2-7 to 2-9: More on Matter

text book page 36-39

Matter is made of Atoms

• Macroscopic observations: based on what you can see, feel, or smell

(macro= large; scopic= viewing or observing)

• Melting/boiling point, head of fusion, temperature, and mass are all properties of large chunks of matter, also called macroscopic properties

• Uses microscopic model to explain the behaviour of matter

(micro= small; means 1 millionth in SI units)

2-7 Atoms

·         Idea that matter is made of atoms became popular during the early 1800s

• Atom means smallest possible piece of something, too small to be seen with the human eye, normally represented with spheres of various sizes and colours

2-8 Elements

• An element contains only one kind of atom. If more than one kind of atom 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

• Numbers are assign to each kind of atom, called the atomic number

• Elements can exist as a solid, liquid or gas

• Solid: atoms are stuck together so it holds its shape, while vibrating slightly

• As temperature increases, the atoms in the solid starts vibrating more and more, until they overcome the forces that hold them together, allowing them to flow past one another in the form of a liquid.





solid                                liquid                             gas    


• Liquid: takes the shape of its container due to gravity pulling it down

• As temperature increases even more, the atoms move with suck energy that they totally escape from the liquid and move far apart in the form of a gas

• Elements can exist as individual atoms as well as larger units

• Molecules: particles made of more than one atom

• Elements have different melting and boiling points because some atoms are bigger than others. It takes more energy to vibrate the bigger atoms that it does for smaller atoms.

2-9 Compounds

• All 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





Compounds


• Heat and electricity can decompose the compounds because they are forms of energy

• Compounds can exist as solids, liquids, and gases, like elements

• Not all compounds are made of molecules. When melted, some compounds break into ions, which are particles that have an electric charge

• Compounds that melt to form ions conduct an electric current

• Compounds that do not melt to form ions do not conduct

• The only way to know which compounds are ionic and which compounds are molecular is to check them for conductivity

~~Jason Zhang