Observations and results
Did your hygrometer show that it is more humid in the bathroom after a shower than in a normal room in your home? When it was used outside, did the hygrometer give a higher reading when it was more humid, such as when it rained, compared with when it was dryer?
In the bathroom after a shower, if the room is small and the door was closed the entire time, the humidity can reach around 100 percent. If calibrated correctly, the hygrometer should give a reading of about 100 percent. In other rooms the humidity will probably be much lower than this, depending on how humid it is where you live and other factors (such as whether a humidifier or aquarium is being run). If you compared the readings of your hygrometer with another instrument that measures humidity, such as a psychrometer or an electric hygrometer, you may find that your hygrometer is 20 percent to 30 percent inaccurate, but you can recalibrate it using these devices to increase its accuracy.
As mentioned earlier, hair strands are made of protein molecules called keratins. Protein molecules are built from amino acids. In a hair strand, the keratin molecules are mainly held together by two forces: chemical cross-links between cysteines (a type of amino acid) and weaker hydrogen bonds. The keratins in hair have many such bonds, making a strand strong and flexible. The hydrogen bonds can be disrupted by water vapor in the air, with each keratin binding to water in the air instead of each other. In fact, this is what causes hair strands to regularly expand and contract in moist and dry air, respectively.
More to explore
Hair Keratin from Swiss Institute of Bioinformatics, Protein Spotlight
Hair Structure from Harley Street Hair Clinic
Understanding Relative Humidity and the Hygrometer by The Science Company
Make a Hygrometer with Strands of Hair from Science Buddies
This activity brought to you in partnership with Science Buddies