Unit 2: Introduction to Chemistry All the background needed for the rest of Chemistry 11 All the background needed for the rest of Chemistry 11

2.1 Learning Outcomes standard and scientific notation Calculators & exponents (EE,EXP, ^) conversion factors (CF)

2.1 Vocabulary Words

2.1 A Standard notation (St. N), scientific notation (Sc. N) and using your calculator Sc. N is used to express very large or extremely small numbers as a coefficient raised to a power of 10. Sc. N is used to express very large or extremely small numbers as a coefficient raised to a power of 10. The exponent for 10 can be a positive number (lg numbers) or a negative number (sm. numbers). The exponent for 10 can be a positive number (lg numbers) or a negative number (sm. numbers).

For example, the mass of the earth is about 1,317,000,000,000,000,000,000,000 pounds. This would be extremely difficult to write out each time. Using scientific notation, we would write the same number as x For example, the mass of the earth is about 1,317,000,000,000,000,000,000,000 pounds. This would be extremely difficult to write out each time. Using scientific notation, we would write the same number as x 10 24

Standard notationScientific notationUsing calculator (EE, EXP, ^) x EE x EXP -5

Rules for writing large numbers in scientific notation: Write 123,456,000 in scientific notation

All whole numbers have a decimal point: 123,456,000. All whole numbers have a decimal point: 123,456,000. Move the decimal point to the left: Move the decimal point to the left: Count the number of spaces moved the decimal point: 8 =exponent= 10 8 Count the number of spaces moved the decimal point: 8 =exponent= 10 8 In scientific notation, our number is written as x 10 8 In scientific notation, our number is written as x 10 8

Rules for writing small numbers in scientific notation: Write in scientific notation Write in scientific notation

Move the decimal point to the right so that the number to the left of the decimal point is greater than or equal to 1 and smaller than 10: Move the decimal point to the right so that the number to the left of the decimal point is greater than or equal to 1 and smaller than 10: Count the number of spaces we moved the decimal point: = 7 spaces to the right= Our exponent will be Count the number of spaces we moved the decimal point: = 7 spaces to the right= Our exponent will be In scientific notation, our number is written as 1.23 x In scientific notation, our number is written as 1.23 x 10 -7

C. Practicing converting between standard and scientific notation 1,897,432,000 1,897,432,000 3,874,000 3,874,000 1,000,000,000,000,000 1,000,000,000,000, ,000,000, ,000,000, ,932, ,932, x x x x x x x x x x 10-1

B. Using your calculator…..

Which button on your calculator is used for expressing “to the power of 10” (EE, EXP, ^…)?

What steps do you need to take to write a negative exponent? For example: 1.0 x 10 -7

TIP: - When calculating with power, the EXP or EE button replaces the 1.0 x 10 9 in the number. - For example if I am to enter 1.79 x into my calculator, I would enter: 1.79 EXP 23

Try these calculations: 5x10 3 g x 0.2 g 5x10 3 g x 0.2 g 6.02 x atoms x 3 atoms 6.02 x atoms x 3 atoms 27 / 1.9 x / 1.9 x x x 2.7 x x x 2.7 x Remember, these are ways to represent REALLY big or small numbers….x10…means to the power of __, not times 10 Remember, these are ways to represent REALLY big or small numbers….x10…means to the power of __, not times 10

2.1 B. Conversion Factor using old fashion Word Problems: Sample Questions: If a car can go 80 km in 1 hour, how far can it go in 8.5 hours? Answer: # km = 8.5 hours x 80 km = 680 km 1 hour

How many milligrams are in 8 kg of sugar? Answer: # mg = 8 kg x 1x10 3 g x 1 mg = 8 x 10 6 mg 1 kg 1x10 -3 g 1 kg 1x10 -3 g

Conversion factor (CF): a fractional expression relating or connecting two different units or prefixes A fraction with a value = 1 A fraction with a value = 1 CF are used to change from one unit to another CF are used to change from one unit to another always include units in every step always include units in every step

For every unit conversion use the following steps: U = I x CF Identify the U nknown amount and units Identify the U nknown amount and units Identify the I nitial amount and units Identify the I nitial amount and units List the CF (s) that will relate or connect the I units to the U units List the CF (s) that will relate or connect the I units to the U units Solve (the units of the I must cancel with the units of the bottom of the CF) Solve (the units of the I must cancel with the units of the bottom of the CF) See SWB examples on page 10 – 14 See SWB examples on page 10 – 14

If a car can go 80 km in 1 hour, how far can it go in 8.5 hours? Answer: # km = 8.5 hours x 80 km = 680 km 1 hour

How many milligrams are in 8 kg of sugar? Answer: # mg = 8 kg x 1x10 3 g x 1 mg = 8 x 10 6 mg 1 kg 1x10 -3 g 1 kg 1x10 -3 g

2.1 C Multiple CF’s: Always create a plan: Always create a plan: L  gal  $ or mL  L  kL Each “  ” represent a CF Each “  ” represent a CF can be computed in separate steps or all in one step can be computed in separate steps or all in one step See SWB examples on page See SWB examples on page 14-15

Sample Question with many CF’s How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h).

Sample Question How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). U

Sample Question How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). U I

Sample Question How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). U I CF

Sample Question How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). U I CF Other CF?

Sample Question How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). How many days would it take to fly to mars in a space shuttle if it had enough supplies? Mars is 90 million km from Earth (the shuttle in Earth orbit travels at km/h). U I CF Other CF? = 1 day 24 hours

One step answer: # days = 9.0 x 10 7 km x 1 hour x # days = 9.0 x 10 7 km x 1 hour x 1 day km 24 hrs = days

Two step answer: # hours = 9.0 x 10 7 km x 1 hour = 3.2x10 3 hrs km # days = 3.2x10 3 hrs x 1 day = 1.3x10 2 days 24 hrs