Implement this lesson:
This should be one of the first lessons taught to give students a robust understanding of what pH is.
Learning objective:
Students will be able to recognize that pH is one way scientists measure ocean acidification, understand the pH scale, acids and bases, understand that a small shift in the pH scale represents a much large shift in the chemical balance
Next Generation Science Standards (NGSS)
Common Core ELA Standards
Informational Text Grades 4-8:
1 – Refer to details and examples in a text when explaining what the text says explicitly and when drawing inferences from the text 4 – Determine the meaning of general academic and domain-specific words or phrases in a text 7 – Interpret information presented visually, orally, or quantitatively and explain how the information contributes to an understanding of the text in which it appears.
Writing Standards Grades 4-8:
1 – Write opinion pieces on topics or texts, supporting a point of view with reasons and information 2 – Write informative/explanatory texts to examine a topic and convey ideas and information clearly 4 – Produce clear and coherent writing in which the development and organization are appropriate to task, purpose, and audience
Common Core Math Standards
Mathematical Practices:
Construct viable argument and critique the reasoning of others Attend to precision Measurement and Data Grades 4-5 Represent and interpret data
Next Generation Science Standards
4 Structure, Function, and Information Processing 4-LS1-1 Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction
Science and Engineering Practices: Engaging in Argument from Evidence
Crosscutting Concepts:
Cause and Effect Systems and System Models 3-5 Engineering Design 3-5ETS1-2 Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
Science and Engineering Practices Constructing Explanations and Designing Solutions
Crosscutting Concepts:
Influence of Science, Engineering, and Technology on Society and the Natural World MS Human Impacts MS-ESS3-3 Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment
Science and Engineering Practices: Constructing Explanations and Designing Solutions
Crosscutting Concepts:
Cause and Effect Influence of Science, Engineering, and Technology on Society and the Natural World
Texas Essential Knowledge and Skills (TEKS)
K.6A use the senses to explore different forms of energy such as light, thermal, and sound
K.9B examine evidence that living organisms have basic needs such as food, water, and shelter for animals and air, water, nutrients, sunlight, and space for plants
K10B identify basic parts of plants and animals
1.6(A) identify and discuss how different forms of energy such as light, thermal, and sound are important to everyday life
1.10(A) investigate how the external characteristics of an animal are related to where it lives, how it moves, and what it eats
2.9(A) identify the basic needs of plants and animals
2.9(B) identify factors in the environment, including temperature and precipitation, that affect growth and behavior such as migration, hibernation, and dormancy of living things
2.9(C) compare the ways living organisms depend on each other and on their environments such as through food chains
3.9(A) observe and describe the physical characteristics of environments and how they support populations and communities of plants and animals within an ecosystem
5.9(A) observe the way organisms live and survive in their ecosystem by interacting with the living and nonliving components.
5.9(B) describe the flow of energy within a food web, including the roles of the sun, producers, consumers, and decomposers
5.9(C) predict the effects of changes in ecosystems caused by living organisms including humans, such as the overpopulation of grazers or the building of highways
5.9(D) identify fossils as evidence of past living organisms and the nature of the environment at the time using models
Overview:
About a quarter of the carbon dioxide emitted into the atmosphere from the burning of fossil fuels, ends up in our ocean. Carbon dioxide is an “acid gas” and causes the ocean to become more acidic, which is represented by a lower pH. Although pH is just one piece of the acidification chemistry puzzle, understanding the pH scale, which tells us how basic or acidic a liquid is a great first step in understanding how our ocean’s waters stay in balance. Even though the ocean waters aren’t acidic, a small shift in this balance in pH, can make a big difference for marine organisms, just as it does in the human body.
Materials:
- 15 sheets of paper
- index cards
- everyday house liquids with different pH values (see bottom of the lesson)
- An object to represent the ocean (snowglobe, vat of water, marine creature, etc)
Advanced Prep:
- Write the numbers “1” through “14” of different 8”x11” sheets of papers.
- Place sheets with numbers 1-14 in numerical order in line from left to right (along a table, or along floor depending on setting).
- Write “8.1 on 5”x7” index and place on right upper corner of “8” paper
Procedure:
- Introduce the pH scale (0-14). Anything above 7 is a basic (alkaline) anything below 7 is acidic, 7 is neither an acid or a base, but neutral 0= the strongest acid. Acid: usually sour, stings if touched, reacts or degrades metals 14= strongest base. Base is bitter, slippery if touched, dissolves fats and oils
- Ask student to pick household item (or offer them one) and ask them to place it on the scale to make their best guess at the pH of the item. Refer to “pH values of everyday objects” below. You can encourage them by telling them they are getting “hotter” or “cooler,” or closer or further away if they are looking for direction. Or ask question about the substance such as “Does it taste sour?”.
- Explore as many items as time and interest allow saving the “ocean” for the last. When handing student the “ocean” let them know how special the ocean is and offer a prize for placing this is the right place on the scale (if available). You can discuss the decrease in our ocean’s pH over past century. One hundred years ago the ocean was at pH =8.1 and our ocean today at pH of 8.0 May be hard to believe that a 0.1 difference means much but if the pH changes by ½ of that in our blood (just 0.05 decrease), it can cause headaches, confusion, feeling tired, tremors, sleepiness, and make it hard for the brain function. (“healthy blood pH= 7.45, called “acidosis” when blood pH = 7.4). Scientists have seen some of these same effects in some of the fish that live in the ocean (i.e. clownfish [Nemo], who may become confused and swim towards a predator in a more acidic ocean.
- Carbon dioxide is an “acid gas” and causes the ocean to become more acidic (represented by a decrease on the pH scale). Carbon dioxide emissions/pollution into our atmosphere from things like: -driving our cars, boats, planes, trains -using electricity in our home -removing trees (deforestation) that hold Carbon dioxide in their leaves, preventing it from ending up in the ocean
Questions to Ask:
Pre-experiment
- Do you know what an acid is? A base? Would you like to learn about it?
- Did you know there are acidic and basic substances we use and possibly eat each day?
- Do you know what is causing this change in ocean pH?
Post-experiment
- Can you think of anything you can do to help lower the amount of carbon dioxide we release in to the atmosphere, which eventually ends up in the ocean?
Extensions:
-Complete the same experiment except using pH indicators to create a ‘rainbow’
Evaluation:
-Produce a presentation (oral, graphic/technological) representing the results of the experiment. Include theories as to why these results are important and what it could mean to the marine environment and animals with a calcium carbonate shell. Have students (individually or as a class) develop a solution to the problem of increasing ocean acidity. Have them compare different ideas and evaluate the effectiveness of differing solutions.
Approximate pH of Everyday or Household Objects • larger battery =2.2 • vinegar= 2.8 • coca-cola = 2.5 (classic) can range up to 4.2 with other brands • lemon=2.3 • grapefruit = 3.0-3.3 • orange= 3.0-4.0 • apple= 3.5 • banana= 5.0 • milk= 6.5 • water bottle pH= 7 (6.5-8 depending on brand) • human blood= 7.4 • ocean pH= 8.1 now 8.0 • baking soda= 8.4 • Tums, antacid= 10.5 • bleach= 12.6 • drain cleaner = 14