2339039
| Questão | Responda |
| What are compounds? | substances in which 2 or more elements are chemically combined. |
| what does chemical bonding involve? | Transferring or sharing electrons in the highest energy level. |
| What structure is obtained after a chemical bond? | noble gas structure. |
| What are formed when ions are transferred? | ions |
| what ions are formed when atom lose electrons? | Positive |
| What ions are formed when atoms gain electrons? | Negative |
| What charge do group 1 metal ions have? | +1 |
| What charge do group 7 halide ions have? | -1 |
| How are ionic compounds held together? | Strong electrostatic forces of attraction between oppositely charged ions. |
| When are covalent bonds formed? | When atoms share pairs of electrons. |
| Give 4 examples of simple covalent molecules? | H2, Cl2, O2, HCl, H2 O , NH3, CH4 |
| Give two examples of giant covalent structures. | Diamond and Graphite |
| What is another name for a giant covalent structure? | macromolecule |
| What is a metal? | A giant structure of atoms arranged in a regular pattern. |
| What is important about the outer shell electrons in a metal? | They are delocalised, so they are free to move about in the structure. |
| Do simple molecules have a high or low melting points and boiling points? | Low |
| Why are the melting and boiling points low in simple molecules? | They have weak inter-molecular forces, which are easily broken. |
| Why do simple molecules not conduct electricity? | The molecules have no overall charge. |
| What is the name for a giant structure? | Lattice |
| Do ionic structures have a high or low melting and boiling point? | High |
| Why are the melting and boiling points high in ionic structures? | Large amounts of energy are required to break the strong bonds. |
| When do ionic compounds conduct electricity? | When the compound is molten or dissolved in water (so the ions are free to move). |
| Why do giant covalent structures have very high melting points? | The covalent bonds are very strong. |
| Why is diamond so hard? | Each carbon atom has bonds to 4 other carbon atoms. |
| Why is graphite so soft and slippery? | Each carbon atom has 3 bonds to other carbon atoms; this causes distinct layers to form- the layers have no covalent bonds, so they can slide over each other. |
| Why does graphite conduct heat and electricity? | One electron from each atom is delocalised, so it is free to move. |
| Give three uses of fullerenes. | Drug delivery into the body, in lubricants, as catalysts and in nanotubes to reinforce materials. |
| What properties do the delocalised electrons give to metals? | Conduct heat and electricity. |
| Why can metals be bent and shaped? | The layers of atoms can slide over each other. |
| How are alloys usually made? | Mixing two or more different metals. |
| Why are alloys harder than pure metal? | The different sized atoms make it more difficult for the layers to slide over each other; this is because the regular pattern is disrupted. |
| What is special about shape-memory alloys? | They return to their original shape after being deformed. |
| What do the properties of polymers depend upon? | What they are made from and the conditions used. |
| What is the difference between thermosoftening and thermosetting polymers? | Thermosetting polymers have cross links between the chains, so they do not melt when heated. Thermosoftening polymers have no crosslinks and layers can slide over each other. |
| What size are nanoparticles? | 1-100 nm |
| Why are nanoparticles useful to us? | They have different properties to larger molecules. |
| Give 3 examples of how nanoparticles could be used. | New computers. New catalysts. New coatings. Sensors. Stronger and lighter construction material. New cosmetics. |
| What is the relative atomic mass of a proton? | 1 |
| What is the relative atomic mass of an electron? | Very small (almost 0) |
| What does the mass number tell us? | The number sum of protons and neutrons. |
| What are isotopes? | Atoms of the same element with a different number of neutrons. |
| What is the relative formula? | The sum of the relative atomic masses. |
| What is the relative formula mass of a substance also known as? | One mole |
| Why do we use instrumental methods (such as gas chromatography)to detect elements and compounds? | They are more accurate, sensitive, rapid and good for small samples. |
| For what is paper chromatography used? | Detecting artificial colours. |
| Give an example of an instrumental method. | Gas chromatography linked to mass spectrometer (GM-MS) |
| What does gas chromatography do? | Separates a mixture of compounds. |
| What does a mass spectorometer do? | Identifies the substance leaving the column. |
| What else can the mass spectrometer do? | Provide the relative molecular mass of each substance. |
| How do we calculate the % of an element in a compound? | Mass of the element ÷ formula mass of the compound |
| What is the empirical formula of a compound? | The simplest ratio of atoms |
| Why is it not possible to get the full theoretical amount of product in a reaction? | The reaction may be reversible, Products maybe lost in separation, Some reactants may react differently than expected. |
| What is a yield? | The amount of product obtained. |
| How do we calculate the % yield? | Mass obtained ÷ theoretical yield x 100 |
| what is a reversible reaction? | Where the products react to produce the original reactants. |
| Give two ways of calculating the rate of a reaction. | Amount of reactant used ÷ time or Amount of product formed ÷ time |
| When do chemical reactions occur? | Particles must collide with sufficient energy. |
| What is the minimum amount of energy particles need to react called? | Activation energy |
| Why does increasing temperature increase the rate? | The particles move faster and collide more frequently and energetically. |
| Why does increasing the pressure increase the rate of a reaction? | Increases the frequency of collisions. |
| Why does increasing concentration increase the rate? | Increased frequency of collisions. |
| Why does increasing surface area increase the rate of the reaction? | Increased frequency of collision. |
| How do we increase the surface area? | Make the particles smaller. |
| What is a catalyst? | A chemical which increases the rate of a reaction, but it is not used up. |
| Why are catalysts used in industrial processes? | To reduce costs. |
| What is the name for a reaction that transfers energy to the surroundings? | Exothermic |
| What type of reaction does the graph show? | Exothermic |
| Give 2 examples of exothermic reactions. | Combustion, many oxidation reactions, and neutralisation. |
| Give two uses of exothermic reactions. | Self heating cans and hand warmers |
| What is the name of a reaction that takes in energy from the surroundings? | Endothermic |
| What type of reaction does the graph show? | Endothermic |
| Give an example of an endothermic reaction. | Thermal decomposition |
| Give a use for endothermic reactions. | Sports injury packs. |
| What can you say about reversible reaction that is exothermic in one direction? | It is endothermic in the opposite direction. |
| What does the symbol (s) mean? | Solid |
| What does the symbol (aq) mean? | Aqueous- in solution |
| Give three ways of making salts? | Acid + metal or Acid + insoluble base or Acid + alkali |
| How are insoluble salts made? | Precipitation reactions |
| What is the name given to metal oxides and hydroxides? | Bases |
| What is the name for soluble hydroxides? | Alkalis |
| What does the salt depend on? | The acid used and the metal in the base or alkali |
| What salts do we get from hydrochloric acid? | Chlorides |
| What salts do we get from sulphuric acids? | Sulphates |
| What salts do we get from nitric acids? | Nitrates |
| What type of solution is formed when ammonia dissolves in water? | Alkaline solution |
| Which salts are made from ammonia? | Ammonium salts |
| For what do we use ammonium salts? | Fertilisers |
| Which ions make a solution acidic? | H+ |
| What ions make a solution alkaline? | OH- |
| How do we measure acidity and alkalinity? | The pH scale |
| What happens during neutralisation reactions? | The H+ ions react with the OH- ions to form water. |
| When are ions free to move? | When the substance is molten or dissolved. |
| What is electrolysis? | Using electricity to break down compounds into their elements. |
| What is the name for the chemical being broken down? | Electrolyte |
| Where do positive ions move? | To the cathode (negative electrode) |
| What is electroplating? | Using electrolysis to coat a metal with another metal. |
| What happens at the negative electrode? | Positive ions gain an electron (reduction) |
| What happens at the positive electrode (anode)? | Negative ions lose electrons (oxidation). |
| What happens if there is a mixture of ions? | The products formed depend on the reactivity. |
| How are reactions at the electrodes represented? | Half equations. |
| How is aluminium manufactured? | Electrolysis of aluminium oxide with cryolite. |
| What forms at the negative electrode? | Aluminium |
| At which electrode is oxygen produced? | the positive electrode (anode) |
| Why is carbon dioxide produced? | The oxygen quickly reacts with the carbon rods that are used as the electrodes. |
| What is produced in the electrolysis of brine? | Hydrogen, chlorine and sodium hydroxide H- used to make margarine Cl- used in bleach, disinfectants, plastic NaOH- used to make soaps and detergents |
| What do we make from sodium hydroxide? | Soap |
Quer criar seus próprios Flashcards gratuitos com GoConqr? Saiba mais.