2Chemistry is……the study of the composition, structure, and properties of matter and the changes it undergoes
3Anything that has mass and occupies space MatterAnything that has mass andoccupies spaceMassA measure of the amount of matterWeightThe measure of the force of gravityacting on an object
4AtomThe smallest unit of an element that maintainsthe properties of that element
5By asking questions scientists can classify matter into: Mixtures – two or more substances that are not chemically combined with each otherand can be separated by physical means. The substances in a mixture retain their individual properties.Solutions – a special kind of mixture where one substance dissolves in another.Elements – simplest form of pure substance. They cannot be broken into anything else by physical or chemical means.Compounds – pure substances that are the unions of two or more elements. They can be broken into simpler substances by chemical means.
6Types of Chemical Formulas • An empirical formula gives the relative number of atoms of each element in a compound; i.e., the smallest whole number ratio that is possible. • A molecular formula gives the actual number of atoms of each element in a molecule of a compound Molecular Empirical Hydrogen peroxide H2O HO Water H2O H2O Glucose C6H12O CH2O • A structural formula uses lines to represent covalent bonds, and shows how the atoms in a molecule are joined together: H—O—O—H H—O—H O=C=O
7Homogeneous – a substance that is the same throughout Homogeneous – a substance that is the same throughout. Heterogeneous – a substance that is different throughout.
8Separation of a Compound The Electrolysis of water Compounds must be separated by chemical means.With the application of electricity, water can beseparated intoits elementsReactant ProductsWater Hydrogen + OxygenH2O H O2
11Properties of Matterdepend on the amount of matter that is present.Extensive propertiesVolumeMassIntensive propertiesdo not depend on the amount of matter present.Melting pointBoiling pointDensity
12Physical ChangeA change in a substance that does not involve a change in the identity of the substance.Example:A change insize, shapecolor etc.Phase Changes
13Phase DifferencesSolid – definite volume and shape; particles packed in fixed positions.Liquid – definite volume but indefinite shape; particles close together but not in fixed positions
14Gas – neither definite volume nor definite shape; particles are at great distances from one another Plasma – high temperature, ionized phase of matter as found on the sun.
15Phase changes occur when a substance changes state from… A solid to liquid…meltingA liquid to solid…freezingA liquid to gas…boilingA gas to liquid…condensingA solid to gas…sublimingA gas to a solid…deposition
17The heat that is being added to a given state that does not result in a temperature increase is being used to overcome the intermolecular forces between the particles.The heat added to a solid to convert it to a liquid is called the heat of fusion. (fusion means melting)You add heat to get a solid to melt. When you condense a liquid back to a solid, you get that heat back!Melting and freezing are only different in which way heat flows in or out of a substance.
18The same occurs at the boiling/condensation point The same occurs at the boiling/condensation point. The heat put in to a liquid to convert it to a gas is called the heat of vaporization.When a gas is condensed to a liquid, then that heat is again released.Boiling and condensation are only different in the direction of heat flow in or out of a substance.
22Chemical ChangeA change in which one or more substances are converted into different substances. Something new is created.Heat and light are often evidence of a chemical change.
23Catalyst – a substance that increases the rate of a chemical reaction without itself being permanently changed. Entropy – the measure of disorder in a substance.
24Physical properties shape. size texture. hardness odor. mass color Physical properties shape size texture hardness odor mass color state freezing point magnetism melting point
25More physical properties More physical propertiesconductivity (conducts electricity) malleability (can be hammered into sheets) ductility (can be drawn into wires) solubility (will dissolve in another substance) density (mass / volume)
26Chemical propertiesFlammibiltyReactivityCombustibilityAcidic or basic
27Properties of MetalsMetals are good conductors of heat and electricityMetals are malleableMetals are ductileMetals have high tensile strengthMetals have luster
28Examples of MetalsPotassium, K reacts with water and must be stored in keroseneMercury, Hg, is the only metal that exists as a liquid at room temperature
29Properties of Nonmetals Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.Nonmetals are poor conductors of heat andelectricityNonmetals tend to be brittleMany nonmetals are gases at room temperature
30Examples of NonmetalsSulfur, S, was once known as “brimstone”Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure
31Properties of Metalloids Metalloids straddle the stairstep.They have properties of both metals and nonmetals.Metalloids are more brittle than metals, less brittle than most nonmetallic solidsMetalloids are semiconductors of electricitySome metalloids possess metallic luster
32Silicon, Si – A Metalloid Silicon has metallic lusterSilicon is brittle like a nonmetalSilicon is a semiconductor of electricity
33Number of naturally occuring elements is 90 Sir ramsey discovered the Noble gases, octets, group 8, helium familyAccuracy – nearness of a measurement to its accepted valuePrecision – agreement between numerical values of a set of measurements.