Chemistry: Measurements Uncertainty, & Sig Figs

Qualitative observations

descriptions of what you observe

Quantitative observations

• Made by comparing something against a scale

• Include both a number and a scale unit

How to Report Measurement

certain value + estimated value ± uncertainty + units

Graduated Cylinder

3.65 mL ± 0.05 mL

Buret

3.36 mL ± 0.02 mL

Precision

how close the measurements in a series are to each other

Accuracy

how close each measurement is to the actual value

Density

Mass/Volume

0.032

A) 1

B) 2

C) 3

D) 4

E) 5

B) 2

12.010

A) 1

B) 2

C) 3

D) 4

E) 5

E) 5

210

A) 1

B) 2

C) 3

D) 4

E) 5

B) 2

319.3 x 23.566

A) 7524.6238

B) 7524.624

C) 7524.62

D) 7524.6

E) 7525

E) 7525

A) 117

B) 110

C) 120

D) 100

E) 200

4000/34

D) 100

(11.1 - 3.52) x 14.69

A) 111.3502

B) 111.3

C) 111

D) 110

E) 100

E) 100

A) 12 mph

B) 12 mph ± 1 mph

C) 12.0 mph ± 0.5 mph

D) 12.00 mph ± 0.05 mph

E.) 12.0 mph ± 1 mph

C) 12.0 mph ± 0.5 mph

9,000,000,655.00

Scientific notation

9.000000655 × 10⁶

Normal Notation	Scientific Notation
0.00000834

Scientific Notation

8.34 × 10⁻⁶

Normal Notation	Scientific Notation
1.21

Scientific Notation

1.21 × 10⁰

Normal Notation	Scientific Notation
14.82

Scientific Notation

1.482 × 10¹

Normal Notation	Scientific Notation
299,800,000.

Scientific Notation

2.998 × 10⁸

mega (M)

1 X 10⁶

kilo (k)

1 X 10³

deci (d)

1 X 10^-1

centi (c)

1 X 10^-2

milli (m)

1 X 10^-3

micro (µ)

1 X 10^-6

nano (n)

1 X 10^-9

pico (p)

1 X 10^-12

Convert 3.8 cm into inches if you know that

 1 inch = 2.54 cm

A) 1.496 inches

B) 9.652 inches

C) 9.6 inches

D) 1.5 inches

E) 2 inches

D) 1.5 inches

What is Chemistry?

The study of matter, its properties, the changes that matter undergoes, and the energy associated with these changes.

Law of Conservation of Matter

“Matter can neither be created nor destroyed”

Matter

anything that occupies space and has mass

Element

• the simplest type of substance with unique physical and chemical properties

• consists of only one type of atom

• cannot be broken down into any simpler substances by physical or chemical means

Molecule

• structure that consists of two or more atoms that are chemically bound together

  • behaves as an independent unit

Mixture

• group of two or more elements and/or compounds that are physically intermingled (not chemically bonded)

What is this?

Mixture

Physical Changes

changes in the properties of matter that do not effect matter’s composition

Chemical Changes

changes in the properties of matter that change matter’s composition

Solid to Liquid

melting

Liquid to Gas

vaporization

Liquid to Solid

freezing

Gas to Liquid

condensation

Solid to Gas

sublimation

Gas to Solid

deposition

Energy

• anything that has the capacity to do work (cause change) or transfer heat

• can interact with matter to cause physical and/or chemical changes

• has no mass or volume

How do you sense energy?

Motion, Light, and Heat

Scientific Method

Observe —> Analyze —> Hypothesis —> Test —> Explain

Potential Energy

energy due to position of object

Kinetic Energy

energy due to motion of object

Endothermic

“energy in”, energy has to be added to overcome the forces of attraction between the molecules of a substance

Exothermic

“energy out”, heat is released

Endothermic Reactions

Melting, Vaporization, Sublimation

Exothermic Reactions

Condensation, Freezing, Deposition

AMU

Atomic Mass Unit

What is X?

Atomic Symbol

What is A?

Mass Number, Z + N

What is Z?

Atomic Number, Number of Protons

What is N?

Number of Neutrons

Isotopes

atoms of an element with same number of protons but different number of neutrons, same atomic number, different mass number

Ion

charge atom that has either more or less electrons than protons

Cation

ions with a positive charge; have less electrons than protons

Anion

ions with a negative charge; have more electrons than protons

How many protons?

86

How many neutrons?

16

The elements in the modern periodic table are arranged by….

increasing atomic number (Z) + columns and rows to emphasize periodic properties

The columns are collectively called…

families or groups

The rows are collectively called…

periods

The following is the Bohr model for which atom?

Nitrogen

The following is the Bohr model for which atom?

Magnesium

valence electrons

electrons in the outer most shell

Elements with the same number of valence electrons have…

similar reactivity

The noble gases are the most ______________ on the periodic table. 

stable (least reactive) elements

Metals tend to lose their own valence electrons, thereby becoming ______

cations

Nonmetals tend to gain extra valence electrons, thereby becoming ______

anions