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**A quantity that has both a number and a unit**

Measurement A quantity that has both a number and a unit

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Scientific Notation A way of writing either very large or very small numbers. One number to the left of the decimal point multiplied by a power of 10.

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Accuracy A measure of how close a measurement comes to the true value . To evaluate accuracy your measurement must be compared to the true measurement

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Precision A measure of how close a series of measurements are to each other. To evaluate precision two or more measurements must be compared to each other.

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Determining Error Accepted value – the correct value based on reliable references Experimental value – the value measured in the lab

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**Error = experimental value**

- accepted value % error = lerrorl x 100 accepted value

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**Significant Figures (sig figs)**

in measurements always depend on the instrument being used for the measurement. include all digits that are known plus one digit that is estimated.

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**All measured numbers are significant figures.**

All non-zero numbers are measured. Zeros that are acting as place holders are not measured.

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Is the zero measured? Leading zeros are never measured. Captured zeros are always measured. Trailing zeros are only measured if there is a decimal in the number.

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Measurements must always be reported to the correct number of sig figs because calculated answers often depend on the number of sig figs in the values used in the calculations.

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**Significant figures in calculations**

In general a calculated answer cannot be more precise than the least precise measurement from which it was calculated.

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**Sig figs in addition and subtraction**

Round your answer to the same number of decimal places as the measurement with the least number of decimal places.

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**Sig figs in multiplication and division**

Round your answer to the same number of significant figures as the measurement with the least number of sig figs.

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**How many sig figs? 0.05730 meters 0.00073 grams 8.750 x10-2meters**

liters 1.072 grams 98,000 meters

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**Round to 3 sig figs 87.073 meters 4.3621 x 108grams 0.0152 meters**

9009 centimeters millimeters grams

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**Calculate and round correctly**

61.2m m +8.6m = (5.3 x 104) + (1.3 x 103) = (9.12 x 10-1) – (4.7 x 10-2) = 34.61cm -17.3cm = 14.2g g g = 349.0m – 12.52m – 8.24m=

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**Calculate and round correctly**

7.55m x 0.34m = 2.10cm x 0.70m = 2.4526m/ 8.4 = 22.4cm x 11.3cm x 5.2cm = 8432m/ 12.5 = 1.26 x 104/ 1.7 x 10-2 =

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**International System of Units (SI)**

kilogram(kg) measures mass meter(m) measures length kelvin(K) measures temperature second(s) measures time Mole(mol) measures amount

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**Volume Is a derived unit.**

SI unit of volume is the amount of space occupied by a cube that is 1 m along each edge The liter is a common unit of volume = a cube 10cm on each edge.

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Temperature The SI unit is the kelvin. The Kelvin temperature scale is directly related to kinetic energy. So zero energy = 0K K = oC + 273 oC = K - 273

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Conversion Factors A ratio of equal measurements. 1 meter = 100 centimeters 1 m , cm cm m

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Dimensional Analysis A way to analyze and solve problems using the units, or dimensions , of the measurement.

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**How many minutes are in exactly one week.**

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**An experiment requires that each student use an 8**

An experiment requires that each student use an 8.5-cm length of Mg ribbon. How many students can do the experiment with 570-cm of ribbon available? 67 students

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Convert 0.044 km to meters 4.6 mg to grams 0.107 g to centigrams 15 cm3 to liters 7.38 g to kg 6.72 s to milliseconds

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**The radius of the potassium atom is 0. 227 nm**

The radius of the potassium atom is nm. Express this radius in centimeters. 2.27 x 10-8 cm

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**Density Is the ratio of an objects mass to its volume.**

It can also be thought of as an equality. Density of gold=19.3g/cm3 19.3g Au = 1 cm3 Au

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**Gold has a density of 19. 3 g/cm3**

Gold has a density of 19.3 g/cm3. What is this density in kilograms per cubic meter ? 1930 kg/m3

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**A student finds a shiny piece of metal she thinks is aluminum**

A student finds a shiny piece of metal she thinks is aluminum. She measures the mass to be 612 g and the volume to be 245 cm3. Is the sample aluminum? Why or why not?

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**What is the volume of 4.62 g of mercury?**

What is the mass of 2.00 L of corn oil? What is the volume of 1.25 kg of air?

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Chapter 2 Data Analysis. I. SI Units Scientists adopted a system of standard units so all scientists could report data that could be reproduced and understood.

Chapter 2 Data Analysis. I. SI Units Scientists adopted a system of standard units so all scientists could report data that could be reproduced and understood.

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