Science · Beginner
Science You Half-Remember
Physics, chemistry, biology and earth science fundamentals, with the common myths dismantled.
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
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 02
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.
Sample 03
What is the true nature of the process that forms rust on iron objects?
Show the answer and why
Answer: Rusting is an inorganic chemical oxidation process involving oxygen and moisture.
Rust formation is an inorganic chemical oxidation process involving iron, oxygen, and water. It is not biological decay caused by micro-organisms.
Rusting is an inorganic chemical oxidation process in which iron reacts with oxygen and water to form iron oxides.
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