WHAT IS

Chemistry is the science in which substances are examined to find out: 1) What they are made of 2) How they act under different conditions 3) How they are combined or separated to form other substances. Table salt (NaCl) is made up of the elements sodium and chlorine. Chlorine gas is extremely poisonous.

Everything around us is made up of chemicals! Why do we study chemistry? Everything around us is made up of chemicals! AND YOU! Chemistry and physical/chemical reactions are everywhere. In this picture even, chemistry comes into the picture when a grass seed begins to grow through the process of photosynthesis.

SOME COMMON CHEMICALS Baking Soda - Sodium bicarbonate Aspirin – acetylsalicylic acid Nail polish remover - acetone Battery acid – sulfuric acid Chalk – calcium carbonate Vitamin C - ascorbic acid  Vinegar – acetic acid

Chemical Properties are the characteristics that we can use to describe or identify different substances. Properties include: - state (solid, liquid, gas) - colour - texture - luster (shiny or dull) - crystal structure - taste - odour - solubility (how well it dissolves in water) - freezing/melting/boiling points - behavior (does it burn, rot, explode)

Changes in Chemistry Matter can change. There are two types of changes: 1) Physical Changes 2) Chemical Changes

Physical Changes Physical Change: No new substance is produced. Physical changes can be reversed. Involves the movement of atoms, but not changing the: Number of atoms Type of atoms Or how the atoms are bonded (put together). Melting ice, no new substance, it can be reversed by introducing cold… no atoms for types of atoms were changed.

Other Examples of Physical Changes! Looks as though a chemical change has occurred because the sugar dissolves within the water, but if you heat it up then the sugar begins to separate itself as again because it is still apart of the solution. Crystallizing sugar. Drying hair. Slicing a pineapple. Ironing clothes. Washing clothes. Cutting paper Dissolving iced tea crystals in water.

Change of State Triangle SOLID LIQUID GAS Change of State Triangle melting freezing sublimation condensation evaporation Sublimation is the transition of a substance directly from a solid to a gas without passing through the intermediate liquid phase.

Chemical Changes Chemical Change: One or more new substances are formed. The substances formed have different properties (colour, odor, texture, taste, luster, etc.) New and different bonds are formed. The same number and type of atoms are present after a chemical they are just in a new order. Before the reaction. During the reaction. After the reaction.

Think About It! The average piece of wood is made of many glucose (sugar) molecules all bound together. When glucose is burned (combined with oxygen) the word equation is: glucose + oxygen  carbon dioxide + water O—O + + Does it look to you as though there are the same types and numbers of atoms at the beginning of the reaction as there is at the end of the reaction?

Word equations do not tell us anything about the number of atoms involved in a chemical reaction. In order to have that type of information we need to look at a reaction’s chemical equation. The chemical equation is: C6H12O6 + 6O2 -----> 6CO2 + 6H2O (glucose)

Clues to Indicate a Chemical Reaction brand new colour new odor gas is created precipitate forms light is given off change in temperature

Other Examples of Chemical Changes Cooking Rotting Rusting Exploding

Chemical reactions involve: Reactants: the substances that exist before the reaction has occurred. Products: the substances that exist after the reaction has occurred.

Two categories of chemical reactions: Exothermic: a chemical reaction in which energy is given off to the surroundings (exo=exit). The final product will feel warmer. Endothermic: a chemical reaction in which energy is absorbed. The final product will feel cooler.