Knox Academy. S4 Chemistry

Transcription

1 Unit 2: Nature s Chemistry Summary Book Name:

2 Summary 2.1: Plants and their Products 1. Animals eat as food, humans grow particular plants as food crops. 2. Plants produce carbohydrates, and oils which are used as a source of energy by our bodies. 3. Energy is released by food using the process of. a. In the presence of sufficient oxygen _ respiration occurs. glucose + oxygen carbon dioxide + water b. In the absence of sufficient oxygen _ respiration occurs. glucose alcohol + carbon dioxide (in yeast) glucose lactic acid (in plants) 4. Plants based foods contain protein molecules, our bodies use these for _ and repair of tissues. 5. Vitamins and contained within plant products are used to maintain a healthy body. a. is required for haemoglobin production, haemoglobin is then used to manufacture red blood cells. b. Calcium is required to build strong _ and teeth. c. Vitamin _ is required to maintain healthy connective tissue, without enough vitamin _ in our diet we begin to develop conditions such as scurvy. d. Vitamin _ is required for our bodies to be able to take in calcium from our food. Vitamin _ is found in oily plants such as nuts, our bodies may also manufacture vitamin _ using sunlight and other chemicals found in plants that we eat as part of our diet. 6. Fats and oils found in plants can be broken down in our bodies to release _ acid molecules. Certain fatty acid molecules are essential in maintaining human health. Unit 2: Nature s Chemistry: Summary Notes 1

3 7. Plants and their products provide the basis for the manufacture of various consumer products from pharmaceuticals, cosmetics,, foods and medicines. 8. Essential oils may be extracted from plants using the process of steam distillation the oils may then be used in a variety of consumer products. a. Peppermint and spearmint oils are used in. b. Lemon, rosemary and orange oils are used in. c. oil is used in hand creams and body lotions. d. oil is used in sinus sprays and decongestants. e. oil is used in massage oils. 9. Essential oils are the basis of many perfumes and aftershaves, the exact combination of oils is determined by the _ required. Summary 2.2: Biochemical Reactions 1. Photosynthesis is the process used by plants to capture light energy from the sun and use it to manufacture glucose molecules from simple substances (water and carbon dioxide) found in the environment. During the process of glucose production, oxygen gas is produced as a _ product. a. Word equation: chlorophyll carbon dioxide + _ glucose + light energy b. Balanced chemical equation: Unit 2: Nature s Chemistry: Summary Notes 2

4 2. Aerobic respiration is the process used by all organisms, in the presence of sufficient oxygen, to extract the energy stored in their food (glucose). During the process of aerobic respiration, carbon dioxide and water are produced. a. Word equation: glucose + carbon dioxide + water b. Balance chemical equation: 3. In nature, the balance of gases in the Earth s atmosphere is maintained by the processes of photosynthesis and respiration. 4. Human activities, such as burning fossil fuels or cutting down large sections of green plants, have increased the concentration of dioxide in the Earth s atmosphere. Increased concentrations of carbon dioxide in the Earth s atmosphere are believed to contribute to increases in _ temperatures commonly called Global Warming. Summary 2.3: Carbohydrates 1. Carbohydrates are a group of compounds made up of, hydrogen and oxygen only. 2. They may be divided into two groups, depending on their structure: a. Simple sugars such as _, fructose, maltose, sucrose and lactose. b. Complex carbohydrates such as starch, _ and glycogen. Unit 2: Nature s Chemistry: Summary Notes 3

5 3. We can identify the presence of reducing sugars as they cause Benedict s Solution to change colour from to orange on heating. Sucrose is the only simple sugar which is _ a reducing sugar. 4. We can identify the presence of starch using solution. Starch causes iodine solution to change from brown to blue/black. 5. Each carbohydrate molecule is made up of one or more saccharide subunits. A saccharide subunit contains _ carbon atoms. The number of saccharide subunits dictates the class of carbohydrate. a. Monosaccharide sugars contain a _ six carbon subunit - e.g. glucose and fructose C 6 H 12 O 6. b. Disaccharide sugars contain _ six carbon subunits e.g. maltose and sucrose C 12 H 22 O 11. c. Polysaccharide carbohydrates contain six carbon subunits joined together e.g. cellulose, starch and glycogen. 6. Isomers are two different chemicals which share the chemical formula but have different structural formulae, i.e. their atoms arranged differently. As they have different structural formulae they will participate in different reactions. 7. sucrose and maltose both have the chemical formula C 12 H 22 O 11, they are _. They react differently to Benedict s solution. Maltose causes Benedict s solution to change colour from blue to on heating, sucrose does not. 8. Starch is a polysaccharide made up of a chain of many _ molecules joined together. The glucose molecules join together by the process of condensation polymerisation. During condensation polymerisation, many monomers join together to form a polymer. In the process of joining together a _ molecule is also released, for every link between adjacent glucose molecules one molecule of _ is released. 9. Enzymes found in plants catalyse the reaction between adjacent monomers, and allow the condensation reaction to proceed at environmental conditions (a lower Unit 2: Nature s Chemistry: Summary Notes 4

6 _ ). 10. Starch may be broken down by the process of. During a hydrolysis reaction, a smaller molecule is used to break the link between two monomers of a condensation reaction. To break off an individual sugar molecule from a starch chain, a molecule of _ is used to break the link between the adjacent sugar molecules in the chain. 11. Enzymes found in the human digestive system catalyse the hydrolysis of starch into sugars. The enzymes allow the reaction to proceed at environmental conditions (a lower temperature). Prior Learning 2.1: Hydrocarbons 1. A fuel is a substance that we can to release energy. 2. Fossil fuels are made up of the fossilised remains of creatures that lived of years ago. Their remains are changed by heat and pressure into the substances we know today as fossil fuels. a. Crude oil and natural gas are made of the remains of _ and plants that lived millions of years ago. b. Coal and peat are made of the remains of that lived millions of years ago. 3. Fossil fuels are and found in limited quantities. Once reserves are used up it will take millions of years to replenish them. It is expected the world will face a fuel crisis within the next _ years. 4. Burning fossil fuels to release energy has many problems associated with it. a. Many fossil fuels contain compounds with _ in them. If sulphur is burned, sulphur dioxide is produced. Production and release of sulphur dioxide into the atmosphere is associated with rain. b. Burning fossil fuels releases huge quantities of dioxide into the atmosphere. Increased concentration of carbon dioxide in the Unit 2: Nature s Chemistry: Summary Notes 5

7 atmosphere is associated with Warming. 5. A chemical reaction where heat energy is released is said to be. During an exothermic chemical reaction, the reaction mixture s temperature _. 6. A chemical reaction where heat energy is taken is said to be endothermic. During an endothermic chemical reaction, the reaction mixture s temperature. 7. We may use recently plant materials as fuels. We refer to these as Biomass fuels. Examples of biomass fuels include wood, wood products (paper), carbohydrates and alcohol. 8. Use of biomass fuels is considered to be carbon _, as long as replacement plants are planted on production of the fuel before it is burned. 9. To allow a fuel to burn, it is necessary to ensure there is a fuel, oxygen and heat energy present. This can be summarised using the fire triangle: 10. are a group of molecules that modern society relies upon to meet energy needs. Hydrocarbons are found in coal, oil, natural gas and peat. 11. A hydrocarbon molecule is made up of hydrogen and carbon atoms. 12. The alkanes are a group of hydrocarbon compounds with similar structures and therefore chemical properties. They all share the same _ formula C n H 2n+2. The alkanes are an example of a series. Unit 2: Nature s Chemistry: Summary Notes 6

8 Name Chemical Formula Structural Formula methane ethane propane butane pentane hexane heptane octane 13. The _ are another homologous series of hydrocarbons. They share the same general formula C n H 2n. 14. Alkanes are said to be _ as they contain only single C-C bonds. _are said to be unsaturated as they contain at least one C=C bond within their molecules. 15. We can test for saturation using _ solution. An unsaturated molecule causes the _ decolourisation of bromine solution. A saturated molecule is unable to cause the rapid decolourisation of bromine solution. Unit 2: Nature s Chemistry: Summary Notes 7

9 Name Chemical Formula Structural Formula ethene propene butene pentene hexene heptene octene 16. Crude oil provides society with the main source of alkanes and alkenes which are used as fuels or to make other products such as plastics. When extracted from the Earth, _ oil is not in a useable form and must be processed to produce useable groups of molecules called fractions on the basis of differences in boiling point. This is called fractional. Unit 2: Nature s Chemistry: Summary Notes 8

10 17. Crude oil tends to contain more chain molecules than short chain molecules. Modern society requires a greater supply of the short chain molecules than is available. To meet the demands of the chemical industry, longer chain hydrocarbon molecules are _ to produce a mixture of saturated and unsaturated shorter chain hydrocarbons. Some unsaturated hydrocarbon molecules are produced from saturated hydrocarbon molecules as there are insufficient atoms available to produce all saturated product molecules. octane hexane + ethene C 8 H 18 C 6 H 14 + C 2 H 4 no. carbon = no. carbon = no. hydrogen = no. hydrogen = 18. When a hydrocarbon is burned, we say it has undergone a reaction. a. Combustion of a hydrocarbon in the presence of sufficient supplies of oxygen produces water (hydrogen oxide) and carbon dioxide. This is called combustion. hydrocarbon + oxygen carbon dioxide + water b. Combustion of a hydrocarbon in the presence of insufficient supplies of oxygen produces water (hydrogen oxide) and carbon monoxide. This is called combustion. hydrocarbon + oxygen carbon monoxide + water 19. We can write a balanced chemical equation to show the exact quantities of chemicals involved in chemical reactions. Balanced chemical equations may be applied to combustion reactions involving hydrocarbon molecules. a. Octane undergoes complete combustion. Unit 2: Nature s Chemistry: Summary Notes 9

11 b. Ethane undergoes incomplete combustion. c. Hexane undergoes incomplete combustion. 20. The finite nature of fossil fuel resources and the environmental impact of using fossil fuels is driving society to explore _ methods of energy production. An energy source which is easily replenished is said to be renewable. Renewable energy sources are not necessarily environmentally friendly. a. Tidal: potential impact on marine life b. Solar: occupies large areas of land disturbing movement of animals c. Hydro-electric: floods large valleys, preventing the natural movement of fish d. Hydrogen: potentially explosive, requires electricity to generate it in the first place. e. Ethanol: most cost effective method of production is from the products of crude oil. Production by fermentation is cost intensive and produces quantities of carbon dioxide a greenhouse gas. f. Biomass: burning plant material releases huge quantities of carbon dioxide and carbon particles (soot) into the air. Most plants contain sulphur compounds, burning these releases sulphur dioxide into the atmosphere contributing to acid rain. g. Biodiesel: production requires highly toxic chemicals currently obtained from crude oil. Burning biodiesel releases Unit 2: Nature s Chemistry: Summary Notes 10

12 huge quantities of carbon dioxide into the atmosphere. h. Wind: many residents of proposed areas consider wind turbines to be unsightly and ruin the visual appearance of an area, others oppose the introduction of wind turbines due to noise and increase traffic required during the building and maintenance phases. 21. Some sources of renewable energy are dependent upon _ or other forces of nature, changes to weather patterns due to Global Warming may impact on the future ability to harness the natural resources and produce energy by renewable means. Summary 2.4: Hydrocarbons 1. Cycloalkanes are a homologous series of hydrocarbons with the general formula C n H 2n. All their molecules are _ and contain only single C-C bonds. 2. The structural formulae of cycloalkanes show the atoms arranged as cyclic molecules or ring structures. The simplest member of the homologous series is C 3 H The group of a compound determines the types of chemical reactions the molecule may participate in. 4. Alkenes contain the functional group C=C. They are unsaturated and can rapidly decolourise _ solution. 5. Alkanes contain the functional group C-C. They are saturated and will _ rapidly decolourise bromine solution. 6. Cycloalkanes contain the functional group C-C arranged in a cycle or ring structure. They are saturated and will _ rapidly decolourise bromine Unit 2: Nature s Chemistry: Summary Notes 11

13 solution. 7. Isomers are compounds which share the same chemical formula but have the atoms arranged differently to form different formulae. 8. Systematic names can be used to differentiate between different isomers. a. Identify the functional _ of the molecule. b. Identify the _ chain of carbons containing the functional group. c. Number the carbon chain from the end of the molecule to the number attributed to the functional group. d. Write the name of the longest chain, identifying the position of any functional group e.g. C=C. e. Identify any branches or groups and their associated carbon atoms. f. List the branches or side groups in alphabetical order separating the branches from the main name with a. g. In front of the branches, list the numbers of the carbon atoms that the branches or side chains are attached to. Separate the numbers using. 9. Physical properties of a substance refer to changes of physical _. Physical properties usually refer to the pure substance. e.g. For any homologous series, as the number of carbon atoms _ so do the melting and boiling points. 10. Unsaturated hydrocarbons can have halogen or hydrogen atoms added to their molecules by the process known as. 11. If halogen atoms (such as bromine or chlorine) are added to an unsaturated molecule the process is known as. Unit 2: Nature s Chemistry: Summary Notes 12

14 12. When bromine solution is mixed with ethene, an addition reaction occurs. 1,2-dibromoethane is produced. a. word equation b. formulae equation c. structural formulae equation (highlight and identify functional groups) 13. If atoms are added to an unsaturated molecule the process is known as hydrogenation. 14. When hydrogen gas is mixed with oct-3-ene, an addition reaction occurs. Octane is produced. a. word equation b. formulae equation c. structural formulae equation (highlight and identify functional groups) 15. If a saturated hydrocarbon has hydrogen atoms removed from their molecules, an _ hydrocarbon is formed. This process is known as dehydrogenation. Unit 2: Nature s Chemistry: Summary Notes 13

15 16. When pentane has 2 hydrogen atoms removed from its molecule, pent-2-ene and a molecule of hydrogen as produced. a. word equation b. formulae equation c. structural formulae equation Summary 2.5: Alcohols 1. are a homologous series of compounds, with similar chemical properties and the same general formula. (C n H 2n+1 OH) 2. Alcohols all contain the (-OH) functional group. 3. When naming alcohol molecules, we number the carbon atoms to minimise the number associated with the carbon to which the hydroxyl group is attached. e.g. propan-1-ol has the hydroxyl group attached to carbon _ whereas propan-2-ol has the hydroxyl group attached to carbon _. 4. _ is the alcohol commonly found in alcoholic drinks. 5. Ethanol can be produced by the fermentation of sugars found in fruits and vegetables. The alcoholic drink produced is determined by the source of the plant material. a. Vodka is produced using Unit 2: Nature s Chemistry: Summary Notes 14

16 b. Whisky is produced using c. Cider is produced using d. Wine is produced using 6. Fermentation is another name for the process of _ respiration (respiration carried out in the absence of oxygen gas). 7. As with any biochemical process occurring in living things, anaerobic respiration is controlled by a series of enzymes. Enzymes and other catalysts allow chemical reactions to proceed at much _ (environmental) temperatures. 8. Enzymes are extremely sensitive to temperature and. The conditions at which an enzyme works best are called the _ conditions. 9. If an enzyme is exposed to too high a temperature it will no longer be able to function and assist the reaction to proceed at a lower temperature. When the enzyme is no longer able to function it is said to be _. 10. Yeast cells are able to produce an alcohol solution of 14% maximum by the process of fermentation. At 14% the concentration of ethanol proves for the yeast cells. To further increase the concentration of ethanol in a solution requires the process of. 11. Ethanol has a boiling point of C whereas water has a boiling point of _ C. We can separate ethanol from a solution of ethanol in water by the process of distillation, due to their differences in _ point. 12. A _ reaction involves adding the atoms necessary to make water molecules to another molecule, usually using a catalyst and temperature. The hydration of ethene produces _. a. word equation b. balanced chemical equation Unit 2: Nature s Chemistry: Summary Notes 15

17 c. structural formulae equation (highlight and state functional groups) Unit 2: Nature s Chemistry: Summary Notes 16

18 13. A dehydration reaction involves removing the atoms necessary to make water molecules from another molecule, usually using a catalyst and a high temperature. The dehydration of ethanol produces. a. word equation b. balanced chemical equation c. structural formulae equation (highlight and state functional groups) 14. When an alcohol is burned in air (undergoes a reaction) carbon dioxide and water are produced. alcohol + oxygen carbon dioxide + water 15. When ethanol burns in air, carbon dioxide and water are produced. Carbon dioxide changes limewater from clear to cloudy and cobalt chloride paper from blue to pink. a. word equation b. balanced chemical equation 16. During a combustion reaction, heat energy is released. The quantity of heat energy (E h ) released by a burning fuel may be calculated by experiment. E h = c m ΔT Where, c = 4.18 (specific heat capacitance of water) m = mass of water (in kg) being heated ΔT = change in temperature of the water Unit 2: Nature s Chemistry: Summary Notes 17

19 17. The value of heat energy released calculated from experimental results is never as high as the theoretical value. This is due to heat energy being to the surroundings and combustion of the alcohol leading to soot forming on the can. Incomplete combustion does not in itself release as much energy as complete combustion. Summary 2.6: Carboxylic acids and Esters 1. The carboxylic acids are a homologous series of carbon based compounds which contain the carboxyl functional group (-COOH). 2. As they form a homologous series, the carboxylic acids have similar chemical properties and share the general formula C n H 2n+1 COOH. 3. When naming carboxylic acids, we minimise the associated with the functional group and name the molecule according to the same rules discussed in section 2.4: hydrocarbons. 4. Bee stings and ant venom contain _ acid. Vinegar is a dilute solution of ethanoic acid. 5. Traditionally, ethanoic acid is produced by the _ of ethanol. During oxidation, ethanol C 2 H 5 OH is converted into ethanoic acid CH 3 COOH. a. word equation b. structural formulae equation (highlight and state functional groups) 6. Oxidation reactions can involve the removal of, addition of oxygen or of electrons. 7. Reduction reactions are the chemical opposite of reactions. Reduction reactions can involve the addition of hydrogen, removal of hydrogen Unit 2: Nature s Chemistry: Summary Notes 18

20 or _ of electrons. 8. Hydrochloric, sulphuric and nitric acids are all described as acids. When placed in water 100 % of their molecules dissociate to release hydrogen ions. 9. Carboxylic acids are described as acids when placed in water a small proportion of their molecules dissociate to release hydrogen ions. 10. Partial dissociation of ethanoic acid results in a 1.0 mol l -1 solution of ethanoic acid having a much ph (less acidic) than a 1.0 mol l -1 solution of hydrochloric acid. 11. Carboxylic acids are found in a variety of places in nature, and have a variety of uses. a. Benzoic acid is used as a preservative. b. Citric acid is widely found in citrus fruits and gives a _ taste to many sweets and foods. c. Butanoic acid is produced by sour _ products. d. Hexanoic acids contributes to _ particular odour. e. Human body odour (BO) is the result of enzymes producing carboxylic acids from compounds found in _. 12. Carboxylic acids can undergo a reaction with alcohols to produce pleasant smelling ester compounds. Ester compounds may be used as scents, flavourings and. 13. Ethyl ethanoate is an example of an ester, it is formed by refluxing ethanol with ethanoic acid in the presence of a concentrated sulphuric acid catalyst. a. Word equation Unit 2: Nature s Chemistry: Summary Notes 19

21 b. Structural formulae equation (highlight and state functional groups) 14. An ester link is also called a carboxylate group all ester molecules contain this functional group. 15. The name of an ester is dictated by the alcohol and carboxylic acid that are used to make it. The _ forms the first part of the name and the carboxylic acid the second part. a. Ethyl propanoate is formed from _ and propanoic acid. b. Methyl ethanoate is formed from methanol and acid c. Octyl salicylate is formed from _ and salicylic acid. Unit 2: Nature s Chemistry: Summary Notes 20