Prior Knowledge Questions (Do these BEFORE using the Gizmo .)
1. Acids are substances that produce hydrogen ions (H+) when dissolved in water. Lemon juice
is an example of an acid.
A. What does lemon juice taste like?
...
Prior Knowledge Questions (Do these BEFORE using the Gizmo .)
1. Acids are substances that produce hydrogen ions (H+) when dissolved in water. Lemon juice
is an example of an acid.
A. What does lemon juice taste like? A lemon is sour
B. What does it feel like if lemon juice gets in your eye? It burns because of the acidity
2. Bases are substances that produce hydroxide ions (OH-) when dissolved in water. Hand
soap is an example of a base.
A. What does soap feel like? It’s sudsy, slippery, and lathers
B. What does soap taste like? It tastes chemically
C. What does it feel like if soap gets in your eye? It also burns your eye
Gizmo Warm-up
1. Indicators change color in acids or bases. What is the color of the pH paper?
Orange, pink, blue, and yellow
2. Compare the paper to the pH color chart. What is the pH of ammonia?
11 is the pH
3. Is ammonia acidic or alkaline?
Ammonia is alkaline
Goal: Find the pH of 18 common substances.
1. Test: Use the Gizmo to find the pH of each of the available substances. Classify each
substance as acidic (pH < 7), alkaline (pH. > 7), or neutral (pH = 7).
0-14 pH indicator paper
Material in the tube pH value Acidic, alkaline, or neutral?
baking soda 8 alkaline
bleach 11 alkaline
coffee 5 acidic
Cola 2 acidic
drain cleaner 13 alkaline
hand soap 9 alkaline
juice (lemon) 2 acidic
juice (orange) 3 acidic
juice (tomato) 5 acidic
milk 7 neutral
milk of magnesia 10 alkaline
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oven cleaner 13 alkaline
saliva (human) 6 acidic
shampoo 6 acidic
stomach acid 1 acidic
vinegar 4 acidic
water (distilled) 7 neutral
water (ocean) 8 alkaline
2. Summarize: Compare all the acidic substances and all the alkaline substances.
A. In general, what types of substances tend to be acidic?
Citrus juices, certain fruits…liquids.
B. What types of substances tend to be alkaline?
Cleaning supplies
Goal: Find the pH of substances in a more accurate way.
1. Test: Before you begin testing with the 4.5-7.5 paper, list the pH values of the
substances below that you found using the 0-14 pH indicator paper. Then find the pH
of each substance with the 4.5-7.5 paper.
4.5-7.5 pH indicator paper
Material in the tube pH value (0 to 14 paper) pH value (4.5 to 7.5 paper)
Coffee 5 5
Milk 7 6.5
Oven cleaner 13 7.5
Saliva (human) 6 6.5
Shampoo 6 7
Stomach acid 1 4.5
Water (distilled) 8 7
2. Analyze: Compare the pH values in each column.
A. How do these values compare?
The values are almost the same
B. What is an advantage of using the 4.5-7.5 paper?
There is a smaller range of alkaline and acidic, more accuracy
C. What is a disadvantage of using the 4.5-7.5 paper?
The range can be too small to properly get some of the amounts pH
D. Given the results from two kinds of indicator paper, which substances appear to be
neutral (pH = 7)?
Milk, distilled water, and shampoo
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