Acids, Alkalis & pH · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Reading pH and testing solutions

Science · Matter & Materials · ages 12-13
Name ______________________   Date ____________

  1. Which pH value is neutral for a water-based solution at 25°C?

    • 0
    • 7
    • 14

  2. A lemon juice sample has pH 2 at 25°C. How is this water-based sample classified?

    • Acidic
    • Alkaline
    • Neutral

  3. For dilute water-based solutions at the same temperature, a higher concentration of H⁺ ions means a lower pH.

    Circle one:   True   False

  4. A bicarbonate of soda solution has a measured pH of 9 at 25°C. Which classification fits?

    pH at 25°C. Ticks: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. Marked values: 7, 9. 01234567891011121314pH at 25°C
    • Acidic, because 9 is below the top of the scale
    • Alkaline, because 9 is above the neutral value
    • Neutral, because any value close to 7 is neutral

  5. An indicator chart marks deep red as pH 1 to 2. A water-based sample tested at 25°C gives that colour. What can you conclude?

    • It has a low pH and is acidic
    • It has a high pH and is alkaline
    • It has the neutral pH value of 7

  6. Two points on a pH scale are equally far from 7. One point is at pH 3. What is the value of the other point above 7?

    Answer: ______________

  7. In a supervised test at 25°C, alkali is added to an acid. The indicator chart shows green at pH 7. Which conclusion fits?

    • The mixture must contain only pure water with no dissolved salt
    • The mixture must stay neutral even if more alkali is added
    • The mixture is neutral at the measured temperature

  8. Priya tests vinegar with blue litmus. It turns red, but she calls the vinegar neutral. What does this result actually show?

    • Vinegar is acidic: it turns blue litmus red
    • Vinegar is neutral: every colour change signals neutrality
    • Vinegar is alkaline: an alkali turns blue litmus red
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading pH and testing solutions W1-mt_AN2kJE6I0s-s1

  1. 7 · At 25°C, neutral pH is 7. Values below it are acidic and values above it are alkaline.
  2. Acidic · At 25°C, pH below 7 is acidic. The sample's pH is 2, so it is acidic.
  3. True · Higher hydrogen ion concentration means lower pH in these solutions. Concentration compares the amount in a given volume.
  4. Alkaline, because 9 is above the neutral value · At 25°C, pH above 7 is alkaline. The measured value 9 is above 7.
  5. It has a low pH and is acidic · The chart places the result at pH 1 to 2. Both values are below 7, so the sample is acidic. This alone does not establish whether the acid is strong or weak.
  6. 11 · 7 - 3 = 4 units. A point 4 units above 7 is 7 + 4 = 11. This describes scale positions, not amounts needed for neutralisation.
  7. The mixture is neutral at the measured temperature · At 25°C, pH 7 is neutral. Salt may remain dissolved, and adding excess alkali can make the mixture alkaline.
  8. Vinegar is acidic: it turns blue litmus red · An acid turns blue litmus red. A neutral solution leaves blue litmus blue. One unchanged strip alone would not establish neutrality.
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