Short interactive lessons that ask a question before they explain. One session takes about ten minutes and ends with questions to check what you have understood.
Assume √2 is a fraction in lowest terms and show both parts are even: proof by contradiction.
Class 11 · Physics Units and Measurement FreeA measurement is a number and a unit. Seven SI base units define every other unit in physics.
Class 11 · Physics Units and Measurement FreeThe significant figures of a measurement are the reliable digits plus one estimated digit.
Class 11 · Physics Units and Measurement FreeProducts keep the fewest significant figures; sums keep the fewest decimal places.
Class 11 · Physics Units and Measurement FreeThe dimensions of a quantity state which base quantities it is made from, and with what powers.
Class 11 · Physics Units and Measurement FreeIf two sides of an equation have different dimensions, it is wrong. A match does not prove it right.
Class 11 · Chemistry Counting Atoms by Weighing FreeMixtures and pure substances, elements and compounds, and the physical methods that separate a mixture.
Class 11 · Chemistry Counting Atoms by Weighing FreeMeasured values carry units and a stated number of significant figures. Precision and accuracy differ.
Class 11 · Chemistry Counting Atoms by Weighing FreeFive patterns in the masses and volumes of reacting substances, explained by Dalton’s atomic theory.
Class 11 · Chemistry Counting Atoms by Weighing FreeThe mole is 6.022 × 10²³ particles, chosen so that the formula mass in grams is one mole.
Class 11 · Chemistry Counting Atoms by Weighing FreePercentage composition gives mole ratios, the empirical formula, and with the molar mass, the molecular formula.
Class 11 · Chemistry Counting Atoms by Weighing FreeA balanced equation gives mole ratios, which give the amounts formed and the limiting reagent.
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