The Particle Theory Chapter 2

The Particle Theory More than 2000 years ago, a Greek philosopher Democritus suggested that matter was made of tiny particles too small to be seen. He thought if you kept cutting a substance into smaller and smaller pieces, you would find the building blocks of matter.

4 Principles of the Particle Theory 1. All matter is made of tiny particles. 2. All particles of one substance are the same. - Different substances are made of different particles. 3. The particles are always moving. - The more energy the particles have, the faster they move. 4. There are attractive forces between particles. - These forces are stronger when the particles are closer together.

The particle theory helps to explain two categories of substances that are encountered in chemistry.

Two Categories of Substances Category 1: Pure Substances - contains only one kind of particle - Types: elements and compounds Category 2: Mixtures - contains two or more different pure substances - Types: homogeneous and heterogeneous mixtures

Category 1: Pure Substances Type 1: Elements – pure substances that cannot be broken down into simpler substances - Examples: think Periodic table (oxygen, hydrogen) Type 2: Compounds – pure substances that contain two or more elements - Examples: Water (H 2 O), sugar (C 6 H 12 O 6 )

Category 2: Mixtures Type 1: Homogeneous (also known as solutions) – may be made up of solids, liquids or gases - this mixture is uniform (the same) throughout - Examples: air, alloys, kool aid, white vinegar, orange juice without the pulp Type 2: Heterogeneous – see each part easily, separated physically - this mixture is not uniform throughout - Examples: pizza, garbage, beach sand, vegetable soup

How to Classify Mixtures When two pure substances are mixed together, they may mix smoothly or unevenly. If the substances mix well with one another, the mixture is called a solution. If the particles don’t mix well together then we have a heterogeneous mixture.

Classify the Following Salt and water solution Pizza heterogeneous mixture Garbage heterogeneous mixture Air solution

Atoms and Molecules Atoms - each atom is made of one type of element - scientists now call the particles in the particle theory atoms - the periodic table of elements has 118 elements Molecules - contains two or more atoms joined together in combinations - Ex. C 4 H 8 – contains 4 carbon atoms and 8 hydrogen atoms

Guess the Molecule I have 2 hydrogen atoms I have 1 oxygen atom I am water

Guess the Molecule I have 10 hydrogen atoms I have 2 oxygen atoms I have 7 carbon atoms I have 4 nitrogen atoms I am desired in the morning but avoid me in the evening Cola drinks have contain me I am what makes coffee special I am caffeine

Guess the Molecule I have 6 hydrogen atoms I have 6 oxygen atoms I have 6 carbon atoms Everybody needs me I will help keep colds away You can get me by eating oranges I am vitamin C

Guess the Molecule I have 8 hydrogen atoms I have 4 oxygen atoms I have 9 carbon atoms I am used quite often by teachers, usually in pairs I am white in color You need water when you use me I will make you feel better I am aspirin