CH 1 notes

# Heterogenous mixtures are not uniform and have two

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Heterogenous mixtures are not uniform and have two phases: oil and vinegar, apple cider, smog, any saturated solution, oatmeal with raisins, etc. 1.5 and 1.6 Significant Figures and Measurements / SI Units Measurement : The comparison of a physical quantity to a fixed standard. ie: the fixed standard for the second is based on the radioactive decay of a certain elemental isotope. Every measurement is subject to experimental error. ‘Human error’ is never used as a scientific explanation for why an experiment doesn’t work. Accuracy : The proximity of a single measurement to its true value. This refers to a single measurement. Let’s say the true pH of rain water is 6.97. Your pH meter reads the water’s pH as 6.99 and another student’s pH meter reads 6.77, which is more accurate? Precision: The proximity of a set of values obtained from identical experimental measurements. Measurements can be precise but not accurate. Units of Measurement (SI ): There are basic and derived units. The 5 Basic Units :

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Derived Units: A unit with 2 or more basic units. ANY OTHER unit of measurement is a derived unit. The unit of Force is a Newton (N = g x m 2 ). Velocity, molarity, viscosity, acceleration, etc are all derived units. S.I. Prefixes : Attached to a unit to increase or decrease its size by a power often. Be able to write any number in scientific notation and vice versa. Large numbers have positive powers of ten and small numbers have negative powers of ten. Write the following numbers in scientific notation: 6,324.5 0.0044500 0. 00144
10.2 0.10 0.000000000006 Significant Figures : Reflect the accuracy of a measurement. The more decimal places in a value the more accurate the measurement. 10 is less accurate than 10.0. 10.000000 is more accurate than 10.00 o 1 g/1000 mg is a conversion factor . Conversion factors are used to change from one unit to another. o Conversion factors are exact numbers and have an infinite number of significant figures. Notice that in the previous example the answer has the SAME number of sig. figs. as the given quantity.

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- Temperature o Celsius to Kelvin: T K = T C + 273 o Celsius to Fahrenheit: T C = (T F – 32) / 1.8
1.7 Derived Units and Density

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