Date: 9-11-13Day Plan: Presentations

Scientific Notation Tomorrow

Density vs. Weight Pre-lab (lab tomorrow)

Opener: A. 0.002030 D. 0.004300 B. 1.005 E. 1000.1 C. 0.00860 F. 230.1 + 2.4234

G. 2.0550 X 2.433 =

A. 0.002030 (4) D. 0.004300 (4)

B. 1.005 (4) E. 1000.1 (5)C. 0.00860 (3) F. 230.1 + 2.4234 =232.5 G. 2.0550 X 2.433 =5.000

DensityWhy some things float and others sink.

Mass: the amount of matter that an object containsMeasured in gramsAlways remains constant

Weight: a force that measures the pull of gravity on a certain massMeasurement can change depending on

locationExample: on the moon

DiscoveryEducation Mass Vs. Weight Video Clip

First things first…mass vs. weight

Ratio of mass of an object to it’s volumeIntrinsic property

Depends on the composition of an object, not on the size of the sample

Demo (human density demo)

Density = mass ÷ volumeUnits: g/mL or g/cm3

Density

DensityPhysical property of matterEverything has a unique densityThe measure of the relative "heaviness" of

objects with a constant volumeHow closely "packed" or "crowded" the

material appears to be

Important DensitiesDensity of AIR:

0.0013 g/mLDensity of WATER:

1.00 g/mL

VolumeThe amount of space an object takes upUnits of measurement:

LitersMillilitersCentimeters cubed (cm3)

Measuring VolumeWe can measure the volume of regular

object using the formula length x width x height.

10 cm

9 cm

8 cm

Length

Height

Width

_______ X _______ X _______ = ________Length Width Height Volume (cm3)

Measuring VolumeWe can measure the volume of

irregular object using water displacement.

Amount of H2O with object = ______

About of H2O without object = ______

Difference = Volume = ______

Reading a graduated cylinderRead the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water.

What is the volume of water in the cylinder? _____mL

Calculating Density

A copper penny has a mass of 3.1 g and a volume of 0.35 cm3. What is the density of copper?

Step 1: List Variables

Step 2: List equation Density = mass ÷ volume

Step 3: Substitute and Solve= 3.1 ÷ 0.35 = 8.8571

g/cm3

Practice

Known Variables Mass = 3.1 g Volume = 0.35 cm3

Unknown Variables Density= ?

A student finds a shiny piece of metal that she thinks is aluminum. In the lab, she determines that the metal has a volume of 245 cm3 and a mass of 612 g. Calculate the density.

Density = 612 ÷ 245Density = 2.50 g/cm3

More Practice

A bar of silver has a mass of 68.0 g and a volume of 6.48 cm3. What is the density of silver?

Density = 68.0 ÷ 6.48 Density = 10.5 g/cm3

One More…

Density VideoBuoyancy- an upward

force exerted by a liquid, gas or other fluid, that

opposes the weight of an immersed object