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1 clear, tall, airtight container (such as a large empty plastic jar with a screw top or a glass canister with an sealed lid)

potting soil

small plants (such as mosses, ferns, philodendron, pothos, African violets)

pebbles or broken flowerpot chips

filtering charcoal (not barbecue charcoal) Note: You can find this at pet stores.

2 small thermometers (about 4-5 inches long)

paper towel or cloth

water

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Wipe clean the inside of your container with paper towel or cloth.

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Place a one-inch layer of pebbles in the container.

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Next, cover the pebbles with a thin layer of fine charcoal.

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Then add about 1 inch of potting soil over the charcoal.

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Create a little hole in the soil. Place one or two small plants in the terrarium. You may need to add a little more soil so the roots are covered.

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Water the plants until the soil is moist but not soggy. (You may want do this over the sink or a large dish.)

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Place a small thermometer on the soil, near the edge of the container so it's easy to read the temperature.

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Cover your container with an airtight lid.

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Place the terrarium in a window that's well lit, but not too sunny. Place the second thermometer next to the terrarium.

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Over the next few days, observe your terrarium closely. If water droplets don't form on the sides, add a little more water. If mold develops, remove the top and leave it off for a few days to let the soil dry out a little. Chances are you won't ever need to water the soil because water from the leaves will form water vapor, then condense into water droplets inside the top.

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Observe and record how the plants grow inside your terrarium. Also keep a chart of temperature readings inside and outside the container. Was there a difference?

Why do you think that is? Compare your findings with a friend or classmate. You should find that the more sunlight a terrarium receives, the bigger the temperature difference inside and outside the terrarium.