Matter is Made of Atom2.7--2.9

-Up to this point you have made observations by what you can see, feel,or smell. such observations are macroscopic observations
-Melting point, boiling point, heat of fusion, temperature, and mass are all properties of large chunks of matter and are called macroscopic properties
-A microscopic model (micro is a prefix meaning small; when used with SI units, it means 1Million) to explain the behavior of matter.


2-7: Atom
-Small particles like atoms and molecules are discussed int he popular literature as though they were as common as toads and warts.
-the original idea of atoms was developed long before as a kind of armchair argument.
-Atom: the smallest possible piece of something
-Chemists use spheres to help them imagine what is happening in the microscopic world.




2-8: Element
-more than one kind were present, it should be possible to separate the two kinds of atoms, producing different substances with different properties.
-there are as many kinds of atoms as there are elements, 109.
-an element can exist as solid, liquid or gas.
-most elements seem to exist as individual atoms , but some elements exist as larger units
-Particles made of more than one atom are called molecules.
-There is no simple way to tell which elements exist as individual atoms in a gas and which exist as larger clusters of atoms
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2-9: Compounds
-all compounds must be made of two or more kinds of atoms
-Molecules have definite shapes as well as definite composition, but you do not have to worry about why until later.
-since compounds are made of two or more kinds of atoms, the different atoms can be separated if enough energy is supplied to break the compound apart.
-heat and electricity are forms of energy and both heating and electrolysis can supply the energy needed to decompose the compound
-not all compounds are made of molecules. Sodium chloride melts to form positively charged sodium ions and negatively charged chloride ions.
-Ions: are particles that have and electrical charge.
-the only way to know which compounds are ionic and which compounds are molecular is to check them for conductivity