Chem Exam 1
Mass
a measure of the amount of matter in an object
Weight
a measure of the gravitational force that the earth or other large body exerts on an object
Length
longest dimension of an object
Temperature
a measure of the average kinetic energy (motion) of the atoms or molecules that compose the matter
1 x 10^3
1000
1 x 10^-3
0.001
Absolute zero (–273 °C or –459 °F)
the temperature at which molecular motion virtually stops, lower temperatures do not exist
To go from Celsius (°C) to Kelvin (K) use the equation...
K= C+273.15
To go from Celsius (°C) to Fahrenheit (°F) use the equation...
F= 1.8(C)+32
Speed
a measure of meters per second (m/s)
Volume
a measure of space; it has units of length cubed (cm^3)
Accuracy
refers to how close the measured value is to the actual value
Precision
refers to how close a series of measurements are to one another or how reproducible they are
Random Error
causes one measurement to differ slightly from the next, it comes from unpredictable changes during an experiment, will round out
Systematic error
always affects measurements the same amount or by the same proportion, provided that a reading is taken the same way each time, it is predictable but will not round out
Significant figures
the number of digits important to determine the accuracy and precision of measurement, such as length, mass, or volume
Significant figures in 3002
4
Significant figures in 7 x 10^5
1
Significant Figures in 0.0042
2
When multiplying and dividing significant figures...
find the least number of significant digits in any of the numbers
When adding and subtracting significant figures...
find the least number of significant digits to the right of the decimal point
The term that is related to the reproducibility (repeatability) of a measurement is...
precision
Density
amount of matter in a given space
Density can be used to identify substances because...
no two substances have the same density
Density is a physical property because...
can be observed/measured without changing the object
Volume formula
m/d
Density formula
m/v
Mass formula
d x v
Work
action of a force (push or pull) applied through a distance
Energy
capacity to do work
Potential energy
energy associated with position or composition, stored energy
Kinetic energy
energy associated with movement, motion
Law of conservation of energy
energy is always conserved in a physical or chemical change; it is neither created nor destroyed
Thermal energy
energy associated with the temperature of an object, it is a type of kinetic energy because it is associated with the motion of individual atoms
Unit of energy
joule (J or kJ)
Kinetic energy formula
KE=1/2mv^2
Potential energy formula
m x h x gravity
Exothermic (negative)
system loses heat to the surroundings, the energy of the system decreases whereas the energy of the surroundings increases
Endothermic (positive)
system gains heat from surroundings, the energy of the system increases whereas the energy of the surroundings decreases
Is the burning of natural gas in a stove exothermic or
endothermic?
exothermic (negative)
Units Raised to a Power
when building conversion factors for units raised to a power, remember to raise both the number and the unit to the power
Molecules
particles formed when two or more atoms bond together in specific geometric arrangement
Atoms
particles that constitute the fundamental building blocks of ordinary matter, free atoms are rare in nature
Small differences in atoms and molecules can result in...
large differences in the substances that they compose
State
physical form (solid, liquid, gas)
Composition
type of particles
Solid matter
molecules pack closely to each other in fixed locations, they do not move around, has a fixed volume and rigid shape
Liquid matter
molecules pack about as closely as they do in solid matter but they are free to move relative to each other, fixed volume but not a fixed shape
Gaseous matter
molecules have a lot of space between them, free to move relative to one another, these qualities make gases compressible
Element
a substance that cannot be chemically broken down into simpler substances
Compound
a substance composed of two or more elements in fixed, definite proportions
Homogeneous mixture
made of multiple substances,but it appears to be one substance
Heterogeneous mixture
made of multiple substances, whose presence can be seen
Scientific method
process for understanding nature by observing nature and its behavior, and by conducting experiments to test our ideas
Hypothesis
a tentative interpretation or explanation of the observations