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2.6 SI Units

2.6 SI Units. The International System of Units, SI, is a revised version of the metric system Correct units along with numerical values are critical when communicating measurements. The are seven base SI units (Table 2.1) of which other SI units are derived.

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2.6 SI Units

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  1. 2.6 SI Units • The International System of Units, SI, is a revised version of the metric system • Correct units along with numerical values are critical when communicating measurements. • The are seven base SI units (Table 2.1) of which other SI units are derived. • Sometimes non-SI units are preffered for convience or practical reasons

  2. 2.6 SI Units – Table 2.2

  3. Common SI Prefixes • Units larger than the base unit

  4. Common SI Prefixes • Units smaller than the base unit

  5. Common SI Prefixes • A mnemonic device can be used to memorize these common prefixes in the correct order: • The Great Monarch King Henry Died By Drinking Chocolate Mocha Milk Not Pilsner

  6. 2.7 Units of Length • The basic unit of length is the meter • Prefixes can be used with the base unit to more easily represent small or large measurements • Example: A hyphen (12 point font) measures about 0.001 m or 1 mm. • Example: A marathon race is approximately 42,000 m or 42 km.

  7. 2.7 Concept Practice 15. Use the tables in the text to order these lengths from smallest to largest. a. centimeter b. micrometer c. kilometer d. millimeter e. meter f. decimeter - 3 - 1 (smallest) - 6 (largest) - 2 - 5 - 4

  8. 2.8 Units of Volume • The space occupied by any sample of matter is called its volume • The volume of rectangular solids can be calculated by multiplying the length by width by height • Units are cubed because you are measuring in 3 dimensions • Volume of liquids can be measured with a graduated cylinder, a pipet, a buret, or a volumetric flask

  9. 2.8 Units of Volume • A convenient unit of measurement for volume in everyday use is the liter (L) • Milliliters (mL) are commonly used for smaller volume measurements and liters (L) for larger measurements • 1 mL = 1 cm3 • 10 cm x 10 cm x 10 cm = 1000 cm3 = 1 L

  10. 2.8 Units of Volume

  11. 2.8 Concept Practice 17. From what unit is a measure of volume derived? A: Volume is a length measurement cubed.

  12. 2.8 Practice 18. What is the volume of a paperback book 21 cm tall, 12 cm wide, and 3.5 cm thick? A: 882 cm3 → 880 cm3; 8.8 x 102 cm3 19. What is the volume of a glass cylinder with an inside diameter of 6.0 cm and a hiegth of 28 cm? V=πr2h A: 790 cm3; 7.9 x 102 cm3

  13. 2.9 Units of Mass • A person on the moon would weigh 1/6 of his/her weight on Earth. • This is because the force of gravity on the moon is approximately 1/6 of its force of Earth. • Weight is a force – it is a measure of the pull on a given mass by gravity; it can change by location. • Mass is the quantity of matter an object contains • Mass remains constant regardless of location.

  14. 2.9 Units of Mass • The kilogram is the basic SI unit of mass • It is defined as the mass of 1 L of water at 4°C. • A gram, which is a more commonly used unit of mass, is 1/1000 of a kilogram • 1 gram = the mass of 1 cm3 of water at 4°C.

  15. 2.9 Concept Practice 20. As you climbed a mountain and the force of gravity decreased, would your weight increase, decrease, or remain constant? How would your mass change? Explain. A: Your weight would decrease; mass would remain constant. 21. How many grams are in each of these quantities? a. 1 cg b. 1 μg c. 1 kg d. 1mg A: 0.01g 0.000001g 1000g 0.001 g

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