The image you've provided is an
answer key for a worksheet titled *"Acids, Bases, and the pH Scale"*. It includes two questions with their correct answers already filled in. Let's go through each question and explain the solution in detail.
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Q.1: Fill in the blanks with suitable words.
a) The _pH scale_ measures how acidic or basic a substance is.
✔ Explanation: The pH scale is a logarithmic scale used to specify the acidity or basicity of a solution. It quantifies the concentration of hydrogen ions (H⁺) in a solution.
b) pH scale ranges from _0_ to _14_.
✔ Explanation: The standard pH scale goes from 0 to 14. This range covers all possible acidities and basicities of aqueous solutions at room temperature.
c) A solution has a pH of 7, it's _neutral_.
✔ Explanation: A pH of 7 indicates neutrality — this is the pH of pure water at 25°C. At this point, the concentrations of H⁺ and OH⁻ ions are equal.
d) A pH less than 7 is an _acid_, with _lower_ numbers indicating stronger acids.
✔ Explanation: Solutions with pH < 7 are acidic. The lower the number (closer to 0), the higher the concentration of H⁺ ions, meaning the stronger the acid. For example, lemon juice (pH ~2) is more acidic than vinegar (pH ~3).
e) A pH greater than 7 is a _base_, with _higher_ numbers indicating stronger bases.
✔ Explanation: Solutions with pH > 7 are basic (or alkaline). Higher values (closer to 14) indicate stronger bases. For example, baking soda (pH ~9) is mildly basic, while bleach (pH ~12–13) is strongly basic.
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Q.2: Fill the blanks with following words to identify ranges of the pH scale.
Given words:
neutral,
acidic,
basic
Below the pH scale bar (from 0 to 14), there are three labeled boxes:
- From
0 to 6: labeled as
acidic
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7: labeled as
neutral
- From
8 to 14: labeled as
basic
✔ Explanation:
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Acidic (0–6): Solutions with low pH have high H⁺ ion concentration.
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Neutral (7): Equal H⁺ and OH⁻ concentrations; neither acidic nor basic.
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Basic (8–14): Solutions with high pH have low H⁺ ion concentration and high OH⁻ ion concentration.
This visual representation helps students understand that:
- The further left on the scale (toward 0), the more acidic.
- The further right (toward 14), the more basic.
- The center (7) is neutral.
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✔ Summary of Key Concepts:
| pH Range | Classification | Example |
|---------|----------------|--------|
| 0 – 6 | Acidic | Lemon juice, vinegar |
| 7 | Neutral | Pure water |
| 8 – 14 | Basic | Baking soda, soap, bleach |
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Final Answer Recap:
Q.1 Answers:
a) pH scale
b) 0, 14
c) neutral
d) acid, lower
e) base, higher
Q.2 Answers:
- 0–6 → acidic
- 7 → neutral
- 8–14 → basic
This worksheet effectively teaches the fundamentals of the pH scale, helping students classify substances based on their acidity or basicity.
Parent Tip: Review the logic above to help your child master the concept of acids bases and ph worksheet.
