Mrs/Nagwan Essa Topic 1 1 Mrs/Nagwan Essa Topic 1 1) When nitrogen dioxide is cooled, it forms a yellow liquid and then pale yellow crystals. These crystals are heated and the temperature is measured every minute. The following graph can be drawn. D temperature yellow liquid B C pale yellow crystals A time (i) Describe the arrangement and movement of the molecules in the region A–B. ................................................................................................................................... (ii) Name the change that occurs in the region B–C .................................................................................................................................... 2 Ethanoic acid is a colourless liquid at room temperature. It has the typical and forms compounds called ethanoates. acid properties (a) A pure sample of ethanoic acid is slowly heated from 0 oC to 150oC and its temperature is measured every minute. The results are represented on the graph below. F D temperature B C A time 2 E Mrs/Nagwan Essa Topic 1 (i) Name the change that occurs in the region D to E. (ii) What would be the difference in the region B to C if an impure sample had been used? (iii) Sketch on the graph how the line would continue if the acid was heated to a higher temperature. (iv) Complete the following table that compares the separation and movement of the molecules in regions C to D with those in E to F. C to D separation (distance between particles) E to F ................................. ................................. ................................. movement of particles Can particles move apart to fill any volume? random and slow ................................. ................................. ................................. 3 Ozone is a form of oxygen. Ozone is present in the upper atmosphere and it prevents dangerous solar radiation from reaching the Earth’s surface. Some of the chemicals that diffuse into the upper atmosphere decompose ozone. Chemicals that have this effect are methane (CH4), chloromethane (CH3Cl ) and an oxide of nitrogen (NO2). (i) Which of these three chemicals diffuses the most slowly? Give a reason for your choice. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... 3 Mrs/Nagwan Essa 4) Topic 1 The Kinetic Theory explains the properties of matter in terms of the arrangement and movement of particles. (a) Nitrogen is a gas at room temperature. Nitrogen molecules, N 2, which are spread far apart move in a random manner at high speed. (i) How does the movement and arrangement of the molecules in a crystal of nitrogen differ from those in gaseous nitrogen? .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (b) Use the ideas of the Kinetic Theory to explain the following. (i) A sealed container contains nitrogen gas. The pressure of a gas is due to the molecules of the gas hitting the walls of the container. Explain why the pressure inside the container increases when the temperature is increased. .................................................................................................................................... .................................................................................................................................... (ii) The following apparatus can be used to measure the rate of diffusion of a gas. constant pressure applied gas syringe metal foil gas escapes through small hole in foil gas The following results were obtained. temperature / C rate of diffusion in cm3 / min nitrogen 25 1.00 chlorine 25 0.63 nitrogen 50 1.05 gas Explain why nitrogen diffuses faster than chlorine. .................................................................................................................................... .................................................................................................................................... Explain why the nitrogen diffuses faster at the higher temperature. .................................................................................................................................... 4 Mrs/Nagwan Essa Topic 1 5) The diagram below shows part of the Water Cycle. cloud H2O(l) H2O(g) Sun rain land H2O(l) sea (a) (i) State the name of each of the following changes of state. H O(l) H O(g) 2 2 name .......................................................................................................................... H O(g) H O(l) 2 2 name .......................................................................................................................... (ii) Which one of the above changes of state is exothermic? Explain your choice. .................................................................................................................................... .................................................................................................................................... (b) When liquid nitrogen boils the following change occurs. N2(l) N2(g) The boiling point of nitrogen is very low even though the bond between the atoms in a nitrogen molecule is very strong. Suggest an explanation. ........................................................................................................................................... ............................................................................................................................................ 5 Mrs/Nagwan Essa Topic 1 6) The diagram shows a heating curve for a sample of compound X. F D 80 E temperature / C B 15 C A time a. Is X a solid, a liquid or a gas at room temperature, 20 C? ............................................................................................................................................ b. Write an equation for the equilibrium which exists in region BC. ............................................................................................................................................ c. Name the change of state which occurs in region DE. ............................................................................................................................................ d. Explain how the curve shows that a pure sample of compound X was used. ........................................................................................................................................... ............................................................................................................................................ 7) A small amount of liquid bromine is added to a container which is then sealed. Br2(l) Br2(g) molecules have spread uniformly to occupy the whole container. ........................................................................................................................................... ........................................................................................................................................... ............................................................................................................................................ 6 Mrs/Nagwan Essa Topic 1 8) The diagrams below show simple experiments on the speed of diffusion of gases. porous pot allows gas molecules to diffuse air hydrogen porous pot air air higher level same level large beaker coloured liquid diagram 1 diagram 2 higher level air carbon dioxide large beaker diagram 3 Complete the following explanations. Diagram 1 has been done for you. Diagram 1 There is air inside and outside the porous pot so the rate of diffusion of air into the pot is the same as the rate of diffusion of air out of the pot. The pressure inside and outside the pot is the same so the coloured liquid is at the same level on each side of the tube. Diagram 2 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ............................................................................................................................................ 7 Mrs/Nagwan Essa Topic 1 Diagram 3 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... 9) (a) Different gases diffuse at different speeds. (i) What is meant by the term diffusion? ............................................................................................................................................. ................ ............................................................................................................................ . (ii) What property of a gas molecule affects the speed at which it diffuses? ............................................................................................................................................. (b) Helium is a gas used to fill balloons. It is present in the air in very small quantities. Diffusion can be used to separate it from the air. Air at 1000 C is on one side of a porous barrier. The air which passes through the barrier has a larger amount of helium in it. (i) Why does the air on the other side of the barrier contain more helium? ............................................................................................................................................. (ii) Why is it an advantage to have the air at a high temperature? .................................................. .......................................................................... ................. ................ ............................................................................................................................ . (c) Most helium is obtained from natural gas found in the USA. Natural gas contains methane and 7% helium. One possible way to obtain the helium would be to burn the methane. Suggest another method, other than diffusion, by which helium could be separated from the mixture of gases in natural gas. ............................................................................................................................................. 2 Explain each of the following in terms of the kinetic particle theory. (a) The rate of most reactions increases at higher temperatures. .................................................................................................................................................... ............................................................................................................................. ....................... ............................................................................................................................. ....................... .................................................................................................................................................... 8 Mrs/Nagwan Essa Topic 1 b) A liquid has a fixed volume but takes up the shape of the container. A gas takes up the shape of the container but it does not have a fixed volume. liquid gas .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .............................................................................................................................................. ..... 10) Compound X is a colourless liquid at room temperature. A sample of pure X was slowly heated from –5.0 C, which is below its melting point, to 90 C, which is above its boiling point. Its temperature is measured every minute and the results are represented on the graph. F 90 C D E temperature B t C –5 C C A time (i) Complete the equation for the equilibrium present in the region BC. X(s) (ii) .................... What is the significance of temperature t C? ......................................................................................................................................... 9 Mrs/Nagwan Essa (iii) Topic 1 What is the physical state of compound X in the region EF? ................ (iv) What would be the difference in the region BC if an impure sample of X had been used? ............................................................................................................................................. 11) Gases diffuse, which means that they move to occupy the total available volume. (i) Explain, using kinetic particle theory, why gases diffuse. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (ii) When the colourless gases hydrogen bromide and ethylamine come into contact, a white solid is formed. CH3CH2NH2(g) + HBr(g) CH3CH2NH3Br(s) white solid The following apparatus can be used to compare the rates of diffusion of the two gases ethylamine and hydrogen bromide. gives off HBr(g) gives off CH3CH 2NH 2(g) A B C cotton wool soaked in conc. hydrobromic acid cotton wool soaked in ethylamine(aq) Predict at which position, A, B or C, the white solid will form. Explain your choice. ............................................................................................................................................. ............................................................................................................................................. 10 Mrs/Nagwan Essa Topic 1 12) Concentrated ammonia solution gives off ammonia gas. Concentrated hydrochloric acid gives off hydrogen chloride gas. Ammonia, NH3, and hydrogen chloride, HCl, are both colourless gases. Ammonia reacts with hydrogen chloride to make the white solid ammonium chloride. Apparatus is set up as shown. cotton wool soaked in concentrated hydrochloric acid cotton wool soaked in concentrated ammonia solution A B C D glass tube After ten minutes a white solid forms in the tube where the gases meet. (a) (i) Write the chemical equation for the reaction of ammonia with hydrogen chloride. ....................................................................................................................................... (ii) Name the process by which the ammonia and hydrogen chloride gases move in the tube. ....................................................................................................................................... (iii) At which point, A, B, C or D, does the white solid form? Explain why the white solid forms at that point. the solid forms at .............. explanation ......................................................................................................................... ............................................................................................................................................. (iv) The experiment was repeated at a higher temperature. Predict how the results of the experiment would be different. Explain your answer. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. 11 Mrs/Nagwan Essa Topic 1 13) Matter can exist as solid, liquid or gas. The arrows show some changes of state. A solid B C liquid gas (a) Name the changes of state represented on the diagram. (i) A ................................................................................................................................... [1] (ii) B ................................................................................................................................... [1] (iii) C ................................................................................................................................... [1] (b) Explain why energy has to be supplied to turn a liquid into a gas. .................................................................................................................................................... .............................................................................................................................................. [1] (c) The diagrams represent the same number of particles of a gas in two containers, D and E, which have different volumes. The two containers are at the same temperature. D E In which container will the pressure be higher? Explain your answer. .................................................................................................................................................... .................................................................................................................................................... ..................................................................................................................................................... 12 Mrs/Nagwan Essa Topic 1 (d) The apparatus shown was set up. plastic trough S solid ammonium dichromate solid silver nitrate water After five minutes, a red solid appeared along the line marked S on the diagram. (i) Explain why a red solid appeared along the line marked S. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. (ii) The experiment was repeated at a higher temperature. What effect, if any, would this have on the time taken for the red solid to appear? Explain your answer. ............................................................................................................................................. ............................................................................................................................................. 13 Mrs/Nagwan Essa Topic 1 14) The graph shows how the temperature of a substance changes as it is cooled over a period of 30 minutes. The substance is a gas at the start. 300 S 250 T V 200 W X temperature 150 / C Y Z 100 50 0 0 10 20 time / minutes 30 Each letter on the graph may be used once, more than once or not at all. (a) Which letter, S, T, V, W, X, Y or Z, shows when (i) the particles in the substance have the most kinetic energy, ....................................................................................................................................... (ii) the particles in the substance are furthest apart, ....................................................................................................................................... (iii) the substance exists as both a gas and a liquid? ....................................................................................................................................... (b) Use the graph to estimate the freezing point of the substance. .............................. C (c) Name the change of state directly from a solid to a gas. .............................................................................................................................................. (d) When smoke is viewed through a microscope, the smoke particles in the air appear to jump around. (i) What term describes this movement of the smoke particles? ....................................................................................................................................... (ii) Explain why the smoke particles move in this way. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................ 14 Mrs/Nagwan Essa 15) Topic 1 (a) Dust particles in the air move around in a random way. (i) What term describes the random movement of the dust particles? ....................................................................................................................................... [1] (ii) Identify the particles in the air which cause the random movement of the dust particles. ....................................................................................................................................... [2] (iii) Explain why the dust particles move in this way. ............................................................................................................................................. ............................................................................................................................................. ....................................................................................................................................... [2] (b) When chlorine gas, Cl 2, is put into a gas jar, it spreads out to fill the gas jar. When bromine gas, Br2, is put into a gas jar, it also spreads out to fill the gas jar. The process takes longer for bromine gas than for chlorine gas. gas jar gas start (i) later What term describes the way that the gas particles spread out? ....................................................................................................................................... (ii) Use data from the Periodic Table to explain why bromine gas takes longer to fill a gas jar than chlorine gas. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................ (iii) Explain why increasing the temperature increases the rate at which the gas particles spread out. ............................................................................................................................................. ............................................................................................................................................. 15 Mrs/Nagwan Essa Topic 1 16) Element X can undergo the following physical changes. gaseous X boiling or evaporation 2 4 liquid X 3 1 solid X (a) (i) Give the scientific name for each of the numbered physical changes. 1 .......................................................................................................................................... 2 .......................................................................................................................................... 3 .......................................................................................................................................... 4 .......................................................................................................................................... (ii) Explain why the changes shown are physical changes. ............................................................................................................................................. ............................................................................................................................................. (iii) One difference between boiling and evaporation is the rate at which the processes occur. State one other difference between boiling and evaporation. ............................................................................................................................................. ............................................................................................................................................ (b) Describe the separation, arrangement and motion of particles of element X in the solid state. separation .................................................................................................................................. arrangement .............................................................................................................................. motion ........................................................................................................................................ 16 Mrs/Nagwan Essa Topic 1 17) Z is a covalent substance. In an experiment, a sample of pure solid Z was continually heated for 11 minutes. The graph shows how the temperature of the sample of pure Z changed during the first 9 minutes. 240 220 200 180 160 140 temperature / C 120 100 80 60 40 20 0 0 1 2 3 4 5 6 7 8 9 10 11 12 time / minutes (c) What is the melting point of pure Z? .............................. C (d) The sample of pure Z began to boil at 9 minutes. It was boiled for 2 minutes. Use this information to sketch on the grid how the temperature of the sample of pure Z changed between 9 minutes and 11 minutes. (e) The sample of pure Z was continually heated between 2 minutes and 5 minutes. Explain, in terms of attractive forces, why there was no increase in the temperature of the sample of pure Z between 2 minutes and 5 minutes. .................................................................................................................................................... .................................................................................................................................................... ................................................................................................................................................... 17 Mrs/Nagwan Essa Topic 1 (f) Describe how the motion of particles of pure Z changed from 0 minutes to 2 minutes. .................................................................................................................................................... .................................................................................................................................................... (g) The experiment was repeated using a solid sample of impure Z. Suggest the differences, if any, in the melting point and boiling point of the sample of impure Z compared to the sample of pure Z. melting point .............................................................................................................................. boiling point ............................................................................................................................... (h) A sample of pure Z was allowed to cool from 120 C to 20 C. The total time taken was 8 minutes. Starting from point , sketch on the grid how the temperature of the sample of pure Z changed between 0 minutes and 8 minutes. 200 180 160 140 120 temperature / C 100 80 60 40 20 0 0 1 2 3 4 5 6 7 time / minutes 18 8 9 10 11 12
