Lesson 2 of 12 · 8 min
Properties, SI units and measurement
NCERT § "Properties of Matter and their Measurement"
Carry Diya's tumbler to the Moon and her digital kitchen scale would show about 30 g. Did the water lose 150 g on the way?
The lesson in notes
In short
Physical properties such as colour, melting point, boiling point and density can be observed without changing the identity of the substance; chemical properties such as acidity or combustibility show up only when a chemical change happens.
The SI system has seven base quantities: length (metre, m), mass (kilogram, kg), time (second, s), electric current (ampere, A), thermodynamic temperature (kelvin, K), amount of substance (mole, mol) and luminous intensity (candela, cd).
Mass is the amount of matter in a body and stays the same everywhere; weight is the force of gravity on it and can change from place to place.
Volume has the SI unit m³; in the laboratory 1 L = 1000 mL = 1000 cm³ = 1 dm³.
Density is mass per unit volume; its SI unit is kg m⁻³, though g cm⁻³ is more common in the laboratory.
Temperature is reported in °C, °F or K; the kelvin scale has no negative values because 0 K is the lowest possible temperature.
Conversions: K = °C + 273.15 and °F = (9/5)(°C) + 32.