The first 200 people to sign up at https://brilliant.org/stevemould/ will get 20% off an annual subscription that gives you access to the full archive of Daily Challenges and every single course Moles (in chemistry) are really clever and useful. The definition involves a really big number called Avogadro's Number and on its own is really unhelpful when trying to understand what the Mole is actually for! The best way to get your head around this unit (Mol) is to look at the problem that is solves. Along the way you'll find out about Atomic Mass Units, isotopes and some dodgy chemical equations! You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Joseph Galliera Nathan Williams Matthew Cocke Glenn Watson Mark Brouwer Joseph Rocca Joël van der Loo Doug Peterson Yuh Saito Rashid Al M Andrew Reeder You can buy my books here: https://stevemould.com/books Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk/