Chapter 1, Lesson 1.pdf

General Chemistry: 201 Chapter 1, Lecture 1  The Study of Chemistry What is Chemistry? Chemistry is the study of the properties and behavior of matter. Matter – anything that occupies space and has mass.  Chemistry: The Central Science Chemistry is often referred to as “The C...

General Chemistry: 201 Chapter 1, Lecture 1  The Study of Chemistry What is Chemistry? Chemistry is the study of the properties and behavior of matter. Matter – anything that occupies space and has mass.  Chemistry: The Central Science Chemistry is often referred to as “The Central Science” because it is key to all other sciences. Chemistry : is the study of matter  Its chemical and physical properties.  Chemical and physical changes it undergoes.  Energy changes of these processes. Macroscopic and microscopic Figure 1-2 p4 Physical Properties Physical Properties can be measured or obtained (Melting Point, Boiling Point, density,..etc) without changing the composition of the material. Physical Properties can be used to separate mixtures Physical Change: Produce a recognized change in the appearance but does not alter the chemical makeup (composition) of a substance. Change is reversible. Ex: Melting of solid ice is a physical change. In this case only change in form takes place and the change is reversible.(water molecules retain its identity) Examples: Qualitative Quantitative Color Density Odor Melting point Taste Boiling point Feel Compressibility  States of Matter Matter exists in three forms: solid, liquid, and gas. Solid Solid: A substance that has a definite shape and volume. Particles are so close together with regular arrangement (crystalline) Liquid: A substance that has a definite volume but that changes shape to fill the container. Liquid Gas: A substance that has neither a definite volume nor a definite shape. Many substances, such as water, can exist in all three states depending on the temperature. The conversion of a substance from one state into another is known as change of Gas state.  Solid, liquid, Gas The three states - the solid state, the liquid state, and the gaseous state - of water are shown in the Figure below. Intensive and Extensive Properties Intensive Property : Independent of the quantity of substance (Ex: color, hardness, melting boiling point, density)) Extensive Property: Depends on the quantity of the substance (Ex: mass, volume, length, weight) What about temperature ???? Intensive properties Chemical Properties Chemical properties: describe the potential to undergo chemical changes Chemical Change: Changes the chemical (composition) of a substance as a result of a chemical reaction. Change is irreversible. Chemical Reaction is a process of rearranging, replacing, or adding atoms to generate a new substance Rusting of iron is a chemical change. Here, iron combines with oxygen and produces a new substance rust. Wood + O2 CO2 + H2O + heat Iron + O2 Iron oxide (rust) Language of Chemistry: Elements Chemical Element: It is the pure substance that cannot be decomposed by ordinary means to other substances. mercury bromine iodine copper cadmium Red phosphorus Language of Chemistry: Pure substance Pure Substance: Involves one component. Uniform in its chemical composition and properties. Sugar and water are pure substances. A pure substance can be a chemical compound or an element Elements names Periodic Table The elements, their names,, and symbols are given on the PERIODIC TABLE Compound/molecule The language of Chemistry: Molecule A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by a MOLECULAR FORMULA H2 O C8H10 N4O2 caffeine Element, compound or mixture? A. a compound B. a mixture of two elements C. a mixture of a compound and an element D. a compound E. an element F. an element G. a mixture of two compounds H. an element I. a compound Classification of Matter Classification of Matter Mixture: Involves more than one substance. Composition and properties may vary. Different amounts of sugar dissolved in water will determine sweetness of water. Sugar & water is an example of a mixture. Homogeneous Mixture: has a uniform composition (one phase) & is called (visibly indistinguishable parts) Ex: Mixture of water and alcohol Heterogeneous Mixture: has a non- uniform Composition (more than one phase). (Visibly distinguishable parts) Ex: Mixture of sand and water Example Which one of these mixture is homogeneous? And Which one is heterogeneous?  CONCEPT CHECK! Which of the following is a homogeneous mixture? Pure water Gasoline Jar of jelly beans Soil Copper metal 24 The classification of matter is summarized in the Fig below. Separation of mixtures Filtration is used to separate liquids from solids. The filter paper retains the solid because the particles of the solid are too large to pass through the pores, or openings, in the paper. Micropore filters, which have pore sizes small enough to retain bacteria, are used to produce sterile water, and sterile pharmaceutical preparations.  Separation of mixtures A distillation apparatus. If two liquids are to be separated, the liquid with the lower boiling temperature will vaporize at a lower temperature and leave the distillation flask before the higher-boiling liquid (depends on volatility). The vaporized liquid leaves the flask and enters the condenser, a long glass tube with a glass jacket surrounding it through which cold water is circulated. There the cooled vapor condenses to a liquid and is collected in the receiving flask. A solution of a solid also can be separated by this technique, in which case the solid remains in the distillation flask. Thin-layer chromatography can separate complex mixtures and allow the identification of each compound. Chromatography Electrolysis of Water - Chemical separation