Unit 1 scientific processes and measurement
This presentation is the property of its rightful owner.
Sponsored Links
1 / 64

Unit 1: Scientific Processes and Measurement PowerPoint PPT Presentation


  • 58 Views
  • Uploaded on
  • Presentation posted in: General

Unit 1: Scientific Processes and Measurement. Science: man made pursuit to understand natural phenomena Chemistry: study of matter. Safety Resources. Hazard Symbols blue – healthred – flammability yellow – reactivitywhite – special codes Scale: 0 to 4 0 = no danger

Download Presentation

Unit 1: Scientific Processes and Measurement

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Unit 1 scientific processes and measurement

Unit 1: Scientific Processes and Measurement


Unit 1 scientific processes and measurement

Science: man made pursuit to understand natural phenomena

Chemistry: study of matter


Safety resources

Safety Resources

Hazard Symbols

blue – healthred – flammability

yellow – reactivitywhite – special codes

Scale: 0 to 4

0 = no danger

4 = extreme danger!


Msds material safety data sheet

MSDS – Material Safety Data Sheet

  • gives important information about chemicals

    first aid, fire-fighting, properties, disposal, handling/storage, chemical formula…


Scientific method

Scientific Method

  • General set of guidelines used in an experiment


Hypothesis

Hypothesis

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


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

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.


Unit 1 scientific processes and measurement

Law

  • States phenomena but does not address “why?”

  • Examples: Newton’s Laws of Motion, Law of Conservation of Mass


Theory

Theory

  • Broad generalization that explains a body of facts

  • Summarizes hypotheses that have been supported through repeated testing


Qualitative observations

Qualitative Observations

Non-numerical descriptions in an experiment

Example: Color is blue…


Quantitative observations

Quantitative Observations

  • Observations that are numerical

  • Example: the mass is 9.0 grams


Parts of an experiment

Parts of an Experiment

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


Unit 1 scientific processes and measurement

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


Unit 1 scientific processes and measurement

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


Unit 1 scientific processes and measurement

  • “DRY MIX” - way to remember definitions and graphing

  • DRY – dependent, responding, y-axis

  • MIX – manipulated, independent, x-axis


Nature of measurement

Nature of Measurement

Measurement - quantitative observation

consisting of 2 parts

Part 1 - number

Part 2 - scale (unit)

Examples:

  • 20grams

  • 6.63 x 10-34Joule seconds


Measuring

Measuring

  • Volume

  • Temperature

  • Mass


Reading the meniscus

Reading the Meniscus

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

Try to avoid parallax errors.

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

Graduated Cylinders

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


Measuring volume

Measuring Volume

  • 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

Use the graduations to find all certain digits

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

Estimate the uncertain digit and take a reading

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

10 mL Graduate

What is the volume of liquid in the graduate?

6

6

_ . _ _ mL

2


100ml graduated cylinder

100mL graduated cylinder

What is the volume of liquid in the graduate?

5

2

7

_ _ . _ mL


Self test

Self Test

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

The cylinder contains:

7

6

0

_ _ . _ mL


The thermometer

The Thermometer

  • 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

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

Reading the Thermometer

Determine the readings as shown below on Celsius thermometers:

8

7

4

3

5

0

_ _ . _ C

_ _ . _ C


Measuring mass the beam balance

Measuring Mass - The Beam Balance

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


Balance rules

Balance Rules

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

Mass and Significant Figures

  • 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

Determining Mass

1. Place object on pan

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


Check to see that the balance scale is at zero

Check to see that the balance scale is at zero


Read mass

1

1

4

? ? ?

Read Mass

_ _ _ . _ _ _


Read mass more closely

1

1

4

4

9

7

Read Mass More Closely

_ _ _ . _ _ _


Uncertainty in measurement

Uncertainty in Measurement

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


Why is there uncertainty

Why Is there Uncertainty?

  • 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

Precision and Accuracy

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

Rules for Counting Significant Figures - Details

  • Nonzero integersalways count as significant figures.

  • 3456has

  • 4sig figs.


Rules for counting significant figures details1

Rules for Counting Significant Figures - Details

  • Zeros

  • Leading zeros do not count as

    significant figures.

  • 0.0486 has

  • 3 sig figs.


Rules for counting significant figures details2

Rules for Counting Significant Figures - Details

  • Zeros

    Captive zerosalways count as

    significant figures.

  • 16.07has

  • 4 sig figs.


Rules for counting significant figures details3

Rules for Counting Significant Figures - Details

  • Zeros

  • Trailing zerosare significant only if the number contains a decimal point.

  • 9.300 has

  • 4 sig figs.


Rules for counting significant figures details4

Rules for Counting Significant Figures - Details

  • Exact numbershave an infinite number of significant figures.

  • 1 inch = 2.54cm, exactly


Sig fig practice 1

Sig Fig Practice #1

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

Rules for Significant Figures in Mathematical Operations

  • 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

Sig Fig Practice #2

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 operations1

Rules for Significant Figures in Mathematical Operations

  • 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

Sig Fig Practice #3

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


Unit 1 scientific processes and measurement

Scientific Notation

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


Unit 1 scientific processes and measurement

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

0.000000000000000000000000000000091 kg

x 602000000000000000000000

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


Unit 1 scientific processes and measurement

Scientific Notation:

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


Unit 1 scientific processes and measurement

.

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


Unit 1 scientific processes and measurement

2.5 x 109

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


Unit 1 scientific processes and measurement

0.0000579

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


Unit 1 scientific processes and measurement

5.79 x 10-5

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


Unit 1 scientific processes and measurement

Review:

Scientific notation expresses a number in the form:

M x 10n

n is an integer

1  M  10


Calculator instructions

Calculator instructions

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


Unit 1 scientific processes and measurement

Try…

2 x 1014 / 3 x 10-3 = ?

2 x 10-34 x 3 x 1023

4.5 x 1023 / 5.26 x 10-14


The fundamental si units le syst me international si

The Fundamental SI Units(le Système International, SI)


Metric system prefixes use with standard base units

Metric System Prefixes (use with standard base units)

Kilo1031000KING

Hecta 102100HENRY

Deca10110DIED

Unit 1001UNEXPECTEDLY

Deci10-10.1DRINKING

Centi10-20.01CHOCOLATE

Milli10-30.001MILK


Conversion unit examples

Conversion Unit Examples

1 L = 1000 mL1 Hm = ______ m

1 m = ____ cm1 Dm = _____ m

1 kg = 1000 g___ dm = 1 m


Metric system prefixes use with standard base units1

Metric System Prefixes (use with standard base units)

Tera10121,000,000,000,000THE

Giga1091,000,000,000GREAT

Mega1061,000,000MIGHTY

Kilo1031000KING

Hecta 102100HENRY

Deca10110DIED

Unit 1001UNEXPECTEDLY

Deci10-10.1DRINKING

Centi10-20.01CHOCOLATE

Milli10-30.001MILK

Micro10-60.000001MAYBE

Nano10-90.000000001NOT

Pico10-120.000000000001PASTUERIZED?


Conversion unit examples1

Conversion Unit Examples

1 L = 1000 mL1 m = ______ nm

1 m = ____ cm1 Dm = _____ m

1 kg = 1000 g___ dm = 1 m

1 Mm = _____ m1 Gb = _____ byte


  • Login