Solutions-NCERT-Class-6-Science-Curiosity-Chapter-8-A Journey through States of Water-CBSE

Thirav is not correct. Ice and water are the same substance in two different physical states—solid and liquid. You can verify this by placing an ice cube in a cup at room temperature and observing it melt back into liquid water, or by placing liquid water in a refrigerator freezer to freeze it into ice.

Puddle water disappears through a combination of evaporation into the air as invisible water vapour and absorption/seeping into the ground soil.

Water disappears when wet clothes dry on a line, mopped floors dry, washed utensils lose surface water, sweat evaporates from skin, or water is sprinkled on a hot cooking pan.

The water sprinkled on a hot pan rapidly converts into steam and water vapour due to the high temperature.

Hand sanitiser rapidly evaporates from liquid into gas due to exposure to air and warmth from your hands.

The droplets come from invisible water vapour present in the surrounding air. When warm air contacts the cold outer surface of the tumbler, the water vapour cools and converts into liquid water droplets through condensation.

Liquid water evaporates into water vapour inside the utensil. When the rising vapour touches the cooler inner lid surface, it condenses back into liquid water drops.

During cool nights and early mornings, plant surfaces become cold. Water vapour in the ambient air comes into contact with these cold surfaces and condenses into liquid dew drops.

• Solid (Ice): Retains a fixed shape regardless of the container; does not flow or spread.
• Liquid (Water): Takes the shape of its container while keeping a constant volume; possesses the ability to flow and spread.
• Gas (Water Vapour): Has no fixed shape or volume; spreads out freely to fill all available space.

Gaseous aroma particles released from hot food spread freely through the air (exhibiting the gas property of spreading through available space) until they reach our nostrils.

Solid candle wax melts into liquid state when heated and freezes back into solid state upon cooling. Coconut oil transitions from liquid to solid state during cold winter conditions when cooled.

The plate provides a larger exposed surface area. A larger surface area exposed to air causes water to evaporate much faster.

Heat from sunlight increases the rate of evaporation. Moving air (wind) carries away moisture surrounding the clothes, speeding up evaporation.

On rainy days, the air already contains a high amount of water vapour (high humidity). High humidity slows down the rate of evaporation.

An earthen pot has porous walls through which water continuously seeps out and evaporates from the outer surface. Because evaporation absorbs heat energy, it cools down the pot and the remaining water inside. Stainless steel is non-porous, so no seeping or evaporative cooling occurs.

Air movement from the fan accelerates the evaporation of sweat from skin. As sweat evaporates, it absorbs heat from the body, producing a cooling effect.

Water vapour is lighter than air. Because it is lighter, it naturally ascends into the upper atmosphere.

As water vapour rises into cooler atmospheric layers, it condenses around microscopic dust particles to form tiny floating droplets (clouds). As droplets collide and merge into heavier drops, gravity pulls them down as rain.

(iv) The conversion of water vapour into its liquid state.

• Explanation: Condensation is specifically defined as the process of conversion of water vapour into its liquid state when it comes into contact with a cooler surface.

•  (i) (b) water colours and (c) acrylic colours: Water colours and acrylic paints use water as a liquid medium. Evaporation of this liquid water allows the paint to dry and set firmly on paper.
• (ii) (b) ink pen: An ink pen deposits liquid ink onto paper. The liquid portion of the ink must evaporate into the air so the writing dries without smudging

• Natural grass contains water. Water evaporates from the grass and the moist soil below it, and evaporation causes a cooling effect, so the surroundings feel cooler.
• Plastic grass has no water to evaporate, so there is no cooling effect, and it simply warms up in the sun.

Hand sanitiser, alcohol (spirit), nail-polish remover (acetone), petrol, perfume, kerosene, ink solvent, and the liquid in a marker pen.

• A fan does not make the air colder; it moves the air. Air moving past wet clothes carries away the water vapour near the cloth and brings in drier air. Lower humidity near the cloth and more air movement make evaporation faster.
• The heat needed for evaporation is taken from the cloth and the surroundings, so the clothes dry. We feel cool under a fan for the same reason: it helps sweat evaporate, and evaporation cools the body.
• So the fan is useful for drying clothes because it speeds up evaporation, not because it supplies cold air.

• Reduces transportation costs: Freshly removed sludge contains a large amount of trapped water. Leaving it exposed to air for 3–4 days allows the water to evaporate, drastically reducing the total weight and volume of the sludge heaps. Transporting lighter, dried material requires fewer trips and lowers fuel costs.
• Enhances worker safety: Evaporation transforms wet, liquid sludge into a drier solid mass. Dry sludge is significantly easier and safer to shovel, pack, and handle without risks of splashing contaminated wastewater on sanitation workers

• Household activities involving evaporation: Hanging washed clothes to dry, mopping floors, drying washed utensils, boiling water during cooking, and sweat drying off skin.
• How understanding evaporation helps: Knowing that heat, surface area, and wind speed increase evaporation helps us dry clothes faster by spreading them out widely, placing them under direct sunlight, or turning on a ceiling fan on humid days

As ice and snow: snow on mountain peaks, glaciers, polar ice caps, icebergs, hail, and frost on cold mornings.

A model answer:

• We all have a right to water for drinking and daily life, but only a small portion of Earth’s water is fit for use and demand is rising with population.
• If we waste or pollute it, others (and future generations) are left without.
• So we must first use it wisely, avoid wastage, and keep water bodies clean.
• Responsibility comes first, so that the right can be enjoyed by everyone.

(Personal opinions are welcome, but support them with reasons.)

• Place a wet cloth on the seat or sprinkle water on it. As the water evaporates, it takes heat from the seat and cools it (cooling effect).
• Even better, park in shade and use a light-coloured cover so it heats up less.