Substance A form of matter that has a uniform and unchanging composition…aka a pure substance
The 3 Physical States of Matter Solid Liquid Gas
Solid Definite shape and volume Atoms/molecules held rigidly in place Non-compressible
Liquid No definite shape; takes the shape of its container; Non-compressible Definite volume Molecules are farther apart than those of a solid, allowing molecules to flow past one another
Gas No definite shape nor volume Gases take the shape & volume of their container Gases are mostly empty space Compressible
What is the physical state of each of the following at room temperature? gold gasoline helium bromine lithium nitrogen
The 3 Chemical Classes of Matter Element Compound Mixture
1. Element A substance that can’t be reduced to a simpler form The building blocks of all substances Made up of only one type of atom
3 Types of Elements Metals: to the left of the “stair-step;” the majority of the elements Non-metals: to the right of the “stair-step” Metalloids: non-metals on the stair step having metal and non-metal properties
2. COMPOUNDS formed when 2 or more different elements join chemically in a definite pattern/ arrangement Can be made or separated by chemical reactions
2 Types of Compounds ionic compounds: made up of a metal and a non-metal portion covalent compounds: composed of non- metals
Which of these are elements and which of these are compounds? Hg NaCl O 2 H 2 O S 8
3. Mixtures 2 or more distinct substances mixed together with variable composition may have distinct phases can be separated by physical methods Distillation Filtration chromotography
2. Distillation A separation technique that is based on differences in the boiling points of the substances involved A mixture is heated until the substance with the lowest boiling point boils to a vapor that can then be condensed into a liquid and collected.
Physical Properties of Matter Physical properties are characteristics that can be observed or measured without changing the sample’s composition intensive properties: are independent of sample size. ie. density, color, boiling point extensive properties are dependent on the amount of material present. ie. mass and volume
Physical Changes of Matter Changes that alter a substance without changing its chemical composition ie. Changes in physical state
Sublimation: solid to gas phase For example: Dry ice
How can you change the physical appearance without changing the state
Chemical Properties of Matter Chemical properties are only observed in chemical reactions Reactivity: the tendency of a substance to undergo a particular chemical reaction when exposed to an agent.
Examples 2H 2 O reactivity to electric current→ 2H 2 (g) + O 2 (g) H 2 O reactivity to alkali metals→ H 2 (g) [Cesium in water causes explosion] Fe reactivity to O 2 + H 2 O (fog)→ Fe 2 O 3 (rust) Iron Oxide (you leave your bike out in the fog and it rusts)
Rubidium,Cesium, & Francium in water http://www.youtube.com/watch?v=jJGqC4v XBms http://www.youtube.com/watch?v=jJGqC4v XBms
Chemical Change A process that involves one or more substances changing into new substances
Reactants: the starting materials in a chemical reaction Products: the newly formed substances from a chemical reaction
4 Indicators of Chemical Change: (often accompany chemical change) color change precipitate formation gas evolution heat evolution or heat absorption
2 Types of Reactions Exothermic: Heat is released/given off during a chemical reaction Endothermic: Heat is absorbed during the chemical reaction
Color Change and Precipitate Formation 2 KI + Pb(NO 3 ) 2 → 2 KNO 3 + PbI 2 (s) http://www.youtube.com/watch?v=RE- dFN7U91M&feature=player_detailpage
Conservation of Mass In a chemical reaction, matter is neither created nor destroyed, but it can change from one form to another. Mass of Reactants= Mass of Products → Material Balance
Conservation of Mass From a lab experiment designed to separate water into hydrogen and oxygen, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How many grams of water were originally present?
Chemistry is the study of the composition of substances and the changes they undergo. In chemistry, a specific language is used when referring to elements.
What do you notice about the letters on the periodic table?
Periodic Table of Elements Groups: (Families) the vertical columns on the periodic table. Periods: Horizontal Rows. Each element is represented by a symbol Symbols are one to three letters The first letter is always capitalized, 2 nd & 3 rd letters are always lower case. Often the chemical symbols coincide with the spelling of the element, but other times the symbols were derived from the Latin name for the element.
Periodic Table of Elements, cont. Metals: Good conductors of heat and electricity. In general, they are malleable, ductile, lustrous, etc Non-Metals: Poor conductors of heat and electricity. Solids are brittle Metalloid: Having characteristics of both metals and non-metals
Law of Definite Proportions: States that regardless of the amount, a compound is always composed of the same elements in the same proportion, by mass. For example, water, is always H 2 O… Which is ~11% Hydrogen And ~89% oxygen
Percent by mass (%): mass of element x 100 Mass of compound
Mass of Compound: the sum of the masses of the individual elements that make up the compound.
Example A sample of an unknown compound contains 5.3 g oxygen and 20.0 g of copper. What is the percent by mass of each element in the compound?
Law of Multiple Proportions States that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers
Ratios: Compare the relative amounts of any items or substances Express the relationship of elements in a compound
Mass Ratio 1. Mass of element in a compound = ratio Mass of other element in compound 2. Mass ratio compound I = small whole # Mass ratio compound II *find the mass ratio for each compound, then divide the two ratios to give a small whole # ratio
Example: Analysis Data of Two Iron Compounds Are Compounds I and II the same compound? If not, use the law of multiple proportions to show the relationship between them. Compound Total Mass Mass Fe (g) Mass O (g) Mass % Fe Mass % O I75.0052.4622.5469.9530.05 II56.0043.5312.4777.7322.27