2455276
Descripción
Fichas por Lauren Crawford, actualizado hace más de 1 año
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Creado por Lauren Crawford
hace más de 9 años
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| Pregunta | Respuesta |
| What is a compound? | A substance in which two or more elements are chemically combined |
| What does chemical bonding involve? | Either transferring or sharing electrons in the highest occupied shells of atoms in order to become stable |
| What is formed by transferring electrons? | Ions |
| What is formed when you lose electrons? | Positively charged ions |
| What is formed when you gain electrons? | Negatively charged ions |
| Ions have the electronic structure of... | a noble gas (group 0) |
| The elements in Group 1, the (a), all react with (b) elements to form (c) in which the metal ion has a single (d) charge | a) alkali metals b) non-metal c) ionic compounds d) positive |
| The elements in Group 7, the (a), all react with the (b) metals to form (c) in which the halide ions have a single (d) charge | a) halogens b) alkali c) ionic compounds d) negative |
| What is an ionic bond? | The strong electrostatic force of attraction between two oppositely charged ions |
| In ionic bonding the forces.... | ...act in all different directions in the lattice |
| What is covalent bonding? | The sharing of electrons between two non-metals |
| What is a macromolecule? | A giant covalent structure that contains a large number of atoms |
| True or false: metals consist of giant structures of atoms arranged in an irregular structure | False. Metals consist of giant structures of atoms arranged in a regular structure |
| Why can metals conduct electricity? | The electrons in the outer shell of metal atoms are delocalised and thus free to move |
| Substances that consist of simple molecules are gases, liquids or solids that have relatively ________ melting and boiling points | low |
| Substances that consist of simple molecules have.... | ...weak intermolecular forces (which are overcome when the substance melts or boils) |
| Why do substances that consist of simple molecules not conduct electricity? | Because the molecules do not have an overall charge |
| Why do ionic compounds have high melting and boiling points? | There are lots of electrostatic forces between the ions which are very strong and thus require a large amount of energy to break the bonds |
| Why can ionic compounds only conduct electricity when melted or dissolved in water? | The ions are free to move and carry the current |
| Give an example of giant covalent structures | Diamond/graphite/silicon dioxide |
| Why do macromolecules have high boiling points? | The atoms are linked by strong covalent bonds |
| Why is diamond very hard? | Each carbon atom forms 4 covalent bonds with other carbon atoms in a giant covalent structure |
| Why is graphite soft and slippery? | Each carbon atom bonds to 3 others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers |
| Why can graphite conduct electricity? | One electron form each carbon atom is delocalised |
| What is a fullerene? | Molecules made up entirely of carbon in the shape of a sphere or a tube |
| What can fullerenes be used for? | Drug delivery into the body, in lubricants, as catalysts and in nanotubes for reinforcing materials e.g. in tennis rackets |
| Why are metals malleable? | The atoms are arranged in layers which means the atoms can slide over each other |
| What is an alloy? | A compound of two or more elements, usually metals |
| Why are alloys harder than pure metals? | The different sized atoms of the metals distort the layers in the structure, making it more difficult to slide over each other |
| What is a shape memory alloy? | A material that when heated to a certain temp, will return to its original shape |
| Thermosoftening polymers consist of... Thermosetting polymers consist of... | ...individual, tangled polymer chains ...polymer chains with cross-links, so they do not melt |
| One nanometre is.. | ... 1x10^-9m |
| The mass of a proton = ? The mass of a neutron = ? The mass of an electron = ? | 1 1 very small |
| What is the mass number? | The total number of protons and neutrons |
| What is an isotope? | Atoms of an element with the same number of protons and electrons but different numbers of neutrons |
| What is meant by the term 'relative atomic mass'? | The comparison of the mass of atoms of the element compared to the carbon-12 isotope |
| What is the relative formula mass of a compound? | The relative atomic mass of an element is the mass of one atom of that element compared to an atom of carbon-12. It is an average value for the isotopes of that element |
| What is one mole of a substance? | The relative formula mass of a substance in grams |
| Advantages of instrumental methods of analysis | Accurate Sensitive Rapid Useful for tiny amounts of a substance |
| What is chemical analysis used to identify? | Additives in food |
| What can paper chromatography identify? | Artificial colours |
| Explain the process of gas chromatography | 1. Different substances 2. carried by a gas 3. travel through a column packed with a solid material at different speeds 4. so that they become separated |
| What do the number of peaks on the output of a gas chromatograph show? | The number of compounds present |
| What does the position of the peaks on the output indicate? | The retention time |
| Advantages of a mass spectrometer | Fast Accurately Can detect very small quantities |
| What gives the molecular mass? | The molecular ion peak |
| What does gas chromatography allow? | The separation of a mixture of compounds |
| What can help identify a substance in GC-MS? | The time taken for a substance to travel through the column |
| What is the equation to find the percentage of an element in a compound? | |
| Reasons for less than 100% yield | 1. the reaction may be reversible 2. some of the product may be lost when separated 3. some reactants may react in ways that weren't expected |
| Equation for percentage yield | |
| Equation to find rate of reaction | Rate of reaction = amount of reactant used/time or Rate of reaction = amount of product formed/time |
| What is activation energy? | The minimum amount of energy required for a reaction to occur |
| What effect does increasing the temp have on a reaction? | It increases the speed of the reacting particles so that they collide more frequently and more energetically - increases rate of reaction |
| What effect does increasing the pressure of reacting gases have on a reaction? | It increases the frequency of collisions and so the rate of reaction |
| What effect does increasing the concentration have on a reaction? | It increases the frequency of collisions and so the rate of reaction |
| What effect does increasing the surface area have on a reaction? | It increases the frequency of collisions and so the rate of reaction |
| What is a catalyst? | A substance which speeds up a reaction, without being changed or used up in a reaction |
| Advantages of catalysts in industry | Saves money Saves energy (work at lower temps) Never get used up |
| Disadvantages of catalysts in industry | Expensive to buy Can only catalyse one type of reaction Catalysts can be 'poisoned' by impurities and stop working |
| When chemical reactions occur, energy is __________ to or from the surroundings | transferred |
| What is an exothermic reaction? | One that transfers energy TO the surroundings |
| Examples of exothermic reactions | Combustion Many oxidation reactions Neutralisation |
| Everyday uses of exothermic reactions? | Self-heating cans and hand warmers |
| What is an endothermic reaction? | A reaction that takes in energy from the surroundings |
| Example of an endothermic reaction? | Thermal decompositions |
| Everyday use of endothermic reactions | Some sports injury packs |
| If a reversible reaction is exothermic in one direction,..... | ....it is exothermic in the opposite direction |
| What are the 4 state symbols? | (l) = liquid (s) = solid (g) = gas (aq) = aqueous |
| Soluble salts can be made from acids by reacting them with.... | Metals (not all metals; some are too reactive/not reactive enough) Insoluble bases Alkalis |
| What is a salt? | A salt is any compound formed by the neutralisation of an acid by a base |
| What can be used to show when an acid and alkali have reacted completely? | An indicator |
| Salt solutions can be __________ to produce solid salts | crystallised |
| Metal oxides and hydroxides are.... | bases |
| Soluble hydroxides are called..... | alkalis |
| The particular salt produced in any reaction between an acid and a base depends on: | The acid used (hydrochloric acid=chlorides, nitric acid=nitrates etc) The metal in the base or alkali |
| Ammonia dissolves in water to produce... | an alkaline solution |
| Ammonia solution is used to produce... | ammonium salts |
| Ammonium salts are good for .... | fertilisers |
| The pH scale us a measure of the _____ or______ of a solution | Acidity or alkalinity |
| Hydrogen ions, H+(aq), make solutions______ Hydroxide ions, OH-(aq), make solutions_______ | Acidic Alkaline |
| In neutralisation reactions, _________ ions react with _________ ions to produce _______ | Hydrogen Hydroxide Water |
| Why would an ionic substance be melted or dissolved in water? (electrolysis) | To allow the ions to move freely within the liquid or solution |
| What happens when you pass an electric current though an ionic substance that is molten? What is this process called? | The substance is broken down into elements Electrolysis |
| What is the substance that is broken down by electrolysis called? | Electrolyte |
| What is electrolysis used for? | For electroplating objects (coating them in metal) |
| At the negative electrode, ________ charged ions _____ electrons | At the negative electrode, positively charged ions gain electrons (reduction) |
| At the positive electrode, _______ charged ions ______ electrons | At the positive electrode, negatively charged ions lose electrons (oxidation) |
| What does OIL RIG stand for? | Oxidation Is Loss Reduction Is Gain |
| If there is a mixture of ions, the products formed depend on the ________ of the elements involved | If there is a mixture of ions, the products formed depend on the reactivity of the elements involved |
| Aluminium is manufactured by the electrolysis of a molten mixture of ___________ and __________ | Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite |
| Aluminium forms at the ______ electrode Oxygen forms at the ______ electrode | Negative Positive |
| The electrolysis of sodium chloride solution produces...... | Hydrogen Chlorine Sodium hydroxide solution |
| Why is cryolite used in the extraction of aluminium? | It lowers the melting point of Al203 thus lowering costs |
| Describe the physical properties you would expect an ionic substance to have | High melting point High boiling point Can conduct electricity when molten Dissolves easily in water |
| Explain how diamond's structure is different from graphite and fullerenes | Each carbon atom forms 4 covalent bonds in a very rigid giant structure, unlike graphite. Fullerenes have carbon atoms arranged in hexagonal rings that form hollow balls or tubes, unlike diamond |
| Give one industrial use for sodium hydroxide | Production of soap |
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