show? How can we measure the rate of reaction? |
Gas syringe |
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What are advantages of using catalysts?
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Reduce costs - Increase the rate of reaction, saves money - plant doesn't need to operate for as long to produce the same amount Allow the reaction to work at a much lower temperature, reduces energy used up (energy cost), which is good for sustainable development & can save a lot of money |
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What are some disadvantages to using catalysts>
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Can be expensive to buy, often need to be removed from the product and cleaned Different reactions use different catalysts They can be poisoned by impurities, so they stop working - have to keep reaction mixture very clean |
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What is an exothermic reaction?
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A reaction which gives out heat energy to the surroundings, usually in the form of heat and usually shown through a rise in temperature |
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Give 3 examples of exothermic reactions
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Neutralisation reactions (acid + alkali) Oxidation |
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What is an endothermic reaction? |
A reaction which takes in energy from the surroundings, usually in the form of heat and is usually shown by a fall in temperature. They are much less common |
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Give an example of an endothermic reaction
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Thermal decompositions e.g. decomposing calcium carbonate to make quicklime. |
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Where are alkalis? |
Alkali = 8 - 14 |
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How can you test the pH of a substance? |
Using an indicator The dye changes colour depending on whether its above or below a certain pH |
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What is an acid, a base and an alkali? |
Base - a substance with a pH of greater than 7 Alkali - a base which dissolves in water. They form OH- ions in water. |
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What do the following state symbols show you? (s), (l), (g), (aq) |
(l) - liquid (g) - gas (aq) - aqueous, dissolved in water |
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What do you get when metals react with acids? |
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How can you make a salt insoluble?
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What does electrolysis mean? |
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How does electrolysis occur? |
-It requires a liquid to conduct the electricity, called the electrolyte -Electrolytes contain free ions - usually the molten or dissolved ionic substance -Electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode. |
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Explain OILRIG |
Reduction involves the los of oxygen, and the gain of electrons Oxidation involves the gain of oxygen and loss of electrons Electrolysis always involves this. |
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What is the electrolyte in electrolysis? |
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What occurs at the positive electrode? |
Lose |
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What occurs at the negative electrode?
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Electrons are given to ions Gain |
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What is produced where in the electrolysis of lead bromide?
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Bromine is produced at the +ve electrode At the -ve electrode, one lead ion accepts two electrons to become one lead atom At the +ve electrode, two bromide ions lose one electron each and become one bromine molecule |
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What is cryolite used for?
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To lower the remperature and costs in electrolysis
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How does electroplating use electrolysis?
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The negative electrode is the metal object you want to plate The positive electrode is the pure metal you want it to be plated with |
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Give an example of when electroplating could be used
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The brass cup at the negative electrode A lump of pure silver at the positive electrode |
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Give 2 positive uses of electroplating
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Conduction - metals like copper conduct electricity very well, often used to plate circuits and computers. |
