The nature of matterChemistry

Substance, Element, Mixture

Take a sample of an unknown material. Divide it into smaller and smaller pieces.

Are the properties remaining the same? Apply the process to the following:

◦ Milk◦ Water◦ Anti-freeze◦ Lead pipe◦ 14k gold◦ Sugar

Water, sugar, protein, fat

H2O

Propylene (or ethylene)glycol, water

Pb, industrially purified

Gold, silver alloy

Sucrose

Properties of Matter

Any characteristic that can be used to

describe or identify matter is a property.

Intensive properties have values that do

not depend upon the amount of matter.

Extensive properties have values that

depend on the sample size.

Physical & Chemical Properties

Physical properties are characteristics that do not involve a change in the chemical makeup of the sample.◦ A change in phase

Chemical properties are characteristics that do involve a change in chemical makeup.◦ Paper burns

Physical Properties

Physical properties are characteristics that do not involve a change in the chemical makeup of the sample.◦ A change in phase

Chemical properties

Chemical properties are characteristics that do involve a change in chemical makeup.◦ Paper burns

Yellow vanadium (VI) is swirled with Jones Reductor and will progressively change color until it reaches the violet vanadium (II). Alternatively, violet vanadium(II) is oxidized through a series of colors by permanganate to a final yellow color.

Density

Density is the ratio of mass (the amount of matter present) to volume (the amount of space that the matter occupies).

The ratio of mass to volume of a substance remains a constant for a given set of circumstances.

Standard measures of density are reported at 1 atmosphere of pressure and a temperature of 25 degrees Celsius.

Density

Density is the ratio of mass (the amount of matter present) to volume (the amount of space that the matter occupies).

The ratio of mass to volume of a substance remains a constant for a given set of circumstances.

Standard measures of density are reported at 1 atmosphere of pressure and a temperature of 25 degrees Celsius.

Example experiment

Early known elements

Earliest recorded history includes information about ten elements (Sb, C, Cu, Au, Fe, Pb, Hg, Ag, S, Sn).

These elements occur naturally in native (+0) state.

Photos by Paul Silverman

Cu

S

Pb

Antiquity to 1800 Gray1800-1849 Green1900-1949 Dark Purple1950-1999 Light Purple2000- 2012 not shown

112 is named Copernicium114 is named Flerovium116 is Livermorium (Lawrence Livermore Laboratories)

Antiquity to Middle Ages (14 elements): unrecorded discoveries up into the Middle Ages (Cu, Cr, Fe, Cu, Zn, Ag, Au, C, S, As, Sn, Sb, Pb, Bi)Middle Ages – 1800 (22 elements): discoveries during the age of enlightenment (H, Be, Mg, Sr, Ba, Y,

Ti, Zr, Mo, Co, Ni, Pt, O, N, W, Mn, Cl, Te, P, U, Al, B)1800–1849 (22 elements): scientific and industrial revolutions (Li, Na, K, Ca, V, Nb, Ta, Ru, Rh, Pd,

Cd, Os, Ir, Si, Se, Br, I, La, Ce, Nd, Tb, Er, Th)1850–1899 (26 elements): the age of classifying elements; application of spectrum analysis techniques:

Boisbaudran, Bunsen, Crookes, Kirchhoff, and others "hunting emission line signatures" (Rb, Cs, Sc, Ra, Tc, Re, Ga, Ge, In, Tl, Po, He, Ne, Ar, Kr, Xe, Pr, Ac, Sm, Eu, Gd, Dy, Ho, Tm, Yb)1900–1949 (13 elements): development of old quantum theory and quantum mechanics (Fr, Hf, Tc,

At, Rn, Pm, Pa, Np, Pu, Am, Cm. Bk, Lu)1950–1999 (16 elements): post Manhattan project; synthesis of atomic numbers 98 and above

(colliders, bombardment techniques)(Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Bk, Cf, Es, Fm, Md, No, Lr)Since 2000 (5 elements): recent synthesis

Organization of Elements

The first work to inventory the elements was published in 1789 by French scientist Antoine Lavoisier.

A surge in discovery of new elements occurred through 1850’s.

The work of John Dalton, 1805, found that elements have a consistent property of atomic mass. He worked to develop the ancient idea of atoms.

Observation of reactions and properties of different elements led Johann Dobereiner’s hypothesis of triads of related elements in 1829. Cl, Br, and I; or Ca, Sr, and Ba. 16 triads were described by 1843.

First Periodic Table

First organizational chart was published by Dmitri Mendeleev in 1869. It had seven horizontal rows (periods) and 18 vertical columns (groups). The primary basis for his organization was the atomic mass. Elements in a group have similar chemical properties.

There are 90 naturally occurring elements. The other elements have been artificially produced by nuclear chemists in high-energy particle accelerators.

Mendeleev’s Table

Medeleev left blanks in his table where he predicted there were elements missing based on the patterns he observed in known elements.

Elements missing from Mendeleev’s Table

Other scientists were able to use Medeleev’s predictions to look for and find Scandium, Gallium, and Germanium.

IUPAC Periodic Table

The periodic table has a total of 32 groups rather than the 18 groups. To fit the chart on a page, the 14 groups that follow lanthanum or actinide are pulled out and displayed below the main chart.

Group 1A: Alkali metals

Lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs) are shiny soft metals.

All react rapidly (often violently) with water to form highly alkaline (basic) products.

Due to the high reactivity, the alkali metals are never found in nature in the pure state, only in combinations with other elements.

Group 1A

Group 2A: Alkaline earth metals

Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) are also lustrous, silvery metals.

These metals are less reactive than Group I metals and produce alkaline products.

Alkaline earth elements are also never found in nature in their pure state.

Group 2A

Group 7A: Halogens

Fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) are colorful, corrosive nonmetals.

Halogens are found in nature only in combination with other elements, example: table salt (NaCl).

Hals means salt in Greek.

Astatine is a halogen, but it occurs in tiny amounts with little known about it.

Group 7A or 17

Group 8A: Noble gases

Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are gases of very low reactivity. He, Ne, and Ar do not combine with any other elements.

Kr and Xe combine with very few elements.

Noble Gases—Group 18

Metals

Metals are the largest category of elements. These are found on the left side of the table.

All (except mercury, Hg) are solids at room temperature.

Most have silvery shine commonly associated with metals.

Most are malleable, not brittle. Metals are good conductors of heat and

electricity.

Nonmetals

Nonmetals (17 in all) are located on the right side of the table.

Their appearance can be characterized by lack of silvery lustre. Only five are solids at room temperature, and they are brittle (carbon, phosphorus, sulfur, selenium, and iodine). Bromine is a liquid. All others are gases.

Some are brightly colored such as sulfur yellow.

All are poor conductors of heat & electricity.

Semimetals

Semimetals occur diagonally from boron (B) to astatine (As) at the base of group 7A. Included are silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te).

Semimetals have intermediate properties.

Silvery in appearance, solid at room temperature, brittle, and poor conductors of heat and electricity.

Measurement

Scientific experimentation is performed in a way that can be replicated by others. It is necessary to use common units and nomenclature.

International System of Units (SI for the French: Systeme Internationale d’Unites) was established by agreement in 1960.

Metric system has seven fundamental units

Physical Quantity Name of Unit Abbreviation

mass kilogram kg

length meter m

temperature Kelvin K

amount of substance mole mol

time second s

electric current ampere amp

luminous intensity candela cd

Prefixes for Multiples of SI Units

Factor Prefix Symbol

1,000,000,000 1.00E+09giga G

1,000,000 1.00E+06mega M

1,000 1.00E+03kilo k

100 1.00E+02hecto h

10 1.00E+01deka da

0.1 1.00E-01deci da

0.01 1.00E-02centi c

0.001 1.00E-03milli m

0.000001 1.00E-06micro

0.000000001 1.00E-09nano n

0.000000000001 1.00E-12pico p

The size of an atom of silicon and the diameter of a star are both measured in meters.

SI units are modified by the use of prefixes to bring the unit into scale for the description of scientific observations.

Scientific notation

For very large or very small numbers, use scientific notation.

The exponential format is A x 10n

A is between 1 and 10.

The exponent, n, is either a positive or negative integer.

Examples: 83,450 = 8.345 x 104

(A x 10n)(B x 10m) = AB x 10m + n

(A x 10n)m = Am x 10m x n

Mass

Mass is the amount of matter.

Matter a generic term of anything with a physical presence.

SI unit is kilogram (kg = 2.205US lb).

Common prefixes: gram = 10-3 kg

milligram = 10-6 kg

microgram = 10-9 kg

Length

SI unit for length is the meter (m = 39.37 in).

Common prefixes: centimeter = 10-2 m

millimeter = 10-3 m

micrometer = 10-6 m

nanometer = 10-9 m

Na atom is 375pm picometer = 10-12 m

Temperature

SI unit for temperature is the Kelvin (omit the word degree)

The size of the unit is equal to the degree Celsius (oC). The unit is equal to one hundredth of the interval between the freezing point of water and the boiling point of water at STP.

0 oC freezing point/ 100 oC boiling point 0 K coldest possible temperature or

absolute zero (-273.15 co)

Prepare for experiments

Measure 100mL of water to use in an experiment to produce reliable results.◦ Equipment: Erlenmeyer flask Scale

Volumetric flask

Beaker

Cooking measure

Hypothesis: (Frances)If the volumetric flask is used then the results will both more precise and more accurate.

Analysis and conclusions

Results:

Conclusion: Write your conclusion based on the data collected, statistical analysis, and the fact that 100 ml of water will have a mass of 100gm at STP.

Weight of 100 ml of Water

Total weight

Measuring device Tare Weight Trial 1 Trial 2 Trial 3Average weight

Net weight

Beaker 217.68 311.27 311.85 314.17 312.43 94.75

Volumetric Flask 57.22 156.93 156.82 156.88 156.8766667 99.65667

Erhlenmeyer Flask 206.93 287.62 297.38 300.69 295.23 88.3

Measuring Cup 418.01 519.74 519.54 518.41 519.23 101.22