ELEMENTS AND COMPOUNDS Science 9

Models of Matter  The Particle Theory of Matter  All matter is made up of tiny particles  All particles of one substance are the same. Different substances are made of different particles  The particles are always moving – the more energy they have, the faster they move  There are attractive forces between the particles – the closer they are, the more attracted they are to one another

Pure Substances  Contains only one kind of particle  Ex. Aluminum, gold, copper, oxygen  Ex. Carbon dioxide, sugar, table salt

Mixtures  Contains at least two different substances  Ex. Pop, bread, ice cream

Classifying Mixtures - Homogeneous  A solution can be made up from solids, liquids or gases  Ex. Air is a solution of gases  Ex. Salt water  Alloys are mixtures of metals

Classifying Mixtures – Heterogeneous  Heterogeneous mixtures have different visible parts  Ex. Pizza, cereal and milk, yogurt and berries

Pure Substances - Elements  Elements cannot be chemically broken down into smaller parts  They are organized on the periodic table  Most are found in nature but an increasing amount are being made synthetically  Ex. Hydrogen, helium, lithium, etc.

Pure Substances - Compounds  Elements can chemically combine to form compounds  Compounds are composed of two or more elements in a fixed proportion  They can be written in chemical formula  Ex. Water is two parts hydrogen, one part oxygen H 2 O CO 2 C 6 H 12 O 6

What is all matter made up of?  Atoms are the basic building blocks of all matter  Every element on the periodic table is composed of one type of atom  The periodic table is composed of over 100 elements, so this means there are over 100 kinds of atoms

Atoms Make Molecules  When atoms join other atoms, they form molecules  They must contain at least two atoms but the amount of combinations are limitless  Sometimes, the atoms are all the same in a molecule, like O 2, and sometimes they are different, like NaCl

Models of Molecules  It is impossible for us to physically see molecules because they are so small  We construct models of them, instead, to help visualize what they look like