Kilogram

High school (ages 12+)
Mathematics & Numbers

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/kilogram

1. What is the SI base unit?
2. What is the unit symbol?
3. Why was the kilogram changed from a water definition to a constant-based definition?
4. How does the Kibble balance help measure a kilogram?

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the SI base unit?The fundamental unit of mass in the International System of Units (SI)
2. What is the unit symbol?kg
3. Why was the kilogram changed from a water definition to a constant-based definition?The original kilogram was the mass of one liter of water, but water changes weight with temperature. Scientists wanted a stable, unchanging standard, so they used fixed physical constants instead.
4. How does the Kibble balance help measure a kilogram?The Kibble balance measures the electrical power needed to balance a kilogram against gravity. By linking electricity to mass through the Planck constant, it shows how heavy a kilogram really is.

Metrology: The scientific study of measurement and its application.
Planck Constant (h): A fundamental constant in quantum mechanics that relates the energy of a photon to its frequency.
Kibble Balance: A metrological instrument used to realize the kilogram by relating electrical power to mechanical force via the Planck constant.
Empirical Definition: A definition based on observation and experiment, rather than theoretical principles.