2 International System of Units Metric systemSIUniversally accepted and understood by scientist around the world
3 Derived units are a combination of base units Example: m/s
4 DensityDensity is a ratio that compares the mass of an object to its volume.Density = mass/volumeD=m/vUnits areg/Lg/mLg/cm3
5 Temperature ◦C increase 1 unit at a time Kelvin increase 1 unit at a timeTherefore to convert from ◦C to KK = ◦C
6 Degrees Celsius SI Unit is Kelvin Boiling point = 100 ◦C Freezing point = 0 ◦CSI Unit is KelvinBoiling point = 373 KFreezing point = 273 K
7 Scientific Notation Contains a number and then raised to a power The exponent tell you how many times the factor must be multiplied by tenIf the number is less then 1 the exponent is negativeIf the number is greater then 1 the exponent is positive
8 When adding or subtracting using exponents, the exponents must be the same If they are not the same in the problem you can change them so they are the same
9 When multiplying and dividing exponents the exponents do not have to be the same.
10 When multiplying first multiply the factors then you add the exponents When dividing first divide the factors then you subtract the exponents
11 Dimensional AnalysisDimensional analysis is a method focused on units that describe matterUse conversion factors to convert from one unit to another35 m = mmConversion factor 1m = 1000mm
12 Accuracy and Precision Accuracy refers to how close a measured value is to an accepted valuePrecision refers to how close a series of measurements are to each other
14 Percent ErrorPercent error is the ratio of error to an accepted value.
15 Percent ErrorA student performs an experiment and determines the density of an object to be 1.54 g/mL. The actual density is 1.58 g/mL. Find the students percent error.
16 Significant FiguresSignificant Figures (sig figs) are the digits that carry meaning contributing to its precision.
17 Rules for Sig Figs1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.2) ALL zeroes between non-zero numbers are ALWAYS significant.3) ALL final zeroes which are to the right of the decimal point are significant4) Zeros that act as placeholders are not significantWhen in scientific notation if you can remove the zeros they are not significant
19 Rule 3 – Rule 4 – 9.70 has 3 significant figures has only 3 significant figures4350 has only 3 significant figures
20 RoundingA calculated number should only have the number of significant figures as the data with the fewest sig figs.
21 Rules for RoundingIf the digit to the immediate right of the last significant figures is less than five, do not change the last significant figureWe need only 3 sig figs3.562 3.56
22 2. If the digit to the immediate right of the last significant figure is greater than five, round up the last significant figure 3 sig figs 4.57
23 If the digit to the immediate right of the last significant figure is equal to five and is followed by a nonzero digit, round up the last significant figure 2.54
24 If the digit to the immediate right of the last significant figure is equal to five and is not followed by a nonzero digit, look at the last significant figure. If it is an odd digit, round it up. If it is an even digit, do not round up. 2.54 2.52
25 Adding and Subtracting When you add or subtract measurements, your answer must have the same number of digits to the right of the decimal point as the value with the fewest digits to the right of the decimal point.Example:1.24 mL mL = mL – 13.8 mL
26 Multiplying and Dividing When multiplying and dividing, your answer must have the same number of sig figs as the measurement with the fewest sig figs.3.65 cm x 3.20 x 2.05 cm = cm3 = 23.9 cm3