Weather Experiments - Thermometer & Hygrometer

Sophia and Olivia are learning about the weather, so we recently did some experiments to demonstrate different aspects of weather. We used Janice VanCleave's Earth Science for Every Kid which has some easy-to-do activities that bring science principles to life and make them easy to understand.

Up and Down

Purpose: To demonstrate how a thermometer works.

Procedure: The girls held the bulb of the thermometer between their fingers.

Sophia watching the temperature rise

on the thermometer.

Heat from their fingers increased the temperature of the liquid inside the thermometer. As the liquid is heater, it expands and rises in the thermometer tube.

Olivia holding the thermometer bulb between her fingers.

She's watching the temperature slowly increase.

Next, they placed the thermometer in a cup of room-temperature water.  The cooler water removed the heat from the liquid in the thermometer.

The girls observing how the temperature decreases

when the thermometer is placed in water.

Then, we placed a few ice cubes in the cup of water and watched the temperature decrease even further. As the water cooled, it contracted and moved down the tube.

Olivia was especially surprised when the ice cubes were added.

The temperature decreased very quickly.

She's saying "Oooo!" as she watches the temperature drop.

According to Earth Science, "Outdoor thermometers are used to measure the temperature of air. Any increase or decrease in the heat content of air causes the liquid inside the thermometer to expand or contract, thus indicating the temperature of the surrounding air."

Wet Air

Purpose: To demonstrate the use of hair in measuring humidity.

Procedure: The girls used a small piece of tape to secure one end of Olivia's strand of hair to the center of the toothpick. We colored one end of the toothpick with a black marker.

The girls working together to attach

the strand of hair to the toothpick.

Then, we taped the free end of the hair strand to the center of the pencil. We placed the pencil across the mouth of the jar with the toothpick hanging inside the jar.

Placing the toothpick into the jar

with the pencil resting on the top.

The toothpick wasn't hanging horizontally, so we added a couple of drops of glue to the light end to balance the toothpick. They made a hair hygrometer (an instrument used to measure humidity - or the amount of water in the air).

The toothpick changes direction during the week. Why? According to Earth Science, "The hair stretches when the humidity increases; with a lower humidity, the hair shrinks. The stretching and shrinking of the hair pulls on the toothpick, causing it to move."