SI Units and Density

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SI Units and Density
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International System of Units (SI)

• adopted in 1960
• seven base units which all others can be derived
• m, kg, K, s, mol, cd, A

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Common Metric Prefixes
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• Length
• a linear measurement
• meter (m)
• common units- cm, m, km

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• Volume
• space occupied by a sample of matter
• cubic meter (m3) but we use the smaller, non-SI
  unit liter (L) most of the time instead
• common units- L, ml, cm3, µL
• should be measured at 0C

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• Mass
• measures the quantity of matter
• kilogram (kg)
• common units- kg, g, mg, µg

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• Temperature
• measures kinetic energy of particles
• kelvin (K)
• common units- K and C

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Density

• an intensive property
• the ratio of an objects mass to its volume
• depends only on the substance, NOT ON THE SIZE
  of the substance
• as temperature increases, density normally
  decreases (thermal expansion)

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Density
D M/V
D density M mass V volume
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Example problem

• A piece of lead has a mass of 56.4 g and a volume
  of 5 cm3. Calculate its density.

given formula
set up problem answer w/ unit of
measurement
M 56.4 g DM/V V 5 cm3
56.4g/5 cm3 10 g/ cm3
cm3 is same as ml so sometimes see g/ml