Yearly Archives: 2016

Chemistry Mole Test Taking Preferences — Mole day is celebrated every year on October 23 from 6:02 am to 6:02 pm. This holiday honors chemistry’s own measurement unit corresponding to Avogadro’s Number: 6.02 x 1023. You can spend the day learning more about the mole, play a few rounds of “Whack a Mole” or have some […]

Fun Chemistry Mole Puns For Mole Day

This entry was posted on October 22, 2016 by Todd Helmenstine (updated on October 11, 2025)

Moving Rulers are Shorter — Relativity tells us moving objects will have different lengths in the direction of motion, depending on the frame of reference of the observer. This is known as length contraction. This type of problem can be reduced to two different frames of reference. One is the frame of reference where a […]

Moving Rulers Are Shorter – Length Contraction Example Problem

This entry was posted on October 18, 2016 by Todd Helmenstine (updated on May 17, 2021)

These are samples of pure chromium metal and chromium crystals. (Alchemist-hp) — Here are interesting facts about chromium, a transition metal with the element symbol Cr and atomic number 24. Chromium is known for being both an essential nutrient, yet toxic element and for its use in making chrome plating. Interesting Chromium Facts Chromium is a member of the transition metal element […]

Chromium Facts – Cr or Atomic Number 24

This entry was posted on October 18, 2016 by Anne Helmenstine (updated on May 17, 2021)

Use tonic water in place of water in slime recipes to get slime that glows blue under a black light. — What’s better than slime? Glowing slime, of course! There’s more than one way to make glow in the dark slime that really glows (not just under black light). Here are easy recipes to try and tips to get the best glowing effect. Tips for Getting the Brightest Glow There key […]

Easy Glow in the Dark Slime Recipes

This entry was posted on October 13, 2016 by Anne Helmenstine (updated on April 5, 2023)

Red Light Appears Green — Everyone knows about the Doppler effect with sound. When a train approaches, the pitch of its sound increases. After it passes, the pitch seems to drop off. This is because the sound waves are compressed (wavelength shortened/frequency increased) ahead of a moving sound source. The sound waves expand (wavelength increased/frequency […]

How Fast Would You Have to Go To Make A ...

This entry was posted on October 12, 2016 by Todd Helmenstine (updated on May 3, 2023)

Ammonia Ball and Stick Model — Many chemical reactions take place until one of the reactants run out. This reactant is known as the limiting reactant. Often it is straightforward to determine which reactant will be the limiting reactant, but sometimes it takes a few extra steps. Consider, for example, burning propane in a grill. The […]

How to Find the Limiting Reactant – Limiting Reactant Example

This entry was posted on October 7, 2016 by Todd Helmenstine (updated on September 4, 2022)

How to Calculate Theoretical Yield — Learn how to calculate theoretical yield. The theoretical yield of a reaction is the amount of product expected from a chemical reaction.

How to Calculate Theoretical Yield – Definition and Example

This entry was posted on October 5, 2016 by Todd Helmenstine (updated on August 7, 2022)

Karat vs Carat — Learn about the difference between carats and karats as the terms apply to gemstones and gold and the origin of the words.

Karat vs Carat – Difference Between Karats and Carats

This entry was posted on September 29, 2016 by Anne Helmenstine (updated on January 9, 2023)

Nobel Prize Medal Facts — Here's a collection of Nobel Prize medal facts, including its chemical composition, how much it's worth, and the medal's design.

Nobel Prize Medal Facts

This entry was posted on September 29, 2016 by Anne Helmenstine (updated on October 12, 2025)