Today, we are learning about the water cycle by making a terrarium and simulating rain, while understanding a very basic concept of how clouds hold water. Did you know that the amount of water on Earth is finite and has been the same since the early formation of the Earth? Yes, the glass of water you might be holding in your hand could have fallen from the sky when Brachiosaurus walked through lakes feeding on plants. And, when knights and kings ruled the land, they drank from wells, your glass of water could have been part of. And that same glass of water might fall from the sky as snowflakes hundred years from now.
To make a terrarium you will need:
- nature's objects: such as bark, moss, marbles, leaves, pinecones, acorns, chestnuts (you can also use pea gravel or potting soil);
- we also added forest animal figurines (buy here);
- water + blue water coloring;
- cotton balls to resemble clouds;
- Gauze to seal the terrarium with a rubber-band.
Since the Earth has a limited amount of water: the water keeps going around and around in what we call a "Water Cycle." This cycle is made up of few main parts:
- Evaporation: the sun heating up water in oceans, rivers, and lakes, and turning it into vapor or steam. Also transpiration: when plants lose water out of their leaves.
- Condensation: when water vapor gets cold (usually high up in the atmosphere where the temperature is cooler), it changes back into liquid, forming clouds.
- Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to Earth in the form of rain, hail, sleet or snow.
- Collection: when water falls back to Earth, it may fall back into the oceans, lakes or rivers or it may end up on land, soaking into the earth and becoming a part of the "groundwater" which plants and animals use to drink. Or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts ... ALL OVER AGAIN!
Children used a dropper and blue-colored water to saturate the "clouds" causing precipitation.
A terrarium (plural: terraria or terrariums) is a glass (or a see-through) container containing soil and plants, which is usually sealed, however, it can also be open to the atmosphere (similar to what we created).
Children learned, while practicing fine motor skills and eye-hand coordination, that when clouds become too heavy, it starts to rain.
This experiment was very illustrative to discuss the water cycle and how it works:
- Through transpiration, the moisture is carried from the soil through the plant's roots to small pores on the leaves.
- Evaporation occurs when tiny drops of water transform from a liquid to a gas (generally due to increased temperature).
- Condensation takes place when the water vapor collects and turns from a gas back into a liquid.
- And finally, precipitation happens when a lot of condensation forms, getting too heavy and falling to the ground, as here in the form of rain.
If you create a sealed terrarium, the heat entering through glass walls would naturally allow for the creation of a small scale water cycle. This happens because moisture from both the soil and plants evaporates in the elevated temperatures inside the terrarium. This water vapor then condenses on the walls of the glass jar and eventually falls back to the plants and soil below, representing a complete natural water cycle.
As the light passes through the transparent terrarium wall, this can also be a fun experiment on photosynthesis, which is an important aspect of plant growth.