K

Kilogram

1 kg = 1000 g; SI base unit of mass; N = kg·m/s²
Quick Reference
Formula / Notation1 kg = 1000 g; SI base unit of mass; N = kg·m/s²
Also Known Askg, kilogram (SI mass unit), mass unit, SI base unit of mass

What is Kilogram?

The SI base unit of mass, symbol kg. One kilogram is defined by fixing the Planck constant at exactly 6.626 × 10⁻³⁴ J·s. In chemistry, masses are often expressed in grams (g) or milligrams (mg). The kilogram is the only SI base unit with a prefix in its name.

Formula & Notation

1 kg = 1000 g; SI base unit of mass; N = kg·m/s²

Other Names / Synonyms: kg, kilogram (SI mass unit), mass unit, SI base unit of mass

Properties & Characteristics

The kilogram (kg) is the SI base unit of mass. Since 2019, it is defined by fixing the Planck constant h = 6.62607015 × 10⁻³⁴ J·s (formerly defined as the mass of the International Prototype Kilogram, a platinum-iridium cylinder). In chemistry, masses of substances are measured in grams (g) or milligrams (mg) for laboratory scale, or in tonnes for industrial scale. Molar mass (M, g/mol) relates mass to moles: n = m(g)/M(g/mol).

Uses & Applications

The kilogram is the basis of all mass-based measurements in chemistry: weighing reagents, calculating stoichiometry (n = m/M), expressing density (kg/m³ or g/cm³), and in SI units of force (N = kg·m/s²), pressure (Pa = kg/m·s²), and energy (J = kg·m²/s²).

Safety Information

No direct safety concern for the unit itself. Accurate mass measurement is critical in chemical safety: weighing errors in pharmaceutical preparation can lead to toxic overdoses; in explosive formulation, wrong mass ratios cause premature detonation or dud results.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Kilogram
Formula 1 kg = 1000 g; SI base unit of mass; N = kg·m/s²
Synonyms kg, kilogram (SI mass unit), mass unit, SI base unit of mass

Frequently Asked Questions

The SI base unit of mass, symbol kg. One kilogram is defined by fixing the Planck constant at exactly 6.626 × 10⁻³⁴ J·s. In chemistry, masses are often expressed in grams (g) or milligrams (mg). The kilogram is the only SI base unit with a prefix in its name.

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