SI and Metric Basics Chapter 1 Includes SI

SI and Metric Basics Chapter 1 Includes SI units, first lab equipment, and unit conversion 1

The 7 SI Units Quantity Unit Length (l) Meter (m) Mass (m) Kilogram (kg) Time (t) Second (s) Temperature (Tx) Kelvin (K) Electric current (I) Ampere (A) Amount of substance (n) Mole (mol) Luminous intensity (? ) Candela (cd) 2

Derived units u Units that are combinations of the base units by multiplication or division. u What to look for: – Units that are fractions (m/s or g/cm 3), that are products (N*m) that have powers (cm 3), other than the 7 SI units. 3

Multiplied or divided units u Treat units as variables: 1. 2. 3. 4. 5. 6. u (m)(m) = m 2 (mol)(mol) = (mol)3 s 2/s = s m 3/m = m 2 3 m + 6 m = 9 m (x)(x) = x 2 Which of these examples does not show the making of a “derived unit”? 4

4 Common Prefixes Prefix Symbol Meaning Multiplies base unit by… Mega M Million 1, 000 Kilo k Thousand 1, 000 Centi c Hundredth 0. 01 Milli m Thousandth 0. 001 5

The 7 SI Units Quantity Unit Length (l) Meter (m) Mass (m) Kilogram (kg) Time (t) Second (s) Luminous intensity (? ) Candela (cd) Take a moment to notice here that the SI unit” for Temperature (Tx)“official. Kelvin (K) mass is not a plain base unit. It is grams the prefix Electric current (I) with. Ampere (A) kilo attached, meaning “ 1, 000 Amount of substance Mole (mol) grams”! (n) 6

Wal-Mart Observations u Solids in bottles are usually measured in grams or kilograms (that’s mass). u Liquids in bottles are usually measured in milliliters or liters (that’s volume). 7

Prefix powers of 10 u Mega is 106 (1, 000) u Kilo is 103 (1, 000) u Centi is 10 -2 (0. 01) u Milli is 10 -3 (0. 001) u Do you notice any pattern here? u These can be used in metric conversions. 8

“Powers for Prefixes” Metric Conversion u Replace a unit prefix with its power of ten. u Multiply number of units by power of 10. u Write new number and a unit with no prefix. u Practice until you are a master of substituting powers for prefixes 9

Power for Prefix Example u Given: 17 kg = u Known: ? g kg means kilogram Kilo means 103 u 17 kg = 17 (103) grams u 17 (103) grams = 17, 000 grams 10

Metric Conversion Stairway u 1. 2. 3. To change a number with a prefix (such as 15 cm) to a number without a prefix (such as m), do the following: Remember that all you are just switching decimal places. Think about which units are larger and which ones are smaller. Use the following chart 11

Metric Conversion Stairway kilo k h da basic b d centi c m milli 12

Using the Stairway example u Given: 15 cm u Desired unit: meter u Meter has no prefix, so we consider it basic. u From the centi step, note how many steps it is to the basic step. u It is two steps to the left. u Move the decimal two places to the left to convert 15 cm to 0. 15 m. 13

Stairway Observations u Moving from right to left, the answer will be a smaller number than the given. u Moving from Left to Right, the answer will be a larger number than the given. u The two numbers’ units make the values equivalent. u There are seven steps on the stairway. Others could be added. 14

Finding Density u If you know both the mass and the volume of an object, you can find the density of the object. u Here’s how: Divide the mass by the volume. u Try the example on the next slide. 15

Density Example u Given: Mass of object = 2, 000 g Volume of object = 140 cm 3 u Formula: D=m/V u Numbers in the formula: D = 2, 000 g / 140 cm 3 u Answer: 14. 3 g/cm 3 16

Finding Age u To find your age in metric units, we will have to convert years to seconds. Here’s how: – Turn years to days (365. 25 days per yr) – Turn days to hours (24 hr per day) – Turn hours to minutes (60 min per hr), – Turn minutes to seconds (60 sec per min) 17

Age Example u Try converting 16 years to seconds. 16 yr (365. 25 days / yr) = 5, 844 days (24 hr / day) = 140, 256 hr (60 min / hr) = 8, 415, 360 min (60 sec / min) = drumrollllll 504, 921, 600 sec 18

Factor Labels u In the example we just used, each number was labeled with a unit. u Mathematically, the units are changed in each step – From years to days to hours to minutes to seconds. – One unit is cancelled out in each step until the desired unit is reached. 19

Turning Pounds into Kilograms u If you ever travel internationally, it may be useful to know your weight in SI units. Here’s how to do it: – Remember that there are 2. 2 lbs per kilogram. – Take your weight and divide it by 2. 2 lbs / 1 kg. u Let’s try an example. 20

Pounds to kilograms example u Given: A man weighs 215 lbs. u Conversion factor: 2. 2 lbs / kg u Divide: 215 lbs / (2. 2 lbs / kg) = u Answer: 97. 7 kg u Notice the unit kg is the only one left. The lbs units have cancelled out. 21

First Lab Equipment u We will be using the following pieces of special lab equipment in our first lab. – Beaker – Graduated cylinder – Temperature probe – TI-84 Graphing Calculator 22

Beaker A cup marked for approximate liquid measurements. u Not very accurate measurements. u 23

Graduated Cylinder marked with lines for measuring liquid volumes accurately. u Sometimes used in finding solid volumes dropped into the liquid. u 24

Temperature Probe A stainless steel thermometer used with the TI-84 graphing calculator u An EZ-link is used to connect the probe to the calculator. u 25