Acid 7 Base. 1. Describe two things hydrochloric acid does in your body system. 2. What does sodium hydrogencarbonate do in your body system?

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1 Acids and Bases acid: a compound that, when dissolved in water, forms a solution with a ph less than 7 base: a compound that, when dissolved in water, forms a solution with a ph greater than 7 ph: the measure of how acidic or basic a substance is When was the last time you put vinegar on your French fries or washed your hands with soap and water? Did you know that you were using acids and bases? An acid is a compound that dissolves in water to form a solution with a ph lower than 7. A base is a compound that dissolves in water to form a solution with a ph greater than 7. Acid 7 Base Acids and bases are present in the foods you eat, the products you use, and the fluids in your body systems. Your stomach, for example, contains strong hydrochloric acid; other organs in your body produce bases to neutralize stomach acid at certain points in the digestive process. Turn to page 62 of the textbook and read Acids and Bases in Your Body. 1. Describe two things hydrochloric acid does in your body system. 2. What does sodium hydrogencarbonate do in your body system? 3. What do buffers do? your answers with those on page Science 10 Module 1 Section 2

2 You are already familiar with some of the properties of many acids and bases through your own personal contact with things you eat or use in your home. For instance, you probably know that lemons and vinegar taste sour, whereas if you ever had soap in your mouth it tastes bitter. Lemons and vinegar are acids (tastes sour), and soap is a base (tastes bitter). You also know that soap is slippery. This is another property of bases. Acids Bases Turn to page 63 of the textbook and read the information in Properties of Acids and Bases and Indicators. 4. Does vinegar feel slippery? Never perform a taste or touch test for acids or bases in the laboratory. 5. Describe two tests for acids and bases that are used in the laboratory. 6. What is an indicator? 7. a. What is litmus paper? b. What colour does litmus paper turn in an acid and in a base? 8. a. What is a universal indicator? b. What colour is the universal indicator shown in Figure A2.33 on page 63 of the textbook in acid, base, and neutral solutions? c. How does a universal indicator differ from litmus paper? your answers with those on pages 100 and 101. Science 10 Module 1 Section 2 93

3 The ph scale is a measure of the hydrogen ion concentration of a solution. The ph tells you how acidic or basic a substance is. The scale is between 0 and 14 with acidic solutions measuring between 0 and 7 and basic solutions measuring between 7 and 14. A change of a ph of 1 on the scale is a 10 change in acidity of the solution. ph of Some Common Substances CLR vinegar lemon milk table salt tap water toilet bowl cleaner ammonia orange juice cola shampoo liquid hand soap baking soda Turn to page 64 of the textbook and read The ph Scale. Study Table A What is the ph of a neutral solution? 10. Draw a line to represent the ph from 0 to 14; then mark the approximate ph of the substances listed on it. soap vinegar normal rain water blood stomach acid your answers with those on page 101. Acid rain occurs when rain water becomes acidic due to pollutants in the atmosphere. To learn more about acid rain, first read infobit on page 64 of the textbook. Then visit the following website: science10 Once there, click on Unit A: Hot Links and scroll down to Text Page 64. You will find a number of links to articles and information sites from credible organizations, like Environment Canada and Alberta Environment. Figure 2.10: Victims of acid rain 94 Science 10 Module 1 Section 2

4 Naming Acids In Lesson 5 you named ionic and molecular compounds using the IUPAC system. The IUPAC system can also be used to name acids. Acids have a hydrogen symbol (H) on the left side of the compound s formula. Organic acids, like CH 3 COOH, are the only exception. For these acids, the hydrogen symbol (H) is on the right. Turn to pages 64 and 65 of the textbook and read Naming Acids. Examine Table A2.18 closely. 11. What is common in the formulas given in Table A2.18? 12. a. Copy and complete the following table by writing the appropriate IUPAC name and common name for each acid. Acid IUPAC Name Other Name HCl(aq) hydrochloric acid H 2 SO 4 (aq) aqueous hydrogen sulfate HNO 3 (aq) H 3 PO 4 (aq) b. How are acids named using the IUPAC system? 13. What are the names of the two organic acids at the bottom of Table A2.18? Methanoic acid (formic acid) is part of what gives you the sting when an ant bites you. Methanoic acid is also present in sweat and pine needles. 14. Give the common name for each of the following acids. a. HCl(aq) b. H 2 SO 4 (aq) c. CH 3 COOH(aq) 15. What are two uses for aqueous hydrogen phosphate, or phosphoric acid? your answers with those on page 101. Science 10 Module 1 Section 2 95

5 Read through the uses for the acids in Table A2.18. How many uses are you familiar with? Naming Bases The formulas of some common bases can be recognized by the presence of a hydroxide ion (OH - ) along with a metal ion or ammonium ion. Turn to page 67 of the textbook and study Table A What did you notice about the bases that contain a metal ion and a hydroxide ion? 17. Copy and complete the following table by writing the scientific name and the common name for the following bases. Formula Scientific Name Common Name NaOH(s) Mg(OH) 2 (s) 18. What are the uses for potassium hydroxide and ammonium hydroxide? 19. You are already familiar with many acids and bases around the house. In a table, list the acids and bases you are familiar with that may be found in a home. your answers with those on pages 101 and Science 10 Module 1 Section 2

6 QuickLab The ph of Common Household Materials Read the entire activity on page 68 of the textbook. If you have access to a supervised laboratory, do Part A. If you do not have access to a supervised laboratory, do Part B. Part A Obtain the materials and equipment required to complete this activity. You can test the materials you listed in question 19 if you wish. Pay special attention to the safety precautions mentioned. 20. Copy and complete the following table. Name of Substance Prediction ph lemon juice tomato juice bleach vinegar soap window cleaner drain cleaner milk baking soda 21. Answer questions 1, 2, and 3 of Questions. your answers with those on pages 102 and 103. Science 10 Module 1 Section 2 97

7 Part B Use the following table to answer question 21 in Part A. Name of Substance Prediction ph lemon juice acid 3 tomato juice acid 4 bleach base 11 vinegar acid 2 soap base 9 window cleaner base 10 drain cleaner base 14 milk acid 6.5 baking soda base 8 98 Science 10 Module 1 Section 2

8 To see some uses of acids and bases around the home, visit the following website: Once there, click on Unit A: Hot Links and scroll down to Text Page 68. You will find a list of informative Internet links. Neutralization What do you think happens when you mix an acid and a base? Turn to page 68 of the textbook and read Neutralization. 22. What happens to the properties of an acid and a base when the two are mixed together? 23. What are the products produced when an acid and a base are mixed? your answers with those on page 103. Looking Back You have now completed the concepts for this lesson. You identified some of the properties of acids and bases. You observed the effect of acids and bases on different indicators and defined ph. You identified some ways of naming acids and bases and recognizing their formulas. You compared the ph of some acids and bases in the home and defined neutralization in terms of the properties of acids and bases. 24. Answer questions 1, 3.a., 3.c., 3.d., 4.a., 4.c., 4.h., 6, and 7 of and Reflect on page 69 of the textbook. your answers with those on page 103. Go to... Go to page 7 of Assignment Booklet 1B and answer questions 28 to 33. Science 10 Module 1 Section 2 99

9 Glossary acid: a compound that, when dissolved in water, forms a solution with a ph less than 7 base: a compound that, when dissolved in water, forms a solution with a ph greater than 7 buffer: a substance that keeps the ph of a solution nearly constant even when small amounts of acid or base are added indicator: a substance that shows whether a solution is acidic or basic neutral: having a ph of 7 neutralization: a process in which an acid and a base are mixed to form a solution that loses the acidic and basic properties ph: the measure of how acidic or basic a substance is universal indicator: a mixture of several indicators that changes colour in a solution as the acidity of the solution changes e.g., litmus and red cabbage juice Suggested Answers 1. Hydrochloric acid in your body system dissolves food and activates an enzyme called pepsin. 2. Sodium hydrogencarbonate neutralizes stomach acid, thus deactivating pepsin. 3. Buffers keep the ph of a solution nearly constant despite the addition of a small amount of acid or base to the solution. 4. No, vinegar does not feel slippery. 5. Reaction with metals and ph are two tests used for acids and bases in the laboratory. Acids react with most metals, whereas bases do not. The ph of acids is less than 7, whereas the ph of bases is greater than An indicator is a chemical that will change colour depending on the ph of a solution. 7. a. Litmus paper is a strip of absorbent paper with a chemical, called litmus, dried on it. Litmus paper is used to determine whether a solution is an acid or a base. b. Red litmus paper remains red in an acid and turns blue in a base. Blue litmus paper turns red in an acid and remains blue in a base. 100 Science 10 Module 1 Section 2

10 8. a. A universal indicator is a mixture of several indicators that changes colour as the ph of the solution changes. b. The universal indicator shown in Figure A2.33 on page 63 of the textbook is pink in an acid and violet in a base. It is yellow in a neutral solution. c. Litmus paper only tells you whether a substance is an acid or a base. A universal indicator gives an estimate of the ph of the solution. 9. The ph of a neutral solution is stomach acid (1.5) vinegar (3) normal rain water (6) blood (7.4) soap (8 10) 0 ACIDIC 7 BASIC A hydrogen symbol (H) and the subscript (aq) is common to the formulas in Table A a. Acid IUPAC Name Other Name HCl(aq) aqueous hydrogen chloride hydrochloric acid H 2 SO 4 (aq) aqueous hydrogen sulfate sulfuric acid HNO 3 (aq) aqueous hydrogen nitrate nitric acid H 3 PO 4 (aq) aqueous hydrogen phosphate phosphoric acid b. In the IUPAC system, acids are named as aqueous substances with the name of the compound. 13. Methanoic acid, HCOOH(aq), and ethanoic acid, CH 3 COOH(aq), are given at the bottom of the table. You will learn more about naming organic acids if you take a chemistry course in your future years. 14. a. muratic acid b. battery acid c. acetic acid 15. Aqueous hydrogen phosphate, or phosphoric acid, is used to provide the sour taste in soft drinks and in fertilizer manufacturing. 16. Bases that contain a metal ion and a hydroxide ion are all solids. Science 10 Module 1 Section 2 101

11 17. Formula Scientific Name Common Name NaOH(s) sodium hydroxide caustic soda Mg(OH) 2 (s) magnesium hydroxide milk of magnesia 18. Potassium hydroxide, KOH(s), is used in tanning leather. Ammonium hydroxide, NH 4 OH(aq), is used in window cleaner. 19. Acids lemon juice fruit juices, pop vinegar some toilet bowl cleaners products that remove lime (e.g., CLR and Limeaway) Bases soap window cleaner oven cleaner drain cleaner household bleach 20. Name of Substance Prediction ph lemon juice acid 3 tomato juice acid 4 bleach base 11 vinegar acid 2 soap base 9 window cleaner base 10 drain cleaner base 14 milk acid 6.5 baking soda base Science 10 Module 1 Section 2

12 21. Textbook questions 1, 2, and 3 of Questions, p to 3. Your completed line, although vertical, should be similar to the following. ph Scale lemon juice (3) vinegar (2) tomato juice (4) milk (6.5) baking soda (8) soap (9) window cleaner (10) bleach (11) drain cleaner (14) acidic basic 22. When an acid and a base are mixed together, the acidic and basic properties disappear. 23. Water and a salt are produced through a chemical process called neutralization. 24. Textbook questions 1, 3.a., 3.c., 3.d., 4.a., 4.c., 4.h., 6, and 7 of and Reflect, p a. basic b. acidic c. acidic d. neutral e. acidic f. neutral g. acidic h. basic i. neutral j. basic 3. a. base c. neither d. acid 4. a. HNO 3 (aq) c. CH 3 COOH(aq) h. aqueous hydrogen bromide or hydrobromic acid 6. A universal indicator will show what the approximate ph is by changing colour at various ph values. Litmus paper will only turn red or blue to indicate whether the solution is acidic or basic respectively. 7. a. The ph of the solution will increase as more NaOH solution is added. b. The conductivity of the solution does not change much as both HCl(aq) and NaOH(aq) are highly conductive as is the NaCl product that is produced. Image Credits All images in this lesson were created by or for Alberta Education with the following noted exceptions: Page 93 bottom Rubberball Productions/Getty Images 94 Photodisc/Getty Images 96 top Photodisc/Getty Images bottom Photodisc/Getty Images Science 10 Module 1 Section 2 103