1. Bear Trap for Feb. 19 1.A proton has a ________ charge. a)Neutral b)Negative c)Positive 2.An electron has a ________ charge. a)Neutral b)Negative c)Positive 3.What is a substance that cannot be separated or broken down into simpler substances by chemical means? ___________________

2. Intro to Chemistry Compounds, molecules and chemical formulas

3. Todays learning goals SWBAT: distinguish between elements and compounds SWBAT: describe molecules and explain how they are formed

4. What is a compound? A compound is a substance made up of two or more different elements that are chemically combined.

5. Compounds Compounds have unique properties. These properties are different than the elements that they contain. Hydrogen and oxygen are elements, individually they are colorless odorless gasses. When they are combined they become the compound commonly known as water.

6. Compounds Apart the elements hydrogen and oxygen are represented by their chemical symbols. – Oxygen = O – Hydrogen = H These gases like to hang out in pairs and are commonly written as H 2 and O 2 When they combine to form the compound of water it is written as H 2 O

7. Compounds The ratio of each element is specific to particular compounds. In water there is one oxygen to two hydrogen atoms. If we change that ratio we get a different compound with different properties. If we add an oxygen to water we get a new compound that is dangerous to drink – H 2 O (water) – H 2 O 2 (hydrogen peroxide)

8. What is a molecule? Molecules are the smallest unit of a substance that keeps all of the physical properties of that substance. Atoms can combine to form millions of molecules, much like letters combine to form different words. As we have discussed, water molecules are formed by two hydrogen and one oxygen atom. H 2 O These three atoms come together and act as a unit with specific properties, that unit is one molecule of the compound water.

9. Molecules Molecules can be made up of atoms of the same unit. For example – O 2 is a molecule of oxygen because there is more than one atom of oxygen. However O 2 is not a compound – Compounds can only be made up of molecules containing more than one type of atom.