DOR: Conversions 1) 40 ft/sec to miles/hr 2) 2.50 m 2 to cm 2

DENSITY AND SI UNITS

Scientific Measurements  SI Units  Significant Figures

SI Units  Measurement system universal to scientists.  Measurement standards (base and derived)  Base unit—  Quantity we can MEASURE  Derived unit--  Quantity provided by CALCULATION

SI Units (cont.) Base  Mass = kilogram (kg)  Length = Meter (m)  Time = Second (s)  Temperature = Kelvin (°K) Derived  Volume = m 3, we will use cm 3 /ml  ml is NOT an SI unit  Density = kg/m 3, we will use g/cm 3 or g/ml

Mass vs. Weight  What is the difference?  How do we measure mass?

Density  Physical property of matter/substances  Used for substance identification  Provides information on how solids/liquids interact  Ratio of a substance’s mass and volume  Density = Mass/Volume  Units = SI Unit (kg/m 3 ), we will use g/cm 3 or g/ml

Example 1: A student records V1= 2.7ml and V2= 3.4 ml after placing an object in a graduated cylinder. The mass of an empty beaker is 1.13g and the mass of both the beaker and substance is 4.13g. What is the object’s density?

Example 2: It has been estimated that there are 4 x mg of gold per liter of sea water. At a price of $22.30 per gram of gold, what would be the value of gold in 1.00 cubic kilometers of the ocean?

Example 3: A metallic sphere has a diameter of inches and a mass of ounces. What is the density of this object, in units of g/cm 3 ?

Homework p. 30 #59, 61, 63, 71 p. 32 #101