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  • Course Biology Global - for use with NGSS (NEW)
  • Unit 1 The Chemistry of Living Things
  • Concept 1.1 Acids and Bases

    • Acids and Bases

    Exploring Acids and Bases

    When you hear the word acidglossary term (opens in a new window), what comes to mind? Do you think about an acid’s harmful effects? Many people think of acid in a negative way, but acids and their counterparts, bases, have many practical uses. They are quite common in our everyday lives. You probably even ate some acids and bases for breakfast today.

    Eating an Orange
    Eating an Orange
    What properties of acids are common in oranges and other citrus fruits?

    Acids and bases have distinct properties that make them useful for many common practices such as cleaning, cooking, and gardening. They are even essential for life in digesting foods and maintaining cellular stability. What are some of the common properties of acids and bases? How do these properties impact their use?

    In this lesson, you will learn the differences between acids and bases, their properties and uses, their involvement in cellular processes, and the way in which they are measured.

    The human body continuously produces acids, bases, and buffers. You probably already know about the acid in your stomach. What is the function of the acid in your stomach? Do you think this is a relatively strong acid? What would happen if the rest of your body were to be exposed to this stomach acid? Your stomach is not the only part of your body producing acids. Working muscle cells can produce acids as well. If you exercise too intensely, your blood is unable to transport enough oxygen fast enough to keep up with the cells’ metabolism. This can result in the accumulation of lactic acid when your cells find ways to function in the absence of oxygen. A burning sensation felt in active muscle from lactic acid buildup forces us to slow down.

    Professional athletes need to be mindful of their body’s lactic acid production during exercise to ensure that they do not damage their bodies. They monitor their lactic acid production to evaluate their fitness level and monitor their improvements, in particular during endurance training. The lactic acid that is produced does not stay in the muscles during training, so the amount of lactic acid produced can be determined by testing a blood sample.

    Lactic Acid Test for Athletes
    Lactic Acid Test for Athletes
    A small amount of blood is collected from the earlobe of an athlete to determine the amount of lactic acid produced during training. How might an athlete use this information to improve his or her workout routine?

    Blood is incredibly sensitive to changes in the concentration of acids and bases dissolved in it. Therefore, a mechanism has evolved to regulate the levels of acids and bases in the blood. How do you think the blood is able to achieve this constant balance?

      Chemical Language of Compounds
      Chemical Language of Compounds
      Chemical symbols are abbreviations for elements and compounds. What is a chemical formula?

    Teacher Note

    Students should answer this using the activity and revisit their answers when they start the Explain part of the concept.

    Explain Question

    Explain the roles that acids, bases, and buffers play in biological systems.

    Teacher Note

    Use this student response to evaluate students’ prior knowledge of the concept. Have students respond to this in their notes and then revisit later on to reflect on their learning and improve.

    Your teacher wants you to resubmit.

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    What role do acids, bases, and buffers play in biological systems?
    Press Space or enter key to Enter Text
     

    Before You Begin

    What do I already know about acids and bases?

    Teacher Note

    Use this formative assessment to evaluate students’ misconceptions that an increase in acidity relates to an increase of pH. Use this either as a class discussion or as a think-pair-share.

    Your teacher wants you to resubmit.

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    Scientists communicate how acidic or basic a solution is using numbers on a pH scale. The pH scale tells you the concentration of hydrogen ions in a solution.  Sort the following household items according to their pH.
    • pure water
    • egg white
    • tomato
    • stomach acid
    • milk
    • lemon
    • baking soda
    • Region 1
    • Region 2
    • Region 3
    • Region 4
    • Region 5
    • Region 6
    • Region 7

    Teacher Note

    This formative assessment is intended to provide the teacher with feedback on students’ prior knowledge of acids, bases, and buffers. Have students work in groups to answer the question and discuss what properties the materials in each category have in common.

    Your teacher wants you to resubmit.

    Screen Resolution - This interactive media is not optimized for the current screen resolution. To view the interactive, try changing your device orientation to a horizontal landscape view.
    Sort these familiar household items as acids, bases, or buffers.
    • lemon
    • baking soda
    • milk of magnesia
    • drain cleaner
    • vinegar
    • dish soap
    • soda
    •
      acid
    •
      base
    •
      buffer
    Incorrect Answer
    Correct Answer

    Teacher Note

    This formative assessment is intended to provide the teacher with feedback on prior knowledge of this topic. Use this student response to evaluate students’ misconceptions that an increase in acidity relates to an increase of pH. Use this for class discussion.

    Your teacher wants you to resubmit.

    Screen Resolution - This interactive media is not optimized for the current screen resolution. To view the interactive, try changing your device orientation to a horizontal landscape view.
    Match each term to its proper description.
    Use this trash can to delete all connections. To delete individual connections, select it and then click on its trash can.
    Delete selected connection.
    Term
    acid
    base
    buffer
    Description
    a solution that can maintain a relatively constant pH, even if it is diluted
    chemicals that lower pH by increasing the hydrogen ion concentration of a solution
    chemicals that increase pH by providing hydroxide ions that lower hydrogen ion concentrations of a solution

    Teacher Note

    This activity is intended to provide the teacher with feedback on prior knowledge of this topic. Have students think-pair-share before constructing a response.

    Your teacher wants you to resubmit.

    Screen Resolution - This interactive media is not optimized for the current screen resolution. To view the interactive, try changing your device orientation to a horizontal landscape view.
    Antacid tablets are used to relieve indigestion and mild stomachaches. Thinking about the properties of acids and bases, describe how an antacid tablet acts to soothe your indigestion.
    Press Space or enter key to Enter Text
     

    Teacher Note

    This formative assessment is intended to provide the teacher with feedback on prior knowledge of this topic. Use this student response to evaluate students’ misconceptions that acid strength is related to the concentration of the acid rather than the ability of the acid to dissociate hydrogen ions in water. Have students complete this in pairs.

    Your teacher wants you to resubmit.

    Screen Resolution - This interactive media is not optimized for the current screen resolution. To view the interactive, try changing your device orientation to a horizontal landscape view.
    You probably know that acids and bases are different from each other. You probably also know that not all acids are alike. Think about these differences and connect the given acids or bases to the following descriptions. Each acid or base can match more than one description.

    Use this trash can to delete all connections. To delete individual connections, select it and then click on its trash can.
    Delete selected connection.
    HCI (stomach acid)
    Acetic acid (vinegar)
    NaOH (drain cleaner)
    strong acid
    weak acid
    strong base
    weak base
    hydrogen donor
    hydroxide donor
    dissociates completely in water
    dissociates partially in water
    pH > 7
    pH = 7
    pH < 7

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    Lesson Question

    • What are the differences between acids, bases, and buffers?
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