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COMPOUNDS 7 TH GRADE SCIENCE
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ELEMENTS & COMPOUNDS ARE THE BASIC BUILDING BLOCKS OF MATTER EACH ELEMENT & COMPOUND HAS SPECIFIC PROPERTIES
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COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ATOMS/Elements BONDED TOGETHER
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COMPOUNDS ARE MADE OF 2 OR MORE DIFFERENT KINDS OF ATOMS BONDED TOGETHER
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Compounds http://web.neo.edu/rjones/Pages/1014new/Lecture/chemistry/chapter_9/pages/chemica l_bonds.html
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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
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COMPOUNDS ARE IDENTIFIED BY A CHEMICAL FORMULA THE ELEMENTS THAT COMBINE TO MAKE THE COMPOUND CHANGE PROPERTIES += NaCl TABLE SALT
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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.
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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)
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Ionic
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Covalent Carbon forms lots of covalent bonds
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Metallic
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A way of writing how many atoms are in a compound.
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Chemical Formulas Written as: C 4 H 10 Butane Written as: CH 4 Methane
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Subscripts= how many atoms = how many total molecules
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FeO 2 H 2 O C 6 H 12 O 6 2Li + 2O 2
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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.
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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.
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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
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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
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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.
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Law of Conservation of Mass http://www.sky- web.net/science/balancing_chemical_equations_examples.htm Alka-Seltzer and Water
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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
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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
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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
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Hg + O 2 HgO
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H 2 + Cl HCl
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Mg + O 2 MgO
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O 2 + H 2 H 2 O
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Fe + Cl 2 FeCl 3
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CH 4 + O 2 CO 2 + H 2 O
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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?
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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.
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9.17.00 1:37 PM35 3.3 Periodic Table Periodic Table: electron behavior The periodic table can be classified by the behavior of their electrons
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