Density

Density measures how much mass is packed into a given volume. The formula is: Density = Mass ÷ Volume, with rearrangements: Mass = Density × Volume, Volume = Mass ÷ Density. The unit of density depends on the units of mass and volume. Common units include g/cm³ (grams per cubic centimetre), kg/m³ (kilograms per cubic metre), and g/ml (grams per millilitre). Note that 1 ml = 1 cm³. Water has a density of 1 g/cm³ or 1000 kg/m³. Objects with density greater than 1 g/cm³ sink in water; objects with density less than 1 g/cm³ float. Different materials have different densities: gold ≈ 19.3 g/cm³, aluminium ≈ 2.7 g/cm³, wood ≈ 0.5-1.0 g/cm³. Density doesn't depend on the amount of material - a small piece of iron has the same density as a large piece. Density problems often require calculating volume from dimensions first. For a cuboid: Volume = length × width × height. For a cylinder: Volume = πr²h. Remember to convert all measurements to consistent units.