CHAPTER 2 Matter and Change 2.1 PROPERTIES OF MATTER EXTENSIVE PROPERTY: Depends on the amount of matter in a sample Comparing the same substances. Diamonds to Diamonds INTENSIVE PROPERTY: Depends on the type of matter in a sample, not the amount of matter Comparing different substances. Diamonds to Cubic Zirconium IDENTIFYING SUBSTANCES Matter: anything that has mass and takes up space. (Has atoms...) Substance: a particular kind of matter that has a uniform and definite composition Mass: measures the amount of matter in a substance Energy is NOT matter! THE STATES OF MATTER Solid Liquid Gas (vapor) 1
SOLIDS Definite Shape Definite Volume Not easily compressed LIQUIDS Indefinite shape > (Takes the shape of it s container) Definite Volume Not easily compressed GASES Indefinite Shape (Takes shape of it s container) Indefinite volume Easily compressed Vapor is a gas that is liquid or solid at room temperature. Solids Liquids Gases Definite Shape Definite Volume Indefinite Shape Definite Volume Indefinite Shape Indefinite Volume Not easily compressed Not Easily Compressed Easily Compressed PHYSICAL CHANGES Alter substances without changing its composition Boil, freeze, dissolve, melt, condense, break, split, crack, crush Chemical Changes. Chemical Rxn Change in Chemical composition C 6 H 12 O 6 6O 2 6H 2 O 6CO 2 2
2.2 MIXTURES NOT A CHEMICAL CHANGE A physical blend of two or more substances Heterogeneous: Different throughout (Pepper Water) Homogeneous: Same throughout (Sugar Water) > Solution = dissolved salt or sugar in water Separating Mixtures Filtration: Filtering solutions to remove the solid or undissolved portion. Distillation: Heating a solution to remove the dissolved portion * Not a Chemical Reaction! Filtration Distillation Distilled Water What does Physical State mean? Shape of substance Fine powder, crystals, coarse, etc. Color of the substance Record your observations? There was a color change. Gas bubbles were produced. There was a temperature change Nothing happened. It exploded... Recognizing Chemical Changes What is a chemical formula? Transfer of Energy (Heat, Light) Change in color (Rust, ashes) Gas formation (H 2, Water vapor, CO 2 ) Formation of precipitate (A solid forms from two liquids) 3
2.3 ELEMENTS AND COMPOUNDS Elements: simplest forms of matter than can exist under normal conditions Compounds: can be separated into simpler substances only by a chemical reaction Chemical vs. Physical properties Pure Substances Compounds are Pure Uniform throughout Atoms must be bonded together Only separated by chemical means. 2NaCl Mg MgCl 2 2Na Pure Substances Elements consists of only 1 type of atom Compounds consists of 2 or more different atoms bonded together Pure or Impure H 2 O Mg O 2 N 2 NaCl H 2 O O 2 Na Mg Sand H 2 O CaCl 2 Impure Substances Mixtures Alloys Salt Water Sugar Water Air Milk Blood Steel: iron, carbon 14 K Gold: Gold, Antimony, copper Bronze: copper, tin Brass: Copper, zinc Pewter: tin, copper, antimony 4
SYMBOLS AND FORMULAS Each element is represented by a chemical symbol 2.4 CHEMICAL REACTIONS One or more substances change into new substances Reactants Products *complete rearrangement of atoms. Parts of a Chemical Reaction N 2 3H 2 2NH 3 Reactants Products Physcial vs. Chemical Recognizing Chemical Changes Physical Properties Dissolving Color Odor Melting Point Boiling Point Malleability (Bending) Hardness Texture Chemical Properties Does it burn? Does it react? Does it rust? Transfer of Energy (Heat, Light) Change in color (Rust, ashes) Gas formation (Water vapor, CO 2 ) Formation of precipitate (A solid forms from two liquids) 5
PHYSICAL CHANGES Alter substances without changing its composition Boil, freeze, dissolve, melt, crush, condense, break, split, crack COMPOUNDS Separated into simpler substances only by a chemical reaction Below: The compound, HCl, is separated by reacting with Mg. HCl Mg MgCl 2 H 2 CONSERVATION OF MASS THE LAW OF CONSERVATION OF MASS mass is neither created nor destroyed CONSERVATION OF MASS If 16 grams of CH 4 reacted with 64 grams of O 2, how many grams of H 2 O are released if 44 grams of CO 2 are produced? CH 4 O 2 CO 2 H 2 O 6