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Class 7 Science — Acidic, basic and neutral substances

Sort everyday substances as acidic, basic or neutral, read what each natural indicator is telling you, and use neutralisation to explain an ant bite and a sour field.

Name: ________________________

  1. 1.An acid solution and a base solution are mixed in the right amounts and the result is neither acidic nor basic. What is this reaction called?

  2. 2.Red rose extract has been added to each of these three test tubes. Tap the tube holding a basic solution.

    Write the number of the part.

    123

  3. 3.Manya is blindfolded and handed two solutions to tell apart. Which kind of indicator could she still use?

    • a) Red rose extract, because it is a strong colour
    • b) Turmeric paper, because turmeric is a familiar spice
    • c) An olfactory indicator, whose smell changes
    • d) Litmus paper, because the strips feel different

  4. 4.Put the steps of making a red rose indicator back into the order the chapter gives them.

    • Crush the petals with a mortar and pestle
    • Wash the fallen rose petals in water
    • Pour hot water over the crushed petals and cover the tumbler
    • Filter off the coloured liquid and keep it as the extract

  5. 5.Match each problem to the treatment the chapter gives for it.

    • Soil that is too acidic
    • Soil that is basic
    • Acidic factory waste
    • treated with manure and composted leaves
    • treated with a basic substance before release
    • treated with lime

  6. 6.A substance that shows one colour in an acid and a different colour in a base has a two-word name in this chapter. What is it?

  7. 7.Each of these was tested with blue and red litmus paper. Sort them by the nature the papers reported.

    Groups: Acidic · Basic · Neutral

    • Vinegar
    • Lime water
    • Salt solution
    • Soap solution
    • Tamarind water
    • Washing powder solution
    • Lemon juice
    • Sugar solution

  8. 8.A drop of an unknown liquid is put on turmeric paper and the yellow does not change. Which two possibilities are still open?

    • a) Nothing is open — turmeric paper settles it
    • b) It is acidic, or it is neutral
    • c) It is acidic, or it is basic
    • d) It is basic, or it is neutral

Answer key — Class 7 Science — Acidic, basic and neutral substances

  1. 1.
    • neutralisation
    • neutralization
    • a neutralisation reaction
    • neutralisation reaction
  2. 2. 2 — Basic
  3. 3. c) An olfactory indicator, whose smell changes
  4. 4. 1. Wash the fallen rose petals in water 2. Crush the petals with a mortar and pestle 3. Pour hot water over the crushed petals and cover the tumbler 4. Filter off the coloured liquid and keep it as the extract
  5. 5. Soil that is too acidic → treated with lime; Soil that is basic → treated with manure and composted leaves; Acidic factory waste → treated with a basic substance before release
  6. 6.
    • acid-base indicator
    • acid base indicator
    • indicator
  7. 7. Lemon juice → Acidic; Tamarind water → Acidic; Vinegar → Acidic; Soap solution → Basic; Lime water → Basic; Washing powder solution → Basic; Sugar solution → Neutral; Salt solution → Neutral
  8. 8. b) It is acidic, or it is neutral