2 Using SI Units SI = International System of Units The standards of measurement used in science are those of the metric systemAll metric units are based on multiples of 10. As a result, you can convert between units easily
3 There are six SI base units From these base units, all other SI units of measurement can be derivedDensity and pressureSI Base UnitsQuantitySI base unitSymbolLengthmetermMasskilogramkgTemperaturekelvinKTimesecondsAmount of substancemolemolVolumemeter cubedm3
5 Length The SI Unit for length is the meter (m) For very large and very small lengths, a unit of length may have a prefixFor small distances, the prefix millimeters (mm) could be usedPrefix milli- means 1/1000, so 1 mm =0.001 m.For large distances....kilometers (km) can be usedThe prefix kilo- means 1000, so 1 km = 1000 m
6 Volume The SI unit of volume is a cubic meter (m3) A more convenient unit of volume for everyday use is the Liter (L), a NON-SI unitA smaller, NON-SI unit of volume is the milliliter (mL)1 mL and 1 cm3 are the same volumeThe units milliliter (mm) and cubic centimeter (cm3) are thus used interchangeably
7 Mass The SI Unit of mass is kilogram (kg) A more convenient unit of volume for everyday use is the gram (g)There are 1000 grams in 1 kilogram (1000g = 1kg)
8 WeightWeight is a force that measures the pull on a given mass by gravity.The weight of an object can change with its locationAn astronaut weighs less on the moon but has the same mass
9 Density mass volume Density = Density is the ratio of the mass of an object to its volumeThe relationship between an object’s mass and its volume tells you whether it will float or sink in a given situationmassvolumeDensity =Density is an intensive property (does not depend on the amount of matter)
10 Units of DensityThe SI unit of density is kilograms per cubic meter (kg/m3)Units of density vary depending on the units for mass and volume being measuredIncreasing density (mass per unit volume)10 g0.53 g/cm319 cm310 cm33.7 cm30.88 cm31.0 g/cm32.7 g/cm311.4 g/cm3
11 Corn syrup sinks below water because it is more dense As shown below, corn oil floats on top of water because it is less denseCorn syrup sinks below water because it is more denseCorn oilWaterCorn syrup
12 Densities of Some Common Materials Solids and LiquidsGasesMaterialDensity at 20°C (g/cm3)Density at 20°C (g/L)Gold19.3Chlorine2.95Mercury13.6Carbon dioxide1.83Lead11.3Argon1.66Aluminum2.70Oxygen1.33Table sugar1.59Air1.20Corn syrup1.35–1.38Nitrogen1.17Water (4°C)1.000Neon0.84Corn oil0.922Ammonia0.718Ice (0°C)0.917Methane0.665Ethanol0.789Helium0.166Gasoline0.66–0.69Hydrogen0.084
13 Density and Temperature Relationship The volume of most substances increases as the temperature increases, while the mass remains the same.Therefore, Density of a substance generally decreases as its temperature increases.Water is an important exception (density increases as temperature increases)
14 PRACTICE PROBLEMA copper penny has a mass of 3.1 g and a volume of cm3. What is the density of copper?
15 PRACTICE PROBLEMA rock is determined to have a mass of 8.2 g. The rock is dropped into a graduated cylinder containing 20.0 mL of water. The volume of the cylinder rises to 31.0 mL. Determine the density of the rock?
16 PRACTICE PROBLEMWhat volume would grams of Gold occupy? (Gold has a density of 19.3 g/cm3)
17 PRACTICE PROBLEMThe density of osmium, which is the densest metal, is g/cm3. What is the mass of a block of osmium that measures 1.00 cm x 4.00 cm x 2.50 cm?