Calculators and lookups
Element data, molar masses and eye-color odds, worked out in the browser.
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Interactive Periodic Table
All 118 elements with 3D atoms, melting and boiling points, trends and a quiz.
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Molar Mass Calculator
Type any formula, brackets and hydrates included, and get the molar mass with every step worked out.
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Mixed Fraction Calculator
Add, subtract, multiply or divide two, three or more mixed numbers, with every step shown and the answer simplified.
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Standard Deviation Calculator
Paste a list or a frequency table and get the sample and population standard deviation, with the full working.
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Baby Eye Color Calculator
The odds of brown, hazel, green or blue eyes from both parents' eye colors, based on six eye-color genes.
Interactive maps
Volcanoes and fossils on maps you can search and zoom.
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World Volcano Map
Every volcano that erupted in the last 12,000 years, with plate boundaries and the volcanoes active this week.
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Fossils Near You
Type a town or ZIP code to see the fossils found near you, then play the history of Earth on the map.
3D models
Labeled models you can rotate, zoom and take apart.
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Cell 3D Model
An animal cell and an E. coli bacterium, with every organelle labeled.
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Skin 3D Model
A block of skin cut open to show its three layers, follicles, glands and nerves.
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DNA 3D Model
The double helix with its backbone, base pairs and hydrogen bonds labeled.
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Atom 3D Model
Any of the 118 elements in Bohr or orbital view. Build your own atom and take the quiz.
Practice, quizzes and games
Chemistry drills with worked answers, printable worksheets and a daily word search.
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Polyatomic Ions Quiz
Name the ion from its formula, or write the formula from its name, with a worked answer each time.
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Naming Ionic Compounds Practice
Name an ionic compound from its formula and see why each answer is right.
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Ionic Compound Formula Writer
Write the formula of an ionic compound from its name, with the charges balanced step by step.
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Polyatomic Ions Flashcards
Printable worksheets and flashcards for the polyatomic ions, in six sets with answer keys.
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Science Word Search
A new science word search every day, plus 28 topic puzzles you can play online or print.
Every interactive tool on 33Science in one place: calculators, maps, 3D models and chemistry practice. They all run in the browser on a phone, tablet or computer, with no download or sign-up.
For students
Start with the interactive periodic table and the molar mass calculator for chemistry homework. The polyatomic ions quiz, the naming practice and the formula writer show a worked solution after every answer, so a wrong answer still teaches the rule.
For teachers
Project a 3D model or the volcano map on the board and turn it as you explain. The polyatomic ions worksheets and the word searches all have a print version. More classroom sheets are on the printables page.