Lecture 39/2/05 :

How dense is a person?

Temperature scale?

0ºF – Freezing point of sat. salt solution

Temperature conversions

Example Convert 77º F to º C and º K.

Temperature and Physical properties Density Changes for liquids with temperature Water (most dense ~ 4ºC)

Extensive properties Depend on the amount of substance Mass Volume Intensive properties Do not depend on the amount of substance Melting point/Boiling point Density

Physical change State (solid, liquid, gas) Size Shape

Chemical change Transform into a different substance Chemical reaction Reactants transform into products Combustion CH 4 (g) + 2O 2 (g) → CO 2 (g) + 2H 2 O (l)

Kinetic-Molecular Theory All matter consists of tiny particles (atoms, molecules, or ions) which are in constant motion

Atomic structure Objects can bear an electrical charge Known since ancient times + and – charge Known for hundreds of years

Atomic Theory John Dalton (1803) Atom is the smallest particle of an element that retains the chemical properties of that element

Radioactivity Henri Becquerel (1896) Uranium emitted rays could darken a photographic plate through paper Madam Curie (1899) Suggested that some substances are “radioactive”