1. Measurement

2. The Quantitative Properties
Basic Units of Measurement
quantitative observations of an extensive property
Measurements are comparisons between what is to be measured and a defined established size (reference point)
Two parts: an amount and a unit. For example: 3.6 Liters
3.6 is the amount, Liters is the unit. The property is volume, since Liters measure volume

3. The Quantitative Properties - Mass
Measures the amount of matter present
Measured with a BALANCE
Basic unit: gram (g)

4. The Quantitative Properties - Length
Measures a straight line distance from one point to another
Measured with a RULER
Basic unit: meter (m)

5. The Quantitative Properties - Volume
Measures the amount of space a piece of matter occupies. 3 dimensional
Measured with a GRADUATED CYLINDER or a RULER
Basic unit (if measured with a graduated cylinder) is LITER (L) and if measured with a ruler (L x W x H) a CUBIC METER (cm3)

6. The Quantitative Properties - Pressure
Measures amount of force exerted by a gas colliding with another object
Measured with a BAROMETER or MANOMETER
Basic units include: ATMOSPHERE (atm), MILLIMETERS OF MERCURY (mm Hg), and POUNDS PER SQUARE INCH (psi)

7. The Quantitative Properties - Moles
Describes number of atoms (element) or molecules (compound) needed to measure a mass in grams
Formula (or molar) mass in grams = 1 mole
6.02 x 1023 atoms or molecules = 1 mole
22.4 L of any gas at standard temp and pressure (STP) = 1 mole

8. The Quantitative Properties - Heat
Form of energy (thermal)
Heat always moves from where it is to where it isn’t. The amount of heat moving is what we detect and turn into temperature
Basic units: JOULE (J) and CALORIE (cal)
Food calorie (C) = 1000 cal

9. The Quantitative Properties - Temperature
Indicates moving heat, heat intensity
Measures average kinetic energy (KE) of molecules
Measured with a THERMOMETER
Scale names and Basic units: CELCIUS (ºC) and KELVIN (K) (also Fahrenheit [ºF] which we don’t really use in science)
Absolute Zero: The temperature at which all molecule motion stops (so everything becomes a solid)

10. 98.6°F
37°C
310°K
Normal Body Temp

11. Converting between Temperature Scales
Know ºC, want K: ºC = K
Know K, want ºC: K – 273 = ºC
Between ºC and ºF: 1.8(ºC) = ºF – 32
(1.8 x ºC) + 32 = ºF ºC = (ºF – 32)
1.8

12. Density Mass per volume Describes how tightly packed particles are
Water’s density changes with temperature but defined as 1.00 g/mL or 1.00 g/cm3
If an object’s density > water’s density, the object sinks when put in water
If an object’s density < water’s density, the object floats when put in water
Density units can be: g/mL or g/cm3 or g/L
Specific gravity – compares density of one object to that of water (or another liquid)

13. D = density M = mass V = volume
V = M
M = D x V D
Density (units) = Specific Gravity (no units – it’s a comparison)

14. Density Practice Problems
Calculate to the correct sig figs. Don’t forget the correct units!
Density Practice Problems
Find the density of a piece of concrete if kg has a volume of 9.0 L.
Find the density of a block that has a mass of 108 grams and measures 2.0 cm x 2.0 cm x 9.0 cm.
If the element Bismuth (Bi) has a density of 9.80 g/cm3, what is the mass of 3.74 cm3?
Magnesium (Mg) has a density of 1.74 g/mL. What is the volume of 56.6 g?
An object with a mass of g is placed in 15.5 mL of water. The water rises to 19.0 mL. What is the object’s density?

15. Accuracy, Precision, and Percent Error “Measure twice, cut once.”
A. Accuracy
How close to the correct answer a measurement is
B. Precision
The closeness of a set of measurements made using the same technique
2 lab groups have similar data on the same object

17. C. Percent Error
Calculated % difference between your answer and the accepted (actual, theoretical, or “correct”) answer
How good a job you did - the smaller the % error, the better the accuracy
(-)% errors mean your answer is smaller than the accepted
(+)% errors mean your answer is larger than the accepted
Formula for calculating % error:
Experimental - actual x 100
actual
Usually rounded to nearest 0.1% (to 1 decimal place)
Experimental = your results
Actual = accepted, theoretical, or “correct” answer

18. Significant Digits In any measurement:
All the certain, precisely determined digits
Uncertain, estimated digit

19. Significant Digit Rules
All non zero digits are significant
Zeroes are tricky:
Trapped zeroes are always significant (ex. 707)
Atlantic (absent decimal points): zeroes on the end are not significant; they’re placeholders (ex. 320)
Pacific (present decimal points): zeroes immediately following the decimal point are not significant; they’re placeholders (ex )
In numbers with decimal points, zeroes at the end are significant (ex )

20. Calculations and Significant Digit Rules
Addition and Subtraction
Round answers to fewest decimal places in the calculation
Measurement with fewest decimal places is least precise data
Calculated answer can’t be better than least precise data
12.3 mm mm
 rounds to 18.6 mm (1 decimal place)

21. Calculations and Significant Digit Rules
Multiplication and Division
Round answers to the number of significant figures in the given
Conversions are exact numbers (definitions), not data so they’re not used to determine sig figs.
108.3 cal x J =  J
cal
Given has 4 sig figs

22. Metric System Universal
Establishes a common and comparable way of measuring
Based on powers of 10 - measurements get bigger or smaller by 10s
Prefixes used to indicate whether indicated measurement is getting bigger by 10s (by multiplying) or smaller by 10s (by dividing)
Works for all types of extensive properties

23. Prefix Symbol Meaning METRIC PREFIXES
Tera T x bigger than basic unit
Giga G x bigger than basic unit
Mega M x bigger than basic unit
Kilo k x bigger than basic unit
Hecto h x bigger than basic unit
Deka da or dk x bigger than basic unit
Basic unit L, m, g, J, cal, mole and others
Deci d x smaller than basic unit
Centi c x smaller than basic unit
Milli m x smaller than basic unit
Micro µ x smaller than basic unit
Nano n x smaller than basic unit
Pico p x smaller than basic unit

24. LARGE M
Go down X k
LARGE
Basic
unit d c
Go up ÷
small m 
small

25. UNIT ANALYSIS CHANGING (CONVERTING) ONE UNIT INTO ANOTHER
WHAT YOU KNOW
WHERE YOU START
WHAT YOU’RE GIVEN
WHAT YOU WANT
WHERE YOU END
WHAT IS UNKNOWN
CONVERSIONS
HOW 2 UNITS ARE EQUAL X =

26. CONVERSIONS
Conversions tell how 2 units are equal. Ex. 1 foot = 12 inches
Conversions can be written 2 ways
Like dominoes, conversions can be played either way.
The way you play the conversion is to help a unit CANCEL!
12 inches
1 foot or
12 inches
1 foot

27. 1.64 feet = ? inches Unknown Know 1.64 feet 1 x = =
Multiply across the tops and divide by the bottoms