Chapter E: Units, Measurements, and Problem Solving Flashcards
Define unit.
A standard quantity used to specify measurements.
Define metric system.
The system of measurements used in most countries in which the meter is the unit of length, the kilogram is the unit of mass, and the second is the unit of time.
Define English system.
The system of units used in the United States and various other countries in which the inch is the unit of length, the pound is the unit of force, and the ounce is the unit of mass.
Define International System of Units (SI).
The standard unit system used by scientists; based on the metric system.
SI Unit: Length
meter; m
SI Unit: Mass
kilogram; kg
SI Unit: Time
second; s
SI Unit: Temperature
Kelvin; K
SI Unit: Amount of Substance
mole; mol
SI Unit: Electric current
ampere; A
SI Unit: Luminous intensity
candela; cd
Define meter.
The SI standard unit of length; equivalent to 39.37 inches.
Define kilogram.
The SI standard unit of mass defined as the mass of a block of metal kept at the International Bureau of Weights and Measures at Sevres, France.
Define mass.
A measure of the quantity of matter making up an object.
Define weight.
A measure of the gravitational pull on an object’s matter.
Define second.
The SI standard unit of time, defined as the duration of 9,192,631,770 periods of the radiation emitted from a certain transition in a cesium-133 atom.
Define kelvin.
The SI standard unit of temperature.
Define temperature.
A measure of the average kinetic energy of the atoms or molecules that compose a sample of matter.
How does thermal energy transfer?
From hot objects to cold ones.
What temperature does water boil on each temperature scale?
F: 212 degrees
C: 100 degrees
K: 373 K
What temperature does water freeze on each temperature scale?
F: 32 degrees
C: 0 degrees
K: 273 K
What temperature is absolute zero on each temperate scale?
F: -459 degrees
C: -273 degrees
K: 0 K
Define absolute zero.
The temperature at which molecular motion virtually stops.
Formula Fahrenheit to Celsius.
C = (F - 32) / 1.8
Formula Celsius to Fahrenheit.
F = (1.8 * C) + 32
Formula Celsius to Kelvin.
K = C + 273.15
Define prefix multipliers.
Multipliers that change the value of the unit by powers of ten.
SI Prefix: exa
E; 10^18
SI Prefix: peta
P; 10^15
SI Prefix: tera
T; 10^12
SI Prefix: giga
G; 10^9
SI Prefix: mega
M; 10^6
SI Prefix: kilo
k; 10^3
SI Prefix: hecto
h; 10^2
SI Prefix: deca
da; 10^1
SI Prefix: deci
d; 10^-1
SI Prefix: centi
c; 10^-2
SI Prefix: milli
m; 10^-3
SI Prefix: micro
µ;10^-6
SI Prefix: nano
n; 10^-9
SI Prefix: pico
p; 10^-12
SI Prefix: femto
f; 10^-15
SI Prefix: atto
a; 10^-18
Define derived unit.
A unit that is a combination of base units. For example, the SI unit of speed is meters per second (m/s), a derived unit.
Define volume.
A measure of space. Any unit of length, when cubed, becomes a unit of volume.
Define liter (L).
A unit of volume equal to 1000 cm^3 or 1.057 qt.
1 mL = __ cm^3
1 cm^3
1 gallon = __ L
3.785 L
What is the last digit in a scientific measurement?
Estimated
Define meniscus.
The crescent-shaped surface at the top of a column of liquid.
Define accuracy.
A term that refers to how close a measure value is to the actual value.
Define precision.
A term that refers to how close a series of measurements are to one another or how reproducible they are.
Define random error.
Error that has equal probability of being too high or too low.
Define systematic error.
Error that tends toward being consistently either too high or too low.
What type of error averages out with repeated trials?
random error
Define significant figures.
In any reported measurement, the non-place-holding digits that indicate the precision of the measured quantity. The greater the number of significant figures, the greater the certainty of the measurement.
Significant Figure Rules.
- All nonzero digits are significant.
- Interior zeroes are significant.
- Leading zeroes are not significant.
- Trailing zeroes after a decimal point are always significant.
- Trailing zeroes before a decimal point are always significant.
- Trailing zeroes before an implied decimal point are ambiguous and should be avoided by using scientific notion.
Define exact numbers.
Numbers that have no uncertainty and thus do not limit the number of significant figures in any calculation.
Where do exact numbers originate from?
- The accurate counting of discrete objects. (3 atoms = 3.00000…)
- Defined quantities (100cm = 1m)
- Integral numbers that are part of an equation (radius = diameter/2)
Significant Figure Rules for Calculations.
- (Multiplication or Division) the same number of significant figures as the factor with the fewest significant figures.
- (Addition or Subtraction) the same number of decimal places as the quantity with the fewest decimal places.
- Round only the final answer!
Define density.
The ratio of an object’s mass to its volume.
Formula density.
density = mass / volume
What type of property is density?
Density is a characteristic physical property of a substance. It is also an intensive property.
Does density depend on temperature?
Yes, density of a substance depends on its temperature.
Define intensive property.
A property such as density that is independent of the amount of a given substance.
Define extensive property.
A property that depends on the amount of a given substance, such as mass.
SI-derived Unit: Density
kg/m^3
Define energy.
The capacity to do work.
Define work.
The result of a force acting through a distance.
Define kinetic energy.
The energy associated with motion of an object.
Define potential energy.
The energy associated with the position or composition of an object.
Define total energy.
A sum of an object’s kinetic energy and potential energy.
Define thermal energy.
The type of kinetic energy associated with the temperature of an object, arising from the motion of individual atoms or molecules in the object.
Define law of conservation of energy.
The law stating that energy can neither be created nor destroyed, only converted from one form to another.
What do we say about systems with high potential energy?
They are unstable as there is a tendency of systems with high potential energy to change in a way that lowers their potential energy.
Formula kinetic energy.
KE = (1/2) mv^2
SI-derived Unit: velocity
meter/second; m/s
SI-derived Unit: energy
Joule (J); kg * m^2/s^2
Define calorie (cal).
A unit of energy defined as the amount of energy required to raise one gram of water 1 °C; equal to 4.184 J.
Define Calorie (Cal).
1 Cal = 1 kcal = 1000 cal; 1 Cal = 4184 J
What do chemical processes almost always involve?
Energy changes
Define exothermic.
Describes a process that releases heat to its surroundings. Processes in which the system loses thermal energy, the change in energy is negative.
Define endothermic.
Describes a process that absorbs heat from its surroundings. Processes in which the system gains thermal energy, the change in energy is positive.
Define dimensional analysis.
The use of units as a guide to solving problems.
1 in = __ cm
2.54 cm
Define conversion factor.
A factor used to convert between two different units; a conversion factor can be constructed from any two quantities known to be equivalent.
