Monday 09 November 2020 Spec 5425 Do Now Define these terms By only drawing pictures Acid Alkali Neutral PROGRESS INDICATORS Good progress Outstanding progress Grade 45 Recall examples of strong and weak acids Describe how an acid or alkali can be weak or strong ID: 1021876
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1. Strong and weak AcidsHT ONLYMonday, 09 November 2020Spec. 5.4.2.5Do Now: Define these terms…. By only drawing picturesAcidAlkaliNeutral
2. PROGRESS INDICATORSGood progressOutstanding progressGrade 4-5Recall examples of strong and weak acids. Describe how an acid or alkali can be weak or strong. Use ionic equations to explain how acids can be strong or weak.Grade 6-7Describe how an acid or alkali can be concentrated or dilute.Calculate in terms of factors the increase or decrease in hydrogen ions Grade 8-9Explain the difference between concentration and strong or weak in terms of acids and alkalis. Explain how the concentration of hydrogen ions relates to the pH number.Monday, 09 November 2020
3. Word Consciousness Monday, 09 November 2020Concentration – Describe the total number of dissolved acid molecules Strength of an acid – Relates to the number of molecules that are ionised to produce hydrogen ions at any given moment Ionised - becoming positively/ negatively charged by either losing or gaining electrons Strong Acids – Fully ionised in solutionWeak Acids – Partially ionised in solution
4. General InformationMonday, 09 November 2020https://www.youtube.com/watch?v=4pIHhXfGZlE
5. ACTIVITY 1 - Recall examples of strong and weak acids. Copy and complete the table by sorting the following into strong and weak acids. Sulfuric acid Nitric acid Citric acid (found in fruit) Hydrochloric acid Carbonic acid (found in fizzy pop) Ethanoic acid (found in vinegar)Monday, 09 November 2020Examples of strong acidsExamples of strong acidsSulfuric acidNitric acidHydrochloric acidEthanoic acid (found in vinegar)Citric acid (found in fruit)Carbonic acid (found in fizzy pop)
6. ACTIVITY 2 - Describe how an acid or alkali can be weak or strong. STRONG ACIDSIONISE COMPLETELY in water. ALL the acid particles dissociate to release H+ ions. E.g. HCl H+ + Cl-Monday, 09 November 2020WEAK ACIDSWeak acids DO NOT IONISE COMPLETELY in water. A SMALL PROPORTION of the acid particles dissociate to release H+ ions.E.g. CH3COOH H+ + CH3COO-TASK – Fill in the gapsAcid s__________ tell you what p___________ of the acid molecules i___________ in water. strengthproportionionise
7. ACTIVITY 3 - Describe how an acid or alkali can be concentrated or dilute.Concentration measures how much acid there is in a certain volume of water. Choose the correct words to write two correct statements. The larger/smaller the amount of acid there is in a certain volume of liquid, the more/less concentrated it is.The larger/smaller the amount of acid there is in a certain volume of liquid, the more/less concentrated it is.Monday, 09 November 2020smallerlesslargermore
8. ACTIVITY 4 - Describe how an acid or alkali can be concentrated or dilute.Think, pair, share: Can you get strong and dilute acids? Can you give an example?YES!Hydrochloric acid is a strong acid. You can get different concentrations of hydrochloric acid, some are more concentrated, others are more dilute. E.g. 2M HCl1M HCl0.5M HCl0.1M HClMonday, 09 November 2020
9. informationThe pH of an acid or alkali is a measure of the concentration of H+ ions in the solution.For every decrease of 1 on the pH scale, the concentration of H+ ions increases by a factor of 10. So, an acid that has a pH of 4 has 10 time the concentration of H+ ions of an acid that has a pH of 5. For a decrease of 2 on the pH scale, the concentration of H+ ions increases by a factor of 100. General rule: Factor H+ ion concentration changes by = 10-x X is the difference in pH, found by subtracting the starting pH from the final pH.The pH of a strong acid is always lower than the pH of a weaker acid if they have the same concentration. Monday, 09 November 2020
10. exampleDuring an experiment, the pH of a solution fell from pH 7 to pH 4. By what factor had the hydrogen ion concentration of the solution changed?Difference in pH = final pH – starting pH = 4 – 7 = -3. Factor that H+ ion concentration changed by = 10-(-3) = 103 (or 1000)Monday, 09 November 2020
11. Activity 5 - Calculate in terms of factors the increase or decrease in hydrogen ions QUESTIONSIf the pH of the solution rises from 2 to 5, what factor has the hydrogen ion concentrated of the solution changed by?If the pH of the solution rises from 8 to 3, what factor has the hydrogen ion concentrated of the solution changed by?If the pH of the solution rises from 1 to 8, what factor has the hydrogen ion concentrated of the solution changed by?If the pH of the solution rises from 14 to 10, what factor has the hydrogen ion concentrated of the solution changed by?Monday, 09 November 2020
12. Activity 5 ANSWERS1. If the pH of the solution rises from 2 to 5, what factor has the hydrogen ion concentrated of the solution changed by?Difference in pH = final pH – starting pH = 5 – 2 = 3. Factor that H+ ion concentration changed by = 10-(3) = 10-3 (or 0.001)2. If the pH of the solution rises from 8 to 3, what factor has the hydrogen ion concentrated of the solution changed by?Difference in pH = final pH – starting pH = 3 – 8 = -5. Factor that H+ ion concentration changed by = 10-(-5) = 105 (or 100 000)Monday, 09 November 2020