Chapter #3 vocabulary (chemistry)
Precision is an indication of how repeatable a measurement is.
True
‐ Unit of measure:
"one" of some standard used to compare an unknown to
Which SD Rule do you find that seems to pop up most in measurements? & Why do you think this is the case?
- Number one and two apply to any digit with a nonzero - They are the first two
102 students
0
II
0
700 jellybeans
0 SDs
1440
3SDs
2.40 cm
3SDs
0.9405 g/cm3
4 SDs
1.05 x 106 cm
4 SDs
200km
1SD
50 °C
1SD
0.010g
2SDs
300. mm
3
0.00540 s
3 SDs
230 ml
3 SDs
130.01200m
8SDs
6. What kind of unit is area or volume?
Area: m2; Volume:m3
(True or False) Measurements in science are complete if you include a number. You just have to use integrity and not lie about the value.
False
Although identifying significant digits in a measurement is a technical process that requires an understanding of the rules, there's really no fundamental purpose for learning about them.
False
Good accuracy is accomplished by the things being measured
False
The main function of bridge notation is to check that you accurately key the calculation into your calculator.
False
There are 100m in one cm
False
When converting, the unit you want to solve for would be placed on the bottom of the "equivalent unit" fraction
False
Significant digits reflect which regarding measuring; accuracy or precision?
Significant Digits are a reflection of how precise a measurement it based on the device used to measure. They matter because the reported values - either what's reported to you or what you write down - reflect HOW CONFIDENT WE ARE THAT THE MEASUREMENT IS WHAT WE SAY IT IS. THIS MUST BE TAKEN INTO ACCOUNT WHEN WE GO FURTHER AND PERFORM CALCULATIONS WITH THE VALUES IN QUESTION. the significant digits of the contributing measurements determine how we round In real life we can overlook this. In aerospace, medicine, biology, nanotechnology, chemistry, etc, we have to follow the rules so whatever we do with them (derived values, buying supplies) account for the level of certainty we have in the original values. The most important thing to remember with regard to significant digits and calculations is that the input value with the least significant digits determines how we are to round our answer. Add: 0.1010g (4SDs) + 34g (2SDs) 34.1010g round to 34g (2SDs)
4. What metric system is currently used worldwide, when was it developed, and how was it adopted?
The international system of units. It was developed during the french revolution (1799), because the old system was impractical for trade
Accuracy is how close the measured value is to the actual or accepted value.
True
It is a good problem‐solving technique to go back to the problem statement several times while working to the solution to be sure you are solving for the right quantity.
True
Significant digits are important for two reasons; one of which is that they indicate the level of precision that goes into your measurement
True
The foundation of conversions is based on the concept of equivalent units; a quantity of one thing is equal to some quantity of another thing.
True
The precision of an instrument is the measure of its accuracy.
True
The purpose for including non‐significant zeros in a number greater than one is to locate the decimal point.
True
The quantity 10050g has two significant digits because there are only two nonzero digits and there is no decimal point.
True
There are 1000mg in one gram
True
There are 100m in 1 hectometer.
True
When you divide the fraction of "equivalent units" it ALWAYS equals one
True
You always have good accuracy with high precision
True
You improve precision by taking measurements with tools that use smaller units
True
You increase accuracy by reproducing a measurement at least three times
True
o Dimension
a characteristic of a thing (temperature,height, mass)
2. What is a "dimension" in chemistry?
a characteristic of something
‐ Conversion factor:
fraction that contains both the original unit and its equivalent value in a new unit used in unit conversion
‐ Accuracy:
a numerical evaluation of how close a measured value is to the actual or accepted value of a dimension measured
‐ Dimension:
a property or characteristic of an object or system
o Graduated
a scale accurately subdivided into measurement units
8. What do these prefixes for the SI metric system mean? Use "meters" as your base unit. a. 10‐9 b. 10‐6 c.10‐3 d. 10‐2 e. 100 f. 103 g.106 h.109
a. (nano) one billionth of a meter b.(micro) one millionth of a meter c(mili )1 thousandth of a meter ((centih)nhundrethd of a meterf e. base) meter. f. (kilo) 1 thousand of a meter. g. (mega) one million meters h. 109 = (giga) one billion meters
a. Ruler b. Meter stick c. Caliper d. Triple beam balance e. Digital Scale f. Graduated cylinder g. Thermometer h. Stopwatch
a. feet b. meters c. (thickness) d. weight e. weight f. milliters g. kelvin h. seconds
What is the base unit that scientists use to designate: a. Mass, Length, Time and Temperature
a. kilograms b. meters c. seconds d. kelvin
7. Complete the chart below. The first one has been done for you. a. Area b. Volume c. Density d.Energy e. Celsius
a. square meter/ m2 / We have to multiple two dimensions of length (like length times width) b. Cubic meter/ m3/ multiply by 3 dimensions c. kgm3/ kg/m3/ For every (m3) you divide it by 1 kg d. Joule/ J/ Kg x m2/s2 e. Degree celsius/ C / tc=T - 273. 15 (inC)
o Scale
an object with dimensional units lined up to provide means of measuring
‐ Metric:
any measuring system which different sized units are related to each other in multiples of ten
∙ Differentiate between base and derived SI units. -
base units just are but derived units require a math problem
∙ Explain how to determine the significant digits in a measurement.
by using the 6 rules
Convert these: a. 54km to 5400m b. 152.3cm to 1523 m c. 89.2km to 89200000 mm d. 75.2m to _______ km e. 98.22kg to _______ cg f. 5684.65ml to _______ L g. 8965.8kL to _______ L h. 584.69mg to _______ g
d. 0.752km e. f. 5.68465L g. 8965800.0L h. 0.58469g
Multiply and divide measured data so that the correct precision is preserved in the result.
ex : 3sd plus 6sd = 3sd
∙ Describe the factors that affect precision in measurements.
how many lines there are on a ruler, how repeatable it is
‐ Precision:
how repeatable or exact one can make a measurement
1. What is error in a measurement? -
humans are imperfect
∙ Summarize the importance of significant digits in scientific measurements.
it shows the precision of your answer
∙ Identify sources of uncertainty and error in measurements.
men are unreliable, mans tools are unreliable, mans situation is unreliable
If you were measuring the width of the room, which device would you use?
meter stick
‐ Significant digits:
only those digits known for certain plus the last one estimated unit in a measurement
‐ "hecto":
prefix meaning one hundred
‐ "centi":
prefix meaning one hundredth
‐ "deci":
prefix meaning one tenth
‐ "kilo":
prefix meaning one thousand
‐ "milli":
prefix meaning one thousandth
‐ "deca":
prefix meaning ten
∙ Identify (list, choose) the base units and symbols of the SI -
seconds(s), kelvin(K), kilograms(kg), meter(m)
Measurement
something next to a known unit
‐ Derived unit:
special unit derived from various mathematical combinations of the base units.
1. In your own words, describe measuring.
taking something from an unknown quantity and comparing it to a known quantity
Meter:
the SI base unit for reporting on the dimension of length
‐ Kilogram:
the SI base unit for reporting on the dimension of mass
‐ Kelvin:
the SI base unit for reporting on the dimension of temperature
‐ Second:
the SI base unit for reporting on the dimension of time
‐ Kilogram per cubic meter:
the SI base unit for the derived dimension of density
‐ Cubic meter:
the SI base unit for the derived dimension of volume
Square meter
the SI based unit for the derived dimension of area
‐ Measurement:
the act of comparing an unknown quantity to a standard unit
3. What is the difference between the "metric" system of measurement versus our US standard system?
the metric system is all tens, the us system has different conversions for everything
∙ Describe the properties of the metric system.
they are layered in groups of ten
∙ Explain why orderly problem solving is important in chemistry.
we won't always have the answers, God commands us to be smart and problem solve
