The Water Cycle in a Jar: Science to Explore at a Terrarium Workshop

Watch a closed terrarium closely and you may notice tiny droplets gathering on the glass, joining together and trickling towards the soil. That water has travelled through the jar without anyone lifting the lid to refill it.

At a terrarium workshop, building the miniature garden gives you a chance to understand that journey. By choosing suitable plants, adding moisture carefully and observing what changes, you can explore evaporation, transpiration and condensation in something small enough to keep on your desk.

Follow the Water from Soil to Glass and Back

A closed jar helps retain moisture, allowing water to circulate between the growing medium, plants and air. Several processes can happen at once, so watch for connections rather than expecting each stage to take a turn.

Evaporation moves water into the air

Water at the surface of damp soil changes from liquid into water vapour. This happens at ordinary room temperatures; boiling is unnecessary. Energy from the surroundings supports the change.

The vapour itself is invisible. When you see a misty patch on the glass, you are looking at tiny liquid droplets that have already formed through condensation.

Transpiration adds water from plants

Rooted plants absorb water from the growing medium. Some of this water moves through their tissues before being released as vapour, mainly through tiny leaf openings called stomata. This process is transpiration.

Plants therefore contribute to the moisture circulating inside the jar. How much they release depends on their species, available water, light and surrounding humidity.

Condensation makes the movement visible

When moist air beside the glass cools sufficiently, water vapour changes back into liquid. Small beads can appear on the inner walls or beneath the lid.

This is similar to the moisture that gathers outside a chilled drink in Singapore. In the terrarium, however, the droplets being observed are inside the container, formed from moisture already enclosed there.

Water returns to the growing medium

As droplets merge, gravity can pull them down the glass or cause them to fall from the lid. Water then soaks into the growing medium, where it can be stored, absorbed by roots or evaporated again. This entry of water into soil is called infiltration.

Falling drops offer a simple comparison with precipitation. The jar does not reproduce cloud formation exactly: condensation on glass resembles dew formation more closely than clouds suspended in the atmosphere.

Build a Terrarium That Makes Observation Easy

For this activity, ask for a closed setup with a clear container and a suitable lid. An open arrangement loses moisture to the room more readily, making it harder to follow water returning within the jar.

Choose small plants with similar moisture and light requirements. Fittonia and suitably small ferns are useful examples of plants that tolerate humid terrarium conditions. Ask the facilitator which available species suit the container.

Leave space around the plants and keep some glass unobstructed. Avoid pressing leaves against the sides, where moisture can remain trapped against them.

Add water gradually under guidance, aiming for a moist growing medium without waterlogging. Stones at the base may provide space where water collects, but they do not give a jar a drainage outlet. Careful watering still matters.

Try Two Simple Water Cycle Investigations

These activities can begin during the workshop and continue at home. Discuss any comparison involving extra containers with the facilitator beforehand.

Keep a droplet diary

Photograph the same side of the jar in the morning and later in the day for several days. Record whether the glass is clear, lightly misted or covered with larger droplets. Note where the jar stands and when the room’s air conditioning is running.

Look for changes in droplet size and position. A clear patch does not prove the water has disappeared from the container; it may have evaporated, moved down the glass or entered the soil. Several observations reveal more than one photograph.

Compare covered and uncovered containers

Prepare two similar jars with equal amounts of the same growing medium, comparable plants and the same measured starting water. Keep them beside each other in bright, indirect light. Cover one and leave the other open for a short comparison.

Predict which will retain moisture longer, then observe both over several days. If a suitable kitchen scale is available, compare each jar’s mass with its own starting measurement, keeping the lid treatment consistent.

The open jar will generally lose water more readily. Record any water added, since that changes the comparison, and stop before the plants become stressed. Changing only the lid makes your observations easier to interpret.

Read the Jar’s Conditions in a Singapore Home

A terrarium’s position matters more than simply knowing that Singapore is humid. A sunny window ledge and an air-conditioned room expose the same jar to different conditions.

Choose bright, indirect light and avoid direct sun, which can overheat an enclosed container. Do not move the jar into strong sunlight to make droplets appear faster.

Light condensation that appears and clears can be normal. Persistent heavy fogging together with soggy soil suggests excess moisture; briefly opening the lid can allow some to escape. Check the growing medium and plants before deciding what to change.

If the glass stays clear, avoid automatically adding water. Look for drying soil and check the lid’s fit first. Watering needs vary with the container, plants and location, so ask for care guidance specific to your finished arrangement.

Connect the Science to Your Workshop Experience

At Craft Labs’ terrarium workshop in Singapore, trainers explain the ingredients and guide participants through construction. Sessions last approximately one to one and a half hours, and participants take their finished terrariums home. Glass containers, plants, soil and tools are provided.

If your main aim is water cycle learning, explain this when arranging the session and confirm a suitable closed format. Ask how the chosen plants use water and what moisture level to maintain. These questions connect each building decision with the observations you will make afterwards.

Frequently Asked Questions

How soon will droplets appear?

They may appear within hours, but timing varies with moisture and temperature. Allow several days of observation without adding water simply to force condensation.

Can the cycle happen without plants?

Yes. Water can evaporate from damp soil and condense inside a covered jar. Plants add transpiration and let you observe how living things participate.

Does a terrarium make new water?

The visible cycle mainly redistributes water already present. Droplets on the lid are moisture changing state and location, rather than a fresh supply entering the jar.

Does a sealed jar still need energy from outside?

Yes. Light supports photosynthesis, and heat can pass through the container. Retaining water does not make a terrarium independent of its surroundings.

Can children take part in the observations?

Yes. Children can draw droplets, compare photographs and describe changes. Adults should supervise glass handling, tools and assembly, with tasks matched to each child’s abilities.