Quina densitat mesura, en termes senzills
Density is how much mass is packed into a given amount of space — mass divided by volume. It's why a shoebox full of feathers is easy to lift while the same shoebox packed with lead barely budges: same volume, wildly different mass, so wildly different density.
That single relationship — ρ = m ÷ V — connects three quantities so tightly that knowing any two always lets you solve for the third. This calculator handles all three directions, plus straightforward unit conversion when your numbers come in different systems.
La fórmula de la densitat, reordenada de tres maneres
Find density
ρ = m ÷ V
5 kg en un contenidor de 0,002 m³: 5 ÷ 0,002 = 2.500 kg/m³.
Troba la massa
m = ρ × V
2.500 kg/m³ farciment 0,002 m³: 2.500 × 0,002 = 5 kg.
Troba volum
V = m ÷ ρ
5 kg at 2,500 kg/m³: 5 ÷ 2,500 = 0.002 m³.
Els tres exemples descriuen el mateix bloc de material: aquest és el punt del triangle. Un cop coneixeu les dues cantonades, la tercera queda fixada.
Com es compara el teu resultat amb els materials quotidians
A raw number like "2,700 kg/m³" means more once you can place it next to something familiar. Every result on this calculator gets charted against the same five reference points:
| Material | Densitat (kg/m³) |
|---|---|
| Air (sea level) | 1.225 |
| Aigua | 1,000 |
| Alumini | 2,700 |
| Ferro | 7,870 |
| Gold | 19,300 |
This is also the classic way density gets used to identify an unknown material — measure the mass and volume of a sample, work out its density, and compare the result against known reference values like these.
Converting between density units
La densitat es mostra en qualsevol sistema d'unitats que utilitzi el material d'origen: articles científics mètrics en kg/m³ o g/cm³, especificacions d'enginyeria dels EUA en lb/ft³ o lb/in³. Totes les conversions es redueixen a una base comuna:
| Unitat | Equals (kg/m³) |
|---|---|
| 1 g/cm³ | 1,000 |
| 1 g/L | 1 |
| 1 lb/ft³ | 16.018 |
| 1 lb/in³ | 27,679.9 |
Worth remembering as a shortcut: 1 g/cm³ equals exactly 1,000 kg/m³, which is also the density of water — so water's density is 1 in g/cm³, a convenient benchmark for judging whether something will float.
On la densitat s'utilitza realment
- Floating and sinking: an object floats in a fluid when its overall density is lower than the fluid's — the principle behind ship hulls, life jackets, and hot air balloons.
- Material identification: comparing a sample's measured density against known reference values, as in the table above, is a quick way to tell metals or minerals apart.
- Shipping and freight: carriers often charge by dimensional weight, which is really a density calculation — bulky, low-density packages can cost more to ship than their actual weight suggests.
- Chemistry and material science: density feeds into everything from concentration calculations to whether a material will stay suspended in a mixture.
If you're working the mass side of this formula on its own — say, converting a shipment's weight between units — the Calculadora de masses i Weight Calculator handle that directly, and the Calculadora de volum can work out the volume of common shapes if you don't already have it measured.
La densitat no està fixada, la temperatura la canvia
Gairebé totes les substàncies s'expandeixen lleugerament quan s'escalfen i es contrauen quan es refreden, el que significa que la seva densitat baixa quan està calenta i augmenta quan està freda; la mateixa massa ara omple un volum lleugerament diferent. Les mesures de laboratori i les fitxes de dades del material sempre han d'anotar la temperatura a la qual es van prendre, ja que una densitat indicada sense una és només una aproximació.
Water breaks the usual pattern in one famous way: it's actually densest at about 4°C, not at its freezing point. Cool it further and it starts expanding again, which is why ice is less dense than liquid water and floats instead of sinking — a quirk of hydrogen bonding that keeps lakes from freezing solid from the bottom up.
Fonts i lectura addicional
Reference densities are approximate values at typical room conditions and will vary with purity, temperature, and pressure.