Chemistry Chemistry affects just about everything around us. Scientists use chemical knowledge to change, improve, or invent such things as foods, medicines, and materials of all kinds. They also use chemistry to understand the world of living things around us and how the universe itself functions. Knowing the properties of elements and compounds is a major goal of scientists working in the field of chemistry.

Matter Matter is everywhere. Matter is anything that takes up space and has mass. solids liquids gases plasmas

Energy determines the state!

Element A substance made up of only one type of matter Examples: gold, silver, oxygen

Periodic Table Elements listed in a pattern. Name of the element Atomic Number = number of protons in the nucleus Gold 79 Au Symbol Atomic Weight Hydrogen 1 H

Atoms The smallest particles of an element; the building blocks of matter Nucleus: Protons positive charge; equal number of protons and electrons Neutrons no electrical charge; same mass as proton Circling the nucleus: Electrons negative charge; very light

Molecules When atoms combine chemically Neutral particles that are formed when electrons are shared by atoms rather than being gained or lost For example, two pairs of electrons shared by two hydrogen atoms and an oxygen atom make a molecule of water H 2 0 Only the electrons that are farthest out can be shared or transferred. These are called valance electrons.

Compound When two or more different elements combine chemically. The properties of the compound change from the original elements. It can be separated only by chemical means, not by physical properties. Examples: water, table salt, sugar, rust, YOU! Our Silly Putty!

Mixture One element cannot easily be changed into another element. A mixture is a way to combine them. A mixture is when two or more types of matter are combined Mixtures can be separated back out into the two elements through filtering or evaporation. Examples: salt water and peas and carrots.