classification of matter
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Chemistry is the study about how matter is put together, how atoms combine to form molecules , and how the molecules combine to make up the many kinds of matter around us . Classification of Matter. Matter – identified and organized by properties - PowerPoint PPT PresentationTRANSCRIPT
Chemistry is the study about how matter is put together, how atoms
combine to form molecules, and how the molecules combine to
make up the many kinds of matter around us.
Classification of MatterMatter – identified and organized by properties
anything that has mass and takes up space
Properties Chemical – ability to react/combine (both what it
will and won’t react with)- will change the composition
Physical – characteristics observed or measured-will not change the composition
two kinds of physical properties help describe the behavior of a substance undergoing a physical change
1. Extensive- depends on the amount of matter
Ex: mass, length, volume
2. Intensive- does not depend on the amount of Ex: density (regardless of size, each sample of a substance has the same density) color, crystalline shape, melting point, boiling point, phase of the matter (solid, liquid, gas), and refractive index (ability of material to bend light)
Property Physical or Chemical
Intensive or Extensive
SizeDensityColorFlammableCorrosivePhase of matter
Property Physical or Chemical
Intensive or Extensive
Size P EDensity P IColor P IFlammable C N/ACorrosive C N/APhase of matter P I
State (or phase) of matter is always a physical property: Solid, liquid, gas
Phase
Energy – move
Particle spacing
Volume Shape Compressible
Solid Little CloseRigid
Definite Definite
No
Liquid
Some CloseSlide
Definite Not Definit
e
No
Gas Lot Far Not Definite
NotDefinit
e
Yes
Changes in PropertiesPhysical change - does NOT change the
composition (identity) of the substance. Same substance remains after a change has taken place *Size: pounding, bending, grinding, pulling,
or cutting does not change the chemical character of a substance.
*Change of state: melting, boiling, vaporizing *Cutting a piece of wood into smaller pieces,
tearing paper, dissolving sugar in water, hammering copper into a new shape are all examples of physical change.
Chemical change- DOES change composition. After a change has taken place a new substance appearsChanges that produce
a new kind of matter with new, different properties. Burning, digestion, fermenting all form new substances with new and different characteristics.
Sodium- a silvery, soft metal that reacts vigorously with water (Na)
Chlorine- a yellow-green gas that is highly- corrosive and poisonous (Cl)
Yet if these two elements are brought together, they combine to form a white crystalline solid. Table salt (NaCl), which neither reacts with water, nor is poisonous.
Evidence of a chemical change:1. Heat and/or light is produced
2. Production of a gas (bubbles)
3. Odor
4. Color change
5. Formation of a precipitate – a cloudy solid which appears after mixing to clear solutions
Chemical Reactions - a Chemical change has taken place: 2 or more substances have chemically bonded together to create a new substance
Law of Conservation of Mass – matter is neither created nor destroyed. This states that mass remains constant during a chemical reaction. One of the greatest scientific achievements of the 18th century by a Frenchman, Lavoisier (1743-1794)
Mass (of reactants) = Mass (of products)Before After
Chemical Equations: Reactant + reactant product +
product (always on left) (always on
right) ~ arrow shows directions
Ex. 12 g of calcium reacts with 6 grams of fluorine gas to produce calcium fluoride. How many grams of product will be produced?
12 g Ca + 6 g F2 ____ g CaF2 (12 + 6) = (18)
Try itDuring electrolysis you can separate water into
hydrogen & oxygen. If 10.0g Hydrogen & 79.4 g Oxygen were produced, much water was there at the start?
____ g H2O 10.0 g H2 + 79.4 g O2
89.4 g H2O 10.0 g H2 + 79.4 g O2
Mixture- matter that contains two or more different materials
Phase- any region with a uniform set of properties
Ex: sour milk, watery part is one phase while fat is the second phase
Mixtures are divided into two categories1.
Heterogeneous mixture- a mixture that is composed of more than one phase
Ex: granite, sand
2. Homogeneous mixture- materials that consist of only one phase.
If you break a piece of homogeneous matter into smaller pieces, each piece will have the same properties as every other small piece
Ex: salt water, window glass, and air
Separating Mixtures (physical separation)
1. Filtration – through a porous barrier, filters solids from liquids
2. Distillation – different boiling points2 liquids: lowest boiling point vaporizes 1st
3. Crystallization – dissolved solids from a solutions
rock candy left after water evaporates 4. Chromatography – different rate of travel
through a medium identify chemicals, DNA testing, separates
pigments, research
Pure Substances- homogeneous materials that always have the same composition
*Homogeneous mixtures are not pure substances, yet the substances that comprise them are evenly dispersed throughout the mixture
1. Elements- substances composed of only one kind of atom (elements on the P.T.)
Ex: sodium ~ Na, Iron ~ Fe, Neon ~ Ne
2. Compounds- composed of more than one kind of atom (made from multiple elements on the P.T.)
Ex: water ~ H2O, table salt ~ NaCl
Compounds cannot be physically separated, they are chemically bonded
Pure Substances are divided into two categories
Matter
Mixtures
1. 2.
Homogeneous Mixture
Solutions1. 2. 3.
Colloid-1.
2.
3.
Heterogeneous Mixture Suspension
Pure Substances
Element1. 2.
Compound1.
2.
Matter
Mixtures
1. Has Mass2. Has Volume(Occupies Space)
Homogeneous Mixture
Solutions1. 2. 3.
Colloid-1.
2.
3.
Heterogeneous Mixture Suspension
Pure Substances
Element1. 2.
Compound1.
2.
MixturesVariable Composition
Can be physically separated
Homogeneous Mixture
Uniform Throughout (But Proportions can
Vary)
Solutions1. Particles are atoms,
ions, or molecules2. Won’t scatter light3. Ex. Salt Water, Steel, Air
Colloid- Don’t settle out1. Particles larger than
molecule 2. Scatters light
(Tyndall Effect)3. Ex. Smoke, Fog
Heterogeneous MixtureNot uniform ThroughoutEx. Lumpy
SuspensionSolid in LiquidEventually settle outEx. Muddy waterWood, granite, blood
Pure SubstancesDefinite Composition
HomogeneousCan’t be physically separated
Element1. Made of atoms2. Cannot be further
separated by chemical or physical means
(on periodic table Mendeleev arranged in
rows-periods Columns-
groups/families)
Compound1. Chemical combinations
of 2 or more atoms. (elements chemically bonded)
2. Cannot by separated by physical means (CaCl2, NaCl, Sugar, C6H12O6)
Matter
Mixtures
1. Has Mass2. Has Volume(Occupies Space)
Variable CompositionCan be physically separated
Homogeneous Mixture
Uniform Throughout (But Proportions can
Vary)
Solutions1. Particles are atoms,
ions, or molecules2. Won’t scatter light3. Ex. Salt Water, Steel, Air
Colloid- Don’t settle out1. Particles larger than
molecule 2. Scatters light
(Tyndall Effect)3. Ex. Smoke, Fog
Heterogeneous MixtureNot uniform ThroughoutEx. Lumpy
SuspensionSolid in LiquidEventually settle outEx. Muddy waterWood, granite, blood
Pure SubstancesDefinite Composition
HomogeneousCan’t be physically separated
Element1. Made of atoms2. Cannot be further
separated by chemical or physical means
(on periodic table Mendeleev arranged in
rows-periods Columns-
groups/families)
Compound1. Chemical combinations
of 2 or more atoms. (elements chemically bonded)
2. Cannot by separated by physical means (CaCl2, NaCl, Sugar, C6H12O6)
Law of Definite Proportions
% by Mass = Mass of element x 100
Mass of compound
If compounds have the same % by mass, they must be the same
Regardless of amount, a compound is always composed of the same elements in the same proportion by mass
80 g sample of compound contains 20 g of hydrogen. What is the percent by mass of hydrogen?
20 g x 100 = 25%80 g
If 7 g of iron combine with 3 g of oxygen, what is the % by mass of iron? Of oxygen?Hint: Find the total mass 1st
% iron = 7g x 100 = 70%
10 g
%oxygen = 3g x 100 = 30%10g
Try itSample 1 contains 15.0 g of H2 and 120.0 g
of O2 Sample 2 contains 2.0 g of H2 and 32.0 g of
O2 Are they the same compound?
Sample 1 contains 15.0 g of H2 and 120.0 g of O2 Sample 2 contains 2.0 g of H2 and 32.0 g of O2 Are they the same compound?
Sample 1 H2 : 15 x 100 = 11%15 g + 120 g = 135 g 135
O2 : 120 x 100 = 89% 135
Sample 2 H2 : 2 x 100 = 6%2 g + 32 g = 34 g 34
O2 : 32 x 100 = 94% 34
Different percentages so these are different compounds
Intro to the Periodic Table
Vertical columns Horizontal rowscalled groups or
families.
Elements in a group have similar chemical & physical properties.
Numbered from 1-18 from left to right
called periods.
Elements within a period have properties that change progressively across the table.
Metals – (left side) are good conductors of heat and electricity; shiny metallic luster (mostly silver or grayish white); malleable (hammered or rolled into thin sheets); ductile (string into a wire); properties vary according to groups
Nonmetals – (right side) elements that are poor conductors of heat and electricity, dull (no luster); some are gases at room temperature. Br is a liquid; C, P, Se, S & I are solid and much more brittle than metals
Metalloids – (on the stair-step line) – elements that have characteristics of both metals and nonmetals to a limited degree. Less malleable than metals, but not as brittle as nonmetals; some have luster, some don’t; semiconductors of electricity (used in semi-conducting materials found in computers, calculators, watches, TV’s and radios)
Branches of ChemistryOrganic Chem – study of carbon – containing
compoundsInorganic Chem – all substances not classified as
organic (mainly those that do not contain carbon)Physical Chem – the study of properties and changes
of matter and their relation to energyAnalytical Chem – identification of the components
and composition of materialsBiochemistry – substances and processes occurring
in living thingsTheoretical Chem – uses math and computers to
understand the principles behind observed chemical behavior and to design and predict new compounds
Scientific MethodScience- Body of knowledge gained through
systematic observation, experimentation, and study of the physical world.
Math- the language of Science: 16th century-Science made huge progress when it was discovered that nature can be analyzed and described when scientific findings are expressed mathematically they are easy to verify or disprove be experiment
Galileo Galilei (1564-1642) Italian PhysicistFrancis Bacon (1561-1626) English
philosopherCo-Founders of scientific method ~
Extremely effective in gaining, organizing, and applying new knowledge
Scientific method – systematic approach to do research, answer questions, and solve problems
Recognize a problemMake an educated guess-a hypothesis-about
the answerPredict the consequences of the hypothesisPerform experiments to test predictionsFormulate the simplest rule that organizes
the main ingredients: hypothesis, prediction, and experimental outcomes
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