A student conducted an experiment to classify three unknown liquid samples, P, Q, and R.
- When blue litmus paper was dipped into sample P, it turned red.
- When red litmus paper was dipped into sample Q, it turned blue.
- When both blue and red litmus papers were dipped into sample R, there was no change in their color. Additionally, when turmeric paper was used with sample R, no color change was observed.
Based on these observations, correctly identify the nature of samples P, Q, and R, respectively.
Options
Acidic, Basic, Neutral
Basic, Acidic, Neutral
Neutral, Acidic, Basic
Acidic, Neutral, Basic
Explanation
Let's analyze each sample based on the properties of indicators taught in NCERT Class 7 Science:
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Sample P: The observation states that blue litmus paper turned red when dipped into sample P. This is a characteristic property of acidic substances. Acids are known to turn blue litmus paper red.
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Sample Q: The observation states that red litmus paper turned blue when dipped into sample Q. This is a characteristic property of basic (or alkaline) substances. Bases are known to turn red litmus paper blue.
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Sample R: The observations state that sample R had no effect on either blue or red litmus paper, meaning their colors did not change. Furthermore, when turmeric paper was used with sample R, no color change was observed (turmeric paper turns reddish-brown in basic solutions). These combined properties indicate that sample R is a neutral substance. Neutral substances do not change the color of litmus paper, nor do they typically react with turmeric to show a color change.
Therefore, the correct classification for samples P, Q, and R, respectively, is Acidic, Basic, and Neutral. Option A correctly matches this classification, while the other options provide incorrect combinations for the observed indicator changes.