Matter and Measure

Two main systems

English◦ Based on arbitrary measurements that have

lasted through history◦ Conversions are harder to remember

Metric◦ Based on powers of ten◦ Prefixes determine magnitude of power of ten

Scientific Community has accepted certain units as base units

Dimension Unit Symbol

Length Meter m

Mass Gram g

Time Second s

Temperature Kelvin K

Amount Mole mol

Prefix Power Symbol

Giga 109 G

Mega 106 M

kilo 103 k

deci 10-1 d

centi 10-2 c

milli 10-3 m

micro 10-6 μ

nano 10-9 n

pico 10-12 p

Digital Displays are recorded as is◦ Digital Mass Balance, pH meter

Visually Read Scales can always be estimated to smaller increment than marked◦ Rulers, Thermometers, Graduated Cylinders◦ Meter stick Example

0m 0.4m0.2m0.1m 0.3m

Length=??

0.3m0.31m 0.314m

Not all digits(#’s) in a measurement are significant(important)

◦ Suppose the mass of an object is estimated to be 2.5 grams

◦ The volume of that object is measured accurately to 0.6250000cm3

How many decimal places should the density have? 4.0g/cm3 or 4.000000g/cm3

Rules on pages 66-71 of textbook

Shorthand◦ If the decimal point is present, start counting

digits from the Pacific (left) side, starting with the first non-zero digit.

1 2 3

0.00310 (3 sig. figs.)

Shorthand ◦ If the decimal point is absent, start counting

digits from the Atlantic (right) side, starting with the first non-zero digit.

3 2 1

31,400 (3 sig. figs.)

Addition and Subtraction◦ Answer has to have the same number of decimal

places as least decimal places in what you are adding or subtracting

Example◦ 15.62-7.248 = ???

Calculator 8.372 Science 8.37

Multiplication and Division◦ Answer has to have same number of Sigfigs as

least number of Sigfigs in what you are multiplying or dividing

Example◦ 7.55*0.34 = ???

Calculator 2.567 Science 2.6

Short hand way of writing very large and very small numbers◦ Uses only sigfigs

Examples:◦ 602,000,000,000,000,000,000,000◦ 6.02 x 1023

◦ 0.000000000567◦ 5.67 x 10-10

How close a measurement is to correct or accepted value ◦ Bull's-eye on a dartboard

Poor Accuracy Good Accuracy

How close a measurement is to other measurements ◦ Darts close to each other

Poor PrecisionPoor Accuracy

Good PrecisionGood Accuracy

Good PrecisionPoor Accuracy

Measure related to the heat of an object

Measured in °Celsius or Kelvin(no degrees)

Conversion

273 CK

Amount of matter in a given amount of space

Amount of mass in a given volume

V

mD

What is Chemistry?◦ Study of matter and the changes it undergoes

Branches◦ Organic◦ Physical◦ Analytical◦ Biochemical◦ Inorganic

International Union of Pure and Applied Chemistry

Group that names elements and compounds

Meets every few years

Anything that has mass and takes up space, volume

Classified into two categories◦ Substances (Pure)◦ Mixtures

Simplest form of matter

Made up of Subatomic Particles

Different atoms have different properties

Element◦ simplest form of matter that has a unique set of

properties.

◦ arranged into a table, called the periodic table

◦ Can’t be broken down by chemical means

◦ denoted using chemical symbols, O, Cu, Fe Symbols always have the first letter capitalized If needed, any additional letters are not capitalized

Compounds◦ substance of two or more elements chemically

combined in a fixed proportion

◦ Ex. H2O, C6H12O6

◦ Can be broken down by chemical means

Physical blend of two or more substances

Two Types:◦ Homogeneous

◦ Heterogeneous

Homogeneous◦ Composition is uniform throughout◦ Examples: Air, Olive Oil, Stainless Steel◦ Solution is a homogeneous mixture◦ Aqueous Solution is something mixed in water

Heterogeneous◦ Composition is not uniform throughout◦ Examples: Salad Dressing, Chicken Noodle Soup

Differences in physical properties can be used to separate mixtures

◦ Filtration – Separates solids from liquids in heterogeneous mixtures

◦ Distillation – Separates homogeneous liquid mixtures based on different boiling points

◦ Evaporation – evaporate away liquid to leave solid

◦ Chromatography – separation of substances based on polarity

Solid◦ Definite shape and volume◦ Particles are packed tightly together in a regular

geometric pattern◦ (s) used after chemical formulas

◦ Cu(s)

Liquid◦ Definite volume, takes shape of container◦ Particles can slide past each other◦ (l) used after chemical formulas

◦ H2O(l)

Gas◦ Takes shape and volume of container◦ Particles are spread very far apart◦ (g) used after chemical formulas

◦ H2O(g)

Dissolved in water (aq) used after chemical symbols

◦ NaCl(aq)

Solid Liquid Melting Liquid Solid Freezing Liquid Gas Vaporization Gas Liquid Condensation Solid Gas Sublimation Gas Solid Deposition

Temperature does NOT change during a phase change

Physical Property◦ quality or condition of a substance that can be

observed or measured without changing the substance’s composition

◦ Ex: Color, shape, size, mass

Physical Change◦ some properties change, but the composition

remains the same◦ Can be reversible or irreversible◦ Ex: melting, freezing, tearing

Chemical Change◦ change that produces matter with a different

composition than the original matter◦ Ex. burning, rusting, decomposing, exploding,

corroding

Chemical property◦ property that can only be observed by changing

the composition of the substance.◦ Ex: Reactivity with acids, reactivity with oxygen

Boiling Point Physical Green color Physical Shiny Physical Conductivity Physical Solubility Physical Reacts with acid Chemical Reacts with O2 Chemical

Extensive Properties◦ property that depends on the amount of matter in

a sample.◦ Ex: mass, weight, volume

Intensive Properties◦ property that depends on the type of matter in a

sample, not the amount of matter◦ Ex: Density, hardness, viscosity

Capacity to do work Ability to do something

Types:◦ Chemical◦ Electrical◦ Mechanical◦ Potential◦ Kinetic

Exothermic◦ Process when energy is released or given off◦ Ex: Burning, freezing

Endothermic◦ Process when energy is absorbed or taken in◦ Ex: Melting

Observation◦ using five senses to make observations.

Hypothesis◦ proposed explanation for an observation.

Experiment◦ procedure used to test a hypothesis.

Analyze Data◦ check to see if results support hypothesis.

Theory◦ well tested explanation for a broad set of

observations.

Law◦ concise statement that summarizes the results of

many observations and experiments.

Law of Conservation of Mass◦ Mass can not be created or destroyed, only

changed into different forms

Law of Conservation of Energy◦ Energy can not be created or destroyed, only

changed into different forms