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Science · Beginner

Science You Half-Remember

Physics, chemistry, biology and earth science fundamentals, with the common myths dismantled.

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What you will learn

The 9 topics inside Science You Half-Remember

Each topic has its own goal, its own questions and its own mastery score, so you always know which part is still weak.

  • Atoms and molecules

    Explain how atoms are built and how they bond into molecules and compounds.

  • Chemical reactions

    Identify what happens to matter during a chemical reaction.

  • Energy, work and heat

    Distinguish forms of energy and state conservation of energy correctly.

  • Evolution and natural selection

    Describe how natural selection drives change across generations.

  • Forces and motion

    Apply Newton's laws to explain everyday motion.

  • Genetics and DNA

    Explain how genes, DNA and inherited traits relate.

  • Microbes and disease

    Explain how microorganisms cause and spread infectious disease.

  • Plate tectonics and earthquakes

    Explain how moving plates cause earthquakes, volcanoes and mountains.

  • Weather and climate

    Separate short-term weather from long-term climate and explain both.

Example questions

Real questions from this course

These are taken straight from the course. Pick an answer, then open the explanation to see why it is right.

  • Sample 01

    A coastal meteorologist monitors a weak tropical atmospheric depression forming over ocean waters with a surface temperature of 28 degrees Celsius. The surrounding region exhibits high atmospheric moisture and gentle, uniform winds throughout the lower atmosphere. A maritime operator asks whether this storm will turn into a tornado or a hurricane as it grows stronger. How should the meteorologist explain the developmental differences between these weather phenomena?

    Show the answer and why

    Answer: Hurricanes depend on warm ocean heat and low vertical wind shear, whereas tornadoes require strong vertical wind shear within land-based thunderstorms.

    Hurricanes are large-scale oceanic systems powered by warm sea surface moisture and inhibited by strong wind shear, whereas tornadoes are compact terrestrial features produced within convective storms that require vertical wind shear to create spinning updrafts.

    Hurricanes require vast expanses of warm sea surface water and low vertical wind shear to slowly organize over several days. Tornadoes instead form rapidly over land inside severe thunderstorms that rely on strong vertical wind shear to generate localized rotation.

  • Sample 02

    How does a catalyst affect the rate of a chemical reaction without altering the overall yield?

    Show the answer and why

    Answer: A catalyst is regenerated at the end of the process in its original form.

    Catalysts participate temporarily in reaction pathways but emerge intact, meaning a catalyst is regenerated at the end rather than consumed during the reaction.

    A catalyst lowers the activation energy by providing an alternative pathway, and it is regenerated at the end of the process without being consumed.

  • Sample 03

    Why is the mass number of an atom approximated by summing only its protons and neutrons?

    Show the answer and why

    Answer: Electron mass is negligible by comparison to the much larger masses of protons and neutrons.

    A proton or neutron has a mass of about 1 amu, whereas an electron's mass is ~0.00054 amu, making electron mass negligible by comparison when calculating mass number. This defends against the misconception that protons and electrons have about the same mass.

    Protons and neutrons account for almost all the atom's mass because the combined mass of electrons is negligible by comparison.

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