Chemistry
Examples of Metallic Compounds, Sorted by Type and Use
October 12, 2026
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Chemistry
Examples of Metallic Compounds, Sorted by Type and Use
October 12, 2026
Chemistry
Bases in Chemistry: Examples, Properties, and pH Explained
October 12, 2026
Geography
Natural Resources of Malaysia: What It Has and Where
October 12, 2026
Chemistry
Examples of Acids: 15 Common Ones and Where You Find Them
October 12, 2026
Before you buy
Books and gear for science readers, students and classrooms, with the specs, prices and editions checked for every pick.
Free to print
Periodic tables, conversion charts and worksheets as free PDFs in US Letter and A4, with answer keys for the quizzes.
Printable Periodic Table
Free periodic table PDFs in color, black and white, blank with a key, kids and an element list, plus a build-your-own customizer.
Periodic Table with Charges
Common ion charges on every element, in color and black and white, with a blank quiz and answer key.
Metric Conversion Chart & Worksheets
Chart, staircase poster, worksheets and quizzes for 3 levels, with answer keys. US Letter and A4 international versions.
Fresh from the lab
Physics
Measuring Instruments: Types, Uses and How to Choose
A measuring instrument is any device that turns a physical quantity into a number you can read: a…
October 12, 2026
Botany
Endemic Plants of Jordan: 9 Species Found Nowhere Else
Jordan has more than 2,500 recorded plant species and only around 100 of them are endemic, meaning they…
October 12, 2026
Biology
Autotrophs: How Living Things Make Their Own Food
Autotrophs are organisms that make their own food from inorganic sources, such as carbon dioxide, water, and minerals,…
October 12, 2026
Geography
Natural Resources of the United Kingdom: What’s Still Here
TLDR The natural resources of the United Kingdom are North Sea oil and gas, wind and tidal energy,…
October 12, 2026
Chemistry
Potassium Nitrate Benefits: Plants, Teeth, Food, and Health
Potassium nitrate (KNO3) has no single “benefit.” It does four unrelated jobs: it feeds plants, blocks tooth sensitivity,…
October 12, 2026
Geology
Active Volcanoes in the DRC: Nyiragongo and Nyamuragira
Two volcanoes in the Democratic Republic of the Congo erupt in the modern record: Nyiragongo (3,470 m) and…
October 7, 2026
Chemistry
Radioactive Isotopes: Examples, Half-Lives, and Uses
A radioactive isotope is a version of an element with an unstable nucleus. It has the same number…
October 7, 2026
Physics
Physical Quantities: Types, Units and Examples Explained
A physical quantity is a property you can measure, and it always has two parts: a number and…
October 7, 2026
Biology
Endemic Species of Nebraska: What Lives Only Here
TLDR Nebraska has almost no strict endemics, meaning species found nowhere else on Earth. The clearest case is…
October 7, 2026
Why we publish
33Science is an independent publication exploring the natural world — from the chemistry of a single crystal to the life cycle of a star. Clear, curious and rigorously sourced, for readers of every background.
