# SI Units and Density Stating a Measurement

In every measurement there is a

Number followed by a

Unit from a measuring device

### International System of Units (SI)

 seven base units which all others can be derived

 m, kg, K, s, mol, cd, A

### SI measurement

Le Système international d'unités

The only countries that have not

(in western Africa) and Myanmar

(a.k.a. Burma, in SE Asia), but now these are reportedly using metric regularly

Metrication is a process that does not happen all at once, but is rather a process that happens over time.

Among countries with nonmetric usage, the U.S. is the only

country significantly holding out.

The U.S. officially adopted SI in

1866.

Information from U.S.

Metric Association

Common Metric Prefixes

# Matter

 properties are that it has:

mass: amount of matter (atoms) in an object

volume: amount of space an object takes up

density: the mass per unit volume of an object

What some things that are not matter?

 Length

 a linear measurement

 meter (m) common units- cm, m, km

### Volume

 space occupied by a sample of matter cubic meter (m 3 ) but we use the non SI unit liter (L) most of the time instead common units- L, ml, cm 3 , µL should be measured at 0 ° C

### Mass

 this in NOT weight

 measures the quantity of matter

 kilogram (kg)

 common units- kg, g, mg, µg

### Temperature

 measures kinetic energy of particles kelvin (K)

 common units are K and °C

Notice that 1 Kelvin = 1 degree Celsius

Anders Celsius

1701-1744

Lord Kelvin

(William Thomson)

1824-1907

Learning Check

Match L) length M) mass V) volume

### Density

 an intensive or intrinsic

property of matter

 the ratio of an object’s mass to its volume

 depends on only on the substance, NOT ON THE

SIZE of the substance

 as temperature increases, density normally decreases

(thermal expansion)

Back to the

Future

“Your are my density” clip. Back to the Future

D = M/V

### Example problem

A piece of lead has a mass of 56.4 g and a volume of 5.3 cm 3 . Calculate its density.

given formula set up problem answer w/ unit of measurement

M= 56.4 g

V= 5.3 cm 3

D=M/V 56.4g/5.3 cm 3 11 g/cm 3 cm 3 is same as ml so sometimes see g/ml

Density

 mass (g) volume (cm3)

Platinum

Mercury

Aluminum

13.6 g/cm 3 21.5 g/cm 3 2.7 g/cm 3