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What is a Bell Ringer?

What is a Bell Ringer?

-a question that is answered in the beginning of every class

- these NEED to be written in your notebook EVERY day

9/6

What is a Bell Ringer?

A bell ringer is a question that is answered at the beginning of every class. It must done every day at the beginning of class.

List one thing you learned in school yesterday.

3 Truths and a Lie about me...

- I am employed as a beer tester
- I am a certified cytogeneticist
- I have coached an NBA player
- I live in a house with 3 females!

3 Truths and a Lie about me...

- I am employed as a beer tester
- I am a certified cytogeneticist
- I have coached an NBA player
- I live in a house with 3 females!

3 Truths and a Lie about me...

- I am employed as a beer tester
- I am a certified cytogeneticist
- I have coached an NBA player
- I live in a house with 3 females!

3 Truths and a Lie about me...

- I am employed as a beer tester
- I am a certified cytogeneticist
- I have coached an NBA player
- I live in a house with 3 females!

What is Chemistry?

Chemistry?

Two key Questions:

- Why do materials behave as they do?
- Overall properties and reactivity

- How can we take advantage of these properties to something useful?
- New materials or improve existing materials
- Pharmaceuticals, fuels, foodstuffs…

Science is a tool.

Medicine: “I have high cholesterol, what should I do?”

- Eat Cheerios
- Consult your best friend.
- Pray to the god Baa and sacrifice a goat.
- Take cholesterol lowering medication.
- Adjust your diet

Making Gak

PROBLEM:

How do you make GAK, efficiently?

HYPOTHESIS:

= your recipe (amounts of ingredients)

EXPERIMENT:

= order of mixing, and how it was mixed

CONCLUSION:

Explain your results

What is the scientific method?

Finish

Goals

The Last Lecture

What are these?

test

The Scientific Method

- Observe an event.
- Develop a model (or hypothesis) which makes a prediction.
- Test the prediction.
- Observe the result.
- Make your conclusion
- Revise the hypothesis.
- Repeat as needed.
- A successful hypothesis becomes a ScientificTheory.

Medical Science

Patient has high cholesterol

Certain chemicals may dissolve cholesterol deposits.

Give 100 patients these chemicals, give 100 patients placebo.

Same number lower their cholesterol as placebo patients.

Try different combo of chemicals.

Re-run medical test. Observe results.

Lipitor reduces cholesterol.

Everyday Science

Engine won’t turn over.

Predict battery is dead.

Replace battery.

Engine now turns over.

Not needed.

Not needed.

Cars won’t work without a fully charged battery.

Everyday Science

Try a tomato sauce.

Heat pot of tomato sauce.

Taste the sauce - bland.

Use tomato sauce and garlic!

Add garlic, taste - not so bland.

The Final Recipe.

Making Gak

PROBLEM:

How do you make GAK, efficiently?

HYPOTHESIS:

= your recipe (amounts of ingredients)

EXPERIMENT:

= order of mixing, and how it was mixed

CONCLUSION:

Explain your results

List, in order, the steps of the scientific method.

You have $7.25 in your pocket in quarters. How many quarters do you have?

1 dollar

7.25 dollars

4 quarters

X

=

1

= 29 quarters

On 9/23/99, $125,000,000 Mars Climate Orbiter entered Mar’s atmosphere 100 km lower than planned and was destroyed by heat.

1 lb = 1 N

1 lb = 4.45 N

“This is going to be the cautionary tale that will be embedded into introduction to the metric system in elementary school, high school, and college science courses till the end of time.”

- Perform the following conversions -
- 1.76 kg = ____________ dg
- 0.0036 mm = _________ m
- 5.2 x 10-2L = _________ cL

Inference Lab

Counting Significant Figures

RULE 1. All non-zero digits in a measured number are significant. Only a zero could indicate that rounding occurred.

Number of Significant Figures

38.15 cm 4

5.6 ft 2

65.6 lb ___

122.55 m___

Zeros in Front

RULE 2. Leading zeros in decimal numbers are NOT significant.

Number of Significant Figures

0.008 mm 1

0.0156 oz 3

0.0042 lb ____

0.000262 mL ____

Sandwiched Zeros

RULE 3. Zeros between nonzero numbers are significant. (They can not be rounded unless they are on an end of a number.)

Number of Significant Figures

50.8 mm 3

2001 min 4

0.702 lb ____

0.00405 m ____

Trailing Zeros

RULE 4. Trailing zeros in numbers without decimals are NOT significant. They are only serving as place holders.

Number of Significant Figures

25,000 in 2

200. yr 3

48,600 gal ____

25,005,000 g ____

Significant Figures

- The numbers reported in a measurement are limited by the measuring tool
- Significant figures in a measurement include the known digits plus one estimated digit

Significant Numbers in Calculations

- A calculated answer cannot be more precise than the measuring tool.
- A calculated answer must be rounded to match the least precise measurement.

Adding and Subtracting

Only concerned with numbers AFTER the decimal point. Round to the least precise measurement.

25.2one decimal place

+ 1.34two decimal places

26.54

answer 26.5one decimal place

Learning Check

In each calculation, round the answer to the correct number of significant figures.

A. 235.05 + 19.6 + 2.1 =

1) 256.75 2) 256.8 3) 257

B. 58.925 - 18.2 =

1) 40.725 2) 40.73 3) 40.7

Multiplying and Dividing

Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures.

Learning Check

A. 2.19 X 4.2 =

1) 9 2) 9.2 3) 9.198

B. 4.311 ÷ 0.07 =

1)61.582) 62 3) 60

C. 2.54 X 0.0028 =

0.0105 X 0.060

1) 11.3 2) 11 3) 0.041

Theory: A Unifying Principle that explains Facts and Laws

- Theories are not hypothesis
- Continuously revised as new data obtained
- Theory of Evolution

Scientific Laws and Theories

- Law: Repeatedly tested hypothesis that has not been contradicted
- Law of Gravity

- Red
- Far from Earth
- Microscopic
- Hot

- Quantitative
- 700nm wavelength
- 300 million light yr
- Smaller than 1 μm
- 350 °C

Important terms/considerations

for describing matter

- Quantitative vs. Qualitative descriptions

- Qualitative
- Subjective
- Interpretations
- “Brittany is fast”

- Quantitative
- Objective
- Measurable
- “Brittany’s 100m time is 9.8 sec

Important terms/considerations

for describing matter

- Precision vs. Accuracy

- Precise
- Repeatability of a measurement
- Does not take into account the real or true value

- Accurate
- Agreement between the measurement and the true or correct value
- ‘Correct’

Three targets with three arrows each to shoot.

How do they compare?

Both accurate and precise

Precise but not accurate

Neither accurate nor precise

Can you define accuracy and precision?

1.01 g

2.601265g

1.01326g

1.00 g

Precision vs Accuracy

Mass of a paperclip = 1.0003 g

Group 4

1. Which group(s) are most accurate?

2. Which group(s) are most precise?

3. Which group is the most accurate and precise?

Group 3

Group 3

Which clock can be most precise?

For example, at one time the standard for length was the king’s foot. What are some problems with this standard?

MeasurementWhat is our system of measurement based upon?

=

1902 km

BELL RINGER

The distance between Los Angeles and Denver is 1182 miles. How many kilometers is this?

1km = 3281 ft

1182 miles

1 km

5280 ft

x

x

1 mile

3281 ft

=

6240960 km

3281

Stating a Measurement

In every measurement there is a

- Number followed by a
- Unit from a measuring device

The number should also be as precise as the measurement!

** Without a unit – your answer is _________!!!!!!!

NAKED

You have naked numbers??? Oh, the horror!

This ruler can measure to the 10th of a mm

mm. marks

A metric ruler

cm. marks

Measuring

Significant Figures

Estimating the last digit in a measurement

You might estimate the end of the cylinder to be half-way between the lines or 0.05 cm. This digit must be included in the measurement.

Estimating the last digit in a measurement

This measurement should be read as 4.95 cm. This measurement has 3 significant figures.

Reading a metric ruler correctly:

This point can be read as 1.65 cm. or 16.5 mm.

Reading a metric ruler correctly:

This point can be read as 6.70 cm. or 67.0 mm.

We know it is between 35 and 40

We know it is between 36 and 37

Should be read as:

36.4 ml

=

4.96 x 10-4 weeks

BELL RINGER

Convert 300. seconds to weeks.

300. sec

1 min

1 hour

1 day

x

x

x

60 sec

60 min

24 hrs.

1 week

x

7 days

What is Scientific Notation?

- Scientific notation is a way of expressing really big numbers or really small numbers.
- It is most often used in “scientific” calculations where the analysis must be very precise.
- For very large and very small numbers, scientific notation is more concise.

To change standard form to scientific notation…

- If you make the numbersmaller, then you have to make the exponent larger.
- If you make the number larger, then you have to make the exponent smaller.

Example

- Given: 289,800,000
- Use: 2.898 (moved 8 places)
- Answer:2.898 x 108
- Given: 0.000567
- Use: 5.67 (moved 4 places)
- Answer:5.67 x 10-4

To change scientific notation to standard form…

- Simply move the decimal point to the right for positive exponent 10.
- Move the decimal point to the left for negative exponent 10.

(Use zeros to fill in places.)

Example

- Given: 5.093 x 106
- Answer: 5,093,000 (moved 6 places to the right)
- Given: 1.976 x 10-4
- Answer: 0.0001976 (moved 4 places to the left)

3.87 x 10-3

3.00 x 109

2.00 x 100

4.78 x 10-1

PracticeExpress these numbers in Scientific Notation:

(Round to 3 significant digits)

405789

0.003872

3000000000

2

0.478260

Temperature Conversions

A person with hypothermia has a body temperature of 29.1°C. What is the body temperature in K?

K = ˚C + 273

K = 29.1˚C + 273

K = 302.1

=

1.2 x 105 sec

BELL RINGER

How many seconds are in 1.4 days?

1.4 days

24 hours

60 min.

60 sec

x

x

x

1 day

1 hour

1 min.

120960 sec

=

1

Bell Ringer

How many feet in 0.50 kilometers? Remember Sig Figs

100 ˚C

373 K

100 K

180˚F

100˚C

32 ˚F

0 ˚C

273 K

Temperature ScalesFahrenheit

Celsius

Kelvin

Boiling point of water

Freezing point of water

Notice that 1 kelvin = 1 degree Celsius

Calculations Using Temperature

Generally require temp’s in kelvins

K = ˚C + 273

Body temp =

37 ˚C + 273

= 310 K

Liquid nitrogen = -196 ˚C

+ 273 =

77 K

ProblemA piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

Strategy

1. Get dimensions in common units.

2. Calculate volume in cubic centimeters.

3. Calculate the density.

SOLUTION

1. Get dimensions in common units.

2. Calculate volume in cubic centimeters.

3. Calculate the density.

(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3

Note only 2 significant figures in the answer!

Bell Ringer

What is the length of the green line?

. l3. . . . I . . . . I4 . . . . I . . . . I5. . cm

You need to know for the exam

- Precision & Accuracy
- Element Symbols 1-18
- Significant Digits
- Metric System
- Scientific Method

- Scientific notation
- Conversions
- What is Chemistry
- Labs that we have done so far

=

1.31 x 10-5 sec

BELL RINGER

What is 7.9 seconds in weeks?

7.9 sec

1 min

1 hour

1 day

x

x

x

60 sec

60 min

24 hours

1 week

x

7 day

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