Lesson 7 Scientific Notation SI Units Unit Conversions

Transcription

1 Lesson 7 Scientific Notation SI Units Unit Conversions

2 Do Now 6I, 6Ga Copy down info from CJ board. Keep CJs out and open on desk throughout class. On your DO NOW PAGE #4, copy and answer the questions below: Fill in numbers to make the units equal. 1. L = ml 4. dam = m 2. cg = g 5. kg = g 3. dl = L 6. ms = s

3 Practice Packet from last week Keep it in the notes section. Check answers

4 Tests Cannot be handed back until everyone has taken it. May be handed back FRIDAY.

5 Scientific Notation

6 Scientific Notation Scientists often use numbers that are very large (number of atoms in 1 ml of water or 2.7 grams of salt) or very small (diameter of a ribosome or length of a bacterial cell). These numbers are usually bulky to write, so we have a method of writing them in a more compact way using powers of 10.

7 Scientific notation: writing a number as the product of a number between 1 and 10 multiplied by 10 raised to some power

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10 Example #1. Write 5284 in scientific notation.

11 Example #2. Write 4,500,000,000 in scientific notation.

12 Example #3. Write in scientific notation.

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15 Important note: All the digits in the coefficient are significant. How many significant digits in each measurement? g mm L atoms nm

16 Si Units

17 International System of Units (SI Units) The commonly used SI base units are a choice of seven well-defined units which by convention are regarded as dimensionally independent. This system is currently used by most of the countries in the world in scientific, technical, commerce, and industry work.

18 International System of Units (SI Units) MEASUREMENT UNIT UNIT ABBREVIATION LENGTH TIME TEMPERATURE MASS AMOUNT OF SUBSTANCE

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20 Derived units All other measurements are derived from (a combination of) the seven SI units derived through multiplication or division. They have special names: area = volume = density = speed =

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22 Do Now 6I Copy down info from CJ board. Keep CJs out and open on desk throughout class. On your DO NOW PAGE #4, copy and answer the questions below: 1. The SI standard unit for temperature is. 2. The SI standard unit for mass is L written in standard notation is ,000,000 km written in scientific notation is mg written in standard notation is and has significant digits.

23 Metric System & Unit Conversions

24 Metric System: you should memorize how to convert to and from the base unit LARGER THAN THE BASE UNIT BASE UNIT SMALLER THAN THE BASE UNIT Name Kilo- Hecto- Deca- deci- centi- milli- micro- Abbreviatio n 1000 k h da or D d c m µ 1/10 1/100 1/1000 1/1,000,000 Value relative to base unit Expressed in fractions, exponent form, decimal form, and word descriptions 10 3 A thousand times larger than the base unit 10 2 A hundred times larger than the base unit 10 1 Ten times larger than the base unit Gram (g) Liter (L) Meter (m) A tenth of the base unit A hundredth of the base unit A thousandth of the base unit A millionth of the base unit

25 Unit Conversions While the units most commonly used in Chemistry are grams (g) and centimeters (cm), we also must know how to perform dimensional analysis to convert from one unit to another using conversion factors. Three important parts about the unit multiplier: it must cancel (or eliminate) the old unit it must introduce the new unit we are not changing the value of the measurement since the unit multiplier is equal to 1

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28 hm = m One step unit conversions

29 2. 4,198 cg = g One step unit conversions

30 kl = L One step unit conversions

31 g = dag One step unit conversions

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34 hm = dm Two step unit conversions

35 8. 9,100,000 mg = kg Two step unit conversions

36 dam = cm Two step unit conversions

37 dg = dag Two step unit conversions