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 = m3, we will use cm3/ml ml is NOT an SI unit

Density = kg/m3, we will use g/cm3 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/m3), we will use g/cm3 or g/ml

Example 1: A student obtains a mass of 5.03 g for a metal and a volume of 3.24 ml?

Example 2: What is the volume of a substance with a density of 0.824 g/ml and a mass of 0.451g?

Example 3: 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?

Density Problems

1) An object has a mass of 4 grams and a volume of 1.7 cm3. What is it’s density?

2) What is an object’s mass if it’s density is 8.3 g/cm3 and the volume is 4 cm3 ?

3) What is the volume of an object with a mass of 11 grams and a density of 4.2 g/cm3?

4) An object’s mass is found to be 40 grams. When this object is placed in a graduated cylinder with a V1 of 17ml, the V2 becomes 20 ml. What is the object’s density?

Homework

Density Problems