Chapter 2, Section 5

Mass and Volume

August 30, 2011HW: None

• 2.3 Quiz• Honors Requirements• Choose Chapter/Section for presentation– Choose from • Ch. 2.6-2.9, • Ch. 6 (skip 6.5 and 6.8), • Ch. 1

• Find current event

2.3 Quiz

• Differentiate between solutions, suspensions, and colloids

Filter Laser Beam Example

Solution

Suspension

Colloid

2.3 Quiz

• Differentiate between solutions, suspensions, and colloids

Filter Laser Beam Example

Solution Pass through Pass straight through

NaCl in water

Suspension Liquid will pass thru, larger particles caught in filter paper

Stops laser beam Soil in water

Colloid Pass through Scatters/spreads out

Milk

August 30, 2011HW: 2.5 CTG, pg 142, #1-9, 11(Due Friday)

• LO– Determine density of liquids and solids– Correctly use significant figures

• SC– Determine the densities of various

liquid and solid materials– Make measurements in the lab to the

precision of the instruments used– Learn the difference between

accuracy and precision in experimental measurements

– Use density measurements to determine the identity of a material

– Locate sources of the variation in the class’s results

• Do Now– Write LO and SC on new

left side page– WDYS/WDYT-pg 134

• Agenda– Do Now– Investigate – Summary

Investigate Part A-pg 134-136

• Set up notebook for #1-5, OK with teacher• Complete #1-5• Graph data as a class (6a)• Answer questions 6b-f in your notebook using

your graph• Complete #7-9• Show teacher your calculations

Investigate Part B: pg. 136-7

• Set up notebook for #1, 3-6. Ok with teacher• Complete #1, 3-6 using the method shown

below• Calculate Density (#6) using

Density=mass/volume

Summary

• Why do some objects float while other sink?– Be sure to use the terms mass, volume, and

density

September 6, 2011HW: 2.5 CTG, pg 142, #1-9, 11 (Due Wed)

• LO– Determine density of liquids and solids– Correctly use significant figures

• SC– Determine the densities of various

liquid and solid materials– Make measurements in the lab to the

precision of the instruments used– Learn the difference between

accuracy and precision in experimental measurements

– Use density measurements to determine the identity of a material

– Locate sources of the variation in the class’s results

• Do Now– Explain the layers in the

density column.– How is it possible for giant

cruise ships and tankers made of steel to float in the ocean? Explain using density.• I know we already did this, but

I want to see if you understand!

• Agenda– Do Now– Chem Talk– Summary

Part C-Teacher Demo

• http://link.brightcove.com/services/player/bcpid34762914001?bckey=AQ~~,AAAAB_wnNRk~,WN9MweAQd_tBaI99JKgDAcW3bUx7peWv&bctid=84449964001

Chem Talk

• What is density?

• What is the equation for Density?

• A measurement of mass per unit of volume

• Density=mass/volume

D

M

V

D=

Chem Talk• When will objects sink?

• When will objects float?

• When will objects neither sink or float?

• When the object is MORE dense than the liquid, it will sink

• When the object is LESS dense than the liquid, it will float on top

• Objects with the SAME density will suspend in the middle of the liquid.

Chem Talk

• How can you measure the volume of a solid?

• Volume=LxWxH• Volume of an irregular

solid: Use water displacement method

Chem Talk

• Significant Figures: • Measurement should be the same as the smallest division on your measurement instrument.

Chem Talk

• Significant Figures… • Calculations:– Adding or subtracting:

• Arrange the numbers so the decimals line up.

• Complete the addition or subtraction.

• Draw a vertical line to mark the end of your least precise number

• The answer should have the same number of decimal places as the least precise number.

12.76+ 3.875 16.635

Answer=16.64

Chem Talk

• Significant Figures… – Multiplying and Dividing• The result should have NO

MORE Sig Figs than the factor with the LEAST amount of significant figures.

• Counting sig figs– 735=3 sig figs– 2008=4 sig figs (zeros count)– 00.0076=2 sig figs (zeros on

the left don’t count)– 820.00=5 sig figs (zeros on

the right count IF there is a DECIMAL point!)

– 230=2 sig figs (no decimal)

Significant Figure Rules

• There are three rules on determining how many significant figures are in a number:– Non-zero digits are always significant.– Any zeros between two significant digits are

significant.– A final zero or trailing zeros in the decimal

portion ONLY are significant.

Practice

• http://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.html

• Sig Fig Practice 1• Sig Fig Practice 2• Density Practice

Summary

• LO and SC reflection

Relay!

• Get out HW: packet and 2.5 CTG• Density and Sig Fig Relay• 2.5 Quiz

RELAY

• Get a calculator • There are three rules on determining how many significant figures are in a number:– Non-zero digits are always

significant.– Any zeros between two

significant digits are significant.

– A final zero or trailing zeros in the decimal portion ONLY are significant.

D=

D

M

V

RELAY!

• Get a Calculator and be ready for your density relay!