Chemistry Grade 9 UNIT 1-3 PDF

UNIT 1 CHEMISTRY AND ITS IMPORTANCE TABLE OF CONTENT 1. Definition of chemistry 2. Branches of chemistry 3. Scope of chemistry 4. Role of chemistry in different fields 5. Industry 6. Chemical industry 7. Chemical products  What is chemistr...

UNIT 1 CHEMISTRY AND ITS IMPORTANCE TABLE OF CONTENT 1. Definition of chemistry 2. Branches of chemistry 3. Scope of chemistry 4. Role of chemistry in different fields 5. Industry 6. Chemical industry 7. Chemical products  What is chemistry ? Chemistry is a branch of natural science that deals with properties, composition and structure of substance. Substance is a particular kind of matter with uniform properties. Matter is a physical substance that which occupies space posses rest mass. Property of substance is the attribute , quality or characteristics of a substance. Composition is nature of something’s ingredient or constituent; how a whole or mixture is made up. Structure is the arrangement and relationships between the parts of elements of something complex. Transformation of a substance is a marked change in form , nature or appearance.  What are the 5 branches of chemistry? I. Physical chemistry :-studies macroscopic properties , atomic properties and phenomena in chemical system. II. Organic chemistry :-study of substance containing carbon. III. Inorganic chemistry:-study of substance that are not primarily based on carbon. IV. Analytical chemistry:-study of composition of matter. It focuses on identifying, quantifying and separating chemicals in sample of matter. V. Bio chemistry:- the study of chemical process that are occur in living things.  What is the relationship between chemistry and other natural sciences? 1. Biochemistry:-the study of chemistry processes occurring in living matter. 2. Geochemistry:- the study of the processes that control the abundance, composition, and distribution of chemical compounds and isotopes in geologic environments. 3. Physical chemistry: application of the techniques and theories of physics to the study of chemical systems.  What is the role of chemistry plays in production and in the society? A.Agriculture:- to produce : Fertilizer Pesticides Herbicides Insecticides Fungicides B. Food production :-to discover different type of food preservative. C. Medicine:- to provide different life saving medicine. Disinfectant Analgesics Anesthetics Antibiotic Antiseptic Tranquilizer Chemistry also provide medicines like AZT, Taxol & Cisplatin, Penicillin and etc. D. Building construction materials:- by providing building resources like glass, steel, cement and etc.  What are Some common chemical industries in Ethiopia? Industry: is an economic activity concerned with the processing of raw material and manufacture of goods in factories. Chemical industries: are an industry that comprise the companies that manufacture Inorganic and organic industrial chemicals, explosives, fragrance, agrochemicals and others. Chemical products: are produced in chemical industries that are chemical substance or that contains chemical substance. Example of some chemical industries in Ethiopia  unit 2 Measurement and scientific method Measurement is the comparison of a physical quantity to be measured with a unit of measurement that is, with a fixed standard of measurement. Physical quantity is a physical property that can be measured. The international system(SI) uses a particular selection of a metric unit. SI units can be divided into two those are:- base units and derived units Fundamental or basic physical quantities are physical quantities that can be measured directly or can’t expressed or calculated in terms of any other physical quantity.  They are base for derived units. Base Quantity Name of Unit Symbol 1. Length Meter m 2. Mass Kilogram kg 3. Time Second s 4. Electrical current Ampere A 5. Temperature Kelvin K 6. Amount of substance Mole mol 7. Luminous intensity Candela cd Derived Units All other SI units of measurement can be derived from base units (called derived units). Example: Volume is defined as length cubed and has the SI unit of cubic meter (m3). Quantity Definition of Quantity SI Unit Area Length squared m2 Volume Length cubed m3 Density Mass per unit volume kg/m3 Speed Distance traveled per unit time m/s Acceleration Speed changed per unit time m/s2 Force Mass times acceleration of object kg.m/s2 ( newton, N) Pressure Force per unit area kg/(m.s2)( pascal,Pa) Energy Force times distance traveled kg.m2/s2 (joule,J) In chemistry, prefixes are used to represent powers of ten for units, making it easier to express very large or small measurements. Each prefix has a specific multiplier. Uncertainty of measurement: Whenever you measure something there is always some uncertainty. Cause: The person doing the measurement, the measuring device, the environment were the measurement is being made. There are two types of uncertainty. 1. Systematic uncertainty:- it is mainly the measuring devices problems and causes the values to be too large or too small. This type of uncertainty can be eliminated. 2. Random uncertainty:- caused by the person who made the measurement. It can never be eliminated but can be mitigated. Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other.  Significant figures Significant figures are the number of digits in a value, often a measurement, that contribute to the degree of accuracy of the value. Significant figures have the following rules: 1. Any digit that is not zero is significant. Thus, 845 cm has three significant figures. Example:- 1.234 kg has four significant figures. 2. Zeros between nonzero digits are significant. Example:- 606 m contains three significant figures. 7.0408 has five significant figures  3. Zeros to the left of the first nonzero digit are not significant. Their purpose is to indicate the placement of the decimal point. Example, 0.08 L contains one significant figure. 0.0000349 g contains three significant figures. 4. If a number is greater than 1, then all the zeros written to the right of the decimal point count as significant figures. Example:-2.0 mg has two significant figures. 5. For numbers that do not contain decimal points, the trailing zeros (that is, zeros after the last non zero digit) may or may not be significant. Example:-400 cm may have 1,2 or 3 significant figure.  Scientific Notation: is a way to express very large or small numbers in a compact form, using powers of ten. It simplifies calculations and clearly indicates the scale of values in chemical measurements. It is represented in the form of: where: a is a number greater than or equal to 1 and less than 10. n is an integer that indicates the power of 10 by which a is multiplied.  Scientific method Is a systematic procedure for solving problems and explaining natural phenomena The four steps of scientific method are: Observation and formulating of question and formulation of question Data collection and hypothesis Testing hypothesis Analysis and conclusion  Historical Development of Atomic Theories Early Ideas: The concept of atoms dates back to Indian and Greek philosophers. The term “atom” comes from the Greek word "atomos," meaning indivisible. Plato & Aristotle: Plato and his student Aristotle believed everything was made of four elements: Earth, Water, Air, and Fire. Aristotle opposed the atomic theory, arguing that matter is continuous and divisible. Democritus: Proposed the idea that all matter is composed of tiny, indivisible particles (atoms). His ideas were not widely accepted until the 16th-17th centuries.  Law of Conservation of Mass (Antoine Lavoisier): Mass in an isolated system is neither created nor destroyed but transformed. For example, burning wood results in oxygen, carbon dioxide, water vapor, and ash, preserving mass. Law of Definite Proportions (J. Proust): In a compound, elements combine in constant mass ratios, like hydrogen in water (2:18). Mixtures don't obey this law as they are physically combined, not chemically. Law of Multiple Proportions (J. Dalton): When two elements form multiple compounds, the mass ratios of one element with a fixed mass of the other are small whole numbers. Example: CO (16g O) and CO2 (32g O), ratio 1:2.  John Dalton, an English scientist, proposed the first comprehensive atomic theory based on experimental data. His key idea was that matter is made up of indivisible particles called atoms, which combine in simple whole-number ratios to form compounds. Postulates of Dalton’s Atomic Theory: All matter is made up of small particles called atoms. Atoms are indivisible Atoms of a given element are identical in mass and properties. Atoms of different elements have different masses and properties. Atoms cannot be created or destroyed in a chemical reaction. Atoms combine in simple whole-number ratios to form compounds. In chemical reactions, atoms are combined, separated, or rearranged.  The modern atomic theory evolved from Dalton’s work, incorporating discoveries about subatomic particles and the behavior of atoms in various reactions. Postulates of Modern Atomic Theory: All elements are composed of atoms. Atoms of the same element may have different masses (isotopes). Atoms are divisible into subatomic particles: electrons, protons, and neutrons. Atoms of different elements are different in mass and properties. Atoms of an element combine in simple, fixed ratios to form compounds. In chemical reactions, atoms are neither created nor destroyed. Atoms can combine to form molecules or compounds, which can exist in a variety of states and arrangements. The proton was discovered by Eugene Goldstein through his experiments with canal rays. Goldstein observed that when a high voltage was applied to a gas-filled discharge tube, rays traveled from the anode to the cathode, which were later identified as positively charged particles. These particles were named protons by Ernest Rutherford. Protons have a positive charge (+1) and a mass of 1 atomic mass unit (amu), making them much heavier than electrons. They are found in the nucleus of an atom, contributing significantly to the atom's mass.  Anode rays consist of positively charged particles. They are deflected in the opposite direction to cathode rays when passed through a magnetic or electric field because they have a positive charge. The particles in anode rays are heavier than electrons. The rays travel in straight lines in the absence of external electric or magnetic fields. Anode rays can cause ionization of gases and can affect fluorescent screens, producing a glow when they strike certain materials. The nature or e/m ratio of anode rays depends upon the nature of gas. They consisted of material particles.  The electron was discovered by J.J. Thomson during his cathode ray tube experiments. Thomson observed that cathode rays, when subjected to magnetic and electric fields, were deflected, suggesting the existence of negatively charged particles much smaller than atoms. These particles were named electrons. Electrons have a negative charge (-1) and a very small mass, approximately 1/1836th that of a proton. Electrons orbit the nucleus of an atom, and their movement and interactions play a key role in chemical reactions and electrical conductivity.  Cathode rays consist of negatively charged particles (electrons) Cathode rays are deflected towards the positive pole when placed in a magnetic or electric field due to their negative charge. Cathode rays are made of electrons, which are subatomic particles with a much smaller mass compared to protons. In the absence of external fields, cathode rays travel in straight lines. Cathode rays posses kinetic energy (they travel in the speed of light. Cathode rays are composed of electrons, and their behavior is consistent regardless of the type of gas used in the tube.  Millikan's Oil Drop Experiment : was a groundbreaking experiment conducted by Robert Millikan to measure the charge of the electron. In the experiment, tiny oil droplets were suspended between two electrically charged plates. By adjusting the electric field, Millikan was able to balance the gravitational and electric forces acting on the droplets. This allowed him to calculate the charge on each oil drop, ultimately determining that the charge of the electron is approximately 1.6 × 10⁻¹⁹ coulombs. Millikan’s experiment provided crucial evidence for the quantization of electric charge and confirmed the existence of discrete charges carried by electrons. The discovery of the nucleus was made by Ernest Rutherford through his famous gold foil experiment. In this experiment, Rutherford bombarded a thin gold foil with alpha particles and observed their scattering. While most particles passed through the foil, some were deflected at large angles, suggesting the presence of a small, dense, positively charged region at the center of the atom. This led to the conclusion that the atom consists of a tiny, dense nucleus surrounded by mostly empty space, with electrons orbiting outside. This discovery reshaped our understanding of atomic structure and led to the development of the modern nuclear model of the atom. The neutron was discovered by James Chadwick in 1932. Through experiments involving the bombardment of beryllium with alpha particles, Chadwick observed the emission of neutral particles with a mass similar to protons. These neutral particles were identified as neutrons. This discovery completed the understanding of the atom's nucleus, showing that it contains both protons and neutrons, with neutrons contributing to the mass of the atom without carrying a charge.  Atomic Model Dalton thought of atoms as solid indivisible and indestructible spheres. Dalton’s model was called billiard ball model.  J.J. Thomson’s plum pudding model (1897) proposed that the atom is a positively charged sphere with negatively charged electrons embedded within it, like "plums" in a "pudding." This model explained the presence of electrons and the atom's overall neutrality. However, it was later proven incorrect by Ernest Rutherford’s gold foil experiment, which showed that the atom has a small, dense nucleus. Despite its flaws, Thomson’s model was a key step in the development of atomic theory, leading to the nuclear model of the atom. Rutherford's atomic model was based on the results of his gold foil experiment. He discovered that atoms have a small, dense nucleus at their center, which contains positive charge and most of the atom's mass. Rutherford found that when alpha particles were directed at a thin sheet of gold foil, most passed through, but a few were deflected at large angles. This indicated that the positive charge of an atom is concentrated in a tiny nucleus, with the rest of the atom being mostly empty space. Rutherford's model called planetary or solar system model, replaced the earlier Thomson model and led to the understanding that the atom is composed of a central nucleus, surrounded by electrons that move in the surrounding space. This model laid the foundation for later developments in atomic theory, including the Bohr model.  Proposed on atomic model in which the electron move around the nucleus in fixed circular path call orbit. He also introduced terms like: Shells, energy levels, 2n2 rules. Cont. Maximum electron accommodated by main energy level or shell is given by the general formula of 2n2 , where n is main energy level.  The quantum mechanical model of the atom is a probabilistic model that describes the likely locations of electrons in an atom. This model introduced the sub-level for each main energy level of the known atoms. s,p,d,f Orbital is a region where the probability of finding an electron is at maximum Number of orbitals = n2 Maximum electron accommodated in any orbital= 2