CHEM 6 CH 1

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Chemistry

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Terms in this set (21)

Chemistry

The study of the nature, properties, and transformations of matter.

Matter

The physical material that makes up the universe; anything that has mass and occupies space.

Scientific Method

The systematic process of observation, hypothesis, and experimentation used to expand and refine a body of knowledge.

DESCRIBING MATTER

Property:
A characteristic useful for identifying a substance or object.

Physical change: A change that does not affect the chemical makeup of a substance or object.
CHANGES IN MASS, TEMP, DENSITY, SIZE, VOLUME
(ice melting, evaporation)

Chemical change A change in the chemical makeup of a substance.
REACTIONS, FLAMMABLE, RUST, OXIDIZE, COMBUST, COOKING, IRREVERSIBLE CHANGES
(bike rusting, fruit ripening, cooking, bleach hair)

STATES OF MATTER
(temp can determine state)

Solid:
A substance that has a definite shape and volume.

Liquid:
A substance that has a definite volume but assumes the shape of its container.

Gas:
A substance that has neither a definite volume nor a definite shape.

*Change of state:
The conversion of a substance from one state to another—for example, from liquid to gas.*

CHANGE OF STATE R/T TEMPERATURE

GAS
--boiling point (liquid to gas)----
LIQUID
---melting point (solid to liquid)---
SOLID

CLASSIFICATIONS OF MATTER

IS IT A MIXTURE OR PURE SUBSTANCE?

Pure substance: A substance that has a uniform chemical composition throughout.

Mixture: A blend of two or more substances, each of which retains its chemical identity.

IF THE MATTER IS A MIXTURE, HOMOGENEOUS OR HETEROGENEOUS?

Homogeneous mixture: A uniform mixture that has the same composition throughout.
(coffee, salt water, apple juice)

Heterogeneous mixture: A nonuniform mixture that has regions of different composition.
can visualize diff. properties
(rocky road ice cream, wood, beef stew)

IF THE MATTER IS A PURE SUBSTANCE IS IT A COMPOUND OR AN ELEMENT?

Element: A fundamental substance that cannot be broken down chemically into any simpler substance.
(hydrogen, oxygen, aluminum, gold, and sulfur. 118 elements.)

Chemical compound: A pure substance that can be broken down into simpler substances by chemical reactions.
(sugar, salt)

CHEMICAL REACTIONS TO CHEMICAL COMPOUNDS

Reactant: A starting substance that undergoes change during a chemical reaction.

Product :A substance formed as the result of a chemical reaction.

Chemical reaction: A process in which the identity and composition of one or more substances are changed.

Chemical formulaA notation for a chemical compound using element symbols and subscripts to show how many atoms of each element are present. COMPOUNDS: made up of 2+ elements (NH4)3 PO4 Nx3 Hx12 Px1 Ox43 TYPES OF ELEMENTSMETAL: *aluminum, gold, copper, and zinc* malleable element , ductile lustrous appearance good conductor of heat and electricity. (94 left of table) NONMETAL: *Oxygen, nitrogen, sulfur, bromine* poor conductor of heat and electricity. (18 right of table) METALLOIDS: *Boron, silicon, and arsenic* An element whose properties are intermediate between those of a metal and a nonmetal. semi-conductors. (6 zig zag between L & R elements) !!GIVEN PERIODIC TABLE, IDENTIFY A NON-MENTAL/METAL/METALLOID - IS IT S A GOOD CONDUCTOR, ETC?!!CHEMICAL REACTIONS ARE WRITTEN AS CHEMICAL EQUATIONS.REACTANT ----> PRODUCTS "yields"COEFFICIENTS = quantities SUBSCRIPTS & STATES OF MATTER(S) = solid (l) *cursive l* = liquid (G) = gas (AQ) = aqueous *disolved in water* 2NA(s) + H20(l) !!which is the solid!?! - NA !!who has coeffiecient of 2?! - NAPhysical quantityA physical property that can be measured. MUST HAVE A UNIT Unit: A defined quantity used as a standard of measurement.SI units Units of measurement defined by the International System of Units.Mass is measured in kilograms (kg), length is measured in meters (m), volume is measured in cubic meters (m3), temperature is measured in kelvins (K), and time is measured in seconds (s, not sec). 1 kg = (1000)(1 g) = 1000 gMeasuring Mass, Length, and VolumeMass: A measure of the amount of matter in an object. Weight: A measure of the gravitational force that the earth or other large body exerts on an object. Volume: is the amount of space occupied by an object. The SI unit for volume—the cubic meterCOVERTING UNITS1- USE A CONVERSION STATEMENT TO FIND 2 CONVERSION FACTORS. STATEMENT: "4 Quarters= 1 Dollar" FACTORS: 4 quarters 1 dollar ----------- X ---------- = 1 1 dollar 4 quarters "How many quarters are in 13 dollars?" WANTED: quarters GIVEN: dollars WANTED UNIT ---------------- GIVEN UNIT (always on bottom) 13 dollars 4 quarters ----------- X ------------ = 52 quarters 1 dollar 1 mol NA = 23.0g, 124.5g = ___?__ mol? 1 mol NA 23.0g ---------- = --------- 23.0 g 1 mol NA 124.5g . 1 mol NA -------- X ---------- = 5.4 mol NA. 23.0 gSignificant figures: The number of meaningful digits used to express a value.ONLY FOR MEASUREMENTS , NOT COUNTS. 21.1ml 21= certain .1 = estimate ALL ARE SIGNIFICANT. MEASURE LIQUIDS AT THE BOTTOM OF THE MENISCUS. estimate one final place. or point.SIG FIG RULESRULE 1: Zeros in the middle of a number are like any other digit; they are always significant. Thus, 94.072 g has five significant figures. RULE 2: Zeros at the beginning of a number are not significant; they act only to locate the decimal point. Thus, 0.0834 cm has three significant figures, and 0.029 07 mL has four. RULE 3: Zeros at the end of a number and after the decimal point are significant. It is assumed that these zeros would not be shown unless they were significant. Thus, 138.200 m has six significant figures. If the value were known to only four significant figures, we would write 138.2 m. RULE 4: Zeros at the end of a number and before an implied decimal point may or may not be significant. We cannot tell whether they are part of the measurement or whether they act only to locate the unwritten but implied decimal point. Thus, 23,000 kg may have two, three, four, or five significant figures. Adding a decimal point at the end would indicate that all five numbers are significant. Often, however, a little common sense is useful. A temperature reading of 20 °C probably has two significant figures rather than one, because one significant figure would imply a temperature anywhere from 10 °C to 30 °C and would be of little use. Similarly, a volume given as 300 mL probably has three significant figures. On the other hand, a figure of 150,000,000 km for the distance between the earth and the sun has only two or three significant figures because the distance is variable. We will see a better way to deal with this problem in the next section.sig fig examples.94.072 g Five significant figures (9, 4, 0, 7, 2) 0.0834 cm Three significant figures (8, 3, 4) 0.029 07 mL Four significant figures (2, 9, 0, 7) 138.200 m Six significant figures (1, 3, 8, 2, 0, 0) 23,000 kg Anywhere from two (2, 3) to five (2, 3, 0, 0, 0) significant figures