Measuring pH1
Learning objectives:
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Measure the pH of different substances.
Distinguish between an acidic substance and a basic or alkaline one.
Classify and compare substances according to their pH.
Key questions:
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What are acids and bases?
How do you measure the acidity and basicity of a substance?
Open Exploration:
1. Press the red dot on the dropper and put .40L of each substance in the beaker.
2. Record the color of each substance in the chart.
3. Grab the green circle and place it in the beaker to hover over the substance.
4. Record the PH of each substance in the chart.
5. Press the orange circle at the bottom right to reset. And start this process over with a new
substance.
Substance Name:
Water
Battery Acid
Blood
Chicken Soup
Coffee
Drain Cleaner
Hand Soap
Milk
Orange Juice
Soda Pop
Spit
Vomit
Blue
Color
7.00
PH-
Collect and analyze evidence:
Continue exploring the simulation and answer the following questions:
6. Which substance is most acidic within the simulation? What is its pH value?
7. Which substance is most basic within the simulation? What is its pH value?
8. Which substance has a pH value closest to water (pH = 7)?
9. Which substances have the same pH values?
10. What is the PH value of Vomit? Based on this information, what do you think the substances in the
human stomach are, acidic or basic? Why do you think this is the case?
11. Is it possible to change the pH value of a substance? Explore this question using the simulation and
explain:
Add .40L of vomit in the beaker.
• What is the color?
Take the Green circle and get the PH.
• What is the PH?
Click the blue button that says water and add water.
a. What happens to an acidic substance when water is added?
b. Did the PH change?
c. Did the color change?
d. EXPLAIN
12. What happens to a basic substance when water is added?
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Add .40L of hand soap to the beaker?
Add water (Click the blue button that says water)
What happens to a basic substance when water is added?
o Did the PH change?
o Did the color change?
o EXPLAIN
13. In general, when we dilute an acid or a base the pH changes. Which pH value does it change
towards when diluted?
14. Can an acid be converted into a base and vice versa? What do you think?
Conclusions
Answer the next questions individually.
15. How can we know if a substance is acidic or basic?
16. How can we change the pH of a substance?