Live practice

Elements are placed in increasing atomic number. Recurrence of similar valence-shell configurations at regular intervals produces periodic similarity in properties.

Use the mass and charge of one electron, then multiply by the Avogadro constant for one mole.

Add the atomic-mass contributions of every atom in each molecular formula.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Calculate linear density, wave speed and travel time.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Periodic motion repeats after equal time intervals. A single trip or flight is not continuing periodic motion.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Treat each molecule as a sphere of radius 1.5 Å and multiply its volume by Avogadro's number.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

One litre of water has mass about one kilogram. Find heat required per minute and divide by heat of combustion.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

Use t°C=T−273.15 and t°F=(\(\frac{9}{5}\))t°C+32.

Principle and reasoning. Work from the governing physical relation and apply it to every stated part.

For equal load and extension, use ΔL=FL/(AY) and form a ratio.

Gravitational mass has one sign, so no material cancels a gravitational field. An orbiting laboratory is locally weightless, but a large station can detect variation of the field across it. Tides depend on the field gradient.