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CFE Chemistry Unit 1 Chemical Changes & Structure Smithycroft Secondary School National 4 Chemistry Unit 1 Chemical Changes & Structure Name -1- CFE Chemistry Unit 1 Chemical Changes & Structure Chemical Reactions I can state the 4 signs of a chemical reaction I can explain what is an element, compound and mixture Chemistry is the study of chemical substances - what things are made of, how they react with each other and how one substance can be changed into another. List the four signs of a chemical reaction 1. 2. 3. 4. Lesson 2 Reaction rates I can name four things which can speed up a chemical reaction I can draw and interpret graphs to compare reaction rates Chemical reactions can occur at different speeds or rates. Consider the following chemical reactions and complete the table. Decide if they are slow, medium or fast and give another example. Does your partner agree? Reaction Speed or rate Iron nail rusting Bomb Explosion Making Toast List the four ways of speeding up a chemical reaction 1. 2. 3. 4. -2- Another Example CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 3 Inside the atom I can name the 3 subatomic particles, explain where they are found in an atom and state their charge I can explain why atoms are electrically neutral All elements are made up of small particles called ATOMS, with each element made from its own unique type of atom. However, all atoms have a similar atomic structure. Pupil Activity: Investigating atomic structure Complete the diagram by adding appropriate labels. Even though atoms have these sub-atomic particles they are mostly composed of empty space!! Inside the atom Imagine we enlarge an atom until it is the size of a football pitch. The electrons would orbit through the goal posts, the nucleus would be the size of a tennis ball on the centre spot and all the rest of the pitch would be empty space!!! -3- CFE Chemistry Unit 1 Chemical Changes & Structure Complete the table below showing the location and appropriate charges of subatomic particles. Particle Charge Where is it found in atom Electron Neutron Proton Investigating atomic structure Using the information in the table - complete the drawing in the last column of the table. The first one has been done for you. Element Protons Neutrons Electrons Helium 2 2 2 Atom Drawing Electrons Protons neutrons Lesson 3 continued Inside the atom Element Protons Neutrons Electrons Hydrogen 1 0 1 Carbon 6 6 6 -4- Atom Drawing CFE Chemistry Boron Unit 1 Chemical Changes & Structure 5 6 5 Can you explain why atoms are electrically neutral from table above? ____________________________________________ Did you notice that the electrons are in layers? We will discuss this further in electron arrangements. Lesson 4 Atomic & Mass Number I can explain what an atomic number and a mass number are in an atom I can state the mass of subatomic particles Look at the periodic table on page 8 of chemistry data book. Notice that each element has a number above it - this is its unique ATOMIC NUMBER. The atomic number used to be called the proton number, as it tells us the number of protons in the nucleus. Atoms are electrically neutral because the number of protons (+ve charge) is the same as the number of electrons (-ve charge). Investigating atomic number Using your knowledge of atoms complete the table below: Atomic Element Symbol Number O 12 Lithium -5- Protons Electrons CFE Chemistry Unit 1 Chemical Changes & Structure Be 14 Flourine The mass of an atom is very small, at 0.000000000000000000000000167g. This means that a single crystal of an element has millions of atoms! Atoms are so small that they are not measured in grams they are measured in atomic mass units (amu). Atomic & Mass Number Atomic Mass Complete the table. Particle Charge Approximate Where is it mass (a.m.u.) found in atom Electron Neutron Proton Did you notice that an electron has a mass of almost zero? This means that 99.9% of the mass of an atom is located in the nucleus. The number of protons + neutrons in an atom is known as the MASS NUMBER. Chemists use a special system for writing the mass number, atomic number and symbol for an element. It is Mass no. Atomic No. X called nucleotide notation: The mass number is given on top with the atomic number written underneath. The atomic number is always the smaller number! -6- CFE Chemistry Unit 1 Chemical Changes & Structure Atomic & Mass Number Can you work out the number of protons, electrons and neutrons in an atom? Complete the table below using the information provided. Nucleotide Protons Neutrons Electrons 23 Na 11 12 C 6 16 O 8 35 Cl 17 4 He 2 1. 2. What is meant by the atomic number? What is meant by the mass number? Atom story board Choose one of the elements from the table above and complete a story board about your element. Remember to include: Number of protons, neutrons, electrons Location of subatomic particles Label nucleus Atomic number -7- CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 5 Electron Arrangements I can state and draw the electron arrangements for the first 20 elements I can state that elements with the same outer electrons are grouped together. How are the electrons arranged in an atom? Each element has a unique number of electrons orbiting the nucleus of its atoms. This number is the same as its atomic number (number of protons in the nucleus). How are these electrons arranged around the nucleus? 1st energy level 2nd energy level 3rd energy level There is a maximum of 2 electrons in the first shell, 8 in the second and 18 in the third shell. The electrons are organised in these shells or layers and are known as the electron arrangement or electron configuration. The electron arrangements for all atoms can be found in the data booklet. -8- CFE Chemistry Unit 1 Chemical Changes & Structure Electron Arrangements Investigating electron arrangement Using your data booklet, show the electron arrangement for the first 10 elements. Draw these in your jotter. Complete the following diagram to briefly describe how the electrons are arranged in an atom. __________ atom _______________ first _____ level 11+ ______ ______ level third ______ level Explain how the layers are numbered. The number of electrons in the last or furthest away layer is called the number of outer electrons. -9- CFE Chemistry Unit 1 Chemical Changes & Structure Electron Arrangements How does the electron arrangement affect the chemical properties of each element? Consider the following questions: 1. What is the electron arrangement of the sodium atom? 2. What do you notice about all the group 1 electron arrangements? 3. How is group 0 different from other groups with respect to outer electrons? 4. Can you describe a general rule that links the number of electrons to the group number? 5. Can you explain how the outer number of electrons or group number affects the way in which an atom reacts and so affects its chemical properties? 6. Without looking at a periodic table, say which period and in which group you would place the element with electron arrangement 2, 8, 18, 18, 3. Now check to see if you were correct. - 10 - CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 6 Investigating bonding I can state that compounds are held together by bonds I can name the two different types of bonding when elements join together, which affect the properties of their compounds Atoms join together and form bonds between them to make molecules. Investigating bonding Aim: To identify whether compounds which either contain 2 non-metals or metals and non-metals behave differently due to their bonding Substance Contains metal / Conducts electricity Melting point non metals? Solid High / low Solution Sodium Chloride Gelatin Wax Glucose Copper Chloride Potassium Bromide Name two differences between the properties of compounds containing either 2 non-metals or a metal and a non-metal. 1. 2. - 11 - CFE Chemistry Unit 1 Chemical Changes & Structure Investigating bonding How do non-metal atoms bond together? Non-metal atoms like hydrogen and oxygen join to form water by bonds called covalent bonds. What is a covalent bond? Negative Electron Positive nucleus e e + H + H Area of attraction Both positive nuclei attracted to shared pair of negatively charged electrons A covalent bond is the attraction of two nuclei for a shared pair of electrons. In covalent bonding electrons are shared between atoms. As well as having it’s own name, each substance can also be represented by a chemical formula. Here is water: Key: Water Formula: H2O Ammonia Formula: Methane Formula: Nitrogen Oxygen - 12 - Carbon Hydrogen CFE Chemistry Unit 1 Chemical Changes & Structure Investigating bonding Ionic bonding Instead of sharing electrons, atoms can transfer electrons. This is called ionic bonding, and occurs when metals bond with non-metals. Na (2,8,1) Cl (2,8,7) Na+ (2,8) Cl-(2,8,8) Remember atoms are trying to achieve full outer electron levels (e.g. like Neon 2,8) when they bond, so they can get a stable electron arrangement like a noble gas! So that’s what they do they transfer an electron. Ionic bonding involves the transfer of outer electrons. Sodium atom 2,8,1 electron level Loses an electron to get to a full outer electron arrangement now 2,8. Chlorine atom 2,8,7 electron level Gains an electron to get to a full outer electron arrangement now 2,8,8. Complete the following: There are two types of bonding between atoms Bonding. and Ionic/covalent bonding involves the sharing of electrons. Ionic/covalent bonding involves the electrons. - 13 - of CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 7 Covalent Bonding and Formulae I can show covalent bonding as a sharing of electrons by drawing non-metal atoms joined together in a molecule I can work out the chemical formula given the number of atoms of each element in a molecule Can you build & write the chemical formula for the following substances?. Chemical Complete the following table. Diagram butane vinegar acetone Ethylene glycol (antifreeze) aspirin - 14 - Chemical Formula CFE Chemistry Unit 1 Chemical Changes & Structure Covalent Bonding and Formulae Drawing Molecules Use molecular models to build the molecules on the following table. There cannot be any holes left in the atoms. Draw the molecules into the table under 2-D structural formula. Afterward your teacher will tell you the names of these shapes of molecules. Compound 2-D Chemical Structural formula formula Shape Hydrogen Chloride Carbon chloride Hydrogen oxide Carbon Hydride What exactly do atoms do to form a bond? Here are simplified electron arrangement diagrams of a hydrogen atom and a chlorine atom. (Only the outer electrons are shown in fluorine). H 1 F 2,7 Can you see a way that both of these atoms can have full, stable electron arrangements? Draw it on your show me board and in your jotter. - 15 - CFE Chemistry Unit 1 Chemical Changes & Structure Covalent Bonding and Formulae Non-metal atoms achieve a full, stable electron arrangement by __________ electrons with each other. This __________ of electrons is what makes a __________ bond. More Examples: Draw Electron sharing diagrams (with outer electrons only) for the compounds of: a) Hydrogen and chlorine b) Hydrogen and oxygen c) Nitrogen and hydrogen d) Carbon and hydrogen - 16 - CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 8 Ionic bonding I can explain that an ionic bond is caused by electrostatic attraction between ions (charged particles) Ionic compounds are formed between metal and non-metal elements. When we make an ionic compound we transfer electrons. Na 2,8,1 Cl 2,8,7 Na+ (2,8) Cl- (2,8,8) These charged particles are called ions. Ions: Atoms that have a charge because they have gained or lost electrons. Atoms form ions by __________ or __________ electrons. Metal atoms always __________electrons and so always form __________ charged ions. Non-metal atoms form ions with __________ charges because they always __________ electrons. An atom will gain or lose as many __________ as it needs to get a __________ outer shell. Once the ions are formed they are held together in a lattice by bonds caused by electrostatic attraction between positive and negative ions. Na+ Cl- Ionic Bond: The electrostatic attraction between positive and negative ions. - 17 - CFE Chemistry Unit 1 Chemical Changes & Structure Bonding Revision 1. Draw a table and use it to classify these properties as belonging to ionic or covalent substances Low melting and boiling points Form ions when dissolved or molten Usually exists as liquids or gases at room temperature Never conduct electricity High melting and boiling points Conduct electricity when molten or dissolved 2. Usually exists as solids at room temperature Work out if these compounds are ionic or covalent. Name Formula Nitrogen N2 Bonding Name Formula Carbon CO2 dioxide Calcium CaO Oxide Lithium Li2S sulphide Iodine I2 Methane CH4 Aluminium Al2O3 Sodium Na2S oxide sulphide - 18 - Bonding CFE Chemistry Unit 1 Chemical Changes & Structure Lesson 9 Formula of Compounds I can state the chemical formulae of two element compounds. I can explain what the endings –ide, -ate and –ite mean Extension: I can work out chemical formulae using valencies (SVX) Can you work out the formula and names of compounds? Compounds are made when different elements join together, using either covalent or ionic bonds. These compounds get their names from the elements that make them up. The ending of the compound gives us a clue to the elements present. Write the definitions for –ide, -ite and – ate, then complete the following table: -ide ending means -ite or –ate ending means Compound Elements Caesium Bromide Potassium Chloride Magnesium phosphate Boron Fluoride Aluminium oxide Sulphur oxide Potassium Sulphate Calcium Sulphite - 19 - CFE Chemistry Unit 1 Chemical Changes & Structure Formula of Compounds In the previous table we identified the elements present, but how do we work out the actual formula? For some elements, including the noble gases, the formula is just the element symbol. They are said to be monatomic (one –atomed). Complete the table: He Ne Ar Kr Xe Rn Symbol Element He Ne Ar Kr Xe Rn There are 7 non-metal elements that exist as diatomic molecules (2 atoms joined together). H H Element hydrogen N N Nitrogen Oxygen O O Flourine Chlorine F F Bromine Iodine - 20 - Chemical Formula CFE Chemistry Unit 1 Chemical Changes & Structure Diatomic – 2 atoms joined together In most compounds we have to use the combining power of an element or valency to work out the chemical formula. Valency – the combining power of an atom Different elements have different valencies depending on their position in the periodic table. Group No 1 2 3 4 5 6 7 Valency 1 2 3 4 3 2 1 1 2 3 4 5 6 7 0 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Ga Ge As Se Br Kr Sc Ti V Cr Mn Fe Co Ni Cu Zn Chemical Formulae -SVX To work out the formula we use 3 stages. S- symbol, V- valency, Xcross over e.g. NaCl S - Symbols: Na Cl V - Valency 1 1 (Na group 1, so valency 1, Cl group 7 so valency 1) X - X Cross over valencies Na Cl • Formula NaCl - 21 - CFE Chemistry Unit 1 Chemical Changes & Structure If the valency is 1 you do not need to show this in the final formula because the chemical symbol represents one atom. Formula of Compounds Use the valency method to write the formula for each of the following. Answer in your jotter. (a) hydrogen fluoride (f) hydrogen chloride (b) hydrogen sulphide (g) phosphorous hydride (c) nitrogen chloride (h) nitrogen fluoride (d) phosphorous chloride (i) silicon hydride (e) carbon oxide (j) silicon oxide Meaningful names There are some covalent compounds with names which have prefixes which can be used to write the formula. The valency method should not be used when writing the formula for these compounds. Complete the table below. Prefix Meaning Compound mono carbon monoxide di sulphur dioxide tri sulphur trioxide tetra carbon tetrachloride - 22 - Formula CFE Chemistry Lesson 10 Unit 1 Chemical Changes & Structure Chemical Equations I can write a word equation for a chemical reaction I can write simple symbol equations from word equations Can you write a balanced chemical equation? Word equations A word equation is a statement showing the reactants on the left separated by an arrow from the products on the right. For example, zinc combines with oxygen to form zinc oxide. The word equation for this is: zinc + oxygen zinc oxide Complete word equations for the following reactions: (a) Hydrogen joins up with oxygen to form water. (b) Carbon dioxide and water are produced when methane reacts with oxygen. (c) Iron is formed when iron oxide is heated with carbon monoxide. Carbon dioxide is also formed. - 23 - CFE Chemistry Unit 1 Chemical Changes & Structure Chemical Equations Words to symbols Use symbols and formulae to write a chemical equation for each of the following reactions. (a) carbon monoxide + oxygen carbon dioxide (b) sulphur + oxygen sulphur dioxide (c) carbon + oxygen carbon monoxide Lesson 11 Conservation of Mass I can show by experiment the conservation of mass What happens to the mass of materials when chemical changes take place? When a firework sparkler is lit a chemical changes take place –light and heat are given off in an change. The magnesium atoms present in the sparkler are reacting with the oxygen molecules in a combustion reaction to form magnesium oxide. Word equation: Chemical equation: - 24 - CFE Chemistry Unit 1 Chemical Changes & Structure Learning Outcomes - Chemical Changes & Structure Tick Lesson Learning Outcome √ No. 1 2 2 3 I can state some signs of a chemical reaction I can name 3 things which can speed up a chemical reaction I can draw and interpret graphs to compare reaction rates I can name the 3 subatomic particles, explain where they are found in an atom and state their charge 3 I can explain why atoms are electrically neutral 4 I can explain what an atomic number and a mass number are in an atom 4 I can state the mass of subatomic particles 5 5 6 6 7 7 I can state and draw the electron arrangements for the first 20 elements I can state that elements with same number of outer electrons are grouped together. I can state that compounds are held together by bonds I can state that there are two different types of bonding (ionic and covalent) when elements join together, which affect the properties of their compounds I can show covalent bonding as a sharing of electrons by drawing non-metal atoms joined in a molecule I can work out the chemical formula given the number of atoms of each element in a molecule - 25 - CFE Chemistry Unit 1 Chemical Changes & Structure Learning Outcomes - Chemical Changes & Structure Tick Lesson Learning Outcome √ No. 8 9 9 9 I can explain that an ionic bond is caused by electrostatic attraction between ions (charged particles) I can state the chemical formulae of two element compounds I can explain what the endings –ide, -ite and –ate mean Extension: I can work out chemical formulae using valencies (SVX) 10 I can write a word equation for a chemical reaction 10 I can write simple symbol equations from word equations 11 I can show by experiment the conservation of mass - 26 -