Student Booklet C2.1 Acids and Alkalis Reactions rearrange matter Chemical substances are made up of different types of elements, compounds and mixtures, each of which have different properties and uses. Different substances can be made in chemical reactions but the atoms themselves cannot be created or destroyed, only rearranged. There are many different types of chemical reaction, such as synthesis, decomposition and combustion reactions. In this unit you will be learning about acids and alkalis and how to identify them using different indicators. You will also be learning about reactions between acids and alkalis, particularly neutralisation reactions. Atoms are the smallest unit of matter. Elements are made up of one type of atom. Compounds are two or more elements chemically bonded together. Mixtures are two or more elements or compounds not chemically bonded together. Solids, liquids and gases can be represented using the particle model. 1. Which statement describes the motion of the particles in a slab of concrete? £ A. They move when the concrete gets heated £ B. They can vibrate £ C. They do not move at all 2. Ice feels solid but water feels runny. Which idea explains this? £ A. Particles in ice are linked more tightly together £ B. Particles in ice are harder than particles in water £ C. Ice is solid particles but water is liquid particles 3. After a hot shower, water vapour from the shower condenses on the glass. Why? £ A. Particles in the water vapour have lost energy £ B. Particles in the water vapour have gained energy £ C. Glass particles in the shower have lost energy 4. Which of the following are all examples of elements. £ A .Oxygen, hydrogen, potassium £ B. Water, carbon dioxide, helium £ C. Protein, oxygen, water 5. Elements are represented by symbols. What is the symbol for sodium? £ A. NA £ B. Na £ C. So 6. The periodic Table is organised into groups and periods. Using your Periodic Table which group and period is Lithium in? £ A. Group 1, Period 2 £ B. Group 2, Period 1 £ C. Group 1, Period 1 7. Which of these is an observation showing that a chemical reaction has taken place? £ A. There was a change in state £ B. There was a colour change £ C. There was a change in texture from hard to runny 8. Which best explains the difference between an element and a compound? £ A. Elements are made up of one type of atom, compounds are 2 or more elements mixed together £ B. Elements are made up of one type of atom, compounds are 2 or more elements chemically bonded together £ C. Compounds are made up of one type of atom, elements are 2 or more compounds mixed together 9. The formula for nitric acid is HNO3. How many atoms of each element are present? £ A. 1 hydrogen atom, 1 nitrogen atom and 3 oxygen atoms £ B. 3 hydrogen atoms, 3 nitrogen atoms and 3 oxygen atoms £ C. 1 hydrogen atom and 3 nitrate atoms 10. Sugar is mixed into a cup of tea. What is the solute and what is the solvent? £ A. Sugar is the solvent, tea is the solute £ B. Sugar is the solute, tea is the solvent £ C. Water is the solute, tea is the solvent Question Answer What to do next (Fix-It task) 1 B If you answered A or C you need to review the properties of solids. Draw a particle diagram to show the arrangement of particles in a solid and describe the movement of particles. 2 A If you answered B or C you need to review the differences between solids and liquids. Explain the differences between the arrangement of particles in ice and water. 3 A If you answered B or C you need to review the process of condensation. Explain what happens during condensation by referring to the energy of particles and state the name of the opposite process. 4 A If you answered B or C you need to review the difference between elements and compounds. Explain why water and carbon dioxide are not elements. 5 B If you answered A or C you need to review how to use the Periodic Table. Find the symbols for: tin, iron, potassium and lead. 6 A If you answered B or C you need to review the meaning of groups and periods in the Periodic Table. Identify the group and period of oxygen, potassium and chlorine. 7 B If you answered A or B you need to review the differences between a physical and a chemical change. Describe the observations you may see if a chemical change (reaction) has taken place. 8 B If you answered A or C you need to review the difference between elements and compounds. State the definition and an example of each. 9 A If you answered B or C you need to review how to use chemical formulae. Determine how many of each atom are in sulfuric acid (H2SO4), calcium carbonate (CaCO3) and phosphoric acid (H3PO4). 10 B If you answered A or C you need to review the definitions of solute and solvent. State the definitions of solute, solvent, solution and saturated and give an example of a solute being added to a solvent. Great job! Now you’re ready to start learning about acids and alkalis! C2.1 Acids and Alkalis Knowledge Organiser The pH Scale 27. Acids will turn universal indicator red or orange. 1. Substances can be classified into acidic, alkaline and neutral solutions 28. Neutral solutions will turn universal indicator green. 2. The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution 29. Alkaline solutions will turn universal indicator blue or purple. 3. The pH scale can be measured using litmus, universal indicator or a pH probe. 4. A solution with pH 7 is neutral. 5. Aqueous solutions of acids have pH values of less than 7 6. Aqueous solutions of alkalis have pH values greater than 7 7. An aqueous solution is any solution in which the solvent is water Neutralisation 30. In neutralisation reactions an acid reacts with an alkali to form a salt and water. 8. Strong acids have a pH from 0 to 3. 31. Neutralisation forms a neutral (pH7) 9. Weak acids have a pH of 4 to 6. solution. 10. Strong alkalis have a pH from 11 to 14. 32. A salt is a metal compound made from acid. 11. Weak alkalis have a pH from 8 to 10. 33. A salt is formed when the hydrogen in an 12. Strong acids and strong alkalis are both acid is replaced by a metal. corrosive. 13. Weak acids and alkalis are less corrosive. 14. Many substances we use every day are acidic or alkaline. 15. Lemon juice is acidic. 16. Bleach (and many other cleaning agents) are alkaline. C2.1 Acids and Alkalis Knowledge Organiser Indicators Metal Carbonates 17. Indicators will show the pH of the 34. Metal carbonates react with acids in substance by a colour change. neutralisation reactions to form a salt, water and carbon dioxide 18. Litmus indicator can show if a solution is acidic or alkaline. 35. In an open system these products can escape, and the system is neutral 36. In a closed system carbon dioxide reacts with water to form carbonic acid, which makes the system acidic 19. Litmus indicator is red in an acidic solution. 20. Litmus indicator is blue in an alkaline solution. 21. Litmus indicator remains the same colour in a neutral solution. 22. If using litmus paper, blue litmus paper turns red in an acidic solution. 23. Red litmus paper turns blue in an alkaline solution. 24. To remember this, it might be helpful to memorise the rhyme Blue to red, acid is said Red to blue, acid untrue Acid Alkali 25. Universal indicator is sometimes called UI 26. Universal indicator can be used as a liquid solution or as paper strips to dip into a solution. Keyword Definition pH Acid Alkali Acidic Alkaline Solution Universal indicator Litmus paper Salts Chloride Sulphate Nitrate Citrate Carbonate Neutralisation Evaporation Crystallisation Acidification Limewater The pH Scale Starter 1. What does this symbol tell you? ______________________________________________ 2. What does this mean? _______________________________________________________ Foundation: Where might you find this hazard symbol in the lab? _______________________________________________________ Stretch: What does this symbol have to do with the title of today’s lesson? _______________________________________________________ _______________________________________________________ Substances can be classified into acidic, alkaline and neutral solutions, according to the pH scale. The pH scale ranges from 0 to 14, and is a measure of the acidity or alkalinity of a solution. The pH scale can be measured using litmus, universal indicator or a pH probe. Note: acids and alkalis are not actually these colours – the colour scale shows the colour that universal indicator turns when a few drops of it are added to an acidic or alkaline solution. Note: an aqueous solution is any solution in which water is the solvent (the liquid the solute is dissolved in). A solution with pH 7 is neutral. Aqueous solutions of acids have Aqueous solutions of alkalis have pH values of less than 7. pH values greater than 7. 1. Determine if the following statements are true or false: a. The pH scale ranges from 1 to 14 b. pH 1-7 indicates an acidic solution c. pH 7 indicates that the solution is both an acid and alkali d. Three ways to measure the pH of a solution are; using litmus indicator, universal indicator or a pH probe 2. Colour the sections to represent each pH, and then use the boxes at the top of the pH scale to label the pH scale.