BTEC Nationals Applied Science Student Book 1 PDF

Copyright © 2016. Pearson Education Limited. All rights reserved. Principles and Applications of Science I...

Copyright © 2016. Pearson Education Limited. All rights reserved. Principles and Applications of Science I 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  UNIT 1 Getting to know your unit All scientists and technicians need to understand core science concepts. Assessm ent Chemists need to understand atoms and electronic structure to predict You will be assesse d how a range of chemical substances will react to make useful products. Medical professionals need to understand the structure and workings of through a 90-min ute cells when they think about how the body stays healthy as well as when written exam worth 90 diagnosing and treating illness. marks, which is set and marke d by Pearson. Scientists working in the communication industry need a good understanding of waves. How you will be assessed The external paper for this unit will be split into three sections, each worth 30 marks. ▸▸ Section A – Chemistry (Structure and bonding in applications of science, Production and uses of substances in relation to properties) ▸▸ Section B – Biology (Cell structure and function, Cell specialisation, Tissue structure and function) ▸▸ Section C – Physics (Working with waves, Waves in communication, Use of electromagnetic waves in communication) The paper will contain a range of question types, including multiple choice, calculations, short answer and open response. These question types, by their very nature, generally assess discrete knowledge and understanding of content in this unit. You need to be able to apply and synthesise knowledge from this unit. The questions on the paper will be contextualised in order for you to show you can do this. There will be two opportunities each year to sit this paper: January and May/June. Throughout this chapter, you will find assessment practices that will help you prepare for the exam. Completing each of these will give you an insight into the types of questions that will be asked and, importantly, how to answer them. Copyright © 2016. Pearson Education Limited. All rights reserved. 2 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Getting to know your unit UNIT 1 Unit 1 has four Assessment Outcomes (AO) which will be included in the external Principles and Applications of Science 1 examination. These are: ▸▸ AO1: Demonstrate knowledge of scientific facts, terms definitions and scientific formulae Command words: give, label, name, state Marks: ranges from 12 to 18 marks ▸▸ AO2: demonstrate understanding of scientific concepts, procedures, processes and techniques and their application Command words: calculate, compare, discuss, draw, explain, state, write Marks: ranges from 30 to 45 marks ▸▸ AO3: Analyse, interpret and evaluate scientific information to make judgements and reach conclusions Command words: calculate, compare, comment complete, describe, discuss, explain, state Marks: ranges from 18 to 24 marks ▸▸ AO4: Make connections, use and integrate different scientific concepts, procedures, processes or techniques Command words: compare, comment, discuss, explain Marks: ranges from 9 to 12 marks Here are some of the command words. The rest are found in the specification. Command word Definition – what it is asking you to do Analyse Identify several relevant facts of a topic, demonstrate how they are linked and then explain the importance of each, often in relation to the other facts. Comment Requires the synthesis of a number of variables from data/information to form a judgement. More than two factors need to be synthesised. Compare Identify the main factors of two or more items and point out their similarities and differences. You may need to say which are the best or most important. The word Contrast is very similar. Define State the meaning of something, using clear and relevant facts. Describe Give a full account of all the information, including all the relevant details of any features, of a topic. Discuss Write about the topic in detail, taking into account different ideas and opinions. Evaluate Bring all the relevant information you have on a topic together and make a judgement on it (for example, on its success or importance). Your judgement should be clearly supported by the information you have gathered. Explain Make an idea, situation or problem clear to your reader, by describing it in detail, including any relevant data or facts. Copyright © 2016. Pearson Education Limited. All rights reserved. 3 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Getting started Scientists working in a hospital laboratory use a range of core scientific principles. Write a list of core scientific principles you think they might need and why they are useful. Remember these may be to do with physics, chemistry or biology. When you have completed this unit, see if you can add any more principles to your list. A Periodicity and properties of elements A1 Structure and bonding in applications in science The electronic structure of atoms You should already know about the structure of an atom. The nucleus contains positive protons and neutral neutrons. Surrounding the nucleus are energy shells containing negative electrons. You should also know that protons and neutrons both have a relative mass of 1 and that the relative mass of an electron is almost 0. Lab technicians need to understand the electronic structure of atoms. They can use this knowledge to predict how chemical substances will behave and react. The protons and the neutrons are found in the nucleus at the centre of an atom. The electrons are in shells or energy levels surrounding the nucleus. Each shell can hold electrons up to a maximum number. When the first shell is full, electrons then go into the second shell and so on. The maximum number of electrons in each shell is shown 23 Na in Table 1.1. 11 ▸▸ Table 1.1: Maximum number of electrons for each electron shell Electron shell Maximum number of electrons 12 n 11 p 1 2 2 8 3 18 4 32 5 50 ▸▸ Figure 1.1: Simple atomic Copyright © 2016. Pearson Education Limited. All rights reserved. A sodium atom containing 11 electrons has an electron arrangement of 2, 8, 1. structure of sodium This can be represented by a simple Bohr diagram, as shown in Figure 1.1. This is the simple version of electron structure you will have seen at Key Stage 4. Key term Under Bohr’s theory, an electron’s shells can be imagined as orbiting circles around the Orbitals – regions where nucleus. there is a 95% probability However, it is more complicated than this. Electrons within each shell will not have the of locating an electron. An same amount of energy and so the energy levels or shells are broken down into sub- orbital can hold a maximum shells called orbitals. These are called s, p, d and f orbitals. The orbitals have different of two electrons. energy states. The Aufbau principle states that electrons fill the orbital with the lowest available energy state in relation to the proximity to the nucleus before filling orbitals with higher energy states. This gives the most stable electron configuration possible. 4 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 Electrons have the same charge and so repel each other, so if there is more than one Principles and Applications of Science 1 Key terms orbital in an energy level (sub-shell) they will fill them singly until all the orbitals in that sub-shell have an electron in them and then they will pair up. Electron configuration – the Figure 1.2 shows the energy levels of the shells, sub-shells and orbitals for an atom. distribution of electrons in an atom or molecule. Atomic Energy Levels 4f Spin – electrons have two 4d possible states, ‘spin up’ and n54 4p ‘spin down’. In an orbital, each 3d electron will be in a different 4s 3p Energy n53 ‘spin state’. 3s 2p n52 2s Key s n51 n 5 shell ▸▸ Figure 1.2: Energy levels of the shells subshells and orbitals for an atom Step by step: Electron structures 8 Steps When writing out electron structures, you should follow these rules. Half arrows are used to represent each electron in the orbitals. They are drawn facing up and down as each electron in an orbital will have a different spin. 1 The electrons sit in orbitals within the shell. Each orbital can hold up to two electrons. 2 The first shell can hold two electrons in an s-type orbital. 3 The second shell consists of one s-type orbital and three p-type orbitals. This diagram represents lithium. 2p 2p 2p 2s2 Copyright © 2016. Pearson Education Limited. All rights reserved. 1s2 4 The third shell consists of one s-type orbital, three p-type orbitals and five d-type orbitals. 5 Electrons fill the lowest energy level orbitals first. 6 Where there are several orbitals of exactly the same energy, for example, the three 2p orbitals in the second shell, then the electrons will occupy different orbitals wherever possible. 5 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  7 So the electronic structure of nitrogen (which has 7 electrons) is: 2p1 2p1 2p1 2s2 1s2 8 and the electronic structure of a sodium atom (which has 11 electrons) becomes: 3s1 2p2 2p2 2p2 2s2 1s2 Assessment practice 1.1    Copy out the following table and complete the electronic structures for the elements. Three have been done for you. Element Number of electrons Electron structure Hydrogen 1 1s1 Helium Lithium Boron Copyright © 2016. Pearson Education Limited. All rights reserved. Carbon 6 1s2 2s2 2p2 Oxygen 8 1s2 2s2 2p4 Magnesium Chlorine Calcium P ause point Try explaining what you have learned so far. Hint Close the book and write out all the key concepts you have learned so far. What do you know about electronic structure? Could you draw the electronic structure for calcium? Extend What is new compared to what you learned at level 2 about electronic structure? 6 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 One of the tasks of a lab technician is to make up solutions ready for experiments or for Principles and Applications of Science 1 making products. Different types of compounds dissolve in different types of solvents depending on what type of bonding is in the compound. The lab technician must know what type of compound they are using in order to select the correct solvent. Ionic bonding Noble gases (elements in group 0 of the periodic table) have a stable electronic configuration. They have full outer shells. This means they do not react easily and most do not react at all. Elements in the other groups do not have full outer shells. This means that they react to gain stable electronic configurations. Ionic bonding occurs when an atom of an element loses one or more electrons and Key term donates it to an atom of a different element. The atom that loses electrons becomes Ionic bonding – electrostatic positively charged and the atom that gains electron(s) become negatively charged attraction between two because of the imbalance of protons and electrons. oppositely charged ions. For example, the bonding in sodium chloride is ionic. This means that the sodium atom loses the electron in its outer shell to become the positively charged sodium ion, Na+, with the same electron configuration as neon. Chlorine gains an electron to become the negatively charged chloride ion, Cl−, with the same electron configuration as argon. This means that both the sodium ion and the chloride ion have a full outer shell and become stable. The positive charge on the sodium ion and the negative charge on the chloride ion are attracted. Na Cl Na1 Cl2 ▸▸ Figure 1.4: Lattice structure of sodium chloride Copyright © 2016. Pearson Education Limited. All rights reserved. Ionic bond ▸▸ Figure 1.3: Electron transfer and bonding in sodium chloride Key terms Figure 1.3 shows bonding using a dot and cross diagram. The dots and crosses Electrostatic attraction represent electrons in the shells. – the force experienced by oppositely charged particles. Ions containing more than one element can also be formed. For example, in sodium It holds the particles strongly hydroxide, Na+ bonds with the hydroxide ion (OH)–. together. The opposite charges on the ions are what hold them together. This is electrostatic Giant ionic lattice – a regular attraction. arrangement of positive The opposite charged ions in sodium chloride form a giant ionic lattice (see Figure ions and negative ions, for 1.4) where the ions are arranged in a regular pattern. example, in NaCl. 7 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  The strength of the electrostatic force and, therefore, of the ionic bond is dependent on the ionic charge and the ionic radii of the ions. The more electrons a positive ion has, the more shells it will have. If an ion has more shells, then its radius will be bigger than an ion with fewer shells. The electrostatic force is stronger when the ionic charge is higher. However, the force becomes weaker if the ionic radii are bigger. This is because, when the ionic radius is bigger, the ionic charge is spread over a larger surface area. Covalent bonding Covalent bonding usually occurs between atoms of two non-metals. A covalent bond forms when an electron is shared between the atoms. These electrons come from the top energy level of the atoms. A chlorine molecule has a covalent bond (see Figure 1.5). The highest shell in each chlorine atom contains seven electrons. One electron from the highest shell in each atom is shared to give each chlorine atom the electron configuration of argon with a stable full outer shell. Chlorine, Cl2 (a)     (b)     (c) Cl Cl H H O O ▸▸ Figure 1.5: Covalent bonding in (a) a chlorine molecule, (b) a hydrogen molecule and (c) oxygen moelcule Multiple bonds In some covalent molecules, both sharing electrons come from one atom. This is called a dative (coordinate) covalent bond (see Figure 1.6). O O ▸▸ Figure 1.6: The double bonds between the oxygen are formed by two shared pairs of electrons. If three pairs of electrons are shared, then a triple covalent bond is formed. A triple bond is present in a nitrogen molecule (see Figure 1.7). Copyright © 2016. Pearson Education Limited. All rights reserved. N N ▸▸ Figure 1.7: Triple bond in a nitrogen molecule Single bonds have a greater length than double bonds and double bonds have a greater length than triple bonds. The shorter the length of the bond, the stronger the bond is. Therefore, triple bonds are stronger than double or single bonds. A single bond between carbon atoms has a length of 154 pm and a bond energy of 8 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 347 kJ mol−1. A double bond between carbon atoms has a length of 134 pm and a bond Principles and Applications of Science 1 Key term energy of 612 kJ mol−1. A triple bond between atoms has a bond length of 120 pm and a bond energy of 820 kJ mol−1. Lone pair – a non-binding pair of electrons. An ammonium ion contains a dative bond (see Figure 1.8). When ammonia reacts with hydrochloric acid, a hydrogen ion from the acid is transferred to the ammonia molecule. A lone pair of electrons on the nitrogen atom forms a dative covalent bond with the hydrogen ion. positive charge because negative charge because only the hydrogen nucleus the hydrogen has left its has moved to the nitrogen electron behind H H 1 2 H N H Cl H N H Cl H H lone pair dative covalent bond Key term of electrons Organic compound – a ▸▸ Figure 1.8: Dative bond formation in reaction between ammonia and hydrogen chloride compound that contains one or more carbons in a carbon Covalent bonding in organic molecules chain. Carbon makes four covalent bonds so it forms many compounds which are called organic compounds. Methane has the formula CH4. Each carbon atom bonds covalently with four hydrogen H atoms. The carbon gains the stable electron structure of neon and hydrogen gains the stable electron structure of helium. These four bonds mean that methane is not a flat molecule. It has a tetrahedral structure C (see Figure 1.9). This is because the bonds are as separated from each other as possible, H because the negative electron pairs repel each other, with each bond angle being 109.5o. H If you were to build a model of a methane molecule, it would have a 3D shape with a H hydrogen pointing down towards you, one pointing down away from you, one pointing ▸▸ Figure 1.9: Tetrahedral structure down to the side and one pointing up, all connected to the carbon in the centre. of methane Step by step: Building models of organic compounds 3 Steps Copyright © 2016. Pearson Education Limited. All rights reserved. 1 Use molecular model kits to build models of the following organic compounds. methane CH4 ethane CH3CH3 propane CH3CH2CH3. 2 Write down what you notice about the structure of these molecules. 3 Look at one of the carbons in each molecule and the atoms bonded to it. Write down what you notice about the shape. 9 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Organic compounds with three or more carbons in a chain cannot be linear because of the tetrahedral structure around each central carbon (see Figure 1.10). H H H C C H H C C H H H H H ▸▸ Figure 1.10: A butane model Metallic bonding Metals are giant structures of atoms held together by metallic bonds. The metal Key term structure is a regular lattice (see Figure 1.11). Delocalised electrons – Metallic bonding is caused because the electrons in the highest energy level of a metal electrons that are free to atom has the ability to become delocalised. They are free to move through the metal in move. They are present in a ‘sea’ of electrons. This gives the metal nuclei a positive charge, which is attracted to the metals and are not associated negative charge on the delocalised electrons. There is a very strong force of attraction with a single atom or covalent between the positive metal nuclei and the negative delocalised electrons. However, the bond. forces in metallic bonding are not as strong as in covalent or ionic bonding. free electrons from higher energy level of metal atoms 11111 1111 11111 metal ions ▸▸ Figure 1.11: Metallic structure The metal structure is a lattice of positive ions with electrons flowing between these ions. Copyright © 2016. Pearson Education Limited. All rights reserved. P ause point What have you learned about bonding? Hint Describe the differences between ionic, covalent and metallic bonding. Extend Give two examples of elements, compounds or molecules with each type of bond. The electronegativity of two atoms will determine what type of bond will form between them. Key term Electronegativity – the tendency of an atom to attract a bonding pair of electrons. 10 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 Atoms that have similar electronegativities form covalent bonds. Principles and Applications of Science 1 There is a strong electrostatic attraction between the two nuclei and the shared pair(s) of electrons between them. This is the covalent bond. Both atoms have the same electronegativity, and so the electrons are equally shared. The molecule is non- polar (see Figure 1.12). Hydrogen only has one shell containing one electron. This electron from each hydrogen is shared to give each atom the electronic configuration of helium. Oxygen only has six electrons in its highest energy shell. Each oxygen atom shares two of its electrons with another oxygen atom, giving both eight electrons in their outer shell. This makes the atoms in the oxygen molecule stable. Positive nucleus 1 1 Attraction ▸▸ Figure 1.12 : Non-polar covalent bond In most covalent compounds, the bonding is polar covalent (see Figure 1.13). The shared electrons are attracted more to one nucleus in the molecule than the other. The atom with the higher electronegativity will attract the electrons more strongly. This gives the atom a slight negative charge. The other atom in the molecule will have a slight positive charge. Key terms Non-polar molecule – a molecule where the electrons are distributed evenly throughout the molecule. Polar molecule – a molecule with partial positive charge in one part of the molecule and similar negative charge in another part due to an uneven electron distribution. Copyright © 2016. Pearson Education Limited. All rights reserved.  H Br  ▸▸ Figure 1.13: Polar covalent bond 11 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  As the difference in electronegativity between the atoms increases, the bond will become more polar. See Figure 1.14. Type of bond pure covalent polar covalent ionic zero low high Difference of electronegativity ▸▸ Figure 1.14: Electronegativity spectrum The electronegativities of some of the common elements you will use are shown in Table 1.2. It increases across a period and decreases down a group. ▸▸ Table 1.2: Electronegativities of elements Element Electronegativity Fluorine 3.98 Oxygen 3.44 Nitrogen 3.04 Carbon 2.55 Chlorine 3.16 Hydrogen 2.20 Lithium 0.98 Sodium 0.93 Key terms Intermolecular forces Intermolecular forces – Intermolecular forces also affect how chemical substances behave. A laboratory the attraction or repulsion technician must know where these are present and understand how they will affect between neighbouring the behaviour and reactions of chemical substances they are working with. molecules. London dispersion forces Dipole – separation of One type of intermolecular force is called London dispersion forces (also called charges within a covalent temporary dipole – induced dipole forces). They are weak forces present between molecule. non-polar covalent molecules. They are less than 1% of the force of a covalent bond Copyright © 2016. Pearson Education Limited. All rights reserved. (see Figure 1.15). When the electron distribution in a molecule becomes non-symmetrical (i.e. there are more electrons at one end of the molecule than the other), then one end of the molecule can become more positive and one end can become more negative. This causes a temporary dipole. The positive and negative charge in the dipole can disturb the electrons in a nearby molecule, repelling the electrons and so causing (inducing) a dipole in that molecule. The molecule with the temporary dipole and the molecule with the induced dipole attract each other and pull the molecules together. The forces are temporary because the electrons are constantly moving, so electron density in any part of a molecule is constantly changing. Larger molecules have more electrons which can move further so more temporary dipoles can form, meaning the force is bigger. more electrons → more movement → bigger dipoles → stronger attraction 12 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 Principles and Applications of Science 1 H H H H Molecule A Molecule B Even distribution of electrons throughout both molecules. H H H H Molecule A Molecule B Uneven distribution of electrons in Molecule A causes a temporary dipole in the molecule. This will induce a dipole in molecule B as the electrons in Molecule B will be attracted to the positive end of Molecule A. H H H H Molecule A Molecule B This forms a temporary dipole – induced dipole. ▸▸ Figure 1.15: London dispersion forces London dispersion forces are the only forces that exist between noble gases and non‑polar molecules. Assessment practice 1.2    Pentane (C5H12) boils at 309 K and ethane (C2H6) boils at 185 K. This means that pentane is a liquid at room temperature (293 K) and ethane is a gas. Explain why pentane is a liquid at room temperature but ethane is a gas. Dipole-dipole forces Another form of van der Waals forces are dipole-dipole forces. These are permanent Key term forces between polar molecules (see Figure 1.16). Polar molecules have a permanent negative end and a permanent positive end. These oppositely charged ends attract Van der Waals forces – all Copyright © 2016. Pearson Education Limited. All rights reserved. each other. Dipole-dipole forces are slightly stronger than London dispersion forces but intermolecular attractions are are still weak in comparison to a covalent bond. The force is about 1% of the strength van der Waals forces. of a covalent bond. Molecules that have permanent dipole-dipole forces include hydrogen chloride, HCl, and iodine monochloride, ICl. In both cases, the chlorine atom in the molecule is slightly negative. The hydrogen and iodine atoms are slightly positive. d1 d2 d1 d2 attraction ▸▸ Figure 1.16: Dipole-dipole forces There are dipole-dipole forces between molecules of iodine monochloride (ICl). 13 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Hydrogen bonding The strongest form of intermolecular force is a hydrogen bond. These are a special type of dipole-dipole bond and are forces that are about 10% of the strength of a covalent bond. Hydrogen bonds will form when compounds have hydrogen directly bonded to fluorine, oxygen or nitrogen. This is because there is a large difference in electronegativity between hydrogen and these three atoms. This large difference means that very polar bonds are formed so the molecules have permanent dipoles. When two Hd1 of these molecules are close together, there will be an attraction between the positive d2 N d1 end of one and the lone pair of electrons of the other. This is a hydrogen bond. d2 d1 H N H Hd1 This is different to other dipole-dipole forces because there are inner bonding electrons. d1 H d1 The single electron in the hydrogen atom is drawn to the nitrogen (see Figure 1.17), H hydrogen bond oxygen or fluorine atom. There are no non-bonding electrons shielding the nucleus of ▸▸ Figure 1.17: Hydrogen bond in the hydrogen. The hydrogen proton is strongly attracted to the lone pair of electrons on ammonia the nitrogen atom of another molecule. Discussion Hydrogen bonding in water is the reason why water has such unusual properties. For example, solid water is less dense than liquid water, it has a higher boiling point than expected, it is a good solvent for many chemical substances. Research how hydrogen bonding is caused in a water molecule. Work in pairs to list properties of water due to the hydrogen bonding. In groups, explain the properties to other pairs of learners. P ause point Try to describe all the different types of intermolecular forces to a partner. Hint Draw a table showing the different types of intermolecular bonding and their properties. Extend Explain how each type of intermolecular bond affects the properties of the molecules. Quantities used in chemical reactions Balancing equations All chemical reactions can be written as a balanced equation using the chemical formulae for the reactants and the products involved in the reaction. Symbols for elements can be found in the periodic table. The numbers in the formulae show how many atoms of each element there are. You can use the periodic table to predict whether the compound is covalent or ionic. The group numbers will show you how many electrons the atom needs to lose or gain or share to form a bond. Copyright © 2016. Pearson Education Limited. All rights reserved. The equation must balance like a maths equation. There should be the same number and types of atoms on both sides of the equation. Step by step: Writing a balanced equation 5 Steps 1 Write the equation as a word equation, including all the reactants and all the products. 2 Write out the formulae for each substance in the reaction. Note that gaseous elements (except those in group 0) like hydrogen and oxygen are diatomic (molecules with two atoms), so they must be written as H2 and O2. Metal elements and the noble gases are monatomic (one atom). 14 Principles and Applications of Science 1 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Learning aim A UNIT 1 Principles and Applications of Science 1 3 Write out the number of each element on both sides. 4 Make the number of each atom equal on each side. Remember that you cannot change the formula of the compounds. To increase the number of atoms of a particular element, you must place a number in front of the compound it is in. This will affect the number of atoms of all the other elements in the compound. 5 Check that there is the same number of atoms of each element on both sides. Worked Example 1 Write a balanced equation for the following reaction. Ethanol + oxygen → carbon dioxide +water Step 1: Write out the formulae for each substance in the reaction. C2H5OH + O2 → CO2 + H2O Step 2: Write out the number of each element on both sides. left-hand side right-hand side C2 C1 H6 H2 O3 O3 Step 3: Make the number of each atom equal on each side. In this case, start by putting a 2 in front of the carbon dioxide to equal out the carbons. This will also add two more oxygens to the right-hand side. C2H5OH + O2 → 2CO2 + H2O left-hand side right-hand side C2 C12 H6 H2 O3 O35 Put a 3 in front of the water to balance the hydrogens. Remember to add to the oxygens again. C2H5OH + O2 → 2CO2 + 3H2O left-hand side right-hand side Copyright © 2016. Pearson Education Limited. All rights reserved. C2 C12 H6 H26 O3 O357 The carbons and hydrogens are now equal on both sides, so you must multiply the oxygens on the left-hand side to finish balancing the equation. C2H5OH + 3O2 → 2CO2 + 3H2O left-hand side right-hand side C2 C12 H6 H26 O37 O357 This equation is now balanced. 15 Hartley, Joanne, et al. BTEC Nationals Applied Science Student Book 1, Pearson Education Limited, 2016. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/solihull-ebooks/detail.action?docID=4771940. Created from solihull-ebooks on 2023-10-03 08:16:03.  Write a balanced equation for the following reaction: P ause point buta