Chemistry deals with the composition, properties, and interactions of matter, as well as energy changes. There are four main topics in chemistry - what matter is made of, how its particles are arranged, what characteristics it exhibits, and how it undergoes transformations through different types of changes including phase changes, chemical reactions, and nuclear reactions. Scientists make observations, which can be qualitative descriptions or quantitative measurements, to understand the physical and chemical properties of substances.

1. Chemistry 20 – Unit 1 Matter Energy and The Periodic Table What is Chemistry? Chemistry deals with: a) what things are made of ( matter ). b) properties of matter ( characteristics ). c) how matter interacts ( chemical reactions ). d) energy changes ( energy released or absorbed ). Important Terms in Chemistry: a) Matter : anything that has mass and takes up space (has volume ). b) Composition : what kinds of particles are in the matter and how many of each. c) Structure : how the particles are bonded together. d) Properties : characteristics of matter that are used to identify it. e) Transformations : changes in matter *

2. Three types of changes: i) Phase Change : state of matter ( solid, liquid or gas ) Example: H 2 O (s)  H 2 O (l) - Solid – - Liquid – - Gas – - Plasma – definite shape and definite volume varied shape and definite volume varied shape and varied volume gas charged with high energy electricity ( Northern Lights – Fluorescent lights ) ii) Chemical Change : atoms within a substance are rearranged to form new substances Example: 2 H 2 O (l)  2 H 2(g) + O 2(g) iii) Nuclear Change : elements are changed into different elements * Example :

3. Energy : something that gives you the ability to do work Scientific Methods Scientists are always making observations . Observations can be of two types: Qualitative : Quantitative : descriptive statements , using the 5 senses , about what has been observed For example: colour , texture , descriptive size etc measured observations, using instruments For example: 5.0 g (mass), 2.75 cm (length), 2.50 L (volume) Properties of a substance are used to identify a substance. There are 2 types of properties: *

4. Physical Properties : Chemical Properties : the characteristics of a substance that do not involve the change in internal composition of a substance For example: colour , shape , density , melting or boiling point characteristics of a substance that cause it to change (react) into something totally new For example: a substance’s ability to react with an acid *