NCERT Solutions for Class 9 Science Chapter 5 Exploring Mixtures and their Separation
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Page No. 72
Think It Over
Question 1:
Why do suspended articles settle in muddy water over time but not in milk?
गंदे पानी में निलंबित कण समय के साथ नीचे बैठ जाते हैं, लेकिन दूध में क्यों नहीं?
Answer
Suspended particles in muddy water are large and heavy, so they settle down under gravity after some time. Milk is a colloid in which very small particles remain uniformly dispersed and do not settle due to their continuous random motion.
गंदे पानी में निलंबित कण बड़े और भारी होते हैं, इसलिए वे गुरुत्वाकर्षण के कारण समय के साथ नीचे बैठ जाते हैं। दूध एक कोलॉइड है, जिसमें बहुत छोटे कण समान रूप से फैले रहते हैं और लगातार गति के कारण नीचे नहीं बैठते।
Question 2:
How is evaporation different from boiling?
वाष्पीकरण और उबालना में क्या अंतर है?
Answer
Evaporation is a slow process that occurs at the surface of a liquid at any temperature.
Boiling is a rapid process that occurs throughout the liquid at a fixed temperature called the boiling point.
वाष्पीकरण एक धीमी प्रक्रिया है जो किसी भी तापमान पर द्रव की सतह से होती है।
उबालना एक तीव्र प्रक्रिया है जो द्रव के पूरे भाग में एक निश्चित तापमान (क्वथनांक) पर होती है।
Question 3:
Why do you see bright rays of sunlight when it passes through small gaps between the leaves of a dense tree?
जब सूर्य का प्रकाश किसी घने पेड़ की पत्तियों के बीच के छोटे-छोटे अंतरालों से होकर गुजरता है, तो उसकी चमकीली किरणें क्यों दिखाई देती हैं?
Answer
Bright rays of sunlight are visible because tiny dust particles and water droplets present in the air scatter the sunlight. This phenomenon, called the Tyndall effect, makes the path of light visible when it passes through small gaps between the leaves.
सूर्य की चमकीली किरणें इसलिए दिखाई देती हैं क्योंकि हवा में मौजूद धूल के सूक्ष्म कण और जल की बूंदें प्रकाश का प्रकीर्णन करती हैं। इस घटना को टिंडल प्रभाव कहते हैं, जिससे पत्तियों के बीच से गुजरने वाले प्रकाश का मार्ग दिखाई देने लगता है।
NCERT Solutions for Class 9 Science Chapter 5 Exploring Mixtures and their Separation
Page No 76
Pause and Ponder
Question 1:
A common talcum powder contains 4 % m/m zinc oxide, which acts as an antiseptic. How much zinc oxide is present in 300 g of the talcum powder?
Question 2:
Vinegar, used as a food preservative and additive, contains 5 % v/v acetic acid. Glacial acetic acid is a liquid, i.e., 100% acetic acid. If you want to make vinegar from glacial acetic acid, how would you proceed?
Question 3:
Your mother gives you a bottle of orange juice concentrate to mix with water and serve it to your visiting friends. She asks you to mix two tablespoons of the concentrate with water in a glass tumbler. If each tablespoon measures 15 mL and you make 150 mL of juice per person, what is the % v/v of orange juice concentrate in the mixture you prepared?
Page No. 79
Pause and Ponder
Question 4:
Refer to the solubility curves given in Activity 5.2. If equal masses of hot, saturated solutions of compounds ‘A’ and ‘B’ are cooled from 80 °C to 60 °C, which solution is likely to deposit more solid?
Question 5:
Will there be any change in the size of common salt crystals if the rate of evaporation is increased or decreased? Explain.
Page No. 82
Pause and Ponder
Question 6:
State whether the following statements are True or False. Also, correct the False statements.
(i) Salt can be separated from a salt solution by evaporation or distillation.
(ii) Distillation can be used for separation of two liquids even when these have the same boiling point.
(iii) In paper chromatography, the solvent level should be above the sample spot at the beginning of the experiment.
(iv) Evaporation and crystallization are the same processes.
NCERT Solutions for Class 9 Science Chapter 5 Exploring Mixtures and their Separation
Page No. 84
Pause and Ponder
Question 7:
Why do immiscible liquids form two separate layers in a separating funnel?
Question 8:
Is sublimation different from evaporation? Justify
Page No. 88
Pause and Ponder
NCERT Solutions for Class 9 Science Chapter 5 Exploring Mixtures and their Separation
