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Classifying Matter

4.01 – States of Matter

• Anything with mass that takes up space (volume) is matter.

• Exists in 4 states

– Solid

– Liquid

– Gas

– Plasma

4.01 – States of Matter• Solid:

• The particles of a solid are in a tight, fixed position. Since the particles in solids are not free to move around they vibrate just a little. Solids have a set volume and a set shape.

4.01 – States of Matter• Liquid:

• The particles of a liquid are close together, but they are not in a neat arrangement like in a solid. They have enough space to slide past each other. Liquids have a set volume but no set shape.

4.01 – States of Matter• Gas:

• The particles of a gas have a lot of space between them. They move fast and in no order. The volume of gas also increases as temperature increases. Gasses have no set volume and no set shape.

4.01 – States of Matter• Plasma:

• Contains particles that are positively and negatively charged. Atoms begin to lose electrons, creating charged particles that move freely. Plasma, like a gas, has no set volume or shape and can be found in stars, Plasma TVs, and neon signs.

4.01 – States of Matter• Kinetic Theory of Matter

– All matter is composed of tiny particles

– These particles are in constant, random motion

– The particles collide with each other and with the walls of any container in which they are held

– The amount of energy that the particles lose from these collisions is negligible.

4.01 – States of Matter• Kinetic Molecular Theory

– Explains why matter changes states

• Matter changes states due to gain or loss of energy

– Explains why a particular state behaves as it does

• Objects expand when heated

– Explains why the temperature of a substance increases as you heat it

• Temperature of an object is a measure of the average kinetic theory of a substance

• Heating Curves

– A graph of temperature vs. time for heating a substance

4.01 – States of Matter

Pure Substances•Elements –

•Element and atom are not the same• Periodic Table of Elements

•Compounds –•Made from combined elements

4.02 – Classifying Matter


Bromine (Br2) and Oxygen (O2) exist naturally as molecules. Each molecule consists of two atoms bonded together. Even though it is made of molecules it is still an element because it contains only one type of atom.

Element or Compound??1. H20

2. Copper (Cu)

3. C6H12O6

4. NaCl

5. Oxygen (O2)

6. Sodium (Na)


Mixtures-Heterogeneous Mixtures –

Homogeneous Mixtures-Solutions-


Classify the following as an element, compound, or mixture. If mixture, make sure to label homogenous or heterogeneous.1) soda 4) Nitrogen (N)2) water (H20) 5) NH4

3) gravel 6) a taco


• Physical properties • Physical properties are characteristics of a

substance that can be measured without changing the identity of the substance.– Appearance (for example, color or shape)– Odor– Melting point and boiling point– Density– Hardness– Ductility and Malleability (ability to change shape)– Solubility– Electrical and thermal conductivity– Magnetism

4.03 – Properties of Matter

• Chemical properties

• characteristics of a substance that describe the ways it can react to form new materials.

• Chemical properties cannot be measured or studied without changing the composition of the substance.– Flammability and other tendencies to react with

oxygen

– Reaction with acids and bases

– Reaction with water

– Decomposition caused by light or heat

– Tendency to corrode


• Physical Changes• Physical changes are changes that do not

result in the formation of a new substance.

• The substance is still the same because chemical bonds have not been broken or formed, and so the atoms of the molecules are still connected in the same way.


• Chemical Changes• referred to as chemical reactions.

• always produce new substances with properties that are typically very different from those of the reactants.

• some clues that can indicate a chemical change has occurred.

– visible flames

– color change

– bubbling or fizzing

– smoke

– heat or light given off

– formation of a substance in a different state (for example, a solid from two liquids)

• Of these observations, seeing flames is the only sign that always indicates a chemical change. All of the others can sometimes be the result of a physical change.


Event Physical Chemical

Cutting your hair

Mixing sugar and water

Baking soda reacts with baking soda

and forms a gas

A piece of paper is crumpled up

Baking cookies

An aspirin is crushed into a powder

A tree burns to form ashes

Methanol is burned and leaves a

residue

Water freezes to ice

A piece of metal is bent in half

• Law of Conservation of Mass

• Mass cannot be created or destroyed

• To put the law another way, the amount of matter before the change equals the amount of matter after the change.



• The law of conservation of mass is also true for physical changes. An ice cube has the same mass as the water produced when it melts.

• In other cases, conservation of mass is less obvious. If we think about it, we can usually explain cases in which the law of conservation of mass seems to have been violated.

Democritus (400 B.C.)

• Proposed that matter was

composed of tiny indivisible

particles

• Not based on experimental

data

• Greek: atomos

4.04 – Atomic Theory

Alchemy (next 2000 years)

• Mixture of science and mysticism.

• Lab procedures were developed, but alchemists did not

perform controlled experiments like true scientists.


John Dalton (1807)

• British Schoolteacher

– based his theory on others’ experimental data

• Billiard Ball Model

– atom is a uniform, solid sphere


John Dalton

Dalton’s Four Postulates

1. Elements are composed of small indivisible

particles called atoms.

2. Atoms of the same element are identical.

Atoms of different elements are different.

3. Atoms of different elements combine together

in simple proportions to create a compound.

4. In a chemical reaction, atoms are rearranged,

but not changed.


J. J. Thomson (1903)

• Cathode Ray Tube Experiments

– beam of negative particles

• Discovered Electrons

– negative particles within the atom

• Plum-pudding Model


J. J. Thomson (1903)

Plum-pudding Model

– positive sphere (pudding) with negative electrons (plums) dispersed throughout


Ernest Rutherford (1911)

• Gold Foil Experiment

• Discovered the nucleus

– dense, positive charge in the center of the atom

• Nuclear Model


Ernest Rutherford (1911)

• Nuclear Model– dense, positive nucleus surrounded by

negative electrons


Niels Bohr (1913)

• Bright-Line Spectrum

– tried to explain presence of specific colors in hydrogen’s spectrum

• Energy Levels

– electrons can only exist in specific energy states

• Planetary Model


Niels Bohr (1913)

• Planetary Model

– electrons move in circular orbits within specific energy levels

Bright-line spectrum


Erwin Schrödinger (1926)

• Quantum mechanics

– electrons can only exist in specified energy states

• Electron cloud model

– orbital: region around the nucleus where e- are likely to be found


Erwin Schrödinger (1926)

Electron Cloud Model (orbital)• dots represent probability of finding an e-

not actual electrons


James Chadwick (1932)

• Discovered neutrons

– neutral particles in the nucleus of an atom

• Joliot-Curie Experiments

– based his theory on their experimental evidence


James Chadwick (1932)

Neutron Model

• revision of Rutherford’s Nuclear Model


An atom refresher• Matter is anything that takes up space and has

mass.

• All matter is made of atoms

• Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.

4.05 – Properties of Atoms

An atom refresher• An atom has three parts:• Proton = positive• Neutron = no charge• Electron = negative

• The proton & neutron are found in the center of the atom, a place called the nucleus.

• The electrons orbit the nucleus.

Picture from http://education.jlab.org/qa/atom_model_03.gif


What are elements?• Elements are the alphabet to the

language of molecules.

• To make molecules, you must have elements.

• Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way.



http://education.jlab.org/atomtour/fact3.html

http://education.jlab.org/atomtour/fact3.html

More about Elements..

• Elements are the building blocks of all matter.

• The periodic table is a list of all of the elements that can build matter. It’s a little like the alphabet of chemistry.

• The periodic table tells us several things…


8

OOxygen

16

Atomic Number:

Number of protons and it is also the number of electrons in an atom of an element.

Element’s Symbol:An abbreviation for the element.

Elements Name

Atomic Mass/Weight:

Number of protons + neutrons.


Atom Models

• There are two models of the atoms we will be using in class.

• Bohr Model

• Lewis Dot Structure


Bohr Model

• The Bohr Model shows all of the particles in the atom.

• In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.

• In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e.

+

+

-

-


Electrons have special rules….

• You can’t just shove all of the electrons into the first orbit of an electron.

• Electrons live in something called shells or energy levels.

• Only so many can be in any certain shell.


Nucleus

1st shell

2nd shell

3rd shell

Adapted from http://www.sciencespot.net/Media/atomsfam.pdf


Electrons have special rules….

• You can’t just shove all of the electrons into the first orbit of an electron.

• Electrons live in something called shells or energy levels.

• Only so many can be in any certain shell.

• The electrons in the outer most shell of any element are called valance electrons.


So let’s try it….

3

Li

Lithium

7

So let’s try it….

3

Li

Lithium

7

+

++

Protons = 3

Neutrons = 4

(7-3=4)

-

-

-

Electrons = 3

2 in the 1st shell, 1 in the 2nd shell

Lewis Dot Structure• The Lewis Dot Structure

is a bit different from the Bohr model.

• It only shows the element symbol and it’s outer most electron shell.

O•

••• •

•

+ +

+ +

+

++

+

-

-

- -

--

- -


How to…

1. Write the symbol.

2. Start on the right hand side, working your way clockwise around the symbol.

3. Try Lithium


4.06 – The Periodic Table of Elements• 1869, Dmitri Mendeleev, a

Russian chemist, set out to organize the 63 known elements.

• He started by organizing the elements by their mass in ascending order.

• When elements were arranged in order of their mass, he noticed that their physical properties repeated

4.06 – The Periodic Table of Elements• To group elements by similar

properties, Mendeleev had to arrange a few elements out of order by mass.

• the periodic trends did not fit perfectly with the elements’ masses.

• When atomic numbers became known, scientists organized the chart of elements using the number of protons in each element instead of the atomic mass.

4.06 – The Periodic Table of ElementsThe modern periodic table of elements is a valuable resource. Check out the wealth of information contained in the periodic table:

4.06 – The Periodic Table of Elements

•Element name and symbol•Atomic number (number of protons in each atom)•Average atomic mass


•Physical Properties: metal, non-metal, or metalloid


•Electronegativity –ability to attract electrons•Bigger the number, the greater the ability to attract electrons and bond to other atoms•Increases as you go left to right and move up

4.06 – The Periodic Table of Elements•Ionization Energy – energy needed to release an electron•Think, opposite of electronegativity•Increases as you go left to right and up

4.06 – The Periodic Table of Elements•Atomic Radius•Relates to number of energy levels = quantum number•Increases as you go down and to the left


•Valence Electrons – outermost electrons•Elements in the same group have similar valence electrons


•Oxidation Number – number of electrons the atom uses or receives•+ when atom loses electrons, - when atom gains electrons


•Representative Elements•Columns 1-2 and 13-18•Follow trends and behave more predicatably than other groups

4.06 – The Periodic Table of Elements•Exceptions to the Rules•Hydrogen•Placed with metals even though it is a gas•Placed in 1st column to reflect the properties of its electrons

4.06 – Periodic Families

4.06 – Periodic FamiliesAlkali Earth Metals• All metals • The members of the family

include: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr).

• Have one valence electron• They are very reactive

4.06 – Periodic FamiliesAlkaline Earth Metals• All metals • The members of the family

include: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra)

• Have two valence electrons• They are reactive

4.06 – Periodic FamiliesTransition Metals• All metals • The members of the family

include: 21 (Scandium) through 29 (Copper)39 (Yttrium) through 47 (Silver)57 (Lanthanum) through 79 (Gold)89 (Actinium) and all higher numbers.

• Have varying valence electrons• They vary in their reactivity

4.06 – Periodic FamiliesBoron Group • Metals & metalloid• The members of the family

include: Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and Thallium (Tl)

• Have 3 valence electrons• They have some reactivity

4.06 – Periodic FamiliesCarbon Group • Metals, metalloids, nonmetals• The members of the family

include: Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), Lead (Pb)

• Have 4 valence electrons• They have varying reactivities• Bonds with other elements by

sharing

4.06 – Periodic FamiliesNitrogen Group • Metals, metalloids, nonmetals• The members of the family

include: Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), Bismuth (Bi)

• Have 5 valence electrons• They are reactive• Bonds with other elements by

sharing electrons

4.06 – Periodic FamiliesOxygen Group • Metalloids & nonmetals• The members of the family

include: Oxygen (O), Sulfur (S), Selenium (Se), Tellerium (Te), Polonium (Po)

• Have 6 valence electrons• They are reactive• Bonds with other elements by

sharing electrons

4.06 – Periodic FamiliesHalogens• All nonmetals• The members of the family

include: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astinine (As)

• Have 7 valence electrons• They are very reactive

4.06 – Periodic FamiliesNoble Gases• All nonmetals• The members of the family

include: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn)

• Have 8 valence electrons• They are inert, stable, not

reactive

4.06 – Periodic FamiliesActinides• All metals• Fit into the Transition Metals• The members of the family include:

90 – Thorium through 103 Lawrencium

• Very unstable nuclei, radioactive Lanthanides• All metals• Fit into the Transition Metals• The members of the family include:

57 - Lanthanum through 71 - Lutetium• Very unstable nuclei, radioactive

Classifying Matter - Leon County Schools / Homepage · Pure Substances •Elements ... 4.02...

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