Introduction: Matter and Measurement

Chemistry: The study of matter and the changes it undergoes.

Matter: Anything that has mass and takes up space.

States of Matter

Plasma  Lightning is a plasma.  Used in fluorescent light bulbs and Neon lights.  Plasma is a lot like a gas, but the particles are electrically charged.

Classification of Matter Pure Substances Only one substance present Elements cannot be broken into simpler substances Compounds can be broken into elements by chemical means Mixtures Physical combination of 2 or more substances Homogeneous Mixtures One phase present Heterogeneous Mixtures 2 or more visible phases

Substances, Compounds, Elements and Mixtures

Matter  Atoms are the building blocks of matter.

Matter  Atoms are the building blocks of matter.  Each element is made of the same kind of atom.

Matter  Atoms are the building blocks of matter.  Each element is made of the same kind of atom.  A compound is made of two or more different kinds of elements.

Compounds Compounds can be broken down into more elemental particles.

Separating Mixtures: Distillation Separates homogeneous mixture on the basis of differences in boiling point.

Separating Mixtures: Filtration Separates solid substances from liquids and solutions.

Separating Mixtures: Chromatography

Separates substances on the basis of differences in solubility in a solvent.

Classify the following substances as an element, compound or a mixture (homogeneous or heterogeneous). Which are pure substances?  Lightly scrambled egg  Water  Lava lamp  Seawater  Freshly opened root beer  Flat root beer  Sucrose (C 12 H 22 O 11 )

Properties of Matter  Physical Properties: □ Can be observed without changing a substance into another substance.  Boiling point, density, mass, volume, etc.  Chemical Properties: □ Can only be observed when a substance is changed into another substance.  Flammability, corrosiveness, reactivity with acid, etc.

Properties of Matter  Intensive Properties: □ Independent of the amount of the substance that is present.  Density, boiling point, color, etc.  Extensive Properties: □ Dependent upon the amount of the substance present.  Mass, volume, energy, etc.

Changes of Matter  Physical Changes: □ Changes in matter that do not change the composition of a substance.  Changes of state, temperature, volume, etc.  Chemical Changes: □ Changes that result in new substances.  Combustion, oxidation, decomposition, etc.

States of Matter

Chemical Reactions In the course of a chemical reaction, the reacting substances are converted to new substances.

Chemical Reactions

Review Identify the following as either a chemical or physical change.  Combination of sodium and chlorine to give sodium chloride.  Liquefaction of gaseous nitrogen.  Separation of carbon monoxide into carbon and oxygen.  Freezing of water.

Units of Measurement

SI Units  Système International d’Unités  Uses a different base unit for each quantity

Units of Measurement  Mass measure of the quantity of matter in a body 1 pound = 454 g  Weight measure of the gravitational attraction for a body  Length 1 m = inches 2.54 cm = 1 inch  Volume 1 liter = 1.06 qt 1 qt = liter

Measurements in Chemistry Prefixes convert the base units into units that are appropriate for the item being measured.

Exact vs. Inexact  Exact numbers 1 dozen = 12 items 1 gross = 144 items Counted numbers- ex. 3 beakers  Inexact Numbers  Significant figures  digits believed to be correct by the person making the measurement  measure a mile with a 6 inch ruler vs. surveying equipment  Accuracy -how closely measured values agree with the correct value  Precision- how closely individual measurements agree with each other  Scientific notation -way of signifying the significant digits in a number

Accuracy versus Precision  Accuracy refers to the proximity of a measurement to the true value of a quantity.  Precision refers to the proximity of several measurements to each other.

Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy.

Significant Figures  The term significant figures refers to digits that were measured.  When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers.

Significant Figures 1.All nonzero digits are significant. 2.Zeroes between two significant figures are themselves significant. 3.Zeroes at the beginning of a number are never significant. 4.Zeroes at the end of a number are significant if a decimal point is written in the number.

Significant Figures  When addition or subtraction is performed, answers are rounded to the least significant decimal place.  When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation.

Significant Figures - rules multiply & divide rule - easy product has the smallest number of sig. fig. of multipliers

Temperature: A measure of the average kinetic energy of the particles in a sample.

Temperature  In scientific measurements, the Celsius and Kelvin scales are most often used.  The Celsius scale is based on the properties of water. □ 0  C is the freezing point of water. □ 100  C is the boiling point of water.

Temperature  The Kelvin is the SI unit of temperature.  It is based on the properties of gases.  There are no negative Kelvin temperatures.  K =  C

Temperature  The Fahrenheit scale is not used in scientific measurements.   F = 9/5(  C) + 32   C = 5/9(  F − 32)

Density: Physical property of a substance d=d= mVmV

Dimensional Analysis  simple but important way to always get right answer  way to change from one unit to another  make unit factors from statements 1 ft = 12 in becomes 1 ft/12 in or 12in/1 ft 3 ft = 1 yd becomes 3ft/1yd or 1yd/3ft

Dimensional Analysis  simple but important way to always get right answer  way to change from one unit to another  make unit factors from statements 1 ft = 12 in becomes 1 ft/12 in or 12in/1 ft  Example: Express yards in millimeters.