Water Cycle

Evaporate Some Water, Part 2

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In the first Evaporate Some Water experiment, we explored the water cycle and how water can be converted into water vapor using only the energy from the sun. But what happens to water that is not in a stream, lake, or ocean?

The Experiement

Supplies: Two clear glasses of the same size, a marker pen, a piece of cardboard that will cover one of the glasses, tape, food coloring (optional).

What to do: Put a vertical strip of tape on the side of each glass. Measure out enough water to fill each glass about 3/4. Fill each glass with the exact same quantity of water. Add food coloring, if available. On the piece of tape, mark the water level on each glass. Tape the cardboard cover onto one of the glasses so that it does not fall off. Place both glasses in direct sunlight and leave them for a full day of sunlight. Then observe the level in each glass. Which glass had more water evaporated out of it?

What is happening: The piece of cardboard blocked the water vapor from reaching the atmosphere, so the water stayed inside the glass. Blocking the top of the glass created a miniature closed ecosystem, where the water evaporated into the space in the top of the glass, then condensed and returned to the pool of water below. The Earth is a closed ecosystem on a grand scale, with our atmosphere trapping the water and keeping it here, just like the cardboard kept the water in the glass.

Links

To find out more about closed ecosystems and instructions on how to make one of your own, visit NASA’s Climate Kids website!

Evaporate Some Water

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Matter exists in one of four different categories or states – solid, liquid, gas, or plasma. Some molecules can exist in multiple states, while others will only ever be in one. When we think of water, we usually think of the liquid that comes out of our faucet, falls from the sky as rain, or fills creeks, rivers, ponds, lakes, and oceans. The water in these examples is in liquid form, but if you heat up water, it changes. It stops being a liquid and becomes a gas called water vapor. Another common name for this vapor is steam. Similarly, when liquid water gets really cold, it changes state again. This time it becomes a solid – ice.

The water that exists on the surface of the Earth is the same water that has been here for millions of years. On the surface of the planet, water can be found in liquid form (water), or as a solid (snow and ice). Water can also be found in the atmosphere as water vapor. Water moves from the atmosphere to the planet as precipitation. Water moving from the planet to the atmosphere is called evaporation. When there is more energy from the sun present, like on a hot, sunny day, water evaporates more quickly. Humidity refers to the amount of water vapor in the air. High humidity is when a large amount of water vapor is present. Low humidity is when little water vapor is present.

The Experiment

Supplies: A hot sunny day, chalk, a paper cup of water, a flat portion of concrete, a watch or clock.

What to do: Pour some water on the concrete or asphalt to make a puddle about 18 inches in diameter – preferably in full sunlight. Use the chalk to make a circle around the edge of the puddle. Every 15 minutes or so come back to examine the puddle and draw a new circle around it.
What happened to the puddle each time you checked on it? How long did it take for the puddle to disappear entirely?

What is happening: Energy from the sun, in the form of heat, changes the water from liquid to water vapor, causing it to evaporate into the atmosphere.

Links

To learn more about evaporation and the water cycle, head over to the National Geographic Kids website.