Chapter 3 Flashcards
what is precision
upon making repeated measurements, how close the measured values are to each other
What is accuracy?
how close the measured value is to the true value
Which are you improving when you calibrate an instrument?
accuracy
Significant digits are used for what kind of values?
measured
What types of numbers do you disregard the sig digs?
counting
conversion factors
constants
SI unit for mass
kilogram kg
what does second measure
time
What does m represent and measure
meter
length
si temperature?
kelvin
difference between metric and SI
kilogram vs. gram
difference between mass and weight?
weight is a force that measures the pull of gravity on a given mass
mass is a measure of the amount of matter that an object contains
How to convert celsius and kelvin?
K=C + 273
C=K-273
Unit to measure the volume of a solid
centimeter cubed
units to measure the volume of a liquid
mL
L
conversion factor for volume
1 cm cubed
___________
1mL
Anything divided by itself equals
1
What are the equations for density?
d=m/v
m=dv
v=m/d
what is density
the ratio of the mass of an object to its volume
What kind of property is density and why?
intensive - depends on composition not size
What happens to the density of a material if the temperature goes up?
density generally decreases
what is a measurement
a quantity that has both a number and a unit
Why is it important to make correct measurements?
measurements are fundamental to experimental sciences
what happens in scientific notation
a given number is written as the product of two numbers: a coefficient and 10 raised to a power
What must happen to evaluate the accuracy of a measurement
the measured value must be compared to the correct value
what must happen to evaluate precision
you must compare the values of two or more repeated measurements
what is the accepted value
the correct value based on reliable references
what is the experimental value
the value measured in the lab
what is error
the difference between the experimental value and the accepted value
formula for error
experimental value - accepted value
what is percent error
the absolute value of the error divided by the accepted value multiplied by 100%
percent error equation
I error I
——– X100
accepted value
what are significant figures
all of the digits that are known, plus a last digit that is estimated
why must measurements always be reported to the correct number of significant digits?
calculated answers often depend on the number of significant figures in the values used in the calculation
In general, a calculated answer cannot be __________ than the least precise measurement from which it was calculated
more precise
5 common SI units
meter kilogram kelvin second mole
SI for amount of substance
mole
SI for luminous intensity
candela
SI for electric current
ampere
mole abbreviation
mol
candela abbreviation
cd
ampere abbreviation
A
what is volume
the space occupied by any sample of matter
what is temperature
a measure of how cold or hot an object is
what happens with heat
it travels to the lower temperature area
kelvin freezing and boiling points
273.15 and 373.15
what is absolute zero
zero on Kelvin
what is energy
the capacity to do work or to produce heat
what are common units of energy
joule and calorie
which is si for energy
joule
what exactly is a calorie
amount of heat it takes to raise the temperature of 1g of pure water by 1 degree C
conversion factor joules to calories
1 J = 0.2390 cal
1 cal = 4.184 joules
what is a conversion factor
a ratio of equivalent measurements
measurements in a conversion factor….
the numerator is equal to the denominator
when a measurement is multiplied by a conversion factor,
the numerical value generally changes, but the actual size remains the same
what is dimensional analysis
a way to analyze and solve problems using the units, or dimensions, of the measurements
what are easily solved using dimensional analysis
problems in which a measurement with one unit is converted to an equivalent measurement with another unit
