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Unit 1: Scientific Processes and MeasurementPowerPoint Presentation

Unit 1: Scientific Processes and Measurement

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Science: man made pursuit to understand natural phenomena

Chemistry: study of matter

Safety Resources

Hazard Symbols

blue – health red – flammability

yellow – reactivity white – special codes

Scale: 0 to 4

0 = no danger

4 = extreme danger!

MSDS – Material Safety Data Sheet

- gives important information about chemicals
first aid, fire-fighting, properties, disposal, handling/storage, chemical formula…

Scientific Method

- General set of guidelines used in an experiment

Hypothesis

- Testable statement based on observations; can be disproven, but not proven

Which of these is a hypothesis that can be tested through experimentation?

- A)Bacterial growth increases exponentially as temperature increases.
- B) A fish’s ability to taste food is affected by the clarity of aquarium water.
- C) Tadpoles’ fear of carnivorous insect larvae increases as the tadpoles age.
- D) The number of times a dog wags its tail indicates how content the dog is.

Law experimentation?

- States phenomena but does not address “why?”
- Examples: Newton’s Laws of Motion, Law of Conservation of Mass

Theory experimentation?

- Broad generalization that explains a body of facts
- Summarizes hypotheses that have been supported through repeated testing

Qualitative Observations experimentation?

Non-numerical descriptions in an experiment

Example: Color is blue…

Quantitative Observations experimentation?

- Observations that are numerical
- Example: the mass is 9.0 grams

Parts of an Experiment experimentation?

Independent Variable: variable that is being changed or manipulated by YOU

Dependent Variable: variable that responds to your change ---- what you see

Controlled Variables: variables that you keep the same

Control or Control Set-up: used for comparison; allows you to measure effects of manipulated variable

Directly proportional: when one variable goes up, the other also goes up

Indirectly proportional: when one variable goes up, the other goes down

The diagram shows different setups of an experiment to determine how sharks find their prey. Which experimental setup is the control?

A) Q

B) R

C) S

D) T

- “DRY MIX” - way to remember definitions and graphing determine how sharks find their prey. Which experimental setup is the control?
- DRY – dependent, responding, y-axis
- MIX – manipulated, independent, x-axis

Nature of Measurement determine how sharks find their prey. Which experimental setup is the control?

Measurement - quantitative observation

consisting of 2 parts

Part 1 - number

Part 2 - scale (unit)

Examples:

- 20grams
- 6.63 x 10-34Joule seconds

Measuring determine how sharks find their prey. Which experimental setup is the control?

- Volume
- Temperature
- Mass

Reading the Meniscus determine how sharks find their prey. Which experimental setup is the control?

Always read volume from the bottom of the meniscus. The meniscus is the curved surface of a liquid in a narrow cylindrical container.

Try to avoid parallax errors. determine how sharks find their prey. Which experimental setup is the control?

Parallaxerrors arise when a meniscus or needle is viewed from an angle rather than from straight-on at eye level.

Correct: Viewing the meniscusat eye level

Incorrect: viewing the meniscusfrom an angle

Graduated Cylinders determine how sharks find their prey. Which experimental setup is the control?

The glass cylinder has etched marks to indicate volumes, a pouring lip, and quite often, a plastic bumper to prevent breakage.

Measuring Volume determine how sharks find their prey. Which experimental setup is the control?

- Determine the volume contained in a graduated cylinder by reading the bottom of the meniscus at eye level.
- Read the volume using all certain digits and one uncertaindigit.

- Certain digits are determined from the calibration marks on the cylinder.

- The uncertain digit (the last digit of the reading) is estimated.

Use the graduations to find all certain digits determine how sharks find their prey. Which experimental setup is the control?

There are two unlabeled graduations below the meniscus, and each graduation represents 1 mL, so the certain digits of the reading are…

52 mL.

Estimate the uncertain digit and take a reading determine how sharks find their prey. Which experimental setup is the control?

The meniscus is about eight tenths of the way to the next graduation, so the final digit in the reading is .

0.8 mL

The volume in the graduated cylinder is

52.8 mL.

10 mL Graduate determine how sharks find their prey. Which experimental setup is the control?

What is the volume of liquid in the graduate?

6

6

_ . _ _ mL

2

100mL graduated cylinder determine how sharks find their prey. Which experimental setup is the control?

What is the volume of liquid in the graduate?

5

2

7

_ _ . _ mL

Self Test determine how sharks find their prey. Which experimental setup is the control?

Examine the meniscus below and determine the volume of liquid contained in the graduated cylinder.

The cylinder contains:

7

6

0

_ _ . _ mL

The Thermometer determine how sharks find their prey. Which experimental setup is the control?

- Determine the temperature by reading the scale on the thermometer at eye level.
- Read the temperature by using all certain digits and one uncertain digit.

- Certain digits are determined from the calibration marks on the thermometer.
- The uncertain digit (the last digit of the reading) is estimated.
- On most thermometers encountered in a general chemistry lab, the tenths place is the uncertain digit.

Do not allow the tip to touch the walls or the bottom of the flask.

If the thermometer bulb touches the flask, the temperature of the glass will be measured instead of the temperature of the solution. Readings may be incorrect, particularly if the flask is on a hotplate or in an ice bath.

Reading the Thermometer flask.

Determine the readings as shown below on Celsius thermometers:

8

7

4

3

5

0

_ _ . _ C

_ _ . _ C

Measuring Mass flask. - The Beam Balance

Our balances have 4 beams – the uncertain digit is the thousandths place ( _ _ _ . _ _ X)

Balance Rules flask.

In order to protect the balances and ensure accurate results, a number of rules should be followed:

- Always check that the balance is level and zeroed before using it.
- Never weigh directly on the balance pan. Always use a piece of weighing paper to protect it.
- Do not weigh hot or cold objects.
- Clean up any spills around the balance immediately.

Mass and Significant Figures flask.

- Determine the mass by reading the riders on the beams at eye level.
- Read the mass by using all certain digits and one uncertain digit.

- The uncertain digit (the last digit of the reading) is estimated.
- On our balances, the hundredths place is uncertain.

Determining Mass flask.

1. Place object on pan

2. Move riders along beam, starting with the largest, until the pointer is at the zero mark

Uncertainty in Measurement flask.

- A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

Why Is there Uncertainty? flask.

- Measurements are performed with instruments
- No instrument can read to an infinite number of decimal places

Which of these balances has the greatest uncertainty in measurement?

Precision and Accuracy flask.

Accuracy refers to the agreement of a particular value with the truevalue.

Precisionrefers to the degree of agreement among several measurements made in the same manner.

Precise but not accurate

Precise AND accurate

Neither accurate nor precise

Rules for Counting Significant Figures - Details flask.

- Nonzero integersalways count as significant figures.
- 3456has
- 4sig figs.

Rules for Counting Significant Figures - Details flask.

- Zeros
- Leading zeros do not count as
significant figures.

- 0.0486 has
- 3 sig figs.

Rules for Counting Significant Figures - Details flask.

- Zeros
Captive zerosalways count as

significant figures.

- 16.07has
- 4 sig figs.

Rules for Counting Significant Figures - Details flask.

- Zeros
- Trailing zerosare significant only if the number contains a decimal point.
- 9.300 has
- 4 sig figs.

Rules for Counting Significant Figures - Details flask.

- Exact numbershave an infinite number of significant figures.
- 1 inch = 2.54cm, exactly

Sig Fig Practice #1 flask.

How many significant figures in each of the following?

1.0070 m

5 sig figs

17.10 kg

4 sig figs

100,890 L

5 sig figs

3.29 x 103 s

3 sig figs

0.0054 cm

2 sig figs

3,200,000

2 sig figs

Rules for Significant Figures in Mathematical Operations flask.

- Multiplication and Division:# sig figs in the result equals the number in the least precise measurement used in the calculation.
- 6.38 x 2.0 =
- 12.76 13 (2 sig figs)

Sig Fig Practice #2 flask.

Calculation

Calculator says:

Answer

22.68 m2

3.24 m x 7.0 m

23 m2

100.0 g ÷ 23.7 cm3

4.22 g/cm3

4.219409283 g/cm3

0.02 cm x 2.371 cm

0.05cm2

0.04742 cm2

710 m ÷ 3.0 s

236.6666667 m/s

240 m/s

5870 lb·ft

1818.2 lb x 3.23 ft

5872.786 lb·ft

2.9561 g/mL

2.96 g/mL

1.030 g ÷ 2.87 mL

Rules for Significant Figures in Mathematical Operations flask.

- Addition and Subtraction: The number of decimal places in the result equals the number of decimal places in the least precise measurement.
- 6.8 + 11.934 =
- 18.734 18.7 (3 sig figs)

Sig Fig Practice #3 flask.

Calculation

Calculator says:

Answer

10.24 m

3.24 m + 7.0 m

10.2 m

100.0 g - 23.73 g

76.3 g

76.27 g

0.02 cm + 2.371 cm

2.39 cm

2.391 cm

713.1 L - 3.872 L

709.228 L

709.2 L

1821.6 lb

1818.2 lb + 3.37 lb

1821.57 lb

0.160 mL

0.16 mL

2.030 mL - 1.870 mL

Scientific Notation flask.

In science, we deal with some very LARGE numbers:

1 mole = 602000000000000000000000

In science, we deal with some very SMALL numbers:

Mass of an electron =

0.000000000000000000000000000000091 kg

Imagine the difficulty of calculating the mass of 1 mole of electrons!

0.000000000000000000000000000000091 kg

x 602000000000000000000000

???????????????????????????????????

Scientific Notation: electrons!

A method of representing very large or very small numbers in the form:

M x 10n

- M is a number between 1 and 10
- n is an integer

. electrons!

2 500 000 000

9

7

6

5

4

3

2

1

8

Step #1: Insert an understood decimal point

Step #2: Decide where the decimal must end

up so that one number is to its left

Step #3: Count how many places you bounce

the decimal point

Step #4: Re-write in the form M x 10n

2.5 x 10 electrons!9

The exponent is the number of places we moved the decimal.

0.0000579 electrons!

1

2

3

4

5

Step #2: Decide where the decimal must end

up so that one number is to its left

Step #3: Count how many places you bounce

the decimal point

Step #4: Re-write in the form M x 10n

5.79 x 10 electrons!-5

The exponent is negative because the number we started with was less than 1.

Review electrons!:

Scientific notation expresses a number in the form:

M x 10n

n is an integer

1 M 10

Calculator instructions electrons!

2 x 106 is entered as 2 2nd EE 6

EE means x 10

If you see E on your calculator screen, it also means x 10

The Fundamental SI Units electrons!(le Système International, SI)

Metric System Prefixes (use with standard base units) electrons!

Kilo 103 1000 KING

Hecta 102 100 HENRY

Deca 101 10 DIED

Unit 100 1 UNEXPECTEDLY

Deci 10-1 0.1 DRINKING

Centi 10-2 0.01 CHOCOLATE

Milli 10-3 0.001 MILK

Conversion Unit Examples electrons!

1 L = 1000 mL 1 Hm = ______ m

1 m = ____ cm 1 Dm = _____ m

1 kg = 1000 g ___ dm = 1 m

Metric System Prefixes (use with standard base units) electrons!

Tera 1012 1,000,000,000,000 THE

Giga 109 1,000,000,000 GREAT

Mega 106 1,000,000 MIGHTY

Kilo 103 1000 KING

Hecta 102 100 HENRY

Deca 101 10 DIED

Unit 100 1 UNEXPECTEDLY

Deci 10-1 0.1 DRINKING

Centi 10-2 0.01 CHOCOLATE

Milli 10-3 0.001 MILK

Micro 10-6 0.000001 MAYBE

Nano 10-9 0.000000001 NOT

Pico 10-12 0.000000000001 PASTUERIZED?

Conversion Unit Examples electrons!

1 L = 1000 mL 1 m = ______ nm

1 m = ____ cm 1 Dm = _____ m

1 kg = 1000 g ___ dm = 1 m

1 Mm = _____ m 1 Gb = _____ byte

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