Discussion

Which is heavier: a kilogram of feathers or a kilogram of lead?

Formally, density is the ratio of mass to volume for a material

ρ =	m
	V

Units

1000 kg/m³ = 1000 g/l = 1 g/cm³

liquids are typically hundreds of times more massive than gases.

Densities of Selected Materials (~20 ℃, 1 atm)
material	density (kg/m3)		material	density (kg/m3)
acetone	790		kerosene	810
acid, acetic (CH3COOH)	1050		lard	919
acid, hydrochloric (HCl)	????		lead	11,350
acid, sulfuric (H2SO4)	1390		lithium	534
air, 100 K	3.556		lithium 6 deuteride	820
air, 200 K	1.746		lungs	400
air, 293 K	1.207		mayonnaise, traditional	910
air, 300 K	1.161		mayonnaise, light	1000
air, 500 K	0.696		methane, gas, +25 ℃	0.656
air, 1000 K	0.340		methane, liquid, -90 ℃	162
alcohol, ethyl (grain)	789.2		milk, cow, heavy cream	994
alcohol, isopropyl (rubbing)	785.4		milk, cow, light cream	1012
alcohol, methyl (wood)	791.3		milk, cow, whole	1030
ammonia	771		milk, cow, skim	1033
aluminum	2700		mercury	13,594
argon, gas, ~300 K	1.449		monosodium glutamate	1620
argon, liquid, 87 K	1430		nickel	8900
beer, pilsner, 4 ℃	1008		nitrogen (N2), gas, ~300 K	1.145
benzene	870		nitrogen (N2), liquid, 74 K	808
blood	1035		oil, vegetable, coconut	924
body fat	918		oil, vegetable, corn	922
bone	1900		oil, vegetable, olive	918
butane	551		oil, vegetable, palm	915
butter	911		oil, vegetable, peanut	914
carbon	2250		oil, vegetable, soya	927
carbon dioxide, gas, +25 ℃	1.799		osmium	22,500
carbon dioxide, solid, −37 ℃	1101		oxygen (O2), gas, ~300 K	1.308
copper	8960		oxygen (O2), liquid, 87 K	1155
corn starch, loosely packed	540		perchlorethylene	1600
corn starch, tightly packed	630		platinum	21,450
corn syrup	1380		plutonium, α	19,860
diesel	800		salt (sodium chloride)	2165
formaldehyde	1130		silicon	2330
freon 12, liquid	1311		silicon dioxide (quartz)	2600
freon 12, vapor	36.83		silicone	993
gasoline	803		silver	10,490
glycerine	1260		skin	1050
gold	19,300		sodium bicarbonate	2200
grain, barley	620		sugar, sucrose	1550
grain, corn, shelled	720		titanium	4500
grain, corn, ear	900		tungsten	19,300
grain, flax	770		uranium	19,050
grain, millet	640		water, liquid, 100 ℃	958.40
grain, oats	410		water, liquid, 50 ℃	988.03
grain, rice, rough	580		water, liquid, 30 ℃	995.65
grain, rice, hulled	750		water, liquid, 20 ℃	998.21
grain, rye	720		water, liquid, 10 ℃	999.70
grain, wheat	770		water, liquid, 4 ℃	999.98
helium, gas, ~300 K	0.164		water, liquid, 0 ℃	999.84
helium, liquid, 4 K	147		water, ice, 0 ℃	916
hydrogen (H2), gas, 300 K	0.082		water, ice, -50 ℃	922
hydrogen (H2), liquid, 17 K	71		water, ice, -100 ℃	927
honey	1420		water, sea	1025
iron	7870		zinc	7140
iridium	22,400