Matter – Properties and Changes Chapter 2 Matter – Properties and Changes

2.1 Properties of Matter Pure substance (substance) – matter that has a uniform and definite composition. Physical property – quality of a substance that can be observed without changing the substances composition

2.1 Properties of Matter Two Types of Physical Properties Extensive properties – dependent upon the amount of substance present. Mass, volume, and length Intensive properties – independent of the amount of substance present. density

2.1 Properties of Matter Chemical property – of a substance to combine with or change into one or more other substances.

Physical Properties Chemical Properties Melting point Decomposition Boiling Color Density Magnetism Crystalline shape Malleability Ductility Luster Refractive index Decomposition Chemical reactivity Water Acid Precipitation rxn Combustion rxn Odor Taste Hardness solubility

2.1 States of Matter Solids Particles close together -strong forces hold particles together Particles vibrate – held too strongly to break apart Constant shape and volume Almost incompressible

2.1 States of Matter Liquids Particles farther apart - particles are moving fast enough to partially break away Particles stay together – not moving fast enough to escape Constant volume but not shape Almost incompressible

2.1 States of Matter Gases Particles far apart – no attractive forces Particles moving very fast No constant shape or volume Easily compressed Vapor – matter as a gas that is usually a liquid or solid at room temperature

2.1 Uncommon 4th State Plasma High energy and temperature Charged gaseous particles

2.2 Changes in Matter Physical change – change that results in a dramatically different appearance yet leave the composition of the substance unchanged. Crumpling of a sheet of aluminum foil. Changes in state

2.2 Changes in Matter Chemical change – of a process where one or more other substances change into new substances. How do you know if it’s a chemical change has occurred? Color change Solid or liquid precipitate Odor or gas produced. Light or energy involved.

mass reactants = mass products 2.2 Changes in Matter Conservation of Mass Law of conservation of mass – in an ordinary chemical or physical reaction, mass can’t be created or destroyed. mass reactants = mass products

2.2 Changes in Matter

2.2 Changes in Matter A reaction between sodium hydroxide and hydrogen chloride gas produces sodium chloride and water. A reaction of 22.85 g of sodium hydroxide with 20.82 g of hydrogen chloride gives off 10.29 g of water. What mass of sodium chloride is formed in the reaction? 22.85 g 20.82 g 10.29 g sodium hydroxide + hydrogen chloride  sodium chloride + water 22.85 g + 20.82 g = sodium chloride + 10.29 g 43.67 g = sodium chloride + 10.29 g 33.38 g sodium chloride

2.3 Mixtures of Matter Classifying Mixtures Mixture – physical blend of two or more pure substances. Heterogeneous mixture – nonuniform composition. Homogeneous mixture (solution) – uniform composition. Phase – part of a system with uniform composition.

2.3 Mixtures of Matter Separating Mixtures Filtration – separate by passing through a barrier

2.3 Mixtures of Matter Separating Mixtures Distillation – uses differences in boiling points to separate liquid-solid or liquid-liquid mixtures.

2.3 Mixtures of Matter Separating Mixtures Crystallization – formation of pure solid particles from a solution. Chromatography – separate components of a mixture based on the speed they move across another material.

2.4 Elements and Compounds Element – pure substance that can’t be separated into simpler substances Can’t be separated by chemical or physical means. 91 naturally occurring When naming First letter capitalized Others are lowercase

2.4 Elements and Compounds Periodic Table of Elements Row is called a “period” Column is called a “group” or “family” Elements in the same group have similar chemical and physical properties Why is it called a periodic table? There is a “periodic” repetition of the pattern in similar properties as you move from period to period

A column is called a group or family! A row is called a period!

2.4 Elements and Compounds Compound – 2 or more elements combined chemically Can be separated chemically, but not physically About 10 million known compounds 100,000 new each year H2O, NaCl, and C12H22O11 Symbols represent elements Subscripts represent the proportion of the elements in the compound

Classifying Matter Matter Can it be separated physically? No Yes Pure Substance (Definite Composition) Can it be separated chemically? Mixture (Variable composition) Is it uniform? No Yes Yes No Element Examples: carbon, gold, iron, and more Compound Example: water and sodium chloride Homogeneous mixture Examples: air and tap water Heterogeneous mixture Examples: soup and river water

2.4 Elements and Compounds Law of Definite Proportion – in a chemical compound, the masses of the elements are always in the same proportion. 18 g of H2O 100 g H2O H = 2 g O = 16 g H = 11.11 g O = 88.89 g Ratio of O = 16 or 8 H 2 1 Ratio of O = 88.89 or 8 H 11.11 1

2.4 Elements and Compounds Percent by mass – the ratio of the mass of each element to the total mass of the compound

2.4 Elements and Compounds A 134.50-g sample of aspirin is made up of 6.03 g of hydrogen, 80.70 g of carbon, and 47.77 g of oxygen. What is the percent by mass of hydrogen in aspirin? = 4.48327 % = 4.48 %

2.4 Elements and Compounds If you have 945.5 g of aspirin, how much hydrogen do you have? Remember %Aspirin = 4.48% What is 4.48% of 945.5 g? 945.5 g  .0448 = 42.3584 g 42.4 g

2.4 Elements and Compounds Law of Multiple Proportions – if 2 elements form more than 1 compound, the different masses of 1 element that combine with the same mass of the other element are in ratios of small whole numbers. 17 g of H2O2 9 g of H2O H = 1 g O = 16 g H = 1 g O = 8 g O ratio is 16:8 or 2:1

How do you show this law if the second element isn’t the same mass? Law of Multiple Proportions – if 2 elements form more than 1 compound, the different masses of 1 element that combine with the same mass of the other element are in ratios of small whole numbers. What ratio of X combines with a fixed ratio of Y for these two compounds? X = 1.2 g Y = 1.11 g X = 2.6 g Y = 4.8 g = 1.08 gX = .54 gX 1 gY 1 gY 1.08 g to .54 g 2 to 1