unit 1 notes the metric system easier to use because it is a decimal system. every conversion is by...
DESCRIPTION
The Metric System Easier to use because it is a decimal system. Every conversion is by some power of 10. A metric unit has two parts. A prefix and a base unit. prefix tells you how many times to divide or multiply by 10. Example: centimeter prefix Base unit A centimeter= one hundredth of a meterTRANSCRIPT
Unit 1 Notes
The Metric SystemEasier to use because it is a decimal system.Every conversion is by some power of 10.• A metric unit has two parts.• A prefix and a base unit.• prefix tells you how many times to divide or multiply
by 10.• Example:
• centimeter
prefix Base unit
A centimeter= one hundredth of a meter
The Fundamental SI Units (le Système International, SI)
Physical Quantity Name Abbreviation Mass kilogram kg Length meter m Volume Liter L Temperature Kelvin K Amount of Substance
mole mol
Short cut to Converting
how far you have to move on this chart, tells you how far, and which direction to move the decimal place.
The box is the base unit, meters, Liters, grams, etc.
k h D d c m
Short cut to Conversion
Change 5.6 m to millimeters
k h D d c m
starts at the base unit and move three to the right.move the decimal point three to the right
56 00
MEASUREMENTAccuracy and Precision
Types of Measurement
• Quantitative- use numbers to describe• Qualitative- use description without numbers• 4 feet• extra large• Hot• 100ºF
Scientists prefer
Quantitative- easy check.Easy to agree upon, no personal bias.The measuring instrument limits how good the measurement is.
Accuracy vs. Precision• Accuracy - how close a measurement is to the accepted
value
• Precision - how close a series of measurements are to each other
ACCURATE = CORRECTPRECISE = CONSISTENT
Accuracy…
• To determine if data is accurate, ask yourself, “how close is this data point to the actual, accepted, or true value?
• In short, the closer your data is to the accepted or true value, the more accurate your data is.
Precision…
•To determine if your data is precise, ask yourself, “How close are my data points to one another?”
• In short, the closer your
data points are to one another, the more precise your data points are.
Sketch these in your journal…
AccuratePrecise
Not AccuratePrecise
Not AccurateNot Precise
AccurateNot Precise
Differences
Accuracy can be true of an individual measurement or the average of several.
Precision requires several measurements before anything can be said about it.
Percent Error
Indicates accuracy of a measurement
100literature
literaturealexperimenterror %
your value
accepted value
Percent ErrorA student determines the density of a substance to be
1.40 g/mL. Find the % error if the accepted value of the density is 1.36 g/mL.
100g/mL 1.36
g/mL 1.36g/mL 1.40error %
% error = 2.9 %
MeasurementsWhen we measure something, we can (and do)
always estimate between the smallest marks.
21 3 4 5
MeasurementsThe better the marks, the better we can estimate.Scientist always understand that the last number
measured is actually an estimate.
21 3 4 5
Significant FiguresIndicate precision of a measurement.Recording significant figures
Significant figures in a measurement include the known digits plus a final estimated digit
2.35 cm
Significant FiguresCounting Sig Figs
Count all numbers EXCEPT:Leading zeros -- 0.0025Trailing zeros without
a decimal point -- 2,500
Rules for Counting Significant Figures - Details
• Exact numbers have an infinite number of significant figures.
•1 inch = 2.54 cm, exactly
4. 0.080
3. 5,280
2. 402
1. 23.50
Significant FiguresCounting Sig Fig Examples
4 sig figs
3 sig figs
3 sig figs
2 sig figs
Rounding rules
• Look at the number behind the one you’re rounding.• If it is 0 to 4 don’t change it.• If it is 5 to 9 make it one bigger.• Round 45.462 to four sig figs.
In science, we deal with some very LARGE numbers:
1 mole = 602,000,000,000,000,000,000,000 particles
In science, we deal with some very SMALL numbers:Mass of an electron =0.000000000000000000000000000000091 kg
Scientific Notation
Imagine the difficulty of calculating the mass of 1 mole of electrons!
0.000000000000000000000000000000091 kg x 602000000000000000000000 ???????????????????????????????????
Scientific Notation:A method of representing very large or very small numbers in the form:
M x 10n
M is a number between 1 and 10 n is an integer
2 500 000 000
Step #1: Insert an understood decimal point
.
Step #2: Decide where the decimal must end up so that one number is to its left
Step #3: Count how many places you bounce the decimal point
123456789
Step #4: Re-write in the form M x 10n
2.5 x 109
The exponent is the number of places we moved the decimal.
0.0000579
Step #2: Decide where the decimal must end up so that one number is to its leftStep #3: Count how many places you bounce the decimal pointStep #4: Re-write in the form M x 10n
1 2 3 4 5
5.79 x 10-5
The exponent is negative because the number we started with was less than 1.
Scientific Notation
• Converting into Sci. Notation:• Move decimal until there’s 1 digit to its left. Places moved
= exponent.• Large # (>1) positive exponent
Small # (<1) negative exponent• Only include sig figs.
65,000 kg 6.5 × 104 kg
Physical PropertiesA characteristic that can be observed or
measured without changing the identity of the substance
States of Matter
States of Matter• Solids
very low kinetic energy - particles vibrate but can’t move around
Retains size and shapeDefinite shape and volume
States of Matter• Liquids
low kinetic energy - particles can move around but are still close together
Takes the shape of its container
definite volume
States of Matter• Gases
high KE - particles can separate and move throughout container
Easily compressedNo definite shapeNo definite volume
Some Properties of Solids, Liquids, and Gases
Property Solid Liquid Gas
Shape Has definite shape Takes the shape of Takes the shape the container of its container
Volume Has a definite volume Has a definite volume Fills the volume of the container
Arrangement of Fixed, very close Random, close Random, far apartParticles
Interactions between Very strong Strong Essentially noneparticles
Physical ChangeA change in a substance that does not involve a change in the identity of the substance.
Examples:Phase Changes – boiling point, melting point, freezing point
A substance dissolving in another substance - solubility
Chemical Properties• Relates to a substance’s
ability to undergo change that transforms it into a different substance
Ability to : combust, oxidize, neutralize, reactivity, etc.
Chemical ChangeA change in which one or more substances are converted into different substances.
Evidence of Chemical Change: Heat and light Change in color Production of gas Precipitation of a solid
Temperature is Average Kinetic Energy
Fast Slow“HOT” “COLD”
Celcius & Kelvin Temperature Scales
Measuring Temperature
• Kelvin starts at absolute zero (-273 º C)• degrees are the same size• C = K -273• K = C + 273• Kelvin is always bigger.• Kelvin can never be negative.
273 K