ELEMENTS, COMPOUNDS, AND MIXTURES

8 TH GRADE SCIENCE 8.P.1.1 CLASSIFY MATTER AS ELEMENTS, COMPOUNDS, OR MIXTURES BASED ON HOW THE ATOMS ARE PACKED TOGETHER IN ARRANGEMENTS.

ESSENTIAL QUESTIONS

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How does the arrangement of atoms affect the classification of matter?

•

What is the difference between elements, compounds, and mixtures?

HOW DO WE CLASSIFY MATTER?

• What is an element?

• • • A pure substance that is made up of only one kind of atom  H, He, O 2 Organized on the periodic table Represented with a chemical symbol • What is a compound?

• • A pure substance made up of two or more elements that have been chemically combined Represented using a chemical formula  C 6 H 12 O 6 , NaCl • What is a pure substance?

• • Any substance that cannot be physically broken down into simpler substances Includes both elements and compounds

WHAT ARE MIXTURES?

• The physical combination of 2 or more substances • Mixtures are NOT chemically combined • Mixtures can be separated by physical means (filtration, evaporation, distillation) • Mixtures are divided into two groups • Heterogeneous • A mixture that is unevenly distributed • Homogeneous • A mixture that is evenly distributed

COMPARING ELEMENTS, COMPOUNDS, AND MIXTURES

• Creating a foldable: • Fold a blank sheet of paper in half hamburger style • Next, fold the half size into thirds • Carefully cut along the folds of only the top half of folded paper so that you have 3 flaps, then glue down in your notebook

Label each flap with the following information: Flap 1 Title: Elements Flap 2 Title: Compounds Flap 3 Title: Mixtures Elements • • • A pure substance In an element, all atoms are identical and share the same physical and chemical properties Represented with a chemical symbol Compounds • • • A pure substance A compound is a combination of 2 or more elements joined by chemical bonds Represented with a chemical formula Mixtures • • A combination of pure substances A mixture is composed of element(s) and/or compound(s)

ELEMENTS

BEHIND “ELEMENTS” FLAP • Elements are organized on the periodic table • There are over 100 known elements • Elements are represented with a chemical symbol.

• The symbol is at least one letter; the first letter is always capitalized • Example: H (Hydrogen) & He (Helium) INSIDE “ELEMENTS” FLAP • Element examples: • • • Mg (Magnesium) C (Carbon) S (Sulfur) or S 8 • Some elements are diatomic (2 atoms); they occur in nature in groups of two • H 2 , O 2 , Br 2 , Cl 2

Compounds

Behind “Compounds” Flap • What is the difference between a molecule and a compound?

Type of Substance Can it have two or more types of atoms?

Molecule Compound Yes Yes (it must!)

Can it have one type of atom?

Yes No

Can it be an element?

Yes No Inside “Compounds” Flap • • • There are millions of compounds!

Examples: H 2 O, H 2 O 2 , FeO, CH 3 All compounds are molecules, but not all molecules are compounds  O 2 is a molecule, but it’s not a compound

MIXTURES

BEHIND “MIXTURES” FLAP HOMOGENEOUS MIXTURES • These mixtures are evenly distributed and may look like pure substances because they are completely mixed into a single phase • Also called solutions – contain a solute (the substance being dissolved) dissolved in a solvent (the substance doing the

dissolving)

• Examples: salt water, Kool-aid, brass INSIDE “MIXTURES” FLAP HETEROGENEOUS MIXTURES • These mixtures are not evenly distributed • The substances are considered insoluble because one substance will not dissolve in the other • Examples: oil and water, Chex mix, chicken noodle soup

Venn Diagram – Comparing elements, compounds, and mixtures Place the letter for each description in its location on the Venn Diagram A. Pure substance B.

Only one type of atom C. Two or more types of atoms D. Always homogeneous E.

Can be homogeneous F.

I.

Matter G. Can be two or more phases H. There are about 100 different ones Two elements joined by chemical bonds J.

Can be separated by physical change K. Can be broken down by chemical change

Elements

B, H K, I A, D E, F C

Compounds

G, J

Mixtures