MATTER

Dr S. Lawrence

Kane Room 2.04B

simon.lawrence@ucc.ie

Chemistry: The Central Science

Sections 1.1, 1.2 and 1.3 (12th Edition)

CLASSIFICATION OF MATTER

ATOM - the smallest unit of matter (H, Fe, Cl, Zn, C, O, etc.)

(made up of neutrons, protons and electrons)

MOLECULE - two or more atoms bound together

by chemical bonding (O2, NaCl, H2O, C6H12O6)

ELEMENT a collection of atoms of one atom type (H2, S8, He, Cl2, Fen)

COMPOUND collections of different atom types (H2O, FeCl3, CO2)

MIXTURE collections of more than one atom or molecules (H2O + CO2 + C6H12O6)

PURE SUBSTANCE collections of one identical molecule/atom (H2O, S8)

ATOMS

OF AN ELEMENT

e.g. He

MOLECULES

OF AN ELEMENT

e.g. H2

MOLECULES

OF A COMPOUND

e.g. BF3

MIXTURE

OF ELEMENTS

AND A COMPOUND

CLASSIFICATION OF MATTER

USING MODELS

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Only one type of atoms.

ELEMENTS

Different elements have atoms containing different numbers

of protons (in the neutral atom).

Listed in the Periodic Table of Elements.

Molecules are groups of atoms joined together by chemical bonds.

either shared by the atoms

Chemical bonds: attractive forces involving electrons

MOLECULES

or transferred to create ions of opposite charge.

PROPERTIES OF MATTER

Every substance has a unique set of properties

determined by the atoms present in the molecules

Physical - colour, density, melting point, boiling point

Chemical - the way the substance may react to form

other substances (flammability)

MATTER can be converted to ENERGY and vice versa

Einstein equation: E = mc2

PHYSICAL CHANGES AND PROPERTIES

Steam Water Ice Heating Heating

Cooling Cooling

Substances change their physical state, but not composition.

Mixtures form from, or can be separated into, their components.

GAS LIQUID SOLID

Reactants form products

CHEMICAL CHANGES

Atoms combine, but are neither created nor destroyed.

Chemical energy may be released as heat - thermodynamics.

Heating may also accelerate a chemical reaction - kinetics.

A chemical change is when new molecules are formed by

reaction of other atoms or molecules.

2 H2O + Energy 2 H2 + O2

Combustion

Called a chemical reaction

Described by a chemical equation: indicates the numbers

of atoms/molecules involved in the reaction.

BALANCING EQUATIONS

Chemistry the Central Science: 3.1 (12th Edition)

Chemical

Symbol

Meaning Composition

H2O One molecule of water Two atoms of hydrogen and one

atom of oxygen

2H2O Two molecules of water Four atoms of hydrogen and

two atoms of oxygen

H2O2 One molecule of

hydrogen peroxide

Two atoms of hydrogen and two

atoms of oxygen

Chemical Symbols

Thoughts for Balancing Equations

4 Deal first with elements which occur in the fewest

formulae.

1 Chemical symbols stay the same,

i.e. cannot change subscripts.

H2O is water H2O2 is hydrogen peroxide

2 The ONLY thing you can do is to put numbers in

front of formulae.

3 Before you start, count each element it may already be balanced! (it does happen.)

Can change H2O to 2H2O

Balanced No. of Reactants = No. of Products

BALANCING CHEMICAL EQUATIONS - Combustion

CO2 + H2O C2H5OH + O2

1. Write the unbalanced chemical equation

2 CO2 + H2O C2H5OH + O2

2. Balance the carbons first

3. Balance the hydrogen

2 CO2 + 3 H2O C2H5OH + O2

4. Finally, balance oxygen

2 CO2 + 3 H2O C2H5OH + 3 O2

5. Check the sums of atoms

CO2 + H2O CH3OH + O2

1. Write the unbalanced chemical equation

CO2 + H2O CH3OH + O2

2. Balance the carbons first

3. Balance the hydrogen

CO2 + 2 H2O CH3OH + O2

4. Balance the oxygen

CO2 + 2 H2O CH3OH + 3/2 O2

5. Multiply the equation by 2 to get whole numbers

2 CO2 + 4 H2O 2 CH3OH + 3 O2

EXAMPLE: Combustion of methanol

1 C + O2 CO2 2 C + O2 CO 3 S8 + O2 SO2 4 P4 + Cl2 PCl3