The Roots of Atomic Theory; Energy; The Periodic Table

Natural laws

• observations that apply to different systems

• a law is a statement on how a particular phenomenon occurs VS a theory which is an attempt to explain why a phenomenon occurs

  • Law of Conservation of Mass

  • Law of Multiple Proportions

  • Law of Definite Proportions

Law of Conservation of Mass

in a chemical reaction, matter is neither created or destroyed

• the total mass of reactants must equal the total mass of the products

Law of Multiple Proportions

• John Dalton, 1804

• when two elements (A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole number

Law of Definite Proportions

• Joseph Proust, 1979

• all samples of a given compound, regardless of their source or how they were prepared, have the same proportions

Scientific Theory

proposed in 1808 to explain the laws of

• conservation of mass

• definite proportions

• multiple proportions

Atomic theory is based off of logical conclusions from these three laws… Atomic theory is composed of four parts

Dalton’s Atomic Theory

• each element is composed of tiny, indestructible parts called atoms

• all atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements

• atoms combine im simple. whole number rations ot form compounds

• atoms of one element cannot change into atoms of another elements. in chemical reactions, atoms only change the way that they are bound together with other atoms

Which statement is correct according to Dalton’s model fo the atom?

water is composed of many identical molecules that have one oxygen atom and two hydrogen atoms

Which statement is correct according to Dalton’s model of the atom?

neither

Energy

can neither be created nor destroyed. It can only be converted from one form to another.

◦ The total energy of the universe is constant

First Law of Thermodynamics

Energy

Indicated by the symbol ∆ (delta)

Energy

System

the substance undergoing the phase change

The First law requires that total energy