Chemistry: Acids, Bases, and the pH Scale Worksheet

Question 1

A sample has a pH of 3. Is it acidic, basic, or neutral? Explain how you know.

Accepted Answer

The sample is acidic because acids have pH values less than 7.

Question 2

A student tests three liquids. Lemon juice has pH 2, pure water has pH 7, and baking soda solution has pH 9. List the liquids from most acidic to most basic.

Accepted Answer

The order from most acidic to most basic is lemon juice, pure water, and baking soda solution.

Question 3

What pH value is considered neutral? Name one common substance that is close to neutral.

Accepted Answer

A pH of 7 is considered neutral. Pure water is a common substance that is close to neutral.

Question 4

Blue litmus paper turns red when dipped into an unknown liquid. What type of substance is the liquid most likely to be?

Accepted Answer

The liquid is most likely an acid because acids turn blue litmus paper red.

Question 5

Red litmus paper stays red when dipped into vinegar. Does this result prove that vinegar is neutral? Explain.

Accepted Answer

No, this result does not prove vinegar is neutral. Red litmus paper stays red in acids, and vinegar is acidic.

Question 6

A cleaning solution has a pH of 12. Describe one safety precaution you should use when handling it and explain why.

Accepted Answer

You should wear safety goggles and gloves because a solution with pH 12 is a strong base and can irritate or damage skin and eyes.

Question 7

A student says, "All acids are dangerous." Explain why this statement is too simple.

Accepted Answer

The statement is too simple because some acids are weak and found in foods, such as citric acid in oranges, while strong acids can be dangerous and require careful handling.

Question 8

Two solutions have pH values of 4 and 6. Which solution is more acidic, and how many times more acidic is it based on the pH scale?

Accepted Answer

The solution with pH 4 is more acidic. It is 100 times more acidic than the solution with pH 6 because each pH unit represents a factor of 10.

Question 9

A pH indicator turns green in a liquid. The indicator chart says green means pH 7. What can you conclude about the liquid?

Accepted Answer

The liquid is neutral or very close to neutral because the indicator color shows a pH of 7.

Question 10

An acid and a base are mixed carefully in the correct amounts, and the final solution has a pH of 7. What type of reaction happened?

Accepted Answer

A neutralization reaction happened. The acid and base reacted to form a solution that is neutral or close to neutral.

Question 11

Classify each substance as acid, base, or neutral: stomach acid pH 1, soap solution pH 10, and salt water pH 7.

Accepted Answer

Stomach acid is an acid, soap solution is a base, and salt water with pH 7 is neutral.

Question 12

A fish tank should stay near pH 7. A test shows the water is pH 5. Is the water too acidic or too basic, and what should the owner do before adding any chemical treatment?

Accepted Answer

The water is too acidic because pH 5 is below 7. The owner should follow safe aquarium testing instructions or ask an expert before adding any chemical treatment.

Question 13

The table shows four unknown liquids: A has pH 8, B has pH 2, C has pH 7, and D has pH 13. Which liquid is the strongest base?

Accepted Answer

Liquid D is the strongest base because it has the highest pH value, 13.

Question 14

Explain the difference between a strong acid and a weak acid in middle school terms.

Accepted Answer

A strong acid breaks apart more completely in water and can produce a very low pH. A weak acid does not break apart as much and is usually less reactive at the same concentration.

Question 15

A student measures orange juice at pH 3 and milk at pH 6. Which is closer to neutral, and how do you know?

Accepted Answer

Milk is closer to neutral because pH 6 is only 1 unit away from pH 7, while pH 3 is 4 units away from pH 7.

Chemistry: Acids, Bases, and the pH Scale

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