Unit 1 Chemical Changes & Structure. National 4 Unit Rates of Reaction 2. Atomic Structure and Bonding 3. Acids & Bases 4. Energy Changes - 1 -

Transcription

1 National 4 Unit 1 1. Rates of Reaction 2. Atomic Structure and Bonding 3. Acids & Bases 4. Energy Changes - 1 -

2 Learning Intentions Reaction Rates & Atomic Structure Learning Intentions Tick I know the difference between a chemical and physical change. I can state that when a chemical reaction takes place a new substance is formed. I can carry out experiments to measure the rate of a reaction. I am able to describe how changing concentration, temperature and particle size affects the rate of a reaction. I am able to describe how adding a catalyst affects the rate of a reaction. I can interpret graphs and compare the rates of reactions. I am able to add lines to a graph to show how changes in conditions affect the speed of a reaction. I can describe the structure of an atom in terms of protons, neutrons and electrons. I know the mass, charge and location of the 3 sub-atomic particles. I am able to explain why an atom is neutral. I can state the meaning of the terms atomic number and mass number. I can state the electron arrangement of the first 20 elements. I know that a covalent bond is sharing of electrons and an ionic bond is a transfer of electrons. I can carry out experiments to show the properties of covalent and ionic compounds. I can write the chemical formulae for two element compounds using valencies and transition metals. I can use these formulae to write simple equations from word equations

3 Chemical Reactions level 3 prior learning 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. All chemical reactions produce new substances. Most chemical reactions involve some noticeable energy change or change in appearance. Write some signs of a chemical reaction below:

4 Reaction rates Chemical reactions can occur at different speeds or rates. Consider the following chemical reactions and decide if they are slow, medium or fast and give another example. Copy and complete the table Reaction Speed or rate Another Example Iron nail rusting Bomb Explosion Making Toast This series of experiments is designed so that you can identify whether the speed or rate of a reaction can be altered: Experiment 1 Concentration Aim: Results: Record your results in a table and plot a line graph of volume of gas produced vs time taken, with two lines one for the most concentrated acid (2M) and also least concentrated acid (0.5M) Conclusion (what did you find out): On your graph add another line for a reaction using 4M acid

5 Experiment 2 Temperature Aim: Results: Record your results in a table and plot a line graph of temperature vs time taken using points at 20 o C, 40 o C and 60 o C Conclusion (what did you find out): On your graph add another line showing the curve for a reaction at 10 o C. Experiment 3 Particle Size Aim: Method: Working in your group/pairs write a method in your jotter and get your teacher to check it. Results: Record your results in a table and plot a line graph with volume of bubbles produced vs time taken with two lines one for small particle size (crushed marble chips) and also large marble chips. On your graph add a line to show the reaction of powdered marble chips

6 Conclusion (what did you find out): Complete the following sentence: From this series of experiments I was able to identify that: - 6 -

7 Inside the atom 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. Investigating atomic structure ACTIVITY Building an atom Copy and complete the diagram below Even though atoms have these sub-atomic particles they are mostly composed of empty space!! - 7 -

8 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!!! Copy and complete the table below showing the location and appropriate charges of subatomic particles. Particle Charge Where is it found in atom Electron Neutron Proton - 8 -

9 Atomic & Mass Number Look at the periodic table in your 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 = the number of electrons (+ve charge) (-ve charge) - 9 -

10 Investigating atomic number Using your knowledge of atoms complete the table below: Atomic Number Element Symbol Protons Electrons O Lithium Be Fluorine The mass of an atom is very small, at g. 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 Complete the table. Particle Charge Approximate mass (a.m.u.) Electron Where is it found in atom Neutron Proton

11 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 called nucleotide notation: Mass No. The mass number is given on top. Atomic No. The atomic number written at the bottom. The atomic number is always the smaller number!

12 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 Na 12 6 C 16 8 O Cl 4 2 He Questions 1. What is meant by the atomic number? 2. What is meant by the mass number?

13 Investigating atomic structure Use the atom diagrams to help with this investigation. Green- proton, Blue neutron, White - Electron Using the information in the table - make each of the following atoms and then complete the drawing in the last column of the table. The first one has been done for you. Element Protons Neutrons Electrons Atom Drawing Helium Electrons Protons neutrons Hydrogen Carbon Boron

14 From your table can you explain why atoms are electrically neutral? Mention the word layers in your description

15 Electron Arrangements 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? 1 st energy level 2 nd energy level 3 rd energy level 1 st shell = 2 electrons 2 nd Shell = 8 electrons 3 rd Shell = 8 electrons For the first twenty elements we follow the 2,8,8,2 rule. 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

16 Name of Electron Number of Group Outer element Arrangement outer electron electrons Diagram Hydrogen Lithium Chlorine Carbon Magnesium

17 Electron Arrangements Investigating electron arrangement Using the atom diagrams, 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. Sodium 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

18 How does the electron arrangement affect the chemical properties of each element? Your teacher will demonstrate some reactions of alkali metals (group 1 elements). 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 outer 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

19 Investigating bonding Atoms join together and form bonds between them to make molecules. Experiment - Investigating bonding Within this experiment we are going to test a series of substances and relate their properties to their bonding. Aim: Results: Record your results in the table below: Substance Contains metal / non metals? Conducts electricity Solid Solution Melting point High / low Sodium Chloride Zinc Wax Glucose Copper Chloride Iron Potassium Bromide

20 Write a short summary about the properties of compounds containing 2 non-metals A metal and a non-metal. A metal Investigating bonding Covalent V Ionic Non-metal atoms like hydrogen and oxygen join to form water by bonds called covalent bonds. 1. Covalent bond Negative Electron Positive nucleus e e + + H H Area of attraction Both positive nuclei attracted to shared pair of negatively charged electrons

21 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: Water Formula: H 2 O Ammonia Formula: Methane Formula: Key: Nitrogen Oxygen Carbon Hydrogen 2. Ionic Bond 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)

22 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 Loses 1 electron 2,8. Chlorine atom 2,8,7 Gains 1 electron 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 of electrons

23 Covalent Bonding and Formulae Copy and complete the following table. Drawing Molecules Chemical Structural Formula Chemical Formula butane vinegar acetone Ethylene glycol (antifreeze) aspirin

24 Drawing molecules Activity 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 Shape Name Structural Formula of Formula Shape Hydrogen Chloride Carbon Chloride Hydrogen Oxide Ammonia

25 Bonding 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. 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

26 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

27 Ionic bonding 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

28 Na + Cl - Ionic Bond: The electrostatic attraction between positive and negative ions

29 Bonding Revision 1. Put the following properties under the headings, covalent or ionic. Low melting and boiling points Form ions when dissolved or molten Usually exists as liquids or gases at room temperature Conduct electricity when molten or dissolved Never conduct electricity Usually exists as solids at room temperature High melting and boiling points 2. Work out if these compounds are ionic or covalent. Name Formula Bonding Name Formula Bonding Nitrogen N 2 Carbon dioxide CO 2 Calcium CaO Lithium Li 2 S Oxide sulphide Iodine I 2 Methane CH 4 Aluminium Al 2 O 3 Sodium Na 2 S oxide sulphide

30 Formula of Compounds 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 flowchart and table: -ide ending -ite or ate ending -IDE - or - Contains elements Contains 3 elements, including

31 Compound Elements Caesium Bromide Magnesium phosphate Boron Fluoride Aluminium oxide Potassium Sulphate Calcium Sulphite 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

32 There are 7 non-metal elements that exist as diatomic molecules (2 atoms joined together). Element Chemical Formula hydrogen Nitrogen Oxygen Fluorine Chlorine Bromine Iodine 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

33 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Complete the table below Group No Valency Chemical Formulae To work out the formula we use 4 stages. S- symbol, V- valency, X- cross over F Formula Examples Sodium Chloride S - Symbols Na Cl V - Valency 1 1 group 1 group 7 valency 1 valency 1 X -Cross over valencies 1 1 Formula NaCl If the valency is 1 you do not need to show this in the final formula because the chemical symbol represents one atom

34 Hydrogen Oxide S H O V 1 2 X 2 1 F H 2 O Notice how the numbers we use are written after the symbol at the bottom. Formula of Compounds Use the valency method to write the formula for each of the following. Answer the following (a) hydrogen fluoride S H F V 1 1 X 1 1 F (b) hydrogen sulphide

35 S H S V 1 X 1 F (c) nitrogen chloride S N Cl V X F (d) phosphorous chloride S V X F (e) silicon hydride S V X F

36 (f) hydrogen chloride (g) nitrogen fluoride (h) phosphorous hydride (i) carbon oxide (j) silicon oxide

37 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 Formula mono di tri tetra carbon monoxide sulphur dioxide sulphur trioxide carbon tetrachloride

38 Chemical Equations Word equations A word equation is a statement showing the reactants on the left separated by an arrow from the products on the right. Reactants Products 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

39 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 (d) Potassium reacts with fluorine to produce potassium fluoride. (e) Lithium reacts with chlorine. (f) Magnesium reacts with nitrogen

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41 Learning Intentions / Success Criteria Acids & Bases / Energy Changes Success Criteria I know the role acids and alkalis play in the food and drink industry and their impact on our health I know that soluble metal oxides form an alkaline solution and soluble non-metal oxides form acidic solutions I know that the ph of water can only be affected by the addition of soluble substances. I know that an alkali is a soluble base. I have discussed the role non-metal oxides play in the environment I can follow the course of a neutralisation reaction using ph indicator I know that neutralisation reactions can be used to prevent the damage caused by acids I can state that the reactions of acids with alkalis is a neutralisation reaction and I can name the products formed I know when a chemical reaction takes place an energy change usually occurs I can describe an exothermic reaction in terms of energy change and give examples I can describe an exothermic reaction in terms of energy change and give examples Tick

42 Acids & Alkalis in Food Revision You may have previously met the ph scale. complete the sentences below. In your groups copy and The ph scale is a range of numbers from to. All acids have a ph of than 7. All alkalis have a ph than 7. Solutions with a ph = 7, are called substances. Colour in the ph scale. Food & Drink Many natural foods are acidic including oranges and they have a sharp taste. Bicarbonate of soda is an important alkali used in the baking of cakes. Can you make a prediction of the ph of food and drinks?

43 Experiment - ph testing of Foods & Drinks Aim: Method: Follow the instructions given by your teacher Results: Complete the table below Name of food / drink Predicted ph Actual ph Acid, alkali or neutral Can you name some everyday acids and alkalis used in food & drink? 1. What is the ph of an acidic solution and can you name two acidic solutions that you found? 2. Vinegar contains ethanoic acid, CH 3 COOH, Lemonade contains carbonic acid, H 2 CO 3. Circle the correct answers below. Acids contain metal / non-metal elements. 3. Which food or drink tested was the most alkaline, explain your answer?

44 Making Acids How are acids made in the laboratory and in nature? Your teacher will now demonstrate how acids are made. Working with your shoulder partner complete the word equations for the two reactions. carbon + carbon dioxide carbon + dioxide This acid is used in fizzy drinks! + oxygen sulfur + + dioxide This acid is one of the main causes of acid rain

45 Copy and complete the following table of laboratory acids and answer the questions that follow: Name of acid Formula of Acid Elements present Nitric acid HNO 3 Sulfuric acid H 2 SO 4 Carbonic acid H 2 CO 3 Hydrochloric acid HCl Ethanoic acid CH 3 COOH 1. Which type of element is present in all acids? 2. Can you name the element common to all types of acids? 3. The element found in Q2 is present as a charged particle, can you remember what we call this type of particle found in all acids? 4. Acids are produced in 2 steps: 1. By burning in 2. Dissolving the non-metal oxide product in

46 Making Alkalis How are alkalis made in the laboratory and in nature? Previously you learned that all acids contain non-metal elements, but what about alkalis? Experiment - Making alkalis from magnesium metal Aim: Method: teacher. Carefully carry out the instructions given to you by your Results & Conclusion: Record your observations from your experiment in your jotter and your overall findings. Complete the word equation for this reaction Magnesium + Magnesium oxide

47 Using information from the table complete the questions that follow: Name of alkali Sodium Hydroxide Formula of Alkali NaOH Potassium hydroxide KOH Calcium hydroxide Ca(OH) 2 Lithium hydroxide LiOH 1. Which types of elements are present in all alkalis? 2. Which groups in the periodic table do the alkalis come from? 3. All alkalis contain a charged particle or, this particle has the formula and is called the ion. 4. Alkalis are produced in 2 steps: 1. By burning in 2. Dissolving the metal oxide product in. 5. An alkali is a base, a base that can dissolve in water. A base is any substance that can neutralise an acid. These will be investigated in more detail later in the unit

48 Acid Rain One of the main pollution issues facing the planet is acid rain. Rainwater with a lower ph than normal (typical water ph 6.5 to 8.5) is called acid rain. Investigating acid rain Using ICT and other resources, answer the following questions 1. Can you name the two main non-metal oxide gases that are responsible for acid rain? 2. What is the main cause for the production of these gases? 3. What effect does acid rain have on rocks and buildings? 4. Why is acid rain a problem for lakes, rivers and streams? 5. Explain some ways in which soils and crops can be affected by acid rain

49 How do soluble oxides impact our local environment? By studying the water and plant samples in our local area, we can identify whether pollution, including acid rain has affected our environment. Experiment - ph Testing of local water sources Aim: Method: Use the information given to you by your teacher to come up with a method in your jotter. Results: Record your ph values in a results table in your jotter. Conclusion: Typical ph s for drinking water are ph 6.5 to 8.5 (Remember ph 7 is a neutral substance). A ph of less than this value, can indicate possible acid rain contamination. Did you identify whether the ph of water could have been affected by acid rain?

50 Neutralisation What happens when an acid is added to an alkali? Acids can be neutralised when they react with substances that raise the ph of the acid towards 7. Alkalis can also be neutralised when their ph moves towards 7. Experiment - Neutralisation with alkali Aim: Method: Results and Conclusion: 1. How do you know when the acid was neutralised? 2. How did the ph of the acid change as it was neutralised?

51 Repeat the experiment but replace the alkalis with indigestion tablets (which contain metal carbonate). 1. Why do you have acid in your stomach? 2. Why might you crush an indigestion tablet before swallowing it? What is made in the reaction between an acid and an alkali? In previous activities you found out that acids always contain ions and that alkalis always contain ions. During neutralisation of an acid by an alkali these ions react together to form the neutral substance. The other product is formed from the other ions in the acid and the alkali. Acid + alkali water + substance X HCl + NaOH H 2 O + The other product in a neutralisation reaction is called a salt

52 Equation practice Complete the word equations below. nitric + Sodium + water acid nitrate sulfuric + potassium + water acid hydroxide + ammonium ammonium + water acid hydroxide chloride sulfuric + calcium + water acid hydroxide Copy and complete the table below showing the names of salts produced from the different acids and alkalis. Name of Acid Nitric Sulfuric Salt Produced Chloride Name of Alkali Potassium Hydroxide Salt Produced Sodium Calcium

53 Everyday Neutralisation Can you name everyday examples of neutralisation? Describe the everyday example of neutralisation in each of the pictures above Research / Extended Written Exercise At this point the extended written essay on neutralisation in everyday life should be carried out

54 Acid / Carbonate Neutralisation What happens when a metal carbonate is added to an acid? In everyday life metal carbonates are used as indigestion tablets to neutralise acid. Pupil Experiment - Metal Carbonate neutralisation Aim: Method: Results: Record all observations and results from your experiment in your jotter

55 Use the questions below to help write a conclusion for this experiment 1. What happened to the universal indicator in this experiment and what does this indicate about the gas being produced? 2. Limewater is used to test for carbon dioxide if the lime water turns milky- this is a positive test for carbon dioxide. What does your result indicate? 3. Can you describe what has happened to the marble chips? What is made in the reaction between an acid and a metal carbonate? Metal carbonate (marble chips) react with acid to produce carbon dioxide gas & water in a neutralisation reaction. Can you name the other substance formed from your knowledge of acids and alkalis? metal + acid + water + carbon carbonate dioxide Calcium + Hydrochloric + water + carbon Carbonate acid dioxide

56 Equation practice Copy and complete the word equations below. nitric + copper + water + carbon acid carbonate dioxide sulfuric + sodium + water + carbon acid carbonate dioxide + Magnesium + water + CO 2 Acid carbonate chloride When acid rain (sulfuric acid) falls on buildings made from calcium carbonate, a chemical reaction takes place, but what are the products?

57 Metal Carbonate Investigation Is the speed of a metal carbonate neutralisation reaction different for different acids? You know that a metal carbonate will react with an acid to produce a,, and gas. In this investigation you will use different acids to see if they can affect the speed of a reaction. 1. Collect the investigation record sheet, and begin planning your investigation. Remember to make it a fair experiment. 2. Write a conclusion for your results. This investigation will form part of your assessment for this unit

58 Acid/ Metal Oxide Neutralisation Metal oxides that dissolve in water make. What happens when insoluble metal oxides are added to acids? Experiment Acid/metal oxide neutralisation Aim: Method: Results & Conclusions: Record your results and conclusion in your jotter, then answer the following questions: 1. How did you know the acid was neutralised? 2. Complete the word equation for the reaction: 3. What type of substance is made, in addition to water? 4. What is the solid that is left at the bottom of the beaker? 5. How could this excess solid be removed?

59 Energy Changes Experiment: Unusual everyday neutralisation experiments Aim: Method: Mix the chemicals according to the table below. Use a thermometer to measure temperature before and after each chemical is added to find out if there is an increase or decrease in temperature. Results: Record your results in a table: Chemicals Temperature start ( o C) Temperature end ( o C) Temp increase or decrease? Dilute hydrochloric acid (2cm3) + dilute sodium hydroxide (2cm3) Solid ammonium carbonate (small spatula) + dilute ethanoic acid (2cm3) Sodium carbonate crystals (small spatula) + citric acid powder (small spatula) In most reactions, the temperature This shows us that these reactions are as heat is given out. A decrease in temperature shows that heat is taken in from the surroundings and is known as an reaction

60 Watch the teacher demo of sugar and conc. H 2 SO 4. Ice Packs Can you explain what happens when an ice pack is used, and how they work? Hand Warmers Have a look at the hand warmers. Can you explain what happens when a hand warmer is used and how it works? Using ICT and other resources try and find 3 more examples of exothermic and endothermic reactions. Exothermic Endothermic

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