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Y11 2.3 Atomic Structure, Analysis and Quantitative chemistry Where to find resources: Look in k:\staff only\science\chemistry\AQA GCSE Chemistry Here you will find the resources mentioned here and the learning objective sheets. Big red folder in prep room with a series of worksheets and practicals. Yellow folder in prep room with practicals for C2, each one allocated a code to make ordering them easier. Longman p118-133 and Nelson Thorne textbooks p138-155 are available. There are lots of good questions There is a teacher guide for the GCSE chemistry course in the prep room, it is a yellow book giving a good deal of information about the course and suggested teaching order broken down into lessons. It looks like this: C2.3 Atomic Structure, Analysis and Quantitative Chemistry Learning outcomes Subject Area Foundation 1 Atomic Structure 2 Analysing substances Know the use of mass number and atomic number Know the mass of each sub atomic particle. Atoms of the same element with a different number of neutrons are known as isotopes Elements and compounds can be detected using instrumental methods Intermediate Chemical analysis can be used to identify additives in foods gas chromatography allows the separation of a mixture of compounds 3 Quantitative Chemistry Know that is not always possible to obtain the calculated amount of product in a chemical reaction because: (a) The reaction is reversible and does not go to completion (b) Some of the product is lost when it is separated from the reaction mixture (c) Some of the reactants will react in different ways to the expected reaction The amount of product is known as the yield The relative atomic mass(Ar) of an element compares the mass of atoms of that element with the mass of a126C isotope The Ar value is an average value of the isotopes of an element Instrumental methods are accurate, sensitive and can be carried out rapidly Higher Instrumental methods are useful when the amount of sample is small The relative formula mass of a substance in grams is known as one mole of that substance The relative formula mass (Mr) is the sum of the relative atomic masses of the atoms shown in the formula that substance The mass spectrometer can give the relative molecular mass of each of the substances from the column Paper chromatography can be used to identify artificial food colours The time taken for a substance to travel through the column can be used to identify the substance The output from a gas chromatography column can be inked to a mass spectrometer to identify the substances The percentage of an element in a compound can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound .When the actual yield is compared to the theoretical yield it is known as the percentage yield Some chemical reactions are reversible, in which the products of the reaction can react to produce the original reactants. These reactions are represented by an equation such as : A+B C+D Be able to calculate empirical formula from the masses or percentages of the elements in a compound Be able to calculate the masses of individual products in a chemical reaction from the mass of a given reactant and the balanced equation Calculate percentage yield from Actual yield x 100% Theoretical yield Overview This topic covers some very fundamental ideas in chemistry. The first part is a recap of atomic structure and the nature of sub- atomic particles, particularly in terms of the mass of these particles and the ideas of atomic number and Mass number. The idea of isotopes and the definition of relative atomic mass (Ar) is now introduced. Higher candidates will have to calculate the Mr for compounds from a given formula and the concept of the mole is introduced. The next part of the unit relates to analysis in terms of chromatography both paper and gas chromatography. The idea of a mass spectrometer attached to a GC is used to reinforce the idea that compounds can be identified from their Mr value, determined from the molecular ion peak of a mass spectrometer trace for higher candidates The last section is on quantitative chemistry and introduces the idea of various calculations for higher tier with calculations on empirical formula as well as reacting mass calculations and percentage yield All candidates need to know that there are reasons why not all reactants are converted to products as they could be lost in transfer, bi- products can be produced or that the reaction is reversible C2.3 - Atomic Structure, Analysis and Quantitative chemistry Lesson 1 Aims Recap ideas from C1.1 Identify each of the three subatomic particles – protons, neutrons and electrons Recall location, mass and charge of each of the three subatomic particles Identify the numbers of protons, neutrons and electrons for each element in the periodic table including the electron arrangement up to atomic number 20 – calcium Identify the numbers of protons, neutrons and electrons for isotopes of a given element Language and definitions Term Proton Neutron Electron Nucleus Shell / energy level Atomic number Mass number Isotope Definition A sub atomic particle with a mass of 1 and a charge of +1 A sub atomic particle with a mass of 1 and no charge A sub atomic particle with no mass and a charge of -1 The centre of an atom where protons and neutrons are found The location of an electron in an atom Number of protons in an atom Number of protons plus number of neutrons in an atom Atoms of the same element with a different number of neutrons Resources Resource (type) Description Periodic table (WS) A period table for use in GCSE chemistry / science C2.3Fundamentals (PPT) Atomic Structure Card loop (WS) L- C2 3.1c Atomic Structure 1 and 2 (WS) L C2 3.1 b and d A WS which reviews the properties and arrangement of sub atomic particles first covered in C1.1 A worksheet to practice calculating the number of sub atomic particles from the mass number and atomic number and demonstrate difference between isotopes Location Electronic copy in folder In resources folder In resources folder In resources folder In resources folder C -2.3 - Atomic Structure, Analysis and Quantitative chemistry Lesson 2 Aims Use the term of relative atomic mass (Ar) Understand that relative atomic mass compares the mass of atoms with the 12C isotope Understand that the relative atomic mass is the average value for the isotopes of the element Be able to calculate relative formula mass (Mr) of a substance using Ar for each element present in the substance Describe that the mass of one mole of a substance equals the M r in grams Use the relationship mass = Mr x number of moles Language and definitions Term Relative atomic mass (Ar) Relative formula mass (Mr) Mole Definition The relative mass of an atom of a given element compared to an atom of the 12C isotope ( This value is an average which takes account of all the isotopes of the element and their relative abundance This relative mass of a substance is calculated by adding up the relative atomic mass of each atom in the formula for the substance The number of particles found in 12g of a of 12C atoms (6.02 x 1023) Resources Resource (type) The relative mass of animals L C2 3.1a Relative masses (worksheet) LC2 3.2a Finding moles by weighing (practical W/S) L C2 3.2b Using moles / Relative masses and moles (W/S) L C2 3.2c and L C2.3d Also echalk - moles Description This is a good introduction to relative atomic mass particularly for students who struggle with abstract concepts This is simply practice at calculating Relative formula mass If you have time this practical breaks up these theory lessons and may help some students visualise the concept of a mole These worksheets give plenty of examples of questions which allow students to practice questions linking Mr and moles The echalk animation makes a good activity for whole class (a good starter/plenary activity) Location In resources folder In resources folder In yellow chemical practicals folder – In resources folder C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 3 Aims Be able to complete reacting mass calculations (higher) Work out the percentage of an element within a compound by its mass Explain what the empirical formula of a compound is (higher) Be able to calculate the empirical formula from the mass or percentages of the elements in a compound Language and definitions Term Empirical formula Molecular formula Definition The simplest ratio of the relative number of atoms of each element in a compound expressed as a formula The formula of a compound which expresses the actual number of atoms of each element within one molecule Resources Resource (type) Empirical formulae 1 and 2 L C2 3.5b and c (W/S) (Higher) Reacting Mass calculations 1 and 2 (W/S) L C2 3.3 a and b Description These are difficult questions used to practice empirical formula calculations and use of moles Plenty of quite difficult calculations to work through Location In resources folder In resources folder C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 4 Aims Explain why instrumental methods are used to analyse substances Explain how food colourings can be analysed using paper chromatography Describe how gas chromatography can be used to separate mixtures (higher) describe how substances can be used using mass spectroscopy Language and definitions Term Instrumental techniques Gas chromatography Mass spectroscopy Molecular ion Definition An automated method of analysing chemicals A method of analysis that separates chemicals in a very small sample in order to identify their constituents Analytical technique that breaks up molecules into ions and measures their mass/charge ratios The ion formed when a molecule is passed through a mass spectrometer that has not been fragmented Paper Analytical technique that that separates compounds by their relative speeds chromatography in a solvent as it spreads through paper Retention time Time taken for a substance to reach the detector at the end of a gas chromatography column Resources Resource (type) C 2 3.6a Paper Chromatography (practical) C2 3.6b Gas chromatography (W/S) C2 3.6c (Higher) Mass spectroscopy C2 3.6d(higher) Instrumental analysis of food Description A simple practical where the food colourings are analysed using paper chromatography A simple worksheet which shows the use of GC to separate mixtures and shows retention time Powerpoint Chromatography This worksheet shows some examples of mass spectra and the idea of molecular ion peak but you do not need to know about fragmentation peaks! This worksheet is a good round up for all the ideas used in this analysis section and Location In yellow chemical practicals folder – In resources folder GC/MS http://alpha.chem.umb.edu/chemistry/ch361/G C%20and%20GC-MS.ppt In resources folder In resources folder In resources folder revises all the important terms C2.3 - Atomic Structure, Analysis and Quantitative chemistry - Lesson 5 and 6 Aims The amount of product obtained during a reaction is known as the yield The maximum amount of product that can be formed is known as the theoretical yield The percentage yield is = actual yield x 100 % theoretical yield The reaction may not go to completion because it is reversible Some of the product may be lost when it is separated from the mixture Some of the reactants may in different ways to the expected reaction and therefore produce different products Language and definitions Term Actual yield Theoretical yield Percentage yield Reversible reaction Definition Actual yield of product obtained during a chemical reaction Maximum yield obtainable in a chemical reaction based on the reacting mass calculation The yield expressed as a percentage of product obtained divided by the theoretical yield x 100% A reaction in which the products can re-form the reactants Resources Resource (type) C2 3.4b Measuring a percentage yield /Practical C2 3.4a Reversible reactions / practical Description Location This practical involves weighing Yellow practical folder magnesium in a crucible and then heating it to make magnesium oxide and weighing it to calculate percentage yieldneeds accurate balance These 3 practicals show Yellow practical folder examples of reversible reactions – some significant risk assessment for these reactions