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ELEMENTS• Pure substances that

contain only one kind of atom.• Examples: Hydrogen,

Copper, Iron

ATOMS –VS.- MOLECULESSome elements exist as

single atoms.Other elements exist as

molecules.Molecules consist of 2 or more atoms combined in a definite ratio.

COMPOUNDSA substance made up of

atoms of two or more different elements joined by chemical bonds.

WHAT IS THE DIFFERENCE BETWEEN A COMPOUND AND A MOLECULE? A molecule is formed when two or more atoms join together chemically.

A compound is a molecule that contains at least two different elements.

All compounds are molecules but not all molecules are compounds.

Mixture: A sample of matter that contains two or more pure substances (elements and compounds) and has variable composition.

Exhaust –a Mixture

MIXTURES AND COMPOUNDS DIFFER IN TWO WAYS…

• Substances in a mixture keep their individual properties.

• Parts of a mixture are not necessarily present in specific ratios.

SOLUTIONS

Homogeneous mixture: is a substance in which two or more substances are uniformly spread out. Example: salt water, stainless steel, maple

syrup

Solution is another term for homogeneous mixture.

Heterogeneous Mixture: A mixture contains substances that are not evenly mixed.

Example: Orange juice, granite, sand

Salt= NaCl

Properties of Salt:•White solid at room temperature.•The crystals are brittle.•Melting Point 800 oC•Conducts electricity when melted or in aqueous solutions.•Soluble in water.•Unreactive•Safe to store for long periods of time.•Used to season food. Safe to eat.

Properties of Sodium:•Shiny, silvery-white, soft, solid element.•Metallic Element•Melting Point of 98 oC•Boiling Point of 883 oC•Most reactive of all the common elements.•Has to be stored under oil.•Never found as a free element in the environment.•Always found combined with other elements

Properties of Chlorine:•Pale green, poisonous gas with a choking odor.•Kills living cells.•Slightly soluble•Gas until -34 oC then turns into a liquid•Very Reactive

Carbon Dioxide = CO2

Properties of Carbon:•Nonmetal•Fairly unreactive at room temperature.•Reacts with many elements at higher temperatures.•Majority of compounds in living organisms have carbon in them.•Solid at room temperature.•Melting Point 3,527oC•Boiling Point 4,027oC

Properties of Oxygen:•Nonmetal•Colorless, odorless, and tasteless gas•Oxygen reacts during combustion reactions.•Turns into a liquid when cooled to -183 oC.

Properties of Carbon Dioxide:•Colorless, odorless, and tasteless gas.•Changes directly to a solid at -80 oC•Soluble in water•Relatively stable•Extinguishes Fire•Burning carbon compounds in air will make carbon dioxide.

Water = H2OProperties of Hydrogen:

•Lightest most abundant element in the universe.•Nonmetal•Odorless, tasteless, and colorless gas•Very Reactive •Seldom found as a free element •Must be cooled to -253 oC to turn to a liquid.•Does not conduct electricity•Slightly soluble.

Properties of Oxygen:•Nonmetal•Colorless, odorless, and tasteless gas•Oxygen reacts during combustion reactions.•Turns into a liquid when cooled to -183 oC.

Properties of Water:•Occurs on earth in all 3 states of matter•Does not conduct electricity in any of the states•Universal Solvent•Stable Compound•Acts as a medium for chemical reactions

ESSENTIAL QUESTIONS

1.How is a chemical formula used to identify the number and kinds of elements in a compound?

2.How can a formula define a specific compound?

3.Use data to compare the physical properties of a compound to the properties of the elements that comprise it.

4.Use data to compare the chemical properties of a compound to the properties of the elements that comprise it.

5.Must a specific compound necessitate one unique chemical formula?