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Scientific Notation

- Very large or small numbers can be written in scientific notation.
- Scientific notation uses decimals and a power of 10 to represent the original number.
- To write a number is scientific notation, the number must be written with a decimal point after the first digit.

Converting to Scientific Notation

- Write out the entire number.
- Count the number of places you move the decimal point so that the number is after the first digit.
- If you moved the decimal to the LEFT, write 10 raised to the positive of the number of places you moved the decimal.
- If you moved the decimal to the RIGHT, write 10 raised to the negative of the number of places you moved the decimal.

PrecisionAccuracy vs. Precision

Accuracy

The extent to which a measured value agrees with the accepted value

Percent error between experimental or calculated numbers and accepted number

Degree of exactness to which a quantity is measured.

Measurements may be precise, but may not be accurate.

Based on the scale of the measuring devise.

Recording and Reporting Measurements

- When recording a measurement, always record all values given by the devise and the “guess” at the last place value.
- For example, if you measure a strip of paper to be 5.6 cm, you would want to add one more digit to the end of your number based on where you think the paper ends. If it ends right on the 0.6 mark, then your value would be 5.60 cm. If it appears to go halfway between 0.6 and 0.7 your value would be 5.65 cm.

- Water is a “sticky” molecule.
- Water will climb the sides of the glass.
- This is called the Meniscus.

Space Station Issues

- The International Space Station (ISS) is regularly populated with Russians, Americans, Japanese, and Europeans.
- Language is a problem.
- So math is not a problem, one system of units has been adopted.

Measure out 5 feet.

How many meters is that?

The Metric System

- Mass (how heavy things are) is measured in grams.
- Volume (how much space something takes up) is measured in liters.
- Length (how far, long, wide something is) is measured in meters.

Examples of Volume

A Bottle of Soda

2 Liters

Gallon of Milk

3.8 Liters

http://www.citysackers.com/product_info.php?products_id=370

http://www.doobybrain.com/2008/07/24/new-coca-cola-2-liter-contour-bottle/

Prefixes

King Henry Died from drinking chocolate milk

Kilo = 1000

Hecto = 100

Deca = 10

Free = grams, liters, meters

Deci = .1

Centi = .01

Milli = .001

http://www.fanpop.com/spots/chocolate-milk/images/1297950/title/choco-milk-photo

OR….

King Have Diamonds but diamonds cost money

Kilo = 1000

Hecto = 100

Deca = 10

Base unit= grams, liters, meters

Deci = .1

Centi = .01

Milli = .001

http://www.fanpop.com/spots/chocolate-milk/images/1297950/title/choco-milk-photo

Convert 5000 millimeters to meters

Convert 15 deciliters to hectoliters

Practice Conversions

- 9000 mL to DL
- .006 Km to m
- 54 cg to g
- .408 L to dL
- 905Hm to cm
- 9 g to Kg

Importance of the Metric System

Chemists work across the globe to further our understanding.

We need to be able to share our information so that we can make discoveries more quickly.

Conversions Simplify Life

Conversions allow you to represent the same amount in different units.

http://www.fiftybucksaweek.com/tag/eggs/

Consider Eggs

Eggs are not sold individually. You buy eggs or 1 dozen.

1dozen = 12 eggs.

http://www.reuters.com/article/idUSTRE67J34H20100820

Units

Make sure you have the same units on the top and the same units on the bottom

3

1 dozen = x dozen

__________ __________

12 eggs 36 eggs

1 dozen = x dozen

_________ ____________

12 eggs 24 eggs

2

1 dozen = x dozen

_________ __________

12 eggs 15 eggs

?

___________ _____________

12 eggs 15 eggs

Step One: Cross Multiply

Step Two: Divide

Step Three: Check Units

In chemistry we don’t use dozens. We use Moles.

A mole is a number of particles.

Mole Conversions

- One mole of an element has a specific mass.
- We can convert between moles and grams.

1 mole of Carbon = 12 grams

How many moles is 30 grams of Carbon?

How many moles is 59 grams of Oxygen?

Significant Figures

- When using a measuring device, the last digit is always an estimate.
- To make sure all calculations with measurements are accurate, we have to make sure our answers do not have more digits than the original measurements.
- Scientists use significant figures to help solve this issue.
- The more sig figs a measurement has the more precise it is.

What Numbers are Significant?

- All digits other than zero are significant numbers.
- Zeros are significant if:
- It is surrounded by two non-zero digits
- If more than one zero is surrounded by non-zero numbers, all the surrounded zeros are significant
- If a decimal is present, all the zeros after the first non-zero number are significant
- All numbers written in scientific notation are significant

Steps to Counting Sig Figs

Step 1: Is the decimal point present or absent?

Present: start from left

Absent: start from right

Step 2: Start counting with the first number that isn’t zero

Step 3: Once you start counting, count everything, including zeros

The Rules of Zero

How many significant figures?

Pacific

Left

Pacific

Present

Left

Atlantic

Right

Atlantic

Absent

Right

8004

4 Sig Figs

The Rules of Zero

How many significant figures?

Pacific

Left

Pacific

Present

Left

Atlantic

Right

Atlantic

Absent

Right

733

3 Sig Figs

Identify the number of significant figures:

- 1.03690
- 100000
- 900.0
- 0.000002369
- 0.00450
- 10679.0

Do Now:

- Solve for x: x2 – 5 = 29
- How many significant figures: 0.00150
- 18% of 105 is how much?
- What units would you measure the volume of a pool in?
- Convert from scientific notation: 2.3 x 10-4

Calculations with Sig Figs

- When you multiply or divide the answer must have has many sig figs as the least precise number.
- When you add or subtract the answer must have the same number of digits after the decimal place as the number with the fewest digits after the decimal place.

Perform each operation:

- 103 x 2.0
- 300 / 50.00
- 462.7 + 82.697
- 695.336 – 452.2214
- 684.9 x 42.3
- 2369 / 3
- 945.0526 + 1
- 6547.9999 – 4521.0

Graphing

- Remember to SLAP IT
- Scale- does your scale cover all data?
- Label- did you label each axis with units?
- Axis- is your independent variable on the x-axis and your dependent variable on the y-axis?
- Plot Points- are all points properly plotted?
- Investigate- have you looked for trends and relationships between the variables graphed?
- Title!- does your graph have an appropriate title?

Reference Table Graphs

- There are two graphs you need to be familiar with in your reference table.
- They are in Table G: Solubility Curves at Standard Pressure and Table H: Vapor Pressure of Four Liquids.
- To be able to read these graphs, you need to first identify which graph will give you the information you need. The title and axis labels will tell if the graph has the information you need.
- Now you need to identify the scale used on each axis.
- Once these steps are done, use the given information in the problem to determine your missing information.

Example

- What is the solubility of NH3 at 55C?
- At which temperature does NaNO3 have a solubility of 100 g solute/100g H20?
- Which liquid has a vapor pressure of 150 kPa at 90 C?
- At what temperature does water have a water vapor of 101.3kPa?

Using Graphs

- One important piece of information you can use from a linear graph is the slope.
- To find slope, use the formula:

Slope = y2 – y1

x2 – x1

Example:

Find the slope of this graph:

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