C2 Chemistry. Key Recall Questions

Transcription

1 C Chemistry Additional Science Key Recall Questions *Cover up the answers, ask yourself a question (or get your partner to ask you), if you get it right then tick the chart, wrong put a cross. Keep practising until all columns are ticked!

2 Key terms. What is a particle? A general word used by scientists to mean small part of matter (something). What is an atom? The smallest particle that can be recognized as an element. If you break an element into its smaller pieces you can no longer recognize that it is an element.. What is an element? A substance that is composed of only one type of atom.. What is a mixture? Substances which are together (in the same space) but not chemically joined.. What is a compound? Substances in which atoms of two or more elements are chemically combined.. What is a molecule? A word to describe atoms which are chemically joined together. These might be two of the same type of atoms (an element molecule) or two or more different types of atom (a compound molecule). What are the reactants of a chemical reaction? The substances which react together in a chemical reaction. What are the products of a chemical reaction? The substances which are produced as a result of a chemical reaction. Why is it important to show chemical reactions with an arrow? 0. What are the four state symbols used in chemical reactions and what do they mean? The arrows shows reacts to make and signifies that the reactants have been chemically changed into products and cannot be (easily) reversed Solid (s), Liquid (l), Gas (g) and Aqueous (aq) which means dissolved in water 0

3 C. Structure and bonding_. What is a compound? Substances in which atoms of two or more elements are chemically combined.. What are the two ways chemical bonds achieve They transfer or share electrons in the highest the electronic structure of a noble gas? occupied energy levels (shells). What do atoms become when they form chemical Ions bonds by transferring electrons?. What charge do ions have when the atom which Positive (+) formed them lost an electron?. What charge do ions have when the atom which Negative (-) formed them gains an electron?. What charge do ions have when they are formed + from an element in group?. What charge do ions have when they are formed - from an element in group?. What charge do ions have when they are formed + from an element in group?. What charge do ions have when they are formed - from an element in group? 0. Which group of elements do not form ions? Group 0 (noble gases) 0

4 C. Structure and bonding_. What type of electron structure do ions have? The electron structure of a noble gas. What are the elements in group known as? Alkali metals. When they react with non-metals, what charge A single positive charge does the metal ion have in the ionic compound formed?. Can you name any elements in group? Lithium, sodium, potassium, rubidium, caesium, francium (it is important that you at least know sodium is a group element). What are the elements in group known as? Halogens. When they react with alkali metals, what charge A single negative charge does the halide ion have in the ionic compound formed?. Can you name any elements in group? Fluorine, chlorine, bromine, iodine, astatine (It is important that you at least know chlorine is a group element). How are ionic compounds formed? Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions.. What is an ionic lattice? A structure formed as the result of all the electrostatic forces between ions attracting each other. 0. What is the name of the ionic compound formed Sodium chloride when sodium and chlorine form ions? 0

5 . Structure and bonding_. What type of bonding is formed when atoms share Covalent electrons?. How strong are covalent bonds? Very strong. Can you name seven small covalent molecules and Hydrogen (H), Chlorine (Cl), Oxygen (O), give their formula? Hydrochloric acid (HCl), Water (HO), Ammonia (NH) and Methane (CH). Can you name three macromolecules which have Diamond, graphite and silicon dioxide. giant covalent structures?. What are the boiling points of small covalent molecules like and why? They have low melting and boiling points (so are often gases) because the intermolecular forces (forces between molecules, not within) are weak so are easily broken. Do simple covalent molecules conduct electricity They do not conduct electricity because the ad why/why not? molecules do not have an overall electric charge.. What is the structure of a metal like? Metals are giant structures of atoms arranged in a regular pattern. They have positive metal ions with electrons between the ions holding them together with strong electrostatic attraction.. What is special about the electrons in a metal? They are delocalised so are free to move about through the whole structure. Name some reactive metals Potassium, sodium, magnesium, etc. 0. Name some unreactive metals Gold, platinum, silver 0

6 C. How structure influences properties_. When a small covalent molecule like water boils, The weak intermolecular forces are broken (forces what happens to it? between the water molecules).. What is a giant ionic lattice? An ionic compound with a regular structure in which there are strong electrostatic forces in all directions between oppositely charged ions. What are the melting and boiling points of ionic compounds (lattices) like and why? They are high because the forces of attraction are strong, and there are many of them, so a great deal of energy is needed to break these bonds.. Do most ionic compounds conduct electricity? Only when dissolved or melted as this means the charged ions are free to move and can therefore carry a current. Which chemicals are diamond, graphite and silicon dioxide made of?. What are the melting and boiling points of large covalent molecules like diamond, graphite and silicon dioxide like and why?. How are the atoms in diamond arranged and which properties does this mean it has?. How are the atoms and electrons in graphite arranged and which properties does this mean it has? Diamond (Carbon), Graphite (Carbon) and sulicon dioxide (Sulphur and Oxygen or silica ) They are very high because the covalent bonds between atoms are very strong One carbon atom is covalently bonded to four other carbon atoms so diamond is very hard. One carbon atom is covalently bonded to three other carbon atoms to form layers. This means there are delocalised electrons therefore the layers are free to slide over each other because there are no covalent bonds between them. This means graphite is soft, slippery and able to conduct electricity and heat (unlike diamond).. What are fullerenes? Fullerenes are hexagonal rings of carbon atoms. 0. What can fullerenes be used for? They can be used for drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials (e.g. tennis rackets) 0

7 C. How structure influences properties_. In terms of their structure, why do metals conduct Because they have delocalised electrons in their heat and electricity? structures.. What property do the layers in metals give them? They are able to be bent and shaped.. What are alloys? Metals which are usually made from two or more different metals.. Why are alloys harder than pure metals? Because they have different sized atoms (due to the two or more different type of metal) so the layers are distorted and find it difficult to slide over each other.. Can you name a shape memory alloy and describe Nitinol (used in dental braces), shape memory what this term means? alloys can return to their original shape.. What is a polymer? A substance made up from repeating monomers. What do the properties of polymers depend on? What they are made from and the conditions (temperatures, etc.) in which they were made.. What is the difference between how low density They are produced using different catalysts and (LD) and high density (HD) poly(ethane) are made? reaction conditions.. What are thermosoftening polymers? Polymers which consist of individual, tangled polymer chains. This means they do not have strong intermolecular forces between the chains. 0. What are thermosetting polymers? Polymers which consist of polymer chains with cross links. This means that they have string forces between chains so do not melt. 0

8 C. How structure influences properties_. How big are nanoparticles? -00nm (a few hundred atoms). What is the difference between nanoparticles and They have different properties and have a high substances made of the same elements but larger? surface area to volume ratio.. What sorts of new technologies could New computers, new catalysts, new coatings, nanoparticles be used to develop? highly selective sensors, stronger and lighter construction materials and new cosmetics such as sun tan creams and deodorants. C. Atomic structure, analysis and quantitative chemistry_. What are the names of the three parts of an atom? Proton, neutron and electron. What can the mass number of an element tell us? The number of protons and neutrons. What can the atomic number of an element tell The number of protons us?. What is the relative mass and charge of a proton? and +. What is the relative mass and charge of a neutron? and 0. What is the relative mass and charge of an 0 and - electron? 0. What is an isotope? Atoms of the same element which have different numbers of neutrons (e.g. Hydrogen always has proton but can have, or neutrons) 0

9 C. Atomic structure, analysis and quantitative chemistry_. Which isotope is the relative atomic mass of an Carbon ( protons and neutrons), is the atom compared to? average value for the isotopes of carbon.. What is the relative formula mass of a compound? It is the sum of the relative atomic masses of the atoms shown in the formula.. What is the relative formula mass of a substance mole of the substance (which contains.0 x 0 when given in grams? atoms). How do you calculate the relative formula mass of Add all the relative atomic masses of all the atoms carbon dioxide? (C = and O = ) together; CO; Carbon = plus Oxygen = plus another Oxygen = (because it is CO meaning atom of carbon and atoms of Oxygen) so the. Which methods are used to detect elements and compounds and why? relative formula mass is + + = Instrumental methods because they are accurate, rapid and sensitive (think ARS) so can be used to identify elements and compounds in very small samples.. How is chemical analysis particularly useful in the It can be used to identify additives in food. food industry?. Which technique is used to identify artificial Paper chromatography. colours?. Which type of method is Gas chromatography An instrumental method linked to mass spectroscopy (GC-MS) an example of?. What does GC-MS allow scientists to do? Separate a mixture of compounds.

10 C. Atomic structure, analysis and quantitative chemistry_. How is the substance to be analysed in GC-MS carried through the equipment?. What is the substance to be analysed passed through?. What happens to the substance as it passes through the column? Using a gas The gas chromatography column packed with a solid material. Each element or compound within the substance travels through the column at different speeds, so the time taken can be used to help identify the compound.. What is the gas chromatography column linked to? A mass spectrometer. What does the mass spectrometer show? It will give different peaks which show how long each substance was in the column for (retention time). It will also give the relative molecular mass of each of the compounds separated.. What is the name of the peak which shows the molecular mass?. If you want to calculate the percentage of a given element in a compound, which two pieces of information do you need? The molecular ion peak The relative mass of the element and the relative formula mass of the compound. What is the empirical formula? The simplest ratio of elements in a compound. What information do you need to calculate the The masses or percentages of elements in a empirical formula? compound. 0. Why is it not always possible to obtain the calculated amount of a product when carrying out an experiment?. the reaction may not go to completion because it is reversible.. some of the product is lost when separated from the reaction mixture.. Some of the reactants may react in ways different from the expected reaction 0

11 C. Atomic structure, analysis and quantitative chemistry_. What is another name for the amount of product Yield obtained in a chemical reaction?. What is percentage yield? The amount of product obtained compared with the maximum theoretical amount as a percentage (amount of product obtained/theoretical amount x 00). What is a reversible reaction? When the products of a reaction can react together to produce the original reactants.. Give an example of a reaction which is reversible Ammonium chloride ammonia + hydrogen chloride. Hydrated copper sulphate (blue) anhydrous copper sulphate (white) + water C. Rates of reaction. Which two ways can you measure rates of reaction?. Measuring the amount of reaction used in a given amount of time (amount of reactant used/time). Measuring the amount of product formed in a given amount of time (amount of product formed/time). Under what circumstances do chemical reactions When reacting particles collide with each other occur? with sufficient energy.. What is the activation energy of a reaction? The minimum amount of energy particles must have to react.. What are the ways to alter the rate of a reaction Temperature, concentration of reactants in a solution, gas pressure, surface area of solid reactants and presence of catalysts

12 C. Rates of reaction_. Why does increasing temperature increase the rate of reaction?. Why does increasing pressure of reacting gases increase the rate of reaction?. Why does increasing the concentration of reactants in solutions increase the rate of reaction?. Why does increasing the surface area of solid reactants increase the rate of reaction?. How could you increase the surface area of a marble (calcium carbonate) chip? Because it increases the speed of the reacting particles (they have more energy) so they collide more frequently and more energetically. Because it increases the frequency of collisions (particles are closer together) Because it increases the frequency of collisions (more particles so more likely to collide). Because it increases the frequency of collisions (more particles on the surface available for reactions) You could grind it into a powder (if you added up the surface area of each tiny part of the powder this would be greater than surface area the original chip). What is a catalyst? It is a substance which changes the rate of chemical reactions without being used up. Each catalyst is specific to each reaction.. Why are catalysts important in industry? They increase the rate of reaction and therefore can reduce costs.. Can you give some examples of catalysts? Platinum (in the ignition of hydrogen or the oxidation of ammonia). Manganese(IV) oxide or enzymes in yeast/potato (in the decomposition of hydrogen peroxide), etc.

13 C. Exothermic and endothermic reactions. What is an exothermic reaction? A reaction which transfers energy to the surroundings (energy EXits). Can you give three examples of exothermic reactions? Combustion reactions, many oxidation reactions and neutralisation.. Can you name some examples of everyday uses of Self-heating cans (e.g. coffee) and hand warmers. exothermic reactions?. What is an endothermic reaction? A reaction which takes in energy from the surroundings (heat ENters). Can you give an example of an endothermic Thermal decompositions reaction?. Can you name some examples of everyday uses of Sports injury packs. endothermic reactions?. If a reversible reaction is exothermic in one Endothermic direction will it be exothermic or endothermic in the other direction?. Can you name an example of a reversible reaction which is endothermic and exothermic? Hydrated copper sulphate (blue) anhydrous copper sulphate (white) + water This is endothermic in this direction but the reverse reaction is exothermic.. What does soluble mean? Dissolves in a solvent (typically water) 0. What does insoluble mean? Does not dissolve in a solvent (typically water) 0

14 C. Acids, bases and salts_. What are the four state symbols used in chemical (s) solid, (l) liquid, (aq) aqueous and (g) gas. reactions?. What does aqueous mean? Dissolved in water (a solution). What three substances can be used to react with Metals, insoluble bases, alkalis acids in order to make a soluble salt?. What is the difference between a base and an Bases are insoluble metal hydroxides or oxides and alkali? alkalis are soluble hydroxides.. Why can you not use all metals when reacting Some are too reactive (e.g. sodium) and some are them with acid to make a soluble salt? not reactive enough (e.g. gold). How do you make an insoluble salt using an acid Add the base to the acid until no more will react and a base? then filter the excess (unreacted) solid off.. What is used when an acid reacts with an alkali to An indicator make a soluble salt in order to detect when the reaction has happened to completion?. How can you get a solid salt from a salt solution? Crystallise the solutions (allow the water to evaporate leaving behind the salt). Can you suggest how to make sodium chloride? React sodium hydroxide (alkali) with hydrochloric acid (acid) to completion. Use universal indicator to detect a neutral solution which will be green colour. Add charcoal to remove the indicator then filter this away. Crystallise the salt using an evaporating dish and gentle heat.

15 C. Acids, bases and salts_. How do you make an insoluble salt? Mix appropriate amounts of solutions of ions so that a precipitate is formed.. How can precipitation be used in industry? To remove unwanted ions from solutions, e.g. in treating water or effluent.. What are bases? Metal oxides and hydroxides which are insoluble.. What are alkalis? Hydroxides which are soluble.. In a reaction between an acid and a base or alkali, The metal in the base or alkali and the type of acid what does the name of the alt produced depend on? used.. Which type of soluble salt does hydrochloric acid Chlorides. produce when reacted with a base or alkali?. Which type of soluble salt does nitric acid produce Nitrates. when reacted with a base or alkali?. Which type of soluble salt does sulphuric acid Sulphates. produce when reacted with a base or alkali?. If sulphuric acid reacts with potassium hydroxide Potassium sulphate. what is the name of the soluble salt produced? 0. If zinc oxide reacts with nitric acid what is the Zinc nitrate name of the soluble salt produced? 0

16 C. Acids, bases and salts_. When ammonia dissolves in water does it produce Alkaline an acid or alkaline solution?. How is ammonia solution useful? It is used to produce ammonium salts which are useful as fertilisers. Which ion makes solutions acidic? H+. Which ion makes solutions alkaline? OH-. What does the ph scale measure? How acidic or alkaline a solution is (essentially how many H+ or OH- ions are in the solution). What is the range of the ph scale? 0-. What is a neutral ph?. What is the ph of a strong acid? or. What is the ph of a strong alkali? or 0. What is a neutralisation reaction? When and acid and alkali react so the H+ ions react with the OH- ions to produce water. H+(aq) + OH- (aq) HO(l) 0

17 C. Electrolysis. Why must an ionic substance be melted or dissolved in water before electrolysis can be carried out?. In order to carry out electrolysis on lead bromide does it need to be dissolved or melted?. What happens when you pass an electric current through molten lead bromide?. What is the term used for a substance that is broken down by electrolysis?. What happens to the positive and negative ions during electrolysis?. What happens to the positive ions at the negative electrode?. What happens to the negative ions at the positive electrode?. Does oxidation-reduction reactions always involved oxygen?. If there is a mixture of ions in the electrolyte, what will the products formed depend on? Because when solid the ions are strongly attracted to each other so cannot move. Dissolving or melting the ionic substance means the ions are free to move within the liquid or solution. Melted It gets broken down into its elements (lead and bromine) Electrolyte. Positively charged ions move to the negative electrode and negatively charged ions move to the positive electrode. The positive ions gain electrons (reduction) The negative ions lose electrons (oxidation) No, it is about the loss or gain of electrons. Oxidation Is the Loss of electrons and Reduction Is the Gain. (OILRIG) The reactivity of the elements involved. The least reactive will be most likely to gain or lose electrons at the electrodes. 0. How are reactions at electrodes represented? By half equations e.g. Cl- Cl + eor Cl- - e- Cl (where e- represents an electron) 0

18 C. Electrolysis_. What is electroplating? Where electrolysis is used to plate objects for a variety of reasons e.g. copper plating or silver plating (cutlery, etc.). How is electrolysis used to manufacture Using a molten (melted) mixture of aluminium aluminium? oxide and a substance called cryolite.. Why is cryolite required in the electrolysis to It lowers the melting point of aluminium oxide. produce aluminium?. In the electrolysis of aluminium oxide, what is Aluminium formed at the negative electrode?. In the electrolysis of aluminium oxide, what is Oxygen formed at the positive electrode?. Which element are electrodes typically made Carbon from?. If oxygen is formed at an electrode, what usually happens?. What are the products of the electrolysis of sodium chloride solution?. How are the products of the electrolysis of sodium chloride solution use in industry? 0. Can you write the half equation for the oxidation reaction at the positive electrode in the electrolysis of sodium chloride solution?. Can you write the half equation for the reduction reaction at the negative electrode in the electrolysis of sodium chloride solution? The oxygen reacts with the carbon in the electrode to form carbon dioxide and the electrode will need to be regularly replaced. Hydrogen and chlorine (at electrodes). Sodium hydroxide solution is also produced. Sodium hydroxide is important for the production of soap and chlorine for the production of bleach and plastics. Cl - - e - Cl H + + e - H 0