COMPOUNDS 7 TH GRADE SCIENCE

ELEMENTS & COMPOUNDS ARE THE BASIC BUILDING BLOCKS OF MATTER EACH ELEMENT & COMPOUND HAS SPECIFIC PROPERTIES

COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ATOMS/Elements BONDED TOGETHER

COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ATOMS BONDED TOGETHER

Compounds l_bonds.html

COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ATOMS BONDED TOGETHER FOR A COMPOUND TO FORM, A CHEMICAL CHANGE MUST TAKE PLACE (A REACTION) THE ELEMENTS THAT COMBINE MAKE A NEW SUBSTANCE WITH NEW PHYSICAL PROPERTIES COMPOUNDS CANNOT BE BROKEN DOWN PHYSICALLY. REQUIRES A CHEMICAL CHANGE MORE COMMON THAN ELEMENTS += NaCl TABLE SALT

COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA THE ELEMENTS THAT COMBINE TO MAKE THE COMPOUND CHANGE PROPERTIES += NaCl TABLE SALT

Atomic Structure & Chemical Bonds Octet rule= when atoms of elements react, they ten to lose, gain or share electrons to achieve the same electron arrangement as the noble gases.

3 Ways Elements Bond Ionic= loss or gain of electron (metal + non-metal) Metallic= metal atoms share pooled electrons – (pooling=electrons gathered together) Covalent=sharing of electrons (non-metal elements)

Ionic

Covalent Carbon forms lots of covalent bonds

Metallic

A way of writing how many atoms are in a compound.

Chemical Formulas Written as: C 4 H 10 Butane Written as: CH 4 Methane

Subscripts= how many atoms = how many total molecules

FeO 2 H 2 O C 6 H 12 O 6 2Li + 2O 2

Chemical Changes Through Chemical Reactions A chemical reaction – Process in which the physical and chemical properties of the original substance(s) CHANGE as new substances with different properties are formed.

A burning match is a good example of a chemical reaction. Application of a spark to the chemicals on the match head start the chemical reaction. Signs of a chemical change – heat given off, light given off, new substance formed – black material on the match head when the fire is extinguished.

Parts of a Chemical Reaction Reactants – Substances that begins the chemical reaction (chemicals on match head) Products – Substances produced in the reaction (black material on match) In other words: REACTANTS CHANGE INTO PRODUCTS

CHEMICAL EQUATIONS Chemical equations are symbols used to describe the details of a chemical reaction. Shows how the reactants changed into the product. This involves indicating all the atoms involved in the reaction. Fe + O 2 FeO 2 Reactants : Iron and oxygen Product : Ferrous oxide (rust) Plus Sign : Shows substances combine Arrow : Means “yields” takes the place of an = sign

Law of Conservation of Matter Matter cannot be created or destroyed, it just changes forms. The total mass of the reactants must equal the total mass of the product.

Law of Conservation of Mass web.net/science/balancing_chemical_equations_examples.htm Alka-Seltzer and Water

Balancing Equations The number of atoms of the reactants must equal the number of atoms in the product. (Law of Conservation of Matter) Ex: 2Na + Cl 2 -> 2NaCl 4P + 5O 2 -> P 4 O 10

Balancing Equations Rules – Make sure that all atoms are equal on both sides. – You can only add coefficients. Changing the subscripts will change the identity of the compound. – H 2 O & H 2 O 2 EX: 2Na + Cl 2 -> 2NaCl H 2 + O 2 -> 2H 2 O (Not balanced… So…) 2H 2 + O 2 -> 2H 2 O

Balancing Chemical Equations Hg + O 2 HgO H 2 + Cl HCl Mg + O 2 MgO O 2 + H 2 H 2 O CH 4 + O 2 CO 2 + H 2 O Fe + Cl 2 FeCl 3

Hg + O 2 HgO

H 2 + Cl HCl

Mg + O 2 MgO

O 2 + H 2 H 2 O

Fe + Cl 2 FeCl 3

CH 4 + O 2 CO 2 + H 2 O

CAN YOU TELL WHICH IS A MOLECULE OF AN ELEMENT OR A COMPOUND? WHICH SHOWS AN ATOM? CAN YOU TELL WHICH IS A MOLECULE OF AN ELEMENT OR A COMPOUND? WHICH SHOWS AN ATOM?

MOLECULES ARE 2 OR MORE ATOMS ATTACHED TOGETHER – THEY CAN BE THE SAME KIND (ELEMENTS) – THEY CAN BE DIFFERENT KINDS (COMPOUNDS) Examples: H 2 O, NaCl.

:37 PM Periodic Table Periodic Table: electron behavior The periodic table can be classified by the behavior of their electrons