Safety and MeasurementSafety and Measurement

Starting with the basicsStarting with the basics

Lab SafetyLab Safety

Remember that the lab is a place for serious work!

Careless behavior may endanger yourself and others and will not be tolerated!

Remember that the lab is a place for serious work!

Careless behavior may endanger yourself and others and will not be tolerated!

Essential Question 1: What is the difference between precision and accuracy with respect to experimental data?

Essential Question 1: What is the difference between precision and accuracy with respect to experimental data?

Know Want to know Learned

Types of Experimental DataTypes of Experimental Data

Key Concept 1 – Qualitative data deals with descriptions

Key Concept 2 – Quantitative data deals with numbers

Key Concept 1 – Qualitative data deals with descriptions

Key Concept 2 – Quantitative data deals with numbers

Qualitative:-the frame is yellow-the frame looks old-the inside looks

reflective

Quantitative:-the frame measures

4” x 6”-the frame weighs

3lbs-the frame costs $15

Accuracy vs. PrecisionAccuracy vs. Precision

Key Concept 3 – Accuracy refers to how close a measured value is to an accepted value

Key Concept 4 – Precision refers to how close a series of measurements are to one another

Key Concept 3 – Accuracy refers to how close a measured value is to an accepted value

Key Concept 4 – Precision refers to how close a series of measurements are to one another

Accuracy vs. PrecisionAccuracy vs. Precision

Accurate but not precise Precise but not accurate

Accurate and precise Neither accurate nor precise

ErrorError

Error is defined as the difference between the experimental value and an accepted value.

The error equation is: error = experimental value – accepted value.

Percent error expresses error as a percentage of the accepted value.

Error is defined as the difference between the experimental value and an accepted value.

The error equation is: error = experimental value – accepted value.

Percent error expresses error as a percentage of the accepted value.

ErrorError

KC 5: Experimental value is what you get from actually doing the measurement or experiment

KC 6: Accepted (actual) value is the constant value from a textbook or other resource

KC 5: Experimental value is what you get from actually doing the measurement or experiment

KC 6: Accepted (actual) value is the constant value from a textbook or other resource

Percent ErrorPercent Error

A substance has an accepted density of 2.00 g/L. You measured the density as 1.80 g/L. What is the percent error?

A substance has an accepted density of 2.00 g/L. You measured the density as 1.80 g/L. What is the percent error?

Essential Question 2: What are the appropriate SI units for length, mass, time, temperature, quantity of matter, area, volume, and density?

Essential Question 2: What are the appropriate SI units for length, mass, time, temperature, quantity of matter, area, volume, and density?

Know Want to know Learned

SI unitsSI units

Système Internationale d'Unités (SI) is an internationally agreed upon system of measurements.

Key Concept 1: base unit is a defined unit in a system of measurement that is based on an object or event in the physical world, and is independent of other units.

Système Internationale d'Unités (SI) is an internationally agreed upon system of measurements.

Key Concept 1: base unit is a defined unit in a system of measurement that is based on an object or event in the physical world, and is independent of other units.

SI unitsSI units

Length - meter

Mass - kilogram

Time - second

Temperature – kelvin

Quantity of matter – mole

Area – m2

Length - meter

Mass - kilogram

Time - second

Temperature – kelvin

Quantity of matter – mole

Area – m2

Derived SI UnitsVolume – L

Density – g/cm3 or g/mL

Derived SI UnitsVolume – L

Density – g/cm3 or g/mL

Key Concept 2: These are the SI units for the following base

EQ 3: What are the relationships among SI unit prefixes (centi-, milli-, kilo-)?

EQ 3: What are the relationships among SI unit prefixes (centi-, milli-, kilo-)?

Know Want to know Learned

Unit PrefixesUnit Prefixes

Unit PrefixesUnit Prefixes

EQ 4: How are the correct number of significant figures calculated?

EQ 4: How are the correct number of significant figures calculated?

There are 2 different types of numbersExactMeasured

KC 1: Exact numbers are obtained when you count objects or use a defined relationship.

KC 2: Measured numbers are measured with a measuring device so these numbers have ERROR

There are 2 different types of numbersExactMeasured

KC 1: Exact numbers are obtained when you count objects or use a defined relationship.

KC 2: Measured numbers are measured with a measuring device so these numbers have ERROR

Exact NumbersExact Numbers

Counting objects are always exact2 soccer balls4 pizzas

Exact relationships, predefined values, not measured

1 foot = 12 inches1 meter = 100 cm

For instance is 1 foot = 12.000000000001 inches? No

1 ft is EXACTLY 12 inches.

Counting objects are always exact2 soccer balls4 pizzas

Exact relationships, predefined values, not measured

1 foot = 12 inches1 meter = 100 cm

For instance is 1 foot = 12.000000000001 inches? No

1 ft is EXACTLY 12 inches.

Measured NumbersMeasured Numbers

Do you see why Measured Numbers have error…you have to make that guess!

All but one of the significant figures are known with certainty. The last significant figure is only the best possible estimate.

To indicate the precision of a measurement, the value recorded should use all the digits known with certainty.

Do you see why Measured Numbers have error…you have to make that guess!

All but one of the significant figures are known with certainty. The last significant figure is only the best possible estimate.

To indicate the precision of a measurement, the value recorded should use all the digits known with certainty.

Measured NumbersMeasured Numbers

KC 3: When recording measurements, record all known values then best guess

KC 3: When recording measurements, record all known values then best guess

Significant Figures RulesSignificant Figures Rules

Rule 1: Nonzero numbers are always significant.

Rule 2: Zeros between nonzero numbers are always significant.

Rule 3: All final zeros to the right of the decimal are significant.

Rule 4: Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation.

Rule 5: Counting numbers and defined constants have an infinite number of significant figures.

Rule 1: Nonzero numbers are always significant.

Rule 2: Zeros between nonzero numbers are always significant.

Rule 3: All final zeros to the right of the decimal are significant.

Rule 4: Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation.

Rule 5: Counting numbers and defined constants have an infinite number of significant figures.

Significant FiguresSignificant Figures

KC 4: Everything is significant except zeroes, sometimes

KC 4: Everything is significant except zeroes, sometimes

Significant FiguresSignificant Figures

KC 5: When measurements are added or subtracted, the answer can contain no more decimal places than the least accurate measurement.

KC 6: When measurements are multiplied or divided, the answer can contain no more significant figures than the least accurate measurement.

KC 5: When measurements are added or subtracted, the answer can contain no more decimal places than the least accurate measurement.

KC 6: When measurements are multiplied or divided, the answer can contain no more significant figures than the least accurate measurement.

Significant Figures PracticeSignificant Figures Practice

How many significant figures are in the following numbers?.00305

10

120.00006

1.0

3.5x104

6.02x1023

How many significant figures are in the following numbers?.00305

10

120.00006

1.0

3.5x104

6.02x1023

EQ 6: How do scientists record very large or very small quantities?

EQ 6: How do scientists record very large or very small quantities?

KC 1: Scientific notation can be used to express any number as a number between 1 and 10 (the coefficient) multiplied by 10 raised to a power (the exponent).

Count the number of places the decimal point must be moved to give a coefficient between 1 and 10

KC 1: Scientific notation can be used to express any number as a number between 1 and 10 (the coefficient) multiplied by 10 raised to a power (the exponent).

Count the number of places the decimal point must be moved to give a coefficient between 1 and 10

Scientific NotationScientific Notation

5.67 x 105         coefficient        base   

exponent   In order for a number to be in correct scientific notation, the following conditions

must be true:

KC 2: The coefficient must be greater than or equal to 1 and less than 10.

KC 3: The base must be 10.KC 4: The exponent must show the

number of decimal places that the decimal needs to be moved to change the number to standard notation. 

5.67 x 105         coefficient        base   

exponent   In order for a number to be in correct scientific notation, the following conditions

must be true:

KC 2: The coefficient must be greater than or equal to 1 and less than 10.

KC 3: The base must be 10.KC 4: The exponent must show the

number of decimal places that the decimal needs to be moved to change the number to standard notation. 

Scientific NotationScientific Notation

The number of places moved equals the value of the exponent

The exponent is positive when the decimal moves to the left and negative when the decimal moves to the right.

800 = 8.0 x 102

0.0000343 = 3.43 x 10–5

The number of places moved equals the value of the exponent

The exponent is positive when the decimal moves to the left and negative when the decimal moves to the right.

800 = 8.0 x 102

0.0000343 = 3.43 x 10–5

EQ 7: How do scientists collect and analyze data?EQ 7: How do scientists collect and analyze data?