Essentials: Units, Measurements, and Problem Solving

Chapter E

Qualitative Observations

descriptive in nature (e.g., changes in color and physical state)

Quantitative Observations

measurements

• numerical values obtained from instrumentation, glassware, and other measuring devices

• varying precision and accuracy

counted values

• number of cats per household in the US

Meter (m)

standard unit of measure for length

Kilogram (kg)

standard unit of measure for mass

Second (s)

standard unit of measure for time

Kelvin (K)

standard unit of measure for temperature

Mole (mol) (6.02 × 10²³ units)

standard unit of measure for amount of substance

Ampere (A)

standard unit of measure for electric current

Candela (cd)

standard unit of measurement of luminous intensity

°C to K Equation

T(K) = T(°C) + 273.15

°C to °F Equation

°F = 1.8(°C) + 32

Exa (E)

10¹⁸ (1,000,000,000,000,000,000)

Peta (P)

10¹⁵ (1,000,000,000,000,000)

Tera (T)

10¹² (1,000,000,000,000)

Giga (G)

10⁹ (1,000,000,000)

Mega (M)

10⁶ (1,000,000)

Kilo (k)

10³ (1000)

Deci (d)

10^-1 (0.1)

Centi (c)

10^-2 (0.01)

Milli (m)

10^-3 (0.001)

Micro (µ)

10^-6 (0.000001)

Nano (n)

10^-9 (0.000000001)

Pico (p)

10^-12 (0.000000000001)

Femto (f)

10^-15 (0.000000000000001)

Atto (a)

10^-18 (0.000000000000000001)

1 km = ? mi

0.6214 mi

1 m = ? in = ? yd

39.37 in = 1.094 yd

1 ft = ? cm

30.48 cm (exact)

1 in = ? cm

2.54 cm (exact)

1 kg = ? lbs

2.205 lbs

1 lb = ? g

453.59 g

1 oz = ? g

28.35 g

1 L = ? mL = ? cm³

1000 mL = 1000 cm³

1 L = ? qt

1.057 qt

1 gal = ? L

3.785 L

Precision

agreement or closeness of a series of measured values

Accuracy

agreement or closeness of measured value to actual known value

Systematic or Determinate Error

error is in the same direction; either higher or lower than should be

Random or Indeterminate Error

equal probability of measure being lower or higher than should be; difficult to correct or find source

Density

mass / volume

Intensive Physical Property

independent of the amount of substance being measured (mass & volume)

Extensive Physical Property

dependent on amount of substance being measured (density)

Energy

the capacity to do work

Work

the action of a force applied through a distance

Force

a push or pull on an object

Electrostatic Force

the push or pull on objects that have an electrical charge

Kinetic Energy

energy associated with movement

Potential Energy

energy associated with position or composition

1 cal = ? J

4.184 J

1 kcal = ? cal = ? kJ

1000 cal = 4.184 kJ

1 kJ = ? J

1000 J

1 kWh = ? J

3.60 × 10⁶ J

First Law of Thermodynamics

all matter possesses energy

System

the area or location under study

Surroundings

area or location outside the system

Universe

system & surroundings

Exothermic

system loses heat to the surroundings

Endothermic

system gains heat from surroundings

Dimensional Analysis

using units as a guide to solving problems

Conversion Factor

a fractional quantity with the units we are converting from on the bottom and the units we are converting to on top