CHEMISTRYPeriods 5-7

October 9, 2007

PA Standard: 3.4 A

Warm-up for 10/05/09

1. Write down the metric prefixes in symbol and words in order from LARGEST to smallest without looking in your notebook!

(Underline the larger units and base unit.)

2. page 59 #2 ; Write your answer

with the correct formula. REMINDER: UNIT 1 TEST Part 1 is this

Tuesday!

Layout for today’s lesson 1) Go over the warm-up. 2) Spend some time going over the answers

to the HW packet. 3) Discuss briefly what could be on the UNIT

1 TEST (Part 1); including basic concepts, calculations.

4) Give detailed steps to 1-step unit conversions and 2-step unit conversions. ALL of these instructions MUST be written down in your notebooks!

5) HW to be assigned (TBD)

Other important information

Today will be part review day and also the day students will review one of their quizzes.

Tuesday is the unit 1 TEST (Part 1). You MUST be prepared for it.

Each HW this week (T, W, F) will be some short exercises and assigned reading outside of class so that the new material is covered for this week.

The unit 1 TEST (Part 2) is scheduled for Thursday this week.

1-Step unit conversions (using the metric chart)

Question: How many nanometers are in 15 millimeters? (15 mm ? nm)

1. Write down the value you start with including the unit.

2. Set up a fraction so that the units are able to be canceled out.

Here are some questions that need answered: If the unit is on top, where does it need to go in

order to cancel out? (BOTTOM) Where does the final unit have to go? (TOP)

1-Step unit conversions (using the metric chart)

15 mm x _____nm___1 mm

3. Using the chart, which one of the two units is larger in the fraction? (A: the unit farthest to the left)

4. Once the larger unit is determined, place a “1” with this unit! In this case, mm is bigger than nm.

1-Step unit conversions (using the metric chart)

15 mm x __106__nm_ 1 mm

5. Next, look at the exponents on the metric chart listed below for each unit. Take each exponent from the power of 10 and SUBTRACT it.

RULE: Any negative exponent must be changed to positive for this step to work.

(Here: the exponents are -9 and -3. To do the math, take 9 – 3 = 6)

This goes with the power of 10.

1-Step unit conversions (using the metric chart)

15 mm x __106__nm_ = 15,000,000 nm 1 mm

6. Lastly, calculate properly. Everything on top is multiplied; the denominator is then divided.

NOTE: You can also move the decimal the same way as the chart. From the spot after the 5, the decimal is moved six places to the RIGHT.

With the correct sigfigs (2), the answer MUSThave the proper unit at the end.

1-Step unit conversions (using the metric chart)

Here’s another problem: How many micrometers are there in 255,000 nanometers? (255,000 nm ? μm)

255,000 nm x μm nm

Which unit is bigger? What are the exponents for these units?What do you do with these exponents?

1-Step unit conversions (using the metric chart)

255,000 nm x 1 μm = 255 μm

103 nm

This time the exponent is on the

BOTTOM because the larger unit is

on top. The number is divided by the

power of 10 (here 103).

2-Step unit conversions (using the metric chart)

First of all, you need to know when the 2-step problem occurs.

ANYTIME you pass through the BASE UNIT (g, m, L, or s) moving from left to right OR right to left, you have a 2-step problem.

EX: km ? dm pg ? dag cL ? ML TIP: The BASE UNIT is never the final

answer to the problem. (ex: km m)

2-Step unit conversions (using the metric chart)

How many microliters are in 0.00044 kiloliters?

Notice that micro- is to the right of the BASE UNIT (L) and kilo- is to the left.

There are two steps to make this unit conversion possible: 1. Convert the known unit (here kL) to the BASE

UNIT (L). 2. From the base unit, convert to the unknown

unit (here microliters).

2-Step unit conversions (using the metric chart)

The steps are very similar from the 1-step problems.

0.00044 kL x μL kL

1. Write down the value you start with including the unit.

2. Set up a fraction so that the units are able to be canceled out.

Remember: Whichever unit you start with MUST go on the bottom to cancel out.

2-Step unit conversions (using the metric chart)

0.00044 kL x 103 L

1 kL 3. Which unit is larger? How do you know? 4. Subtract the exponents from the chart to

find the numerator. (3 – 0 = 3) 5. Once you convert to the base unit, follow

these steps to determine the unknown value for the metric unit you want to find.

2-Step unit conversions (using the metric chart)

0.00044 kL x 103 L x μL 1 kL 1 L

6. Cancel out the numerator of the first step by putting the same unit in the denominator of the second fraction. The unknown will ALWAYS go on top.

7. Once the “1” is determined for the numerator or the denominator (like above), you place a “1.”

2-Step unit conversions (using the metric chart)

0.00044 kL x 103 L x 106 μL

1 kL 1 L 8. Next, find the difference of the

exponents between the two units. Here, it is the following: 6 – 0 = 6

Remember: the – becomes + 9. Calculate appropriately.

2-Step unit conversions (using the metric chart)

0.00044 kL x 103 L x 106 μL

1 kL 1 L = 0.00044 x 109 = 440,000 μL Try this one: How many

picoseconds are found in 3.08 x 10-7 dekaseconds?

HINT: das s ps

2-Step unit conversions (using the metric chart)

3.08 x 10-7 das x 101 s x 1012 ps

1 das 1 s = 3.08 x 10-7 x 1013 = 3,080,000 ps

PROBLEMS

1. 6000 mm ? pm 2. 0.00488 kg ? dg 3. 3.32 x 106 nL ? ML

WORK THESE OUT!

DO YOUR BEST! ☺

HOMEWORK for 10/10/07

1. Finish the problems!!! 2. Page 67 #37, 38 3. Read page 40; write out definitions! 4. Continue studying for Unit 1 TEST!

Warm-up for 10/10/07

1. Write the powers of 10 for the following prefix symbols: k, p, d, M, μ, n, base, m

2. Place all of these prefix symbols in order by number ONLY from smallest to largest.

The order of the numbers are on the next slide. Do your best.

Answers to the Warm-up

The powers of 10 for each prefix symbol are the following:

(These ALL have 10 to the #)

3, -12, -1, 6, -6, -9, 0, -3 The order of the numbers are:

7, 1, 5, 8, 3, 2, 6, 4 KEEP PRACTICING this metric chart!

Review of the HW from 10/09 6000 mm x 109 pm = 6 x 1012 pm 1 mmOR 6,000,000,000,000 pm

37. a) 6.730 x 10-4 b) 5.000 00 x 104

c) 3.010 x 10-6

38. a) 0.007 050 g b) 40 000 500 mg c) 23 500. mL

LAYOUT for 10/10/07

1. After warm-up and HW, we will continue practicing the unit conversion problems. Friday: Finish the unit conversion quiz

with metric chart. (about 15 minutes)

2. Review anything necessary for the unit 1 part 1 TEST (Thursday!)

Make sure to look at these items for the part 1 TEST!

Chapter 1: Everything EXCEPT unit conversion problems (p. 30 for terms) Know prop. phys. states and changes Evidences of chemical changes (p.8) SI base units (symbols) for chem Metric prefixes – names, symbols, 10x

Density problems (in g/mL ALWAYS) Classification of Matter (p. 28)

Chapter 2: p. 46 (sci. method and terms), accuracy, precision (p.55),sigfigs rules (p.57-58)