Chemistry 20; Unit 1

1.1 Introduction: Science and Technology Science: the study of the natural world with the goal of describing, explaining and predicting substance changes. The purpose of scientific investigations is to create, test, and or use scientific concepts.Technology: the skills, processes and equipment required to manufacture useful products or to perform useful tasks.Chemistry: the physical science that deals with composition, properties, and changes in matter.Chemical change or chemical reaction is a change in which one or more new substances with different properties are formed.Physical changes, such as water freezing to from ice crystals and boiling to form water vapour, during which NO new substances are formed. ( Physical changes sometimes called phase changes or changes of state)Observation: a direct form of knowledge obtained by means of one of the five senses - seeing, smelling, tasting, hearing, or feeling. Observation might be obtained with the aid of an instrument such as a balance or a microscope or stop watch.Qualitative Observation: describes qualities of matter or change in matter; a substances's colour, odour, or physical stateQuantitative Observation: involves the quantity of matter or the degree of change in matter, ALWAYS INCLUDES A NUMBER ; measurement of the length or mass of magnesium ribbonInterpretation: included in the Analysis section of an investigation report. An Indirect form of knowledge that builds on concept or an experience to further describe or explain an observation. Interpretation can be either empirical or theoretical Empirical Knowledge: Observations are always empirical; ex. observation of the colour and size of the flame when magnesium burns Theoretical Knowledge: explains and describes scientific observations in terms of ideas; theoretical knowledge is NOT OBSERVABLE; ex. the idea that "magnesium atoms lose electrons to form magnesium ions, while oxygen atoms gain electrons to form oxide ionsCommunicating Empirical Knowledge - The manipulated variable (independent variable) is on the x-axis while the responding variable (dependent) is on the y-axis- Empirical Hypothesis: preliminary generalizations that require further testing- Empirical Definitions: statements that define an object or a process in terms of observable properties; ex. a metal is shiny, flexible solid- Generalizations: statements that summarize a limited number of empirical results. Usually broader in scope than empirical definitions and often deals with a minor or sub-concept; ex. many metals slowly react with oxygen from the air in a process known as corrosion.- Scientific Laws: statements of major concepts based on a large body of empirical knowledge. Laws are more important and summarize more empirical knowledge than generalizations; ex. the burning of magnesium, when studied in greater detail, illustrates the law of conservation of massLaws must accurately describe and explain current observations and predict future events in a simple manner.

1.2 Classifying Matter

- Pure substances' composition is constant and uniform-Mixtures' composition is variable and may or may not be uniform throughout - Heterogenous Mixture: non-uniform and may consist of more than one phase- Homogenous Mixture: uniform consist of only one phase - The parts of both heterogenous mixtures and solutions can be separated by physical means such as filtration, distillation, chromatography; mechanically extracting one component from the mixture, allowing one component to settle; or using a magnet to separate certain metals.- a pure substance cannot be separated by physical methods; only by means of chemical change involving heat or electricity, called chemical decomposition-Elements CANNOT be broken down into simple substances by any physical or chemical means. Substance composed of only one kind of atom- Entity: a general term that includes particles (sub atomic entities: protons, electrons, neutrons), atoms (smallest entity of an element that is still characteristic of the element), ions, molecules and formula units- Compounds: contains of atoms of more than one element combines in a definite fixed proportion. Substance composed of two or more kinds of atoms- Solutions, unlike elements and compounds, contain entities of more than one substance, uniformly distributed throughout them.

1.3 Classifying Elements - Dimitri Mendeleev's periodic table communicated the periodic law (chemical and physical properties of elements repeat themselves in regular intervals, when the elements are arranged in order of increasing atomic number) - International Union of Pure and Applied Chemistry (IUPAC) governing body for scientific communication and has defined a set of standard conditions- Unless other conditions are specified, descriptions of materials are assumed to be at STANDARD AMBIENT TEMPERATURE AND PRESSURE (SATP). Under these ambient (surrounding) conditions, known as SATP, the materials are at a room temp of 25 degrees celsuis and a pressure of 100kPA- Metals are shiny, bendable, good conductors of heat and electricity; all elements except mercury are solid at SATP.- Non-metals are NOT shiny, not bendable, generally not good conductors of heat and electricity in their solid form. At SATP most non-metals are gases and few are solids. Solid non-metals are brittle and lack the lustre of metals. Most non-metals exist in compounds rather than in element form.- Alkali Metals: group 1 elements soft, silver colour, react violently with water to form basic solutions; also reactive with halogens. Most reactive alkali metals are cesium and francium. - Alkaline Earth Metals: group 2 elements light, reactive metals that form oxide coatings when exposed to air- Halogens: group 17 elementsall extremely reactive, with fluorine being the most reactive- Noble gases: group 18 elements they are special because of their extremely low chemical reactivity- main group elements: the elements in group 1, 2, 12 to 18. of all the elements, the main group elements best follow the periodic law- Transition Elements: group 3 to 11 elements these elements exhibit a wide range of chemical and physical properties- Lanthanoids: ATOMIC NUMBERS 58-71 the rare earth elements include the lanthanoids, and yttrium and scandium- Actinoids: ATOMIC NUMBERS 90-103 the synthetic (not naturally occurring) elements that have atomic numbers of 93 or greater are referred to as transuranic elements

1.4 Theories and Atomic Theories

Communicating Theoretical Knowledge in Science - Theoretical descriptions: are specifics descriptive statements based on theories or models. Ex: "a molecule of water is composed of two hydrogen atoms and on oxygen atom."- Theoretical Hypotheses: are ideas that are untested or extremely tentative. Ex: "protons are composed of quarks that may themselves be composed of smaller particles."- Theoretical Definitions: are general statements that characterize the nature of a substance or process in terms of a non-observable idea. Ex a solid is theoretically defined as "a closely packed arrangement of atoms, each atom vibrating about a fixed location in the substance."- Theories: are comprehensive set of ideas based on general principles that explain a large number of observations. Ex: the idea that materials are composed of atoms is one of the principles of atomic theory; atomic theory explains many of the properties of materials. Theories are dynamic; they continually undergo refinement and change.- Analogies: are comparisons that communicate an idea in more familiar or recognizable terms. Ex: an atom may be conceived as behaving like a billiard ball. All analogies "break down" at some level; that is, they have limited usefulness- Models: are physical, graphic or mental representations used to communicate an abstract idea. Ex: marbles is a vibrating box could be used to study and explain the three states of matter. Like analogies, models are always limited in their application. Dalton's Atomic Theory - Dalton created the modern theory of atoms to explain 3 important scientific laws- the laws of definite composition, multiple proportions, and conservation of mass- Dalton's model of the atom was that of a featureless sphere-by analogy a billiard ball- Atomic Theory: Matter is composed of indestructible, indivisible atoms, which are identical for one element, but different from other elements