General Chemistry PDF

GENERAL CHEMISTRY Assoc. Prof. Kadriye KIZILBEY [email protected] Properties and Measurement of Matter  1. Purpose of Chemistry Chemistry is the study of matter, which includes us and everything around us. Chemistry is an integral part of our lives. Bec...

GENERAL CHEMISTRY Assoc. Prof. Kadriye KIZILBEY [email protected] Properties and Measurement of Matter  1. Purpose of Chemistry Chemistry is the study of matter, which includes us and everything around us. Chemistry is an integral part of our lives. Because chemistry is related to many other fields of science and many areas of human endeavor, it is sometimes referred to as the “central science” FOR EXAMPLE: Chemists who develop new substances to improve electronic devices such as solar cells, transistors, and fiber optic cables work on topics that chemistry shares with physics and engineering. Chemists who develop new drugs to be used against cancer or viral diseases work in the common areas of chemistry with pharmacology and medicine.  1-1 Scientific Method What distinguishes science from other studies is the method scientists use to obtain knowledge and the special importance of this knowledge. Scientific knowledge can be used to explain natural events and sometimes to predict future events. The scientific method is a combination of observations, experiments, formulation of laws and hypotheses, and theories.  1-2 Properties of Matter Chemistry is the science that deals with the composition and properties of matter. Matter is an object that occupies space, has a property called mass, and has inertia (the state of an object being motionless or at a constant speed). Composition refers to the components of a sample of matter and their relative proportions within the substance. Example: H2O, 11.19% H and 88.81% O (by mass) The properties of matter can generally be grouped into two groups: physical properties and chemical properties. Physical Characteristics and Physical Changes Physical Change: In a physical change, some physical properties of the substance change, but its composition remains unchanged. Physical Property: It is the property that does not change the composition of the substance. For example, color is a physical property. For example, copper can be beaten into sheets. This feature is non-brittleness (malleability). For example, when liquid water freezes to form solid water (ice) (a physical change), its composition is still 11.19% hydrogen and 88.81% oxygen by mass, although it certainly looks different.  Chemical Properties and Chemical Changes Chemical change or chemical reaction, one or more types of substances transform into new substances with different compositions. A chemical change is a change in the composition of matter. An example is the burning of paper. Chemical Property: It is the ability of a sample of a substance to cause (or not to cause) a change in its composition under certain conditions.  1-3 Classification of Substances Matter consists of very small units called atoms. Substances consisting of a single type of atom are called "elements". IUPAC (International Union of Pure and Applied Chemistry) has defined 120 elements today. Chemical compounds are substances formed by the combination of two or more different element atoms. Scientists have identified millions of different chemical compounds. A molecule is the smallest unit that contains the atoms that make up the compound in the same ratio as in the compound. The water molecule is a three-atomic unit in which two hydrogen atoms are bonded to one oxygen atom.  Classification of Matter The composition and properties of an element or compound are the same throughout a given sample and do not vary from one sample to another. Elements and compounds are called "pure substances".  Classification of Matter Describing mixtures of pure substances: Homogeneous mixtures or solutions: They are solutions with uniform composition and properties throughout the solution. For example; Air is a homogeneous mixture of various gases, mainly nitrogen and oxygen elements. Heterogeneous mixtures: Accordingly, the composition and physical properties may vary from one part of the mixture to another. The composition is not uniform throughout the mixture. Generally, heterogeneous mixtures can be easily distinguished from homogeneous ones. For example; sand and water, the components are separated into different regions.  Heterogeneous mixtures formed by one liquid in another liquid (mixture of two liquids that are insoluble in each other) are called emulsion mixtures. For example; butter, margarine, milk, cream (oil\water mixture). Heterogeneous mixtures formed when a solid is not completely dissolved in a liquid but dispersed into small particles are called suspension mixtures. For example; ayran, cooked Turkish coffee. Heterogeneous mixtures formed by a liquid and a gas are called aerosols. For example; deodorants, mist, sprays Separation of Mixtures: A Physical Process (a) Separation of a heterogeneous mixture by filtration: A mixture can be separated into its components by suitable physical methods. The process of separating a solid from the liquid it is in is known as "filtration".  Separation of Mixtures: A Physical Process b) Separation of a homogeneous mixture by distillation: Distillation is the process of boiling a liquid and separating the resulting vapor from its other component by condensing it again. In simple distillation, a volatile liquid is separated from the non-volatile solid dissolved in it. In fractional distillation, the components of a liquid solution are separated from each other by taking advantage of their different volatilities.  Separation of Mixtures: A Physical Process (c) Chromatographic separation of ink into its components: As water passes over the paper, black ink appears as a dark stain. (d) Water dissolves the colored components of the ink, and these components adhere to different areas on the paper depending on their tendency to adhere to the paper. Another separation method is chromatography. It is a separation technique based on the difference in the tendency of compounds to adhere (adsorb) to the surfaces of different solid materials such as paper and starch.  States of matter Matter generally exists in one of three states: solid, liquid, and gas. Solid In a solid, atoms or molecules are in close contact. Sometimes they have a very regular structure known as crystal. H2O(s) ice Liquid Atoms or molecules in a liquid are further away from each other than in a solid. Liquids are fluid. H2O(l) water Gas In a gas, the distance between atoms or molecules is much larger than in a liquid. H2O(g) vapor Gases expand to fill the container they are in.  1-4 Measuring Matter: SI (Metric) Units Chemistry is a quantitative unit. This means that in many cases we can measure a property of a substance and compare it to a standard that has a known value. The scientific system of measurement is known as the "International System of Units (Systeme Internationale d'Unites)" and is abbreviated as SI. This system is the modern form of the metric system, which is based on the unit of length known as the meter (m). 1 meter is the distance traveled by light in a vacuum in 1/299.792.458 seconds, As a result of this definition, the speed of light in vacuum is exactly 299.792.458 m/s and expressed as approximately 300,000 km per second Quantitative data is numbers-based, countable, or measurable.  Units Basic SI Units Lenght meter, m Mass kilogram, kg Time second, s Derived Units Temperature kelvin, K Force Newton, kg m s-2 Amount of Substance mol, mole Pressure Paskal, kg m-1 s-2 Electric Current ampere, A Energy Joule, kg m2 s-2 Non-SI Units Lenght angstrom, Å, 10-8 cm Volume liter, L, 10-3 m3 Energy calori, kal, 4,184 J Pressure Atm = 1,064 x 102 kPa 1 Atm = 760 mm Hg Comparison of Temperature Charts RELATIVE TEMPERATURES Melting point Boiling point of of ice water  Mass Mass (m) describes the amount of matter in an object. Weight (W) is the gravitational force on an object. W=mxg Gravitational acceleration (g) varies slightly from one place to another on Earth. Although the weight of the object varies from one place to another, its mass is the same everywhere. Volume Volume is defined as the space occupied within the boundaries of an object in three-dimensional space. It is also known as the capacity of the object.  1-5 Using Density and Percent Composition in Solving Questions Density is the ratio of mass to volume. d= m/V (g/mL) Chemists usually express mass in grams and volume in cubic centimeters or milliliters. In general, solids are denser than liquids, and both solids and liquids are denser than gases.  Question * What is the mass of an osmium cube with a side length of 1.25 inches? (1 inch = 2,54 cm) d = 22,48 g/cm3  1-6 Uncertainties in Scientific Measurements Precision: It shows the degree of repeatability of the measured quantity. That is, it indicates the closeness between the results when the quantity is measured several times. Accuracy: Shows how close the measurement value is to the accepted or “true” value. Highly precise measurements are not always accurate; It could be a major systematic error. However, measurements with higher precision are more likely to be accurate than those with lower precision. Systematic Errors: These are errors arising from the structure or nature of measuring instruments Random Errors: These are errors caused by the experimenter's skill and ability in reading a scientific instrument. Both limits can lead to errors and yield results being found to be too high or too low.  1-7 Significant Numbers Since numbers are constantly dealt with in engineering, it is very important to express the numbers correctly. A standard notation should be determined here. 4.567,3 Europe 4,567.3 USA Both representations may mean the same thing. Common notation; 4 567.3  If there is a zero (0) at the end of the whole number, the number is written as an exponent to indicate the number of significant digits. Number of significant digits for 6300 m 6,3 x 103 m If the number after the last digit is less than 5, the last digit is left as is and the following digits are discarded. 54,1875 54,2 54,1275 54,1 For example: 0,016880 1,7 x 10-2 168,80 1,7 x 102