Chapter 7: Experiments with Water
पानी के प्रयोग (मृत सागर, उत्प्लावन एवं दांडी यात्रा 1930)
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In offline CTET exams, bubbling 150 bubbles takes 18 to 22 minutes of mechanical time. A single misaligned row can trigger an 8-question domino error. Practice bubble-filling this chapter's solved MCQs inside Mentora's official OMR simulator.
- Dead Sea (मृत सागर) salinity: The saltiest body of water in the world, containing approximately 300 grams of salt in every 1 liter of water.
- Floating in the Dead Sea: Because of its extremely high density, a human being cannot sink in the Dead Sea and floats effortlessly on the surface as if lying down on a bed.
- Buoyancy & Salt Density: A raw egg or fresh lemon sinks to the bottom of a glass filled with plain tap water, but rises and floats on top when substantial salt is dissolved in the water.
- Dandi March (1930 दांडी यात्रा): Historic march led by Mahatma Gandhi from Sabarmati Ashram in Ahmedabad to Dandi seashore in Gujarat to challenge the British salt monopoly and unfair tax laws.
- Solubility in water: Salt, sugar, and lemon juice dissolve in water; chalk powder, sand, oil, and kerosene do not dissolve and form separate layers.
- Trap: CBSE claims the Dead Sea has 100 grams or 500 grams of salt per liter. Correct: Exactly 300 grams of salt per 1 liter of water.
- Trap: CBSE states a lemon floats in fresh water and sinks in salt water. Correct: A lemon sinks in plain fresh water and floats in dense salt water.
- Trap: CBSE claims Dandi March occurred in 1942. Correct: Dandi March took place in 1930 from Ahmedabad to Dandi seashore.
NCERT Core Facts: Water Density, The Dead Sea & Dandi March
Chapter 7 investigates why certain materials float while others sink, explores water density, and introduces the historic 1930 Dandi Salt March.
1. Floating vs. Sinking (Density & Buoyancy)
- Iron Nail vs. Flat Bowl (Poem Experiment):
- A small, solid iron nail sinks immediately to the bottom of a water tub because its weight per surface area is high.
- A broad, lightweight bowl or empty steel dish floats on top of the water because it displaces a large volume of water.
- The Lemon & Salt Water Experiment (Direct CTET Item):
- a.Take a fresh lemon and place it into a glass of plain fresh water → The lemon sinks to the bottom.
- b.Gradually stir spoons of salt into the water → As salt dissolves, water density increases.
- c.When enough salt is dissolved, the lemon rises and floats on the surface!
2. The Dead Sea (मृत सागर)
3. Dandi March (दांडी यात्रा, 1930)
- Historical Context: In 1930, before India gained independence, the British colonial government enacted a law forbidding Indians from harvesting natural sea salt and placed a heavy tax on everyday salt.
- Mahatma Gandhi's Philosophy:
"How can a law not allow us to use freely what nature has given! Salt is an essential daily need of every poor and rich human being."
- The Journey: In 1930, Gandhiji along with hundreds of fellow citizens undertook a long march on foot from Ahmedabad to the Dandi seashore in Gujarat to defy the salt law and crystallize sea salt freely.
Test Your Mastery: Experiments with Water
Authentic CBSE exam questions tested directly from this NCERT chapter.
Dead Sea is an ocean/sea which:
मृत सागर क्या है?
A lemon sinks in normal water, but floats in salty water because the density of:
नींबू साधारण पानी में डूब जाता है लेकिन नमकीन पानी में तैरता रहता है क्योंकि:
Before independence, Mahatma Gandhi's march on foot to Dandi seashore is related to which of the following events and year?
स्वतंत्रता से पूर्व महात्मा गांधी ने जिस दांडी के समुद्र तट तक अपनी प्रसिद्ध यात्रा की थी, वह किस घटना तथा वर्ष से संबंधित है?
What is the salinity of the Dead Sea according to NCERT Class 5 EVS?
According to NCERT Class 5 EVS Chapter 7, the Dead Sea contains approximately 300 grams of salt in one liter of water. This high density allows humans to float effortlessly without swimming.
Why does a lemon float in salt water but sink in fresh water in CTET exams?
A lemon sinks in fresh water because the lemon's density is greater than plain water. When salt is dissolved in water, the density of the salt solution increases, making it denser than the lemon and causing the lemon to float.
In which year did Mahatma Gandhi lead the Dandi March according to NCERT?
Mahatma Gandhi led the Dandi March in 1930 from Sabarmati Ashram in Ahmedabad to the Dandi seashore in Gujarat to protest the British tax on salt.