1. Chemistry

2. Element – a pure substance that cannot be broken down into simpler substances Matter – anything that has mass and occupies space; the material universe is made of.

4. Facts from the Periodic Table Symbol – the alphabetical letter or letters used to represent an element and/or compound. Atomic number – the number of protons in the nucleus of an atom; determines the chemical properties of an element.

5. No two elements’ atoms look the same. That is why each element is different. Atom – the smallest unit of an element.

6. Composition of an Atom Atoms have 5 basic parts: – Protons – positively charged particles in the nucleus of an atom Neutrons – neutral particles in the nucleus of an atom. Protons and neutrons are found in the nucleus. – Electrons – negatively charged particles that spin around the nucleus of an atom in layers called shells.

7. Facts About Atoms Atoms are constantly in motion. Electrons move around the nucleus in paths called shells (or energy levels). – Shell – an energy level containing spinning electrons that surrounds the nucleus of an atom

8. Normally, atoms contain an equal number of protons and electrons making the atom neutral (balanced forces). If an atom loses electrons, it becomes positively charged. If an atom gains electrons, it becomes negatively charged. Ion – an atom that is positively or negatively charged.

9. Charges and Attraction Like charges REPEL. Opposite charges ATTRACT.

10. Atoms may join together (bond) to form a molecule. Molecule – two or more atoms that are chemically combined Water Oxygen

11. – Compound – a molecule made of 2 or more different elements. Compounds/molecules can be made when 2 or more ions bond together.

12. How do we write down what a compound or molecule looks like? Formula – the way we represent compounds or molecules. A formula is made by combining the symbols of the elements from which the molecule or compound is made. NaCl CO 2 C 6 H 12 O 6 H 2 O 2

13. Water H 2 O Ammonia NH 3 (windex) Hydrogen peroxide H 2 O 2 Carbon dioxide CO 2 Salt NaCl

14. Physical Change Physical Change – a change that does not result in the formation of new substances. Examples: grinding salt, breaking glass, cutting wood or paper, dissolving sugar in tea Another example is when a substance changes states (water changing from solid to liquid to gas)

15. States of Matter Atoms/molecules can change state/phases due to temperature or pressure change.

16. Chemical Change Chemical Change – a change that results in the formation of new substances. – Also called a chemical reaction Example: hydrogen gas and oxygen gas combining to form water More Examples: rusting of iron, burning of wood, baking of a cake, & souring of milk ReactantsProducts

17. How do you tell if there has been a chemical change? Chemical changes result in: -Release of a gas -Formation of light -Temperature change -change in color. Chemical changes are more difficult to reverse or “undo”. You can not “un burn” wood, or “de sour” milk.