Unit 2 Acids and Bases: Reading Text [PDF]

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Unit 2 Acids and Bases Reading Text



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Properties of Acids and Bases According to Boyle In 1661 Robert Boyle summarized the properties of acids as follows. 1. Acids have a sour taste. 2. Acids are corrosive. 3. Acids change the color of certain vegetable dyes, such as litmus, from blue to red. 4. Acids lose their acidity when they are combined with alkalies. The name "acid" comes from the Latin acidus, which means "sour," and refers to the sharp odor and sour taste of many acids. The examples are; vinegar tastes sour because it is a dilute solution of acetic acid in water. Lemon juice tastes sour because it contains citric acid. Milk turns sour when it spoils because lactic acid is formed, and the unpleasant, sour odor of rotten meat or butter can be attributed to compounds such as butyric acid that form when fat spoils. In 1661 Boyle summarized the properties of alkalies as follows.  Alkalies feel slippery.  Alkalies change the color of litmus from red to blue.  Alkalies become less alkaline when they are combined with acids.



these compounds can act as a source of the H+ ion in water.



Metal hydrides, on the other hand, contain hydrogen bound to a metal. Because these compounds contain hydrogen in a -1 oxidation state, they dissociate in water to give the H- (or hydride) ion.



The H- ion, with its pair of valence electrons, can abstract an H+ ion from a water molecule.



Since removing H+ ions from water molecules is one way to increase the OH- ion concentration in a solution, metal hydrides are bases.



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In essence, Boyle defined alkalies as substances that consume, or neutralize, acids. Acids lose their characteristic sour taste and ability to dissolve metals when they are mixed with alkalies. Alkalies even reverse the change in color that occurs when litmus comes in contact with an acid. Eventually alkalies became known as bases because they serve as the "base" for making certain salts.



A similar pattern can be found in the chemistry of the oxides formed by metals and nonmetals. Nonmetal oxides dissolve in water to form acids. CO2 dissolves in water to give carbonic acid, SO3 gives sulfuric acid, and P4O10 reacts with water to give phosphoric acid.



Typical Acids and Bases The properties of acids and bases result from differences between the chemistry of metals and nonmetals, as can be seen from the chemistry of these classes of compounds: hydrogen, oxides, and hydroxides.



Metal oxides, on the other hand, are bases. Metal oxides formally contain the O 2- ion, which reacts with water to give a pair of OH- ions.



Compounds that contain hydrogen bound to a nonmetal are called nonmetal hydrides. Because they contain hydrogen in the +1 oxidation state, English for Chemistry



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Metal oxides therefore fit the operational definition of a base.



Typical Acids and Bases Summary Acids 



We see the same pattern in the chemistry of compounds that contain the OH, or hydroxide, group. Metal hydroxides, such as LiOH, NaOH, KOH, and Ca(OH)2, are bases.



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Non-metal Hydrides: HF, HCl, HBr, HCN, HSCN, H2S Non-metal Oxides: CO2, SO2, SO3, NO2, P4O10 Non-metal Hydroxides: HOCl, HONO2, O2S(OH)2, OP(OH)3



Bases 



Nonmetal hydroxides, such as hypochlorous acid (HOCl), are acids.



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The table below summarizes the trends observed in these three categories of compounds. Metal hydrides, metal oxides, and metal hydroxides are bases. Nonmetal hydrides, nonmetal oxides, and nonmetal hydroxides are acids.



Metal Hydrides: HI, LiH, NaH, KH, MgH2, CaH2 Metal Oxides: Li2O, Na2O, K2O, MgO, CaO Metal Hydroxides: LiOH, NaOH, KOH, Ca(OH)2, Ba(OH)2



Source: https://chemed.chem.purdue.edu/genchem/topicre view/bp/ch11/acidbase.php#arrhen



A. Vocabulary Read passage above carefully. Match the vocabularies below with their meaning according to the context given in the passage. 1. 2. 3. 4. 5.



Odor Dilute Attributed Spoil In essence



: ______________ : ______________ : ______________ : ______________ : ______________



6. 7. 8. 9. 10.



Contact Bound Dissociate Abstract Dissolve



: ______________ : ______________ : ______________ : ______________ : ______________



Definitions: a. b. c. d. e. f. g. h. i. j.



Diminish or destroy the value or quality of. Combine with (a substance) through chemical bonding. Extract or remove (something). Fundamentally. A distinctive smell. Make (a liquid) thinner or weaker by adding water or another solvent to it. The state or condition of physical touching. (With reference to a solid) become or cause to become incorporated into a liquid so as to form a solution. Split into separate smaller atoms, ions, or molecules, especially reversibly. Regard a quality or feature as characteristic of or possessed by (someone or something).



B. Reading Comprehension Answer the following questions based on the text above. 1. 2. 3. 4. 5.



Butyric acid is a compound formed when the quality of food decays. Acids dissolving metal is the base for making salts. Metal and nonmetals differences lay in the existence of hydrogen. Hydrogen has different oxidation states when responding to metal or not. Nonmetal oxide causes carbonic, sulfuric, and phosphoric acid to form in the water.



(T/ (T/ (T/ (T/ (T/



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6. Mention some examples of acids with sharp odor and sour taste!



__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 7. According to Robert Boyle, what were the properties of alkalies?



__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 8. Why are metal hydrides categorized as base?



__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 9. Explain the differences of metal and nonmetal oxides! __________________________________________________________________________________ __________________________________________________________________________________



__________________________________________________________________________ 10. Why do nonmetal hydroxides belong to acids? __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________



Language Focus



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Simple Present Example: 1. It is a dilute solution of acetic acid in water. 2. The name "acid" comes from the Latin acidus, which means "sour," and refers to the sharp odor and sour taste of many acids. 3. Nonmetal hydrides, nonmetal oxides, and nonmetal hydroxides are acids. 4. Alkalies change the color of litmus from red to blue. The sentences above are taken from the previous text. In all of the sentences above, it shows that they all describe about fact, opinion or general information. Those sentences use simple present. However, there two different forms of verbs that can be used in simple present. So, how do we differentiate them? Read the following explanation to help you understand the differences between two verbs in simple present.



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Recognizing these two verbs (Form): Simple Present



Singular Subject + V1 (with s/es)



Plural Subject + V1 (without s/es)



Basic uses and functions: 1. Use the present simple for a present state (e.g. feeling, opinion) or general facts 2. Use the present simple for a habitual actions or routines.



Sentence Example: 1. David wants to be an expert chemist 2. She plays video games every Sunday



Sentence Example: 1. I want a pizza for my dinner 2. We meet the director once a week



Practice! Direction: Change the verb in the parentheses into the correct forms of simple present. 1. Hydrogen storage system ______________ (provide) power technology for Tesla battery. 2. He always ______________ (do) his best in chemistry class. 3. Chemical engineers ______________ (store) hydrogen energy systems for renewable energy. 4. We ______________ (not/play) video games every day. 5. _________________ (you/trust) your pharmacologist? 6. She ________________ (not/get) to work on her laboratories before 9 am every day. 7. The girls never _________ (listen) to pop music with their headset on. 8. Hydrogen and oxygen molecules _____________ (produce) water or hydrogen peroxide. 9. Our new neighbor _________ (work) as Analytical Chemist in Vertex Pharmaceuticals. 10. I ___________ (like) yogurt very much.



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Basic Writing



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Read both of the text and analyze whether they are a paragraph or not. Text 1 Italy is one of the most historical countries in the world and therefore has many historical places for tourists to visit. Firstly, it is the Colosseum which was the place where gladiators had to fight each other. Another interesting place is the leaning of Pisa. This attraction is interesting because of its unique style. Venice is also a place that attracts many tourists because of its uncommon city landscape with its canals and bridges that connects the city.



Text 2 Italy is one of the most historical countries in the world and therefore has many historical places for tourists to visit. Firstly, it is the Colosseum which was the place where gladiators had to fight each other. Another interesting place is the leaning of Pisa. This attraction is interesting because of its unique style. Other than that, Italy is also famous for its culinary such as pizza and pasta. Not only that, they also famous for its coffee.



Important Terms Paragraph: a group of sentences that focus on a single idea Topic: the one thing a paragraph is about Topic sentence: the sentence that tells what the paragraph is about Supporting details: those sentences that explain the topic sentence Abridged and modified from Pearson



Visualize Your Understanding! Take a look on the text 1 and text 2, then read the visual explanation below why one of them is a paragraph and the other is not. As it can be seen from the idea map below, text 2 has thesis sentence which does not have appropriate supporting details. Meanwhile, the topic sentence of text 1 have supporting details that connect each other. To write a good paragraph, you have to maintain that the idea focuses on one topic with appropriate supporting details.



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Idea Map



Italy is one of the most historical countries in the world and therefore has many historical places for tourists to visit.



Italy is one of the most historical countries in the world and therefore has many historical places for tourists to visit.



Firstly, it is the Colosseum which was the place where gladiators had to fight each other.



Firstly, it is the Colosseum which was the place where gladiators had to fight each other.



Another interesting place is the leaning of Pisa. This attraction is interesting because of its unique style.



Another interesting place is the leaning of Pisa. This attraction is interesting because of its unique style.



Venice is also a place that attracts many tourists because of its uncommon city landscape with its canals and bridges that connects the city.



Other than that, Italy is also famous for its culinary such as pizza and pasta. Not only that, they also famous for its coffee.



Practice! Take a look on the reading text in the first page of this unit! 1. How many paragraphs are there? ____________________________________________ 2. What is the topic of the text? ______________________________________________ 3. What is the first paragraph of the text? _______________________________________ 4. What are the topic sentences of each paragraph above? Underline the topic sentences! 5. Could you find the supporting details of each topic sentence? Highlight your answers



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