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Chapter 1 Matter, Measurement, and Problem Solving

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  1. Chemistry: A Molecular Approach, 2nd Ed.Nivaldo Tro Chapter 1Matter,Measurement, and Problem Solving Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA

  2. Composition of Matter Atoms and Molecules Scientific Method Tro: Chemistry: A Molecular Approach, 2/e

  3. Structure Determines Properties Tro: Chemistry: A Molecular Approach, 2/e carbon dioxide carbon monoxide • composed of one carbon atom and two oxygen atoms • colorless, odorless gas • incombustible • does not bind to hemoglobin • composed of one carbon atom and one oxygen atom • colorless, odorless gas • burns with a blue flame • binds to hemoglobin • The properties of matter are determined by the atoms and molecules that compose it

  4. Tro: Chemistry: A Molecular Approach Atoms and Molecules • Atoms • are submicroscopic particles • are the fundamental building blocks of ordinary matter • Molecules • are two or more atoms attached together in a specific geometrical arrangement • attachments are called bonds • attachments come in different strengths • come in different shapes and patterns • Chemistry is the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules Tro: Chemistry: A Molecular Approach, 2/e

  5. Tro: Chemistry: A Molecular Approach The Scientific Approach to Knowledge • Philosophers try to understand the universe by reasoning and thinking about “ideal” behavior • Scientists try to understand the universe through empirical knowledge gained through observation and experiment Tro: Chemistry: A Molecular Approach, 2/e

  6. Tro: Chemistry: A Molecular Approach Gathering Empirical Knowledge ─ Observation • Some observations are descriptions of the characteristics or behavior of nature ─qualitative • “The soda pop is a liquid with a brown color and a sweet taste. Bubbles are seen floating up through it.” • Some observations compare a characteristic to a standard numerical scale ─quantitative • “A 240 mL serving of soda pop contains 27 g of sugar.” Tro: Chemistry: A Molecular Approach, 2/e

  7. Tro: Chemistry: A Molecular Approach From Observation to Understanding • Hypothesis– a tentative interpretation or explanation for an observation • “The sweet taste of soda pop is due to the presence of sugar.” • A good hypothesis is one that can be tested to be proved wrong! • falsifiable • one test may invalidate your hypothesis Tro: Chemistry: A Molecular Approach, 2/e

  8. Tro: Chemistry: A Molecular Approach Testing Ideas • Ideas in science are tested with experiments • An experiment is a set of highly controlled procedures designed to test whether an idea about nature is valid • The experiment generates observations that will either validate or invalidate the idea Tro: Chemistry: A Molecular Approach, 2/e

  9. Tro: Chemistry: A Molecular Approach From Specific to General Observations • A scientific lawis a statement that summarizes all past observations and predicts future observations • Law of Conservation of Mass–“In a chemical reaction matter is neither created nor destroyed.” • A scientific law allows you to predict future observations • so you can test the law with experiments • Unlike state laws, you cannot choose to violate a scientific law! Tro: Chemistry: A Molecular Approach, 2/e

  10. Tro: Chemistry: A Molecular Approach From Specific to General Understanding • A hypothesis is a potential explanation for a single or small number of observations • A scientific theory is a general explanation for why things in nature are the way they are and behave the way they do • models • pinnacle of scientific knowledge • validated or invalidated by experiment and observation Tro: Chemistry: A Molecular Approach, 2/e

  11. Scientific Method Procedure designed to test an idea Tentative explanation of a single or small number of observations General explanation of natural phenomena Careful noting and recording of natural phenomena Generally observed occurence in nature Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  12. Tro: Chemistry: A Molecular Approach Relationships Between Pieces of the Scientific Method Tro: Chemistry: A Molecular Approach, 2/e

  13. Classification of Matter States of Matter Physical and Chemical Properties Physical and Chemical Changes Tro: Chemistry: A Molecular Approach, 2/e

  14. Tro: Chemistry: A Molecular Approach Classification of Matter • Matter is anything that occupies space and has mass • We can classify matter based on its state and its composition • whether it’s solid, liquid, or gas • its basic components Tro: Chemistry: A Molecular Approach, 2/e

  15. Tro: Chemistry: A Molecular Approach Classifying Matterby Physical State • Matter can be classified as solid, liquid, or gas based on the characteristics it exhibits Tro: Chemistry: A Molecular Approach, 2/e

  16. Tro: Chemistry: A Molecular Approach Solids • The particles in a solid are packed close together and are fixed in position • though they may vibrate • The close packing of the particles results in solids being incompressible • The inability of the particles to move around results in solids retaining their shape and volume when placed in a new container, and prevents the solid from flowing Tro: Chemistry: A Molecular Approach, 2/e

  17. Tro: Chemistry: A Molecular Approach Crystalline Solids • Some solids have their particles arranged in patterns with long-range repeating order – we call these crystalline solids • salt • diamonds • sugar Tro: Chemistry: A Molecular Approach, 2/e

  18. Tro: Chemistry: A Molecular Approach Amorphous Solids • Some solids have their particles randomly distributed without any long-range pattern – we call these amorphous solids • plastic • glass • charcoal Tro: Chemistry: A Molecular Approach, 2/e

  19. Tro: Chemistry: A Molecular Approach Liquids • The particles in a liquid are closely packed, but they have some ability to move around • The close packing results in liquids being incompressible • The ability of the particles to move allows liquids to take the shape of their container and to flow – however, they don’t have enough freedom to escape or expand to fill the container Tro: Chemistry: A Molecular Approach, 2/e

  20. Tro: Chemistry: A Molecular Approach Gases • In the gas state, the particles have freedom of motion and are not held together • The particles are constantly flying around, bumping into each other and the container • In the gas state, there is a lot of empty space between the particles • on average Tro: Chemistry: A Molecular Approach, 2/e

  21. Tro: Chemistry: A Molecular Approach Gases • Because there is a lot of empty space, the particles can be squeezed closer together – therefore gases are compressible • Because the particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, and will flow Tro: Chemistry: A Molecular Approach, 2/e

  22. Tro: Chemistry: A Molecular Approach Classifying Matter by Composition • Another way to classify matter is to examine its composition • Composition includes • types of particles • arrangement of the particles • attractions and attachments between the particles Tro: Chemistry: A Molecular Approach, 2/e

  23. Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  24. Tro: Chemistry: A Molecular Approach Classification of Matterby Composition • Matter whose composition does not change from one sample to another is called a pure substance • made of a single type of atom or molecule • because the composition of a pure substance is always the same, all samples have the same characteristics • Matter whose composition may vary from one sample to another is called a mixture • two or more types of atoms or molecules combined in variable proportions • because composition varies, different samples have different characteristics Tro: Chemistry: A Molecular Approach, 2/e

  25. Classification of Matterby Composition made of one type of particle all samples show the same intensive properties made of multiple types of particles samples may show different intensive properties Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  26. Tro: Chemistry: A Molecular Approach Classification of Pure Substances  Elements • Pure substances that cannot be decomposed into simpler substances by chemical reactions are called elements • decomposed = broken down • basic building blocks of matter • composed of single type of atom • though those atoms may or may not be combined into molecules Tro: Chemistry: A Molecular Approach, 2/e

  27. Tro: Chemistry: A Molecular Approach Classification of Pure Substances  Compounds • Pure substances that can be decomposed are called compounds • chemical combinations of elements • composed of molecules that contain two or more different kinds of atoms • all molecules of a compound are identical, so all samples of a compound behave the same way • Most natural pure substances are compounds Tro: Chemistry: A Molecular Approach, 2/e

  28. Classification of Pure Substances made of one type of atom (some elements found as multi-atom molecules in nature) combine together to make compounds made of one type of molecule, or an array of ions units contain two or more different kinds of atoms Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  29. Tro: Chemistry: A Molecular Approach Classification of Mixtures • Homogeneous mixtures are mixtures that have uniform composition throughout • every piece of a sample has identical characteristics, though another sample with the same components may have different characteristics • atoms or molecules mixed uniformly • Heterogeneous mixturesare mixtures that do not have uniform composition throughout • regions within the sample can have different characteristics • atoms or molecules not mixed uniformly Tro: Chemistry: A Molecular Approach, 2/e

  30. Classification of Mixtures made of multiple substances, whose presence can be seen portions of a sample have different composition and properties made of multiple substances, but appears to be one substance all portions of an individual sample have the same composition and properties Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  31. Tro: Chemistry: A Molecular Approach Changes in Matter • Changes that alter the state or appearance of the matter without altering the composition are called physical changes • Changes that alter the composition of the matter are called chemical changes • during the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present Tro: Chemistry: A Molecular Approach, 2/e

  32. Physical Changes in Matter The boiling of water is a physical change. The water molecules are separated from each other, but their structure and composition do not change. Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  33. Chemical Changes in Matter The rusting of iron is a chemical change. The iron atoms in the nail combine with oxygen atoms from O2 in the air to make a new substance, rust, with a different composition. Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  34. Tro: Chemistry: A Molecular Approach Properties of Matter • Physical properties are the characteristics of matter that can be changed without changing its composition • characteristics that are directly observable • Chemical properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy • characteristics that describe the behavior of matter Tro: Chemistry: A Molecular Approach, 2/e

  35. Common Physical Changes Processes that cause changes in the matter that do not change its composition State changes boiling / condensing melting / freezing subliming Dissolving of sugar Subliming of dry ice C12H22O11(s) CO2(g) Dry Ice CO2(s) C12H22O11(aq) • Dissolving Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e 35

  36. Tro: Chemistry: A Molecular Approach C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) Common Chemical Changes • Processes that cause changes in the matter that change its composition • Rusting • Burning • Dyes fading or changing color Tro: Chemistry: A Molecular Approach, 2/e

  37. Energy Tro: Chemistry: A Molecular Approach, 2/e

  38. Tro: Chemistry: A Molecular Approach Energy Changes in Matter • Changes in matter, both physical and chemical, result in the matter either gaining or releasing energy • Energy is the capacity to do work • Work is the action of a force applied across a distance • a force is a push or a pull on an object • electrostatic force is the push or pull on objects that have an electrical charge Tro: Chemistry: A Molecular Approach, 2/e

  39. Tro: Chemistry: A Molecular Approach Energy of Matter • All matter possesses energy • Energy is classified as either kinetic or potential • Energy can be converted from one form to another • When matter undergoes a chemical or physical change, the amount of energy in the matter changes as well Tro: Chemistry: A Molecular Approach, 2/e

  40. Tro: Chemistry: A Molecular Approach Energy of Matter − Kinetic • Kinetic energy is energy of motion • motion of the atoms, molecules, and subatomic particles • thermal (heat) energy is a form of kinetic energy because it is caused by molecular motion Tro: Chemistry: A Molecular Approach, 2/e

  41. Tro: Chemistry: A Molecular Approach Energy of Matter − Potential • Potential energy is energy that is stored in the matter • due to the composition of the matter and its position relative to other things • chemical potential energy arises from electrostatic attractive forces between atoms, molecules, and subatomic particles Tro: Chemistry: A Molecular Approach, 2/e

  42. Tro: Chemistry: A Molecular Approach Conversion of Energy • You can interconvert kinetic energy and potential energy • Whatever process you do that converts energy from one type or form to another, the total amount of energy remains the same • Law of Conservation of Energy Tro: Chemistry: A Molecular Approach, 2/e

  43. Tro: Chemistry: A Molecular Approach Spontaneous Processes • Materials that possess high potential energy are less stable • Processes in nature tend to occur on their own when the result is material with lower total potential energy • processes that result in materials with higher total potential energy can occur, but generally will not happen without input of energy from an outside source Tro: Chemistry: A Molecular Approach, 2/e

  44. Tro: Chemistry: A Molecular Approach Changes in Energy • If a process results in the system having less potential energy at the end than it had at the beginning, the “lost” potential energy was converted into kinetic energy, which is released to the environment • During the conversion of form, energy that is released can be harnessed to do work Tro: Chemistry: A Molecular Approach, 2/e

  45. Potential to Kinetic Energy Tro: Chemistry: A Molecular Approach Tro: Chemistry: A Molecular Approach, 2/e

  46. Standard Units of Measure Tro: Chemistry: A Molecular Approach, 2/e

  47. Tro: Chemistry: A Molecular Approach The Standard Units • Scientists have agreed on a set of international standard units for comparing all our measurements called the SI units • Système International = International System Tro: Chemistry: A Molecular Approach, 2/e

  48. Tro: Chemistry: A Molecular Approach Length • Measure of the two-dimensional distance an object covers • often need to measure lengths that are very long (distances between stars) or very short (distances between atoms) • SI unit = meter • about 3.37 inches longer than a yard • 1 meter = distance traveled by light in a specific period of time • Commonly use centimeters (cm) • 1 m = 100 cm • 1 cm = 0.01 m = 10 mm • 1 inch = 2.54 cm (exactly) Tro: Chemistry: A Molecular Approach, 2/e

  49. Tro: Chemistry: A Molecular Approach Mass • Measure of the amount of matter present in an object • weight measures the gravitational pull on an object, which depends on its mass • SI unit = kilogram (kg) • about 2 lbs. 3 oz. • Commonly measure mass in grams (g) or milligrams (mg) • 1 kg = 2.2046 pounds, 1 lb. = 453.59 g • 1 kg = 1000 g = 103 g • 1 g = 1000 mg = 103 mg • 1 g = 0.001 kg = 10−3 kg • 1 mg = 0.001 g = 10−3 g Tro: Chemistry: A Molecular Approach, 2/e

  50. Tro: Chemistry: A Molecular Approach Time • Measure of the duration of an event • SI units = second (s) • 1 s is defined as the period of time it takes for a specific number of radiation events of a specific transition from cesium–133 Tro: Chemistry: A Molecular Approach, 2/e