Gen Chem (1) PDF

L1.1: PARTICULATE NATURE OF MATTER CONTINUITY OF MATTER - Since matter is not void, this means that it is As wood is sawn into pieces, fine specks of divisible and can be cut into pieces over and dust are...

L1.1: PARTICULATE NATURE OF MATTER CONTINUITY OF MATTER - Since matter is not void, this means that it is As wood is sawn into pieces, fine specks of divisible and can be cut into pieces over and dust are produced. These are too small to be seen over again by our naked eyes but they have unique - This started the principle of continuity of arrangement and motion. matter, wherein matter can be broken down into pieces and as you do so, you will not be All kinds of matter are particulate in nature. able to obtain its smallest parts. These particles may be in the form of molecules, atoms, or ions. Atoms are the building blocks of CONTINUITY OF MATTER matter - Leucippus and Democritus thought that all materials are made up of tiny bits of matter MATTER which cannot be divided further. - It is anything that has mass and volume - Greeks referred to this as atom (Greek word - Ancient Greek philosophers were the first to - atomos, meaning indivisible). speculate the nature of matter - They only speculated on the nature of materials around them as they weren’t able to conduct experiments that will validate their assumptions ANCIENT VIEWS ON MATTER a. Materials are made up of one primal matter (Empedoclean Elements) CONTINUITY OF MATTER Discontinuity of Matter b. According to Aristotle, all space is filled up - Matter is made up of particles instead of a with matter, implying that there are no primal material. empty spaces. He described each element as a balance between two quantities Four Main Ideas 1. Matter is composed of discrete particles. 2. There is an empty space between particles of matter. 3. The particles of matter are in constant motion. 4. There are forces that act between the particles. 1. DISCRETE PARTICLES OF MATTER 4. FORCES BETWEEN PARTICLES - A block of wood, can easily be observed as - Intermolecular forces or forces that exist hard, and based on its internal composition, between particles may be attractive or it is made up of compact particles. repulsive. 2. EMPTY SPACE BETWEEN PARTICLES - The particles that make up matter have spaces in between them. - These spaces may be little or huge, depending on the kind of matter. - The water particles (inside) attract one another. - The glass particles and the water particles (outside) repel one another. PARTICULATE NATURE OF THE THREE STATES OF MATTER 3. MOTION OF PARTICLES - The spaces between particles dictate the kind of movement that particles in matter can do. - As temperature increases, particles gain kinetic energy which results in their fast movement. a. SOLID L1.2: PROPERTIES OF MATTER - Solids are like military units. The particles are rigid and close to one another. What is the first thing you notice when you hold and read a book? Is it hard or soft? Is it heavy or light? The notable characteristics of the book are known as its properties. MATTER - It is anything that occupies space and has mass GENERAL PROPERTIES OF MATTER 1. MASS b. LIQUID - Mass is the amount of matter in an object - Liquids are like people in a reunion party. - The more matter is present in an object There are small, random motions but people means the greater its mass. are close to one another. - It is usually expressed in grams (g) or kilograms (kg) - Materials that are compact have relatively greater mass than those with a hollow interior. 2. WEIGHT - It is the measure of force that acts on an object. - It is expressed as the amount of matter (mass) multiplied by the gravitational force that acts on it. ○ The greater the gravitational force c. GAS that acts on an object, the “heavier” - The arrangement of particles in gases are it weighs. similar to a soccer ball game. Players are - It is expressed in newtons (N). far apart and are arranged randomly, creating huge spaces between them. NOTE: Mass and weight are often interchangeable, but these are two different quantities. 3. VOLUME - It is the amount of space occupied by matter - It can be measured using instruments with graduations or by getting the dimensions of the object. - It is expressed in liters (L) for liquids, or cubic length (l3)for solids.  3. BOILING POINT - It is the temperature at which liquid evaporates. - The vapor pressure is equal to the pressure of its surrounding liquid at this temperature. 4. SOLUBILITY - It is the ability of a solute to dissolve in a given solvent. 4. DENSITY - It varies depending on its composition. - It is the ratio between mass and volume. - It is considered as a physical property as - It is expressed in kilograms per cubic meter one can tell whether a material is soluble or (kg/m3) or grams per cubic centimeter not by merely observing its physical (g/cm3). appearance. - It tells how compact an object is. ○ An object with greater mass has These properties may further be classified more compact particles than the as intensive or extensive. These are based on lighter ones. whether a physical property depends on the amount of matter or not. 5. SPECIFIC GRAVITY - It is the ratio of a substance’s density to a a. INTENSIVE PROPERTY standard substance. - These properties do not depend on the - It is also known as relative density. amount of matter. - It is a dimensionless quantity. - Color, Density, Boiling point, Melting point, - Water at 4oC, which is at its densest, is Freezing point commonly used as a standard for comparison of liquids and solids. b. EXTENSIVE PROPERTY - Air at room temperature (20oC) is the usual - These properties depend on the amount of standard for comparison of gases. matter. - Mass, Volume PHYSICAL PROPERTIES - These are qualities that are readily REMEMBER: Physical properties of matter may be observable or measurable without changing categorized as intensive or extensive based on its the matter’s composition. dependence on the amount of matter. - General properties such as mass, volume, weight, density, and specific gravity are all METALLIC PROPERTIES examples of physical properties. - These are qualities that are observed - These are often used to describe or observe specifically in metals. matter. 1. CONDUCTIVITY 1. MELTING POINT - It is the ability of a material to allow heat or - It is the temperature at which a solid matter electric charges to pass through easily. changes to liquid. - Materials can be thermal or electrical - It varies according to its composition of conductors. materials. 2. MALLEABILITY 2. FREEZING POINT - It is the ability of a material to be flattened - It is the temperature at which a liquid turns into thin sheets. into a solid matter.  3. DUCTILITY NOTE: The ease and rate of how an object burns is - It is the ability of a material to be easily the main difference between combustibility and drawn into wires. flammability. Not ALL combustible materials are flammable. REMEMBER: Qualities that are readily observable or measurable without changing the matter’s 3. REACTIVITY composition are known as physical properties. - It is the tendency of a substance to undergo a chemical change. CHEMICAL PROPERTIES - It depends on the chemical structure and - These are the characteristics that can only composition of the substance. be seen when the chemical identity of a Fluorine: most reactive element material is altered. Noble Gases: little to no reactivity - These become evident when a material undergoes a chemical change. REMEMBER: The characteristics that can only be - These highly depend on its composition. seen when the chemical identity of a material is altered are known as chemical properties. 1. BIODEGRADABILITY - It is the capacity of a material to decompose through the actions of microorganisms. - It is observed when a material undergoes decomposition. ○ Organic materials or carbon-based materials have a higher biodegradability compared to the synthetic ones. - Below is the approximate time for common materials to decompose in marine and terrestrial environments: L1.3: PURE SUBSTANCES AND MIXTURES The world offers variety in terms of materials. There are materials that are pure in terms of its composition, like water. Others are combinations of two or more substances. For 2. COMBUSTION example, the atmosphere is made up of different - It is a chemical reaction between a gases. substance (fuel) and oxygen which results in the generation of heat and light in the form of flame. Combustibility: It is the ability of a material to combust or burn. Flammability: It is the ability of a combustible material to catch flame easily. MATTER - Can be classified according to its state or phase Solid Liquid Gas - Can be classified according to its properties General properties Physical properties Metallic properties Chemical properties PERIODIC TABLE OF ELEMENTS - Can be classified according to its - It is the arrangement of all known elements composition according to their chemical properties. Pure substances - It is a useful tool that can help in identifying Mixtures elements that exhibit similar properties PURE SUBSTANCES - It is classified into 3 categories: - It is a kind of matter with a definite or fixed composition a. METALS - It is made up of a specific number of atoms - Leftmost of the periodic table or groups of atoms that are combined - Has the following general properties: through a chemical reaction solid at room temperature - It has definite physical and chemical lustrous properties malleable ductile heat/electricity conductors DID YOU KNOW? Mercury is the only metal that is liquid at room temperature. It is a shiny, silvery liquid metal that forms beads due to its high surface tension. Mercury is also known as quicksilver due to its appearance and mobility. ELEMENT - It is the simplest form of matter b. NONMETALS - It is made up of only one kind of atom - Rightmost of the periodic table - Elements of different kinds also differ in the - Has the following general properties: atoms that make them up opposite of metals - It cannot be decomposed into simpler forms gaseous or dull solids by physical or chemical means poor conductors of heat and - Elements react with one another to form a electricity new substances - 118 elements known to exist arranged in the DID YOU KNOW? Bromine is the only nonmetal Periodic Table of Elements that exists in liquid form at room temperature. ○ 94 of these are naturally occurring ○ 24 of these are synthetic  c. METALLOIDS - Compounds may be classified according to - Staircase-like line between metals and the specific elements present nonmetals in the periodic table - Exhibit properties of both metals and 1. ORGANIC COMPOUNDS nonmetals - Contain carbon and hydrogen - Conducts heat and energy but not as good - Carbohydrates, proteins, lipids, etc. as how metals act as conductors, therefore referred to as semiconductors 2. INORGANIC COMPOUNDS - Do not contain carbon-hydrogen bonds DID YOU KNOW? Silicon and germanium are - CO2, H2O, NaCl metalloids that are widely used in the manufacture NOTE: The properties of elements that make up a of computer chips. compound are different from the properties of the compound formed. COMPOUNDS Sodium chloride (NaCl) or table salt: one Na - They are composed of two or more different atom and one Cl atom elements that are combined in a fixed ratio Its constituent elements are harmful and by a chemical reaction toxic MIXTURES - They consist of two or more pure substances that are combined physically - There is no chemical reaction between the components - Components retain their characteristic properties when mixed together each component has the same chemical makeup it had before the mixture is formed - Many compounds are found in the - They do not have definite proportions and environment definite properties - Some compounds are formed when an - Properties depend on the substances that element reacts with another element are present in it - Some compounds, however, are products of - Mixtures may be further classified as chemical reactions between two or more homogeneous or heterogeneous compounds - Chemical bonds cannot be broken easily a. HOMOGENEOUS MIXTURE - Unlike elements, compounds can be broken - consists of substances that are evenly down into simpler forms by chemical means distributed all - throughout - the components cannot be distinguished from each other by the naked eye - also known as solution, which is composed of two components: 1. Solute: the substance that is dissolved by another substance; exists in smaller amounts 2. Solvent: the dissolving medium in which the solute dissolves; most abundant  Soluble: when substances dissolve L1.4: ELEMENTS AND COMPOUNDS in a given solvent Miscible: when liquids are soluble in Matter can be classified based on its each other at all proportions composition. They can be classified as pure substances or mixtures. Pure substances can be further classified as elements or compounds. Elements and compounds both have definite composition and exhibit specific properties. b. HETEROGENEOUS MIXTURE - consists of substances that are not evenly PURE SUBSTANCES distributed all throughout - a kind of matter with a definite or fixed - the components can be distinguished from composition each other by the naked eye - made up of a specific number of atoms or - can be further classified as colloids or groups of atoms that are combined by a suspensions chemical reaction 1. Colloids - has definite physical and chemical - a heterogeneous mixture with properties particles that are bigger than those - classified into elements and compounds in a solutionn but smaller than those in a suspension - particles do not settle at the bottom even after being left to stand for a long time - exhibit Tyndall effect, or the phenomenon where light is scattered 2. Suspensions ELEMENT - a heterogeneous mixture with - the simplest form of matter suspended particles that are large - made up of only one kind of atom enough to be seen by the naked eye - elements of different kinds also differ in the - particles settle at the bottom of the atoms that make them up container due to gravity COMPOUNDS REMEMBER: To easily distinguish the types of - composed of two or more different elements mixtures, always refer to the uniformity of its that are combined in a fixed ratio by a appearance. Homogeneous mixtures have a chemical reaction uniform appearance while heterogeneous mixtures are not uniform in terms of its appearance.  Both elements and compounds participate SYMBOL: two letters of the common name of in chemical reactions to form new compounds. element Compounds that are physically combined form another kind of matter known as mixtures. PURE SUBSTANCES VERSUS MIXTURES SYMBOL: two letters from their Latin names All matter, whether they are elements, compounds, or mixtures, are made up of tiny particles called atoms. However, the atoms that compose each kind of matter vary in proportion. ELEMENTS - cannot be decomposed into simpler forms DID YOU KNOW? Four new elements have been by physical or chemical means officially added to the periodic table of elements in - react with one another to form a new June of 2016. The four new elements namely substances Nihonium (symbol Nh, atomic number 113), - 118 elements known to exist arranged in the Moscovium (symbol Mc, atomic number 115), periodic table of elements Tennessine (symbol Ts, atomic number 117), and Oganesson (symbol Og, atomic number 118) were CHEMICAL SYMBOL FOR ELEMENTS officially added to the periodic table by the - each element has a symbol that is used International Union of Pure and Applied Chemistry around the world (IUPAC) after a five-month public review period. - symbols for elements may have one letter or two The periodic table of elements is the arrangement of all known elements according to SYMBOL: first letter of the common name of their chemical properties. element PERIODIC TABLE OF ELEMENTS - a list of all known elements in a tabulated form - elements are arranged in such a manner so that elements with similar properties are close together - “periodic” - properties repeat themselves every few elements - each entry: symbol of element + name + METALLOIDS/SEMIMETALS atomic number + atomic mass - exhibit properties of both metals and - elements arranged in rows and columns nonmetal columns: groups, rows: periods - conducts heat and electricity but not as - elements with similar properties are good as how metals act as conductors arranged in the same group - semiconductors (a material that can conduct - shows the division of elements to metals, some electricity better than an insulator) nonmetals, and metalloids - some can conduct electricity as much as metals REMEMBER: The periodic table of elements is a useful tool in identifying elements that exhibit COMPOUND similar properties. - a pure substance that is made up of different elements CLASSIFICATION OF ELEMENTS - atoms are joined together by chemical METALS bonds General properties: - has a definite composition wherein its - lustrous solid at room temperature (except constituent elements always occur in the Hg, which is liquid) same proportion - hardness and tensile strength - ductility and malleability - good heat/electricity conductors - high melting point/boiling point NONMETALS General properties: - either solid or gas at room temperature (except Br2 which is liquid) CHEMICAL REACTION - brittle and dull solids - the process of creating compounds - poor conductors of heat and electricity - chemical change - low melting and boiling points - results in the formation of a new substance (products) with a different identity from the elements or compounds that constitute it (reactants) - kinds: exothermic or endothermic EXOTHERMIC REACTION INORGANIC COMPOUNDS - a chemical reaction that gives off heat (i.e. - a class of compounds lacking combustion reaction) carbon-hydrogen bonds - everything else except carbon comprise most of Earth’s crust ENDOTHERMIC REACTION - a chemical reaction that absorbs heat as it occurs, allowing it to produce new compounds (i.e. photosynthesis) REMEMBER: Organic compounds are those that contain carbon atoms bonded to elements like H, O, and N. Inorganic compounds are those without the element carbon. CATEGORIES OF COMPOUNDS - may be categorized based on the presence IONIC COMPOUNDS of the element carbon: organic or inorganic - compounds that exhibit ionic bonding - may be categorized based on the type of - electron transfer bonding between the constituent elements: - made up of positively charged species ionic or covalent (cations) bonded to negatively charged species (anions) ORGANIC COMPOUNDS - a class of compounds in which one or more carbon atoms are bonded to other elements, most commonly hydrogen, oxygen, or nitrogen - all living things are composed of organic compounds - not all carbon-containing compounds are organic COVALENT COMPOUNDS - compounds that exhibit covalent bonding - electron sharing  MEDICINE PRODUCTS - A food supplement is any substance that is ingested in order to make up for one’s nutrient deficiency or to augment one’s dietary consumption. - This substance can be taken in the form of pills, tablets, pastilles, ampoules, powder in sachets, or liquid drink. HOW ARE CHEMICAL SYMBOLS WRITTEN FOR - Some medicine products are for topical COMPOUNDS? administration or application on a certain - can be represented by chemical formula part of the body. - a combination of chemical symbols of Antibacterial ointments elements that constitute the compound Medicinal soaps - For example, sodium chloride has a - Antiseptics or antimicrobial medicines used chemical formula to prevent infection of wounds.(e.g. agua NaCl (1:1 ratio of Na and Cl). oxigenada, povidone-iodine) - For example, carbon dioxide has a chemical - Aspirin contains an organic compound, formula acetylsalicylic acid, which has CO2 (1:2 ratio of C and O) anti-inflammatory properties. - subscript - to indicate the number of atoms - Antacids are medicines taken to neutralize of a given element the acid in the stomach. FOOD PREPARATION PRODUCTS - Examples: salt, sugar, vetsin (msg) - Other examples of common condiments that are used for food preparation. - Soybean oil, canola oil, and olive oil are all examples of cooking oil that contains fatty acid compounds. REMEMBER: To easily determine the elements CLEANING PRODUCTS that make up a certain compound, always refer to - Cleaning products are chemical products the combination of the element symbols used in the that are used to remove dirt on hard chemical formula of the compound. surfaces. - The purpose of these products is to eliminate dirt such as dust, foul odor, and stain. L1.5: CHEMISTRY OF COMMERCIAL - These products contain elements and PRODUCTS – PURE SUBSTANCES compounds that are known to have cleaning properties. Chemical products are materials that - Bath soaps are a mixture of alkali which can contain chemical substances that are manufactured be sodium hydroxide or potassium and processed for specific purposes such as hydroxide and oils. medication, food preparation, cleaning and - Detergent and bleach both contain maintenance, fuel resources, and construction. compounds with cleaning properties. MAINTENANCE PRODUCTS L2.1: HOMOGENEOUS AND - Maintenance products are used for HETEROGENEOUS MIXTURES servicing, repairing, and restoring various materials or equipment to keep them from Mixtures are a classification of matter which is functioning. made up of two or more pure substances that can Lubricants are oils that are used to have varying compositions. reduce the friction on surfaces of objects that are in contact. There are two classifications for matter Paints are pigmented liquids that are based on composition and properties: used to color or protect the surface Pure Substances of an object. Mixtures - Lubricants and paints as maintenance products. PURE SUBSTANCES - A pure substance cannot be further broken COMPARING CONSUMER PRODUCTS down or purified by physical means. - There are various consumer products that - Each substance has its own characteristic are being offered in the market. properties that are different from the set of - Each product claims to be effective and properties of any other substance. cost-efficient. - However, it is important to consider the MIXTURES components of the chemical products you - Mixtures are combinations of two or more are using to determine whether it is safe, pure substances in which each substance effective, and cost-efficient. retains its own composition and properties. - It is important to consult nutritionists and - In a mixture, substances do not react with experts in consuming food supplements and each other. undergoing certain diets. - Topical medicines like ointments indicate the amount of active ingredients they contain per a specific gram of it. - Chewable antacid tablets with sodium bicarbonate are often administered for fast relief of hyperacidity. - However, for a longer-lasting benefit, milk of magnesia is administered to those who suffer from recurring hyperacidity. - In choosing condiments, always read the REMEMBER: In any mixture, the composition can product label and determine if it contains be varied and each component of the mixture harmful artificial color and flavoring. retains its own properties. REMEMBER: Before purchasing any consumer A mixture can be classified based on the products, it is necessary to compare them on the distribution of the components: basis of their components for use, safety, quality, Homogeneous Mixtures and cost. Heterogeneous Mixtures HOMOGENEOUS MIXTURE SOLUTIONS - It is also referred to as solution. - In a solution, one component is uniformly - It is a combination of two or more dissolved and scattered in another substances that cannot be distinguished component to form a homogeneous from each other. composition. - It has uniform composition and properties. - It consists of two components: the solvent and the solute. SOLVENT - is the one that is more abundant in solutions. It is the dissolving medium. SOLUTE - the component present in less amount in a solution. It is the substance being dissolved. Other examples of solutions include: - When a solute dissolves in a solvent, the - saltwater; solute particles break apart into very small - some alloys, which are homogeneous pieces and get evenly distributed in the bulk mixtures of metals in the solid-state; and of the solution. - air (free of particulate matter or mists). - The particles of a solution are too small to be seen by the naked eye and to be HETEROGENEOUS MIXTURE distinguished from each other. - It is a combination of two or more substances that can be distinguished from REMEMBER: Homogeneous mixtures are mixtures each other. whose components are evenly distributed and - It has varying composition and properties. cannot be distinguished from one another. They are - It can be further classified either as also called solutions. suspensions or colloids. LIQUID SOLUTIONS SOLID SOLUTIONS Other examples of heterogeneous mixtures include: - mixtures of salt and pepper (in which two components with different colors can be distinguished easily from each other by sight), - foggy air (which includes a suspended mist of water droplets), and - vegetable soup. GASEOUS SOLUTIONS TYPES OF COLLOIDS - Gaseous solutions are solutions wherein the Colloids, like solutions, can be classified solvent is in the gaseous phase. based on the physical state of the dispersing - Air is an example of a gaseous solution, medium. They can be classified either as gaseous when it is free of particulate matter or mist. colloids, liquid colloids, or solid colloids. - The components of a heterogeneous mixture are visually distinct from each other. GASEOUS COLLOIDS - It can have two or more phases. - A solid aerosol is formed when the - Heterogeneous mixtures can be further dispersed phase is a solid. An example of a classified based on the distribution of its solid aerosol is smoke. components—namely suspensions and - Smoke contains solid particulate matter or colloids. very small particles that are dispersed in the air. SUSPENSIONS - A liquid aerosol is formed when the - A suspension is a heterogeneous mixture dispersed phase is a liquid. whose solutes do not completely dissolve - Deodorant spray is an example of a liquid and its particles settle into clumps or layers aerosol, where the liquid deodorant solution when left undisturbed. is suspended in the air when it is sprayed. - A separate, distinct layer from the solvent will be formed when the solute settles due LIQUID COLLOIDS to gravity. - A solid disperse phase suspended in a - Particles of a suspension are larger than liquid is called a liquid sol. An example of particles of a solution. liquid sol is ink. - The solid insoluble pigments are suspended in a liquid organic solvent in an ink. On the other hand, a liquid suspended in another liquid is called an emulsion. - Milk is an example of an emulsion as liquid fats and proteins are dispersed in water. A gas suspended in a liquid is called a liquid foam. Mud in water is an example of suspension. When - One example is shaving foam. mud is mixed with water, it is initially hazy. Mud - Air is dispersed in the liquid soap medium to settles at the bottom. They form distinct layers. form the foamy texture in shaving foam. COLLOIDS SOLID COLLOIDS - A colloid is a heterogeneous mixture whose - A gas dispersed in a solid is called a solid solute-like particles are dispersed in a foam. Styrofoam is composed of gas medium. suspended in a solid polymer matrix of - It is made up of a dispersed phase polystyrene. (solute-like particles) and a dispersing - A liquid suspended in a solid is called a gel. medium (solvent-like medium). An example of a gel is Jell-O. - The dispersed phase particles are very light - Liquid water molecules are dispersed in a and minute enough to stay suspended in solid gelatin matrix. the dispersing medium for a long time, - A solid suspended in another solid is called unlike the large particles that settle in a solid sol. suspensions.  - Colored glass is an example of a solid sol TIPS: When differentiating between homogeneous because insoluble solid pigments are and heterogeneous mixtures, you should first look suspended in the solid matrix of the glass. for uniformity. If the mixture has only one phase, it is a HOMOGENEOUS MIXTURE (solution). If it has REMEMBER: Heterogeneous mixtures are two or more phases, it is a HETEROGENEOUS mixtures of two or more phases combined together MIXTURE. with varying composition and properties. The components are visually distinct from each other. A heterogeneous mixture can be classified either as a suspension or colloid. L2.2: SEPARATION OF MIXTURES SOLUTIONS, SUSPENSIONS, AND COLLOIDS Separation techniques for mixtures depend - In a SOLUTION, its particles are very small on its composition. These techniques usually take that they cannot be seen by the naked eye. advantage of the differences in the physical and - In a SUSPENSION, the particles are very chemical properties of substances in a mixture. large that they can be distinguished by the naked eye. MIXTURES - In between the particle size of solutions and - are combinations of two or more pure suspensions are COLLOIDS. substances in which each substance retains its own composition and properties. TYNDALL EFFECT - Light is not blocked by the particles of a They can be classified into two: solution. HOMOGENEOUS MIXTURES - It is a combination of two or more substances that cannot be distinguished from each other. It has uniform composition and properties. HETEROGENEOUS MIXTURES - It is a combination of two or more substances that can be - Light is blocked by the particles of distinguished from each other. suspension. Heterogeneous mixtures can be further classified either as suspensions or colloids. A SUSPENSION is a heterogeneous mixture whose solutes do not completely dissolve and its particles settle into clumps or layers when left undisturbed. A COLLOID is a heterogeneous mixture - Light is dispersed by the particles of whose solute-like particles are dispersed in colloids. a medium. SEPARATION OF HOMOGENEOUS MIXTURES 4. The solvent is moderately volatile and its EVAPORATION boiling point is lower than the melting point - In this process, a solution is heated until it of the solute. boils. - Once it boils, the liquid solvent starts to REMEMBER: In recrystallization, the solute must evaporate and leave behind the solid be soluble in the chosen solvent at high solutes. temperatures, but only sparingly soluble at room temperature. RECRYSTALLIZATION - Recrystallization can be used to separate solutions. - Crystals are allowed to form at lower temperature. - It is a separation technique based on the difference in solubilities of substances in an appropriate solvent at an elevated temperature. (SOLUBILITY refers to the amount of substance that can be dissolved in a given solvent at a certain temperature) This is a distillation setup used on separating - This method requires dissolving the solid components of liquid solutions. compound in an appropriate solvent at an elevated temperature, which increases the DISTILLATION solubility of the solute. - Distillation separates components of a - This separates the solute of interest with solution based on differences in boiling another solute which has low solubility in points between the two liquid components. the solvent. TYPES OF DISTILLATION 1. Simple distillation is used when there is a large difference in the boiling points of the components of the solution. 2. Fractional distillation is used when there is a relatively small difference in the boiling points of the components of the solution. 3. Vacuum distillation is used for compounds with very high boiling points. 4. Steam distillation is used for compounds CHARACTERISTICS OF AN IDEAL SOLVENT IN that are heat-sensitive. RECRYSTALLIZATION 1. The solute must be soluble at high temperatures but only sparingly soluble at room or lower temperatures. 2. The impurities must be insoluble in the solvent. 3. No reaction must occur between the solute and the solvent. PARTS OF A DISTILLATION SETUP - These two phases must have opposite polarities. BASIS OF SEPARATION - The separation is determined by the two competing processes: the adsorption onto the stationary phase and the solubility in the mobile phase. - Solutes that have high solubility in the mobile phase will go along with the mobile phase as it travels on the stationary phase. DISTILLING FLASK - Distilling flask is the laboratory glassware CLASSIFICATIONS OF CHROMATOGRAPHY that is used to contain the mixture that will Chromatography can be classified based on the be distilled. polarity of its phases. - In NORMAL-PHASE CONDENSER CHROMATOGRAPHY, the mobile phase is - Condenser aids in the condensation of the nonpolar and the stationary phase is polar. vapors or the change of vapors to liquids. - In REVERSED-PHASE CHROMATOGRAPHY, the mobile phase is DISTILLATE polar and the stationary phase is nonpolar. - Product of distillation - The pure substance with the lower boiling TIP: Use the mnemonics NPSP for Normal Phase point. Stationary phase Polar. RESIDUE Chromatography can also be classified based on - The substance that remains in the distilling the structure of the stationary phase. flask after distillation. - In COLUMN CHROMATOGRAPHY, the stationary phase is held in a column. REMEMBER: There must be a large difference in - In PLANAR CHROMATOGRAPHY, the the boiling points of the liquid components in order stationary phase is supported on a flat plate. to perform distillation as a separation technique for PAPER CHROMATOGRAPHY liquid mixtures. - In paper chromatography, as the mobile phase runs through the paper upwards, the CHROMATOGRAPHY components of the ink solution separate into - is a separation technique that relies on the its component dyes. differential partition of the components - The result of a chromatography experiment between the two important phases in is called a chromatogram, which is a visual chromatography. record of the result of the separation process. PARTS OF A CHROMATOGRAPHIC SETUP - The mobile phase is the solvent in chromatography that carries the components throughout the stationary phase, which is an adsorbent material that holds the solutes still when interactions are favored. SEPARATION OF HETEROGENEOUS MIXTURES MANUAL PICKING - Manual picking using your hands or tongs can be done in separating the components of these kinds of mixtures. The coffee grounds collected on the filter paper is known as the residue while the brewed coffee is known as the filtrate. FILTER PAPER - The filter paper to be used in filtering suspensions can be prepared in two manners: - filter paper is used when the solids are to be SIEVING collected. - exploits the difference in particle size of solids. - A fluted filter paper is used when the filtrate is to be collected. MAGNETS - can be used to attract magnetic materials. SEDIMENTATION - is the process in which suspended solids will eventually separate from liquids by gravity. - Once the solid particles settle at the bottom, the liquid may be separated through decantation. FILTRATION - a process of separating solids from liquids by allowing the mixture to pass through a filtering material.  - An easier way to separate immiscible liquids is by using a separatory funnel. - It is used to separate two liquids with After the process, the solid particles are separated different densities. from the liquid as they accumulate at the bottom of the container. - The liquid can then be decanted to separate the solids from the liquid. - Different liquids with different densities can be separated into layers using centrifugation as well. - The layers can be separated from one another. TIP: When choosing the separation method to be done on mixtures, you have to first know what type of mixture it is (homogeneous or heterogeneous). CENTRIFUGATION You must also know the phases of its components - is a process in which the suspension or when separated from the mixture. colloid is rotated at very high speeds. It uses a machine called a centrifuge that SOME IMPORTANT APPLICATIONS OF rotates the sample. MIXTURE SEPARATIONS - In the chemical and pharmaceutical industry, separation techniques are used to purify chemicals to acceptable standards. - In the petroleum industry, distillation is often used as a method to purify products. A refinery is an industrial site that is used to refine substances like oil, alcohol, and other substances. - In the wastewater industry, separation Initially, the particles are randomly dispersed in the techniques such as sedimentation, medium. centrifugation, microfiltration, and distillation are used to recover water from used water. - In the field of health and medicine, centrifugation is used to separate the  components of blood or urine for further b. Compound: is a combination of laboratory testing. elements formed by chemical bonds L2.3: DIFFERENTIATING MIXTURES AND DIFFERENTIATING COMPOUNDS AND COMPOUNDS MIXUTRES IN TERMS OF COMPOSITION Oftentimes, students confuse compounds a. CLASSIFICATION OF MATTER with mixtures. To further understand the difference - Pure Substances: Compounds are pure between the two, let’s look at the preparation of substances. Atoms of the elements form your morning coffee. bonds to combine and make up a molecule of a compound. A compound has a uniform Table sugar, or sucrose, is a molecule distribution of these molecules, and atoms composed of two monosaccharides, glucose and of different elements are chemically fructose, bound by a covalent bond. Its molecular combined together in a fixed whole number formula is C12H22O11. It is an example of a ratio. It is represented using its chemical compound formula that represents the symbols of its constituent elements and the number of Compounds are always a single pure atoms of each element in one molecule of substance. It is comprised of only one type of the compound. molecule, no matter how big or complex that - Mixtures: The composition of mixtures can molecule is. Table sugar is not a mixture, because be varied as the ratio of its constituent pure its constituents are not physically combined but substances is not fixed. Mixtures are not chemically combined. represented by a certain formula, unlike compounds. It is often possible to see the MATTER components of a mixture and differentiate - defined as anything that occupies space them visually. and has mass - can be classified into two: b. PHYSICAL AND CHEMICAL a. Pure Substances PROPERTIES b. Mixtures - Pure Substances: Chemical changes result in the formation of compounds with vastly different chemical and physical properties from the elements that constitute them. - Mixtures: Mixtures do not have specific, consistent chemical and physical properties of their own. They only reflect the properties of their constituent substances. c. MASS RATIOS - Pure Substances: Compounds have definite mass ratios. The law of definite PURE SUBSTANCES composition states that a given chemical - any matter that has a fixed composition compound always contains its component having its own chemical identity and elements in a fixed ratio (by mass) and does properties not depend on its source and method of - can be further classified into two: preparation. a. Element: is the simplest form of - Mixtures: Mixtures can be composed of matter varying amounts of substances. They have  a variable mass ratio depending upon what solvent. For example, powdered chocolate quantities of ingredients have been drink dissolves faster in water when stirred. combined in the mixture. Heating involves raising the temperature of the solvent to be able to extract the d. PREPARATION OF COMPOUNDS components of the solute. It allows the - Pure Substances: A chemical reaction is a solute to be better dissolved in it. One process by which the atoms of one or more example of this is when you prepare brewed substances are rearranged to form different coffee or tea. Crushing, or reducing the substances. These are signaled by particle size of a solid solute, will also help observations like change in color or increase the rate of dissolving of solids in temperature, formation of insoluble solids, liquids. Smaller particle sizes will enable the and effervescence. solute to come into contact more often with - Mixtures: Mixtures are prepared based on solvent particles, making it easier for them its type. A homogeneous mixture is a to dissolve. Heterogeneous solid-liquid combination of two or more substances that mixtures are formed when the solid is cannot be distinguished from each other. It naturally insoluble in the liquid and yet they has uniform composition and properties. A are mixed together. These heterogeneous heterogeneous mixture is a combination of mixtures either form a suspension or a two or more substances that can be colloid. In a suspension, components distinguished from each other. It has varying separate over time and two phases. composition and properties. Some solid Preparing colloids requires solid particle homogeneous mixtures are prepared by sizes to be small enough to be dispersed, melting the components first before mixing and stabilizing agents to prevent separation them together. Melting is the application of of solids and the dispersing medium. heat to a solid, so it changes to a liquid above a temperature called the melting e. SEPARATION PROCESS point. Upon cooling, the solid solution is - Pure Substances: Since the constituent made. Liquid mixtures are prepared by elements in compounds are combined mixing two different liquid components. chemically, the only way to separate them is Homogeneous liquid mixtures form liquid through a chemical process as well. A solutions. Aqueous solutions are solutions decomposition reaction is a type of chemical where water is used as a solvent. reaction in which a single compound breaks Heterogeneous liquid mixtures form colloids down into two or more elements or new specifically called emulsions. To prepare a compounds. These reactions often involve liquid-liquid solution, a liquid solute is simply an energy source such as heat or electricity added to a liquid solvent. Dilution is the that breaks apart the bonds of addition of water, or other solvents, to compounds.A reaction is also considered to reduce the concentration of a solution. An be a decomposition reaction even when one emulsion is prepared by mixing two or more of the products are still compounds. immiscible liquids. Emulsions rely on For example, carbonic acid decomposes stabilizing agents, also called emulsifiers so spontaneously at room temperature into that they can mix together to form a colloid. carbon dioxide and water. To prepare a solid-liquid mixture, mix solid - Mixtures: Homogeneous solid-liquid components with the liquids. Homogeneous mixtures may be separated by evaporation solid-liquid mixtures form solutions while or by recrystallization. Homogeneous nonuniform solid-liquid mixtures form liquid-liquid mixtures may be separated by suspensions and colloids. Stirring increases distillation or by chromatography. Some the speed at which a solute dissolves in a heterogeneous mixtures can be separated  by manual picking, sieving, or by using a coated in salt and fermented for an ample magnet. Other methods used to separate amount of time. heterogeneous solid-liquid mixtures are filtration, sedimentation, decantation, and 3. Sweet Drinks centrifugation. - Soft drinks and fruit juices are usually made up of sugars that are dissolved in water. L2.4: CHEMISTRY OF COMMERICAL Flavorings and coloring were added to it for PRODUCTS: MIXTURES variations. - However, when soft drinks are poured into a You encounter mixtures every day without glass, bubbles start to form as the carbon even knowing it. As you have learned previously, dioxide gas dissipates from the solution. people routinely prepare and separate mixtures. Soft drink becomes a heterogeneous mixture. When you prepare your favorite powdered juice drink or your morning coffee, you are 4. Alcoholic Beverages preparing mixtures. When you filter coffee from the - Alcoholic beverages are liquid solutions that coffee grind, you are separating mixtures. are mainly composed of ethanol in water. - Alcoholic beverages can be classified into Mixtures are found in commercial products the following three categories: you use. These commercial products take a. Beers: are brewed mainly from advantage of the differences in the physical and malted barley, hops, yeast, and chemical properties of the constituent substances water. The average alcohol content in a mixture. for beer is 4.5% (4.5 mL ethanol in 100 mL) MIXTURES b. Wines: are made from fermented - combinations of two or more pure grape juice or other fruits.The substances in which each substance retains average alcohol content for wine, its own composition and properties 11.6% (11.6 mL ethanol in 100 mL) - can be classified into two: c. Distilled spirits or liquors: are made by fermentation followed by a. HOMOGENEOUS MIXTURES distillation. The average alcohol - It is a combination of two or more content for liquor, 37% (37 mL substances that cannot be distinguished ethanol in 100 mL) from each other. - It has uniform composition and properties. 5. Liquid Medicines - Liquid medicines, like cough syrup, is an COMMON HOMOGENEOUS MIXTURES FOUND example of a liquid solution. In some cases, IN COMMERCIAL PRODUCTS diluting the concentrated liquid medicine with water is recommended. 1. Vinegar - Medicine tablets are also examples of solid - Vinegar is a liquid solution of acetic acid in solutions as they appear in only one phase. water. Most kinds of vinegar found in the A 500 mg paracetamol tablet weighs more market have 4% acetic acid concentration. than 500 mg due to the additional fillers that hold together the components 2. Fish Sauce - Fish sauce, or patis, is a liquid solution 6. Rubbing Alcohol made from fish or krill that have been - Rubbing alcohol is widely used as an antiseptic, disinfectant solution in the  medical field. The commercially available 3. Condiments rubbing alcohol is a 70% solution of ethyl - Ketchup and mustard can be categorized as alcohol or isopropyl alcohol. suspensions. They are just mixtures of vegetable particles, tomatoes and mustard 7. Dextrose seed, that are ground up and then - Dextrose is a form of glucose (sugar). The edispersed in an aqueous phase. dextrose solution has a usual concentration of 5% to 10% in water (5 g to 10 g in 100 COMPOUND mL water). - a pure substance that is a combination of b. HETEROGENEOUS MIXTURES elements formed by chemical bonds - It is a combination of two or more - consist of atoms of different elements that substances that can be distinguished from are chemically combined together in a fixed each other. ratio - Can be further classified into two: COMPOUNDS MIXTURES 1. SUSPENSION - a heterogeneous mixture whose Have distinct chemical Properties vary solutes do not completely dissolve and physical properties depending on the and its particles settle into clumps or amount and identity of layers when left undisturbed the components Specific mass ratio Variable mass ratio 2. COLLOID - a heterogeneous mixture whose Created through Made by physically solute like particles are dispersed in chemical reactions combining substances a medium Can be separated into Can be separated simpler substances by further into simpler chemical means substances by physical methods IMPORTANT APPLICATIONS OF MIXTURE SEPARATIONS IN COMMERCIAL PRODUCTS 1. Medicines - Medicines, like paracetamol or aspirin, are recrystallized from solution to bring it to acceptable standards. The pure forms are COMMON HETEROGENEOUS MIXTURES then compounded and mixed with fillers FOUND IN COMMERCIAL PRODUCTS homogeneously to make the medicine 1. Tea tablets that we can buy from the local - Tea is a solution. Once you add ice to it, it drugstore. becomes a suspension as the ice can be distinguished easily from the rest of the 2. Petroleum components of the mixture. - In the petroleum industry, distillation is often used as a method to purify products. Crude 2. Black Coffee oil is a solution of different organic solvents. - Black coffee is a solution. However, once It is distilled in refineries to gasoline, you add milk to the mixture, it becomes a kerosene and other petroleum products in colloid. Milk, on its own, is a colloid. order to be acceptable for applications.  3. Tap Water instrument (how close measurements are to - Tap water is a heterogeneous mixture. each other). Thus, separation techniques such as sedimentation, centrifugation, microfiltration, DARTS and distillation are used to recover pure - a good visualization of accuracy and water from tap water. precision - Industrial or even household water bull’s eye or center of the dartboard - treatment includes the processing of tap the true value water to separate water from contaminants, the closer the dart pins are to the making it suitable for usage. bull’s eye, the more accurate they are 4. Blood Centrifugation - In blood centrifugation, the blood extracted from the patient is placed in a centrifuge tube. This will be placed in a centrifuge for a few minutes until the components are completely separated. L3.1: ACCURACY AND PRECISION The dart pins that are close to the target show high In science, measurement is an integral part accuracy. in quantifying matter. A measurement is obtained by comparing a quantity with a standard unit. For weight, the standard unit is kilograms (kg). For length, the standard unit is centimeters (cm) or inches (in). ACCURACY AND PRECISION - All measurements are subject to uncertainty. - The choice of the correct instrument for measurement: the concept of accuracy and The image on the left shows high precision since precision the dart pins are close to one another, while the - “accurate” and “precise” image on the right shows low precision since the - used to describe measurements dart pins are far away from one another. - often interchanged but have different meanings - Precision is not dependent on accuracy. - A set of measurement can be very precise ACCURACY but not accurate. - the closeness of a measurement to the true dart pins land close to one another or accepted value. but are far from the bull’s eye PRECISION ANALYZING ACCURACY AND PRECISION - the degree of agreement between - Analyzing the accuracy and precision of successive measurements using a given measurements - to determine the validity of the data obtained in an experiment.  - Best quality of data if they exhibit high Which group had a more precise set of accuracy and high precision measurements of the mass of a 150 gram metal ball? LET’S PRACTICE 1. The mass of a 75.0 gram standard sample of a substance is measured using an analytical balance. The measurements are listed below. Are the measurements accurate? Are they precise? The range of values for each group are as follows: Group 1 range = 149.5 – 142.7 = 6.8 Group 2 range = 149.7 – 148.1 = 1.6 Group 3 range = 151.2 – 135.9 = 15.3 - The measurements are precise since the values are close to each other. They are Group 2 obtained the most precise measurements also accurate since they are close to the (lowest range), while Group 3 had the lowest true value, which is 75.0 grams. precision (highest range). 2. Describe the precision and accuracy of the REMEMBER: Below is a mnemonic that you can temperature readings for five days as use to easily differentiate accuracy and precision: shown below. - ACcurate is Correct (or Close to real value) - PRecise is Repeating (or Repeatable values). ACCURACY AND PRECISION IN CHEMISTRY - Having accurate and precise measurements is important in presenting data and solution preparation. - A chemist uses different measuring tools to quantify substances that are used in making - The forecasted temperature readings show chemical products. high precision since their values are close to - Having accurate measurements of each one another. However, it may be inferred substance that make up a chemical that the temperature readings are not that productive is important to ensure its quality. accurate since they fall far from the - In chemical preparation, it is necessary to forecasted values. have accurate measurements of substances. RANGE - the difference between the highest and L3.2: ERRORS IN MEASUREMENTS lowest values of measurement - to determine the precision of multiple sets of All measurement, regardless of its accuracy data and precision,are subject to a certain degree of uncertainties. LET’S PRACTICE  These uncertainties may be brought about gross error by the limitations of the instrument used or due to random error the lack of skill of the reader. SYSTEMATIC ERRORS A better understanding of such uncertainties - associated with instruments used to obtain is essential to help ensure accuracy and precision measurements in measurements. - consistent in terms of magnitude and direction UNCERTAINTIES IN MEASUREMENTS - may be further classified: observational, UNCERTAINTIES environmental, and instrumental - expression of the doubt of the result of measurement OBSERVATIONAL ERRORS - always present in science - due to the following: - does not mean that the measurement an incorrect setting of the instrument obtained or the experimental procedure in being used; obtaining such measurement is wrong carelessness; and - an acceptable range of uncertainty is bias of the operator when making established observations - the lower meniscus of the liquid is between 31 and 32 mL - can be assumed to be approximately 31.5 mL - ± 0.5 mL uncertainty A parallax error happens when the reading of measurement is obtained at a different angle. ENVIRONMENTAL ERRORS - due to the external factors that may affect the condition of the measuring instruments Temperature The liquid in the graduated cylinder measures 31.5 Moisture mL. Dirt Vibrations MEASUREMENT ERRORS ERROR - disparity between the measured value and the “true value” of the object being measured. - has different types depending on how it is acquired systematic error  CALCULATIONS OF MEASUREMENT ERRORS ABSOLUTE ERRORS - the absolute value of the difference between actual and obtained measurements RELATIVE ERRORS - the ratio of the absolute error to the measured value Rust is an environmental factor that may affect the performance of an instrument, which may lead to PERCENTAGE ERRORS inaccurate measurements. - shows the extent to which a measurement deviates from the actual value INSTRUMENTAL ERRORS - due to the inherent limitation of an LET’S PRACTICE instrument 1. The actual height of a rookie basketball - improper calibration of the instrument player is 5.80 feet. But when his height was measured prior to the drafting of players, his recorded height was 5.71 feet. Compute for the absolute error of the rookie basketball player’s height. - The absolute error of the rookie basketball player’s height is 0.09 ft. 2. A balikbayan box, with an actual mass of 58.0 kg, approximately weighs 57.8 kg on the airport’s weighing scale. What is the A weighing scale may result in errors in relative error in the mass of the balikbayan measurement due to its inherent limitations. box? RANDOM ERRORS - The relative error in the mass of the - due to random and unpredictable balikbayan box is 0.0003. fluctuations in experimental conditions - occur irregularly 3. The computed percentage error of the - affects precision voltage reading shown by a voltmeter is results obtained may be too high or 1.42 %. If the actual voltage of the battery low connected to the voltmeter is 7.85 volts, inconsistent in both magnitude and what is its measured value? direction - The measured value of the battery GROSS ERRORS connected to the voltmeter is 7.96 volts. - due to mistakes in the analysis of the instrument used as well as in recording the WAYS TO REDUCE MEASUREMENT ERRORS measurement outcomes - care and self-discipline in performing - human error experiments - errors so serious that the experiment has to - regular maintenance of instruments be repeated - calibration of instruments  - use of standard reference materials to - includes all digits measured correctly plus check performance of a method one estimated digit - blank determinations ESTIMATE KEY FORMULA - an approximation of a number based on ABSOLUTE ERROR reasonable assumptions absolute error = |𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 − 𝑎𝑐𝑡𝑢𝑎𝑙 𝑣𝑎𝑙𝑢𝑒| - may be based on indirect measurement, - Use this formula to determine the difference calculations, and models between the actual and obtained measurements RELATIVE ERROR 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑒𝑟𝑟𝑜𝑟 relative error = 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 - Use this formula to determine the ratio of the absolute value to the measured value. The value of pi (π) shown in the calculator has PERCENTAGE ERROR eight significant digits, wherein the last digit is assumed to be an estimated value. 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑠 𝑣𝑎𝑙𝑢𝑒 − 𝑎𝑐𝑡𝑢𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 % error = x 100 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 RULES IN DETERMINING SIGNIFICANT - Use this formula to compute the extent to FIGURES which a measurement deviates from the 1. All nonzero numbers are significant. actual value. Examples: - 1234 has four significant figures. - 45932 has five significant figures. 2. Any zero that is between nonzero L3.3: SIGNIFICANT FIGURES IN numbers is significant. CALCULATIONS Examples: - 100001 has six significant figures. When taking a measurement, it is essential - 2009 has four significant figures. to inform the reader about the level of accuracy and precision used. 3. Leading zeros or any zeros that are to the left of the first nonzero number are Even if you are using a calculator to not significant. compute for the answer, the number of digits Examples: written down is important. - 0.0001 has only one significant figure. - 0.0000231 has three significant figures. Significant figures are used in expressing measurements or in doing mathematical 4. Trailing zeros or any zeros to the right of computations. a decimal point are significant. Examples: SIGNIFICANT FIGURES - 0.000123900 has six significant figures. - the essential digits that contribute meaning - 194.00 has five significant figures. to a certain number - show how precise measurements are  5. Trailing zeros to the right of a nonzero - Round off 1.865 to three significant figures number, but not to the right of a decimal → 1.86 point, are not significant unless 6. If the digit to the right of the last reported specified by a certain math symbol like digit is not exactly 5, then add one to the overline (一) or underline (_). reported digit. Examples: Examples: - 120000000 has two significant figures. - Round off 1.865 to three significant figures - 120000000 has six significant figures. → 1.86 - Round off 1.86501 to three significant REMEMBER: Leading zeros are never significant figures → 1.87 as they are only used as placeholders or put the number in its correct decimal places. On the other REMEMBER: If the number to the right of the digit hand, trailing zeros are significant if they are to the to be rounded off is less than 5, retain the value of right of a decimal point or expressed as significant the digit. If the number to the right of the digit to be using overline or underline. rounded off is greater than 5, add 1 to its value. RULES IN ROUNDING OFF NUMBERS If the digit to the right of the last reported digit is 1. Determine what the last reported digit exactly 5, then add one to the reported digit if the should be, according to the significant figure reported digit is an odd number, and leave it rules presented above. unchanged if it is even. However, if it is not exactly 2. Consider the digit to the right of the last 5, then add one to the reported digit. reported digit. 3. If the digit to the right of the last reported APPLYING SIGNIFICANT DIGITS IN digit is less than 5, then leave the last CALCULATIONS reported digit unchanged and discard all ADDITION/SUBTRACTION digits to the right. - the answer can only have as many decimal Examples: places as the measurement with the fewest - Round off 5.382 to three significant figures decimal places → 5.38 - the accuracy of a mathematical operation is - Round off 1.874 to three significant figures restricted to the least accurate → 1.87 measurement 4. If the digit to the right of the last reported digit is greater than 5, then increase the last reported digit by one and discard all digits to the right. Examples: - Round off 5.386 to three significant figures LET’S PRACTICE → 5.39 Jimin wants to find out the actual mass of the iron - Round off 1.879 to three significant figures filings on the evaporating dish. He used the → 1.88 analytical balance to measure the mass of the evaporating dish with iron filings then measure the 5. If the digit to the right of the last reported evaporating dish alone. The mass of the digit is exactly 5, then add one to the evaporating dish with iron filings is 18.9023 grams re