Ch 2Scientific Measurement

Chemistry is a lot of math!

Warm up

1.Name 3 tools used for measurement.

2.What is a unit? 3.Give an example of a unit.4.Why are units important.

Making Measurements

Qualitative measurements: Give results in a descriptive and non-numerical form

Example: Cookie Monster is Blue

Quantitative measurements: Give results in a definite form – usually as numbers and units

Example: Cookie Monster ate 1 kg of cookies

Ch 2.2

Qualitative or Quantitative?

The Big Mac is $2.29.

The Pop Rocks are blue.

The coffee is hot.

The slurpee is 0 degrees Celsius.

Measurement—a quantity that has both a number and a unit.

For example…I weigh 90! I make 1000 an hour!There are 72 in this class.

Numbers with NO units mean NOTHING…and will be marked WRONG on HW/Tests, etc.

Measurements are fundamental to the experimental science.

International System of Units

SI Units (Systeme Internationale)

Quantity

Unit Symbol

tool

Length Meter m Ruler, meter stick

Mass Gram g Scale/ balance Not the same as weight

Temperature

Kelvin/ Celsius

K / C Thermometer K=C+273

Time Seconds

s Stopwatch

Volume Liter or cm3

L or cm3 Graduated cylinder

1mL=1cm3

Density Mass/Vol g/mL Scale & cylinder

Derived unit

Energy Joule J coulometer Can also use calorie

Amount Mole Mol

SI Units (Systeme Internationale)

Meter (m) for length Use a meterstick to measure

Kilogram (kg) for mass (1 kg = 2.2 lbs)Weight is NOT the same thing as mass!Use a scale to measure

Kelvin (K) for temperature K = oC + 2730 K = absolute zeroUse a thermometer to measureoC is another option, but not Fahrenheit (in the metric system)

Second (s) for timeUse a stopwatch to measure

Mole for the amount of substanceWe will talk about mole later

Liter (L) or m3 for volumeUse a graduated cylinder to measure 1L = 1m3

joule or calorie for energyWe don’t discuss this much in this class…

Mass: amount of matter- Gravity does not affect mass

Weight: measure of gravitational pull

Mass vs Weight

Volume: cm3

amount of space occupied by an object

Density: D= m/vRatio of mass to volumemL=cm3

Derived Units: it is a combination of units

Speed: meters/ second

Metric prefixes:

The metric system utilizes prefixes based on powers of 10.

Prefixes you need to memorize…

milli- (1/1000x), centi-(1/100x), kilo-(1000x)

Metric PrefixesPrefixes you need to memorize…milli- (1/1000), centi-(1/100), kilo-(1000x)

Adding prefixes, gives us a range of size measurements.

Based on a system of 10’s (decimal system)

NOTE that the bigger number goes with the smaller unit.

100 cm = 1 m

All metric units increase or decrease by a power of 10.

Conversion factors: a ratio of equal proportions, expressed as a fraction

Values can often be expressed in more than one form$1 = 4 quarters = 10 dimes = 20 nickels = 100 pennies

1 meter = 100cm = 1000mm = 0.001kmequal values can be shown as a ratio equal to 1; such ratios are called conversion factors…

conversion factors are useful for solving problems in which given measurements must be expressed in some other unit.

Example 1: conversions a. convert 20 meters to millimeters

1. which is smaller? 2. how many of the smaller are in the larger? 3. create a conversion factor 1000mm/1m

1000 mm in 1m

20,000mm

Example 2: conversions b. Convert 20 meters to kilometers 0.02 km

More examples

3. 600 g = __________ kg

4. 8900 mm = __________ m

5. 2.3 s = ___________ms

6. 0.250 kg = __________ mg

7. 6580 cm3 = __________ m3

8. 0.35 m3 = ________ mm3

Answers3) 0.6kg4) 8.9m5) 2300ms6) 250,000mg7) .00658 m3

8) 350000000

Convert each of the following: 1. 3.68 kg = __________ g2. 568 cm = __________ m3. 8700 ml = __________ l4. 25 mg = __________g5. 0.101 cm = __________ mm6. 250 ml = __________ l7. 600 g = __________ kg8. 8900 mm = __________ m9. 0.000004 m = __________ mm10. 0.250 kg = __________ mg

Date SI Unit Practice

Example: 3.68kg * = 3680g 

1000g

1 kg

3.68kg * 103

Use table 2 on pg35! However you won’t get the table for your quiz

What SI unit would you use to measure….

1. The length of a football field?

2. The WIDTH of a strand of hair?

3. The mass of an elephant?

4. The mass of an ant?

5. The distance from school to Sears?

6. The height of your desk?

7. The volume of water in a pool?

8. The volume of water in a spoon?

9. The temperature of this room?

Date: SI Unit Practice

1) 6.5*104 =

2) 6.5*10-4 =

3) .00035 =

4) 35000 =

65000.

.00065

3.5*10-4

3.5*104

SCIENTIFIC NOTATION: move decimal point the number of times ex: 1*105 indicated by the power of 10.

+ means larger number- means smaller number

Convert the following out of or into scientific notation

Volume: mL or cm3

amount of space occupied by an object

Density: D= m/vRatio of mass to volume

Derived Units: it is a combination of units

Speed: meters/ second

Density

<<=

add the symbols <, >, or =to compare the blocks

Ex: A rock has a mass of 10 grams and a volume of 5 cm3. Calculate its density.

Units:

or

Density: D= m/v

volume

massDensity

mL

g3cm

g10g / 5cm3

= 2 g/cm3

D= m/vHow can you find density from a graph?

Density is the slope of the line of mass vs volume.

D= m/v=slope = = riserun

y2- - y1 g X2 – x1 mL

Ex: 11-3 g 11-3mL

= 1 g/mL

1. What mineral is more dense? A, B, or C?- A: it has greatest slope

2. If you put equal volumes of A and B on a balance, which would have a larger mass? - A

http://www.youtube.com/watch?v=-CDkJuo_LYs

Density Calculations

Ex 2. The mass of 10 copper coins is 30 grams. The initial volume of water is 50mL and the volume with the coins if 55mL. Calculate the density of the copper coins.

 

Water displacement is used to find the volume of unusual shape: 1.measure volume of water2.Add an object and measure volume again3.Subtract the volume of object+water from volume of just water

50mL60ml

60-50=10mL

How would temp affect density??

As temperature increases, what happens to density?

If density deals with mass and volume…Does temperature affect mass? Or volume?

Ex: 3. The density of silver is 10.0 g/cm3. If you have a sample size of 17.235 grams, what is the volume of the silver?

HW: ch. 2 section 2 pg 42 answer questions 1-6

Pg 881 #1, 2, 7

Quiz! Next class

Use pg 42 #1,2

And 881 # 1, 2, 7, 9 to study

Table on pg 35

Homework

1.The density of silver is 10.0 g/cm3. If you have a sample size of 17.235 grams, what is the volume of the silver?

2.If you have equal volumes of B(blue line) and C (red line). Which one has a larger mass?

1) 6.5*104 =

2) 6.5*10-4 =

3) .00035 =

4) 35000 =

65000.

.00065

3.5*10-4

3.5*104

SCIENTIFIC NOTATION: move decimal point the number of times ex: 1*105 indicated by the power of 10.

+ means larger number- means smaller number

Convert the following out of or into scientific notation

Accuracy: the closeness of measurements to the actual value

Precision: The closeness of a set of measurements to each other

Ch 2.3

2 technicians measure the density of a new substance: A: 2.000, 1.999, and 2.001 g/mLB: 2.5, 2.9, and 2.7 g/mL

The correct value is 2.480 g/mL

Who is more accurate and who is more precise?

Percent error = *100%

Percent Error: measure of how different your value is form the real value

Value experimental – Value accepted

Value accepted

Example: The density of water at 4 oC is known to be 1.00 g/mL. Kayla experimentally found the density of water to be 1.075 g/mL. What is her percent error?

Significant Figures (Sig. Figs)in Measurements…

Significant Figures: all the digits in a measurement that are known with certainty plus one estimated digit

Significant Figures

When we make quantitative measurements, we care about how good our data is.

How we do this? Significant figures

Slide 1 of 6

Ch 2.3

Rules for Significant Figures:

1.All nonzero numbers are significant

2.Zeros b/t nonzero digits are significant

3.Zeros appearing in front of all nonzero are not significant

4.Zeros at the end of a number and the right of a decimal point are significant

5.Zeros at the end of a number but to the left of a decimal point, if a decimal point is there, are significant. (NOT necessarily significant if no decimal)

Examples:245 G 3 sf

40.7 L87009 km .00958 m 0.09 kg

85.00g9.00000

2000 m

2000. m

35

31

46

1

4

When given a number, you must be able to determine the number of sig.figs. in it.

a) 12,389 = _____All non-zero #’s are significant

b) 0.452 = _____Zeros before a decimal are not imp unless it is part of a whole number

c) 10.26 = _____zeros in between #’s are significant

d) 23.000 = _____Zeros after a decimal are significant IF THERE IS A WHOLE #

e) 6.700 x 107 = _____All numbers in the coefficient of a # in scientific notation are significant

f) 24,000,000 = _____zeros w/out a decimal are NOT significant

Perfect example of why sci.not. is so great…gets rid of insig 0’s

g) 0.00000670 = _____zeros after a decimal but with no whole # are NEVER significant.

Again, use sci.not.

Math with Sig Figs

Conversions with Sig Figs: use same number of sig figs in the original measurement- the conversion factor is considered exact and does not count

4.608 m * =460.8cm 100cm m

Addition and Subtraction with Sig Figs: answer must have same # of sig figs as the number with the fewest digits to right of the decimal

25.1g + 2.03g =

Multiplication and Division with Sig Figs:

answer must use same # sig figs as the # with the fewest sig figs

3.05g / 8.47mL =

27.1g

0.360g

80.0g/ 5mL = 16mL = 20mL

80.0g/ 5.0mL = 16mL

6.5*104 =

6.5*10-4 =

.00035 =

35000 =

65000.

.00065

3.5*10-4

3.5*104

SCIENTIFIC NOTATION: move decimal point the number of times ex: 1*105 indicated by the power of 10.

+ means move to the right- means move to the left

Significant Figures A. State the number of significant digits in each measurement. 

Significant Figures Practice A. State the number of significant digits in each measurement. 

B. Solve the following problems and report answers with appropriate number of significant digits.1)      6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =  2)     1.6 km + 1.62 m +1200 cm =   3)     8.264 g - 7.8 g =    4)     10.4168 m - 6.0 m =   5)     12.00 m+15.001 kg=   6)     1.31 cm x 2.3 cm =  7)     5.7621 m x 6.201 m = 8)    20.2 cm / 7.41 s =   9)    40.002 g / 13.000005 g =

1)      6.201 cm + 7.4 cm + 0.68 cm +12.0 cm =  26.3 cm2)     1.6 km + 1.62 m +1200 cm =   1.2 x 103 or 1203 m3)     8.264 g - 7.8 g =    0.5 g4)     10.4168 m - 6.0 m =  4.4 m 5)     12.00 m+15.001 kg=   can’t add m and kg6)     1.31 cm x 2.3 cm =   3.0 cm2

7)     5.7621 m x 6.201 m =  35.73 m2

8)    20.2 cm : 7.41 s =   2.73 cm/s9)    40.002 g : 13.000005 g = 3.0771g

B practice

Warm up

1. What tool would you use to measure mass?

2. What unit would you use to measure mass?

3. What tool would you use to measure volume?

4. What unit(s) would you use to measure length?

Name the tool and units to measure each:

1. Length

2. Volume

3. Mass

4. Temperature

5. Density

1. Linear Measurements

The length, width, or height of something

Tool?

ruler, meter stick, etc.

Units? Meter (m)Centimeters (cm)Millimeters (mm)

Practice:

2. Volume

The space matter takes up

Tool?

Graduated cylinder, beaker, etc.

Units? Liter (L)Milliliters (mL)cm3

MUST BE EYELEVEL TO MEASURE CORRECTLY!

Practice:

3. Mass

The quantity of matter

Tool?

balance, scale, etc.

Units?Kilograms (kg)Grams (g)

We use digital scales (usually)…so just record what the scale says

Mass continued…

Scale must read zero before you place anything on it!

If you want to measure the mass of something inside a container…you must measure the empty container first.

462.3 g

How much mass does the water have?

450.0 g

4. Temperature

The amount of heat present

Tool?

thermometer

Units?Degrees Celsius (°C)

5. Density?

The amount of matter in a space

Units?g/cm3 or g/mL

Tool?

scale and

ruler or graduated cylinder