Sci Unit B Notes PDF

Science notes Unit B -> matter and chemical change Topic 1-Matter can be described and organized by its physical and chemical properties. HHPS -> hazardous household products symbols -> shapes and colours indicate how dangerous a substance is -> yellow triangle = caution -> orange diamond = warnin...

Science notes Unit B -> matter and chemical change Topic 1-Matter can be described and organized by its physical and chemical properties. HHPS -> hazardous household products symbols -> shapes and colours indicate how dangerous a substance is -> yellow triangle = caution -> orange diamond = warning -> red octagon = danger GHS -> globally harmonized system flammable: if exposed to ignition, sparks, heat may ignite and give off flammable gases corrosive: may cause skin burns and permanent damage explosive: may explode if exposed to fire, heat, shock or friction compressed gas: released gas under pressure can cause tank to become projectile oxidizing: can burn without air or can intensify combustible material toxic: may cause life threatening effects even in small amounts and w/ short exposure health hazard: may cause serious and prolonged health effects on short or long term exposure harmful/irritant: may cause irritation (redness, rash) dangerous to environment: toxic to aquatic organisms & may cause long lasting effects in the environment Organizing matter 3 states of matter -> liquid -> gas -> solid -> (plasma) Everything is classified as ​energy ​or ​matter Properties: characteristics that can be used to describe a substance Physical properties (reversible) -> ​colour -> ​lustre ​- shininess of a substance ->​ melting point​ - changes from a solid to a liquid -> ​boiling point​ - liquid changes to a gas -> ​hardness​ - Moh’s hardness scale -> ​malleability​ - pounded or rolled into sheets -> ​ductility​ - stretched into a long wire -> ​solubility​ - ability to dissolve into another -> ​density​ - amount of mass in a given volume ->​ conductivity​ - conduct electricity or heat Chemical properties (non-reversible) -> reaction with ​acids -> ability to ​burn -> reaction with ​water -> behaviour in ​air -> reaction to ​heat Describe how a substance interacts with other substances. Only observable when a chemical reaction occurs. All matter is either a pure substance or mixture. Physical & chemical properties show whether a substance is “pure” or a mixture Pure substances: made up of one type of matter and has a unique set of characteristics Element: anything on the periodic table. Substance is made up of only one atom. Cannot be broken down Compound: a chemical combination of 2 or more elements in a specific ratio Topic 2-An understanding of the nature of matter has developed through observations over time. Chemistry timeline 8000 BC ->10 000 years ago ->middle east ->​stone age​ ->made simple stone tools ->learned to use and control fire 6000 - ->discovered ​gold​ was good for jewelry;too soft for tools 1000 BC ->copper was used for pots, coins, tools, & jewelry ->heated ​copper​ was more useful 4500 BC ->copper & tin were combined to form bronze ->​bronze age ​->strong & hard ->good for weapons 1200 BC ->​hittites​ discovered iron from rocks ->​iron age​ carbon + iron = steel ->egyptians used juniper tree pigments & resin to preserve bodies (mummies) ->chemistry - greek word ​khemeia​ meaning juice of plant 400 BC ->greek philosopher ​democritus​ labels the “indivisible” particles ​atomos​. By mixing atmos that are different, new materials could be made with unique properties 350 BC ->​aristotle ​believed everything was made up of ​earth, air, water, ​& ​fire​. He was wrong but his popularity made his theory the chosen one for 2000 years 1500 AD ->​alchemists​ created beakers & filters, useful tools in the lab ->alchemy: magic & science ->alchemy: arabic: “the chemist” ->alchemy: pseudoscience ->plaster of paris: al-razi-casts ->​andreas libau​: german: published ->alchemia: 1597: first chemistry textbook 1660 AD ->​robert boyle​ believed that Democritus was right. He believed that tiny particles formed together to make an individual substance. ->Experimented ​with the behaviour of gases 1780 AD ->​lavoisier​ created a system for ​naming chemicals​ ->”father of modern chemistry” 1808 AD ->​john dalton ​suggested that matter was made of elements ->stated a substance can be pure ->stated each element was made up of particles called “​atoms​” ->atoms within an element were identical in mass ->no 2 elements have atoms of the same mass ->​”billiard ball model”​ atoms were sphere 1847 AD ->​j.j thomson​ discovered subatomic particles called electrons (smaller than atom) ->​electrons​ smallest particle of matter, cannot be broken down further, negative charge 1897 AD ->​”raisin bun model”​ positively charged sphere with negative electrons embedded like raisins in a bun ->gave the atom no electrical charge - neutral 1904 AD ->​hantaro nagaoka​ japanese physicist ->positively charged sphere with negatively charged electrons orbiting around it ->​”planet model” 1898 - ->​ernest rutherford​ british scientist said atoms were mainly empty spaces where positive 1907 AD particles could pass -> they had a positively charged centre a ​“nucleus”​. Atom nucleus 1/10 000th the size of an atom  1900s ->​niels bohr​ suggested electrons move in a specific circular orbits ->​”electron shells” ​electrons jumped between these shells by gaining or losing energy Today ->​james chadwick​ british physicist ->nucleus contains positive charges called ​protons​ and neutral charges called ​neutrons Today Organizing the elements Finding a pattern in an unknown helps scientists to organize ideas information. It also helps scientists to interpret what the information means & explain these ideas, based on what they have learned Looking for patterns Early chemists used symbols of the sun & the planets to identify the metallic elements known to them. This later became a problem, when more elements were discovered, because they ran out of planets. John Dalton developed a new set of symbols in the early 1800s to improve communication between chemists. metal gold silver iron mercury tin copper lead symbol celestial body sun moon mars mercury jupiter venus saturn symbol element hydrogen oxygen carbon gold silver mercury Letters instead of pictures Berzelius ​later revised Dalton’s symbols by replacing them with letters, instead of pictures. He represented the elements by their first letter (capitalized) or first two letters for elements with the same first letter (first one capitalized & the second letter was lower-cased) An order for the elements Elements were listed in order of their atomic mass. Atomic mass is the mass of one atom of the element. It is represented in atomic mass unit (amu). John newland​ “​law of octaves​” identified the pattern in which the properties of elements seemed to repeat at regular intervals, similar to the octave scale in music. Finding a pattern Dmitri mendeleev​ later revised the pattern in 1869. Mendeleev collected the 63 elements known at the time & arranged them according to their properties (which he wrote on a file card). He arranged the cards into a “​solitaire​ like” table. By sorting & arranging the elements in this way, Mendeleev was able to identify gaps where elements, not yet discovered, would be able to fit The periodic table today About 118 elements are known today. They are organized into what is called the Periodic Table of Elements. 92 occur naturally on Earth. Oxygen is most abundant Understanding the periodic table Groups or families Periods -> 18 columns ->7 rows ->similar chemical properties ->as you go across a row, it moves from metal to non-metal ->atomic number increases by one Every box in the table contains several pieces of information: Element symbol & name -> use ​latin ​name - Au - Gold - Aurum -> named after ​people​ - Es - Einsteinium - Albert Einstein -> named after ​places​ - Cf - Californium - California -> named after ​planets​ - U - Uranium - Uranus Atomic number An element is defined by the number of ​protons​ it has. Carbon atoms have 6 protons, hydrogen atoms have 1 proton & oxygen atoms have 8 protons. The number of protons an atom has is called the atomic number. The chemical behaviour of an element depends on the number of protons in an atom. Atomic mass The average mass of an element in atomic mass units (amu). The mass in an atom is so small that we use amu. That’s about the mass of one proton or neutron. To find the average number of neutrons for an element simply subtract the number of protons (atomic number) from that atomic mass Protons: atomic number Electrons: atomic number Neutrons: atomic mass - atomic number Patterns of the periodic table of elements metals non-metals metalloids ->solids at room temp. ->often liquid or gas at room ->can be in-between metals & ->malleable temp. non-metals ->have lustre ->not shiny ->conduct electricity ->insulator ->have ductility ->not ductile or malleable alkali metals alkali earth metals halogens noble gases ->most reactive ->react to air & water ->most reactive ->the most stable & especially in air & ->less reactive than non-metals unreactive water alkali metals ->can be used to form ->can make new ->when moving down ->Be,Mg,Ca,Sr,Ba,Ra new, helpful substances substances sometimes the column, the ->F,Cl,Br,I,At ->He,Ne,Ar,Kr,Xe,Rn elements get more reactive ->Li,Na,K,Rb,Cs,Fr Liquids at room temperature are ​bromine ​& ​mercury Topic 3-compounds form according to a set of rules. Chemical formulas A ​combination ​of symbols that represent a ​compound​ and the ​amount​. The formula identifies the elements in the compound and the amount of each element. Water - H​2​O - dihydrogen monoxide Table salt - NaCl - sodium chloride Baking soda - NaHCO​2​ - sodium nitrogen carbonate Bleach - NaOCI - sodium hypochlorite Oxygen - O​2​ and O​3​ - oxygen H​2​O Subscript number represents the number of atoms sub means below. When drawing, check atomic mass to determine which atom is larger. Ionic compounds Ionic compounds are pure substances formed as a result of the attraction between particles of the ​opposite​ charges, called ions. -> pure substances are formed when at least ​one metal ​and ​one non-metal​ combine -> ion comes from the Greek word meaning “to go” or “wander” Properties of ionic compounds -> they have a ​high melting point -> when dissolved in water they conduct ​electricity -> they have a distinct ​crystal shape -> ​solid ​at room temperature Ions An atom or group of atoms that has become electrically charged because it has loss or gained electrons. A ​positive ion​ is an atom that has ​lost​ one or more electrons. A negative ion​ is an atom that has ​gained​ one or more atoms. Cation: -> positively charged -> more protons Anion: -> negatively charged -> more electrons Rules for naming ionic compounds 1. The name of the metal or positive ion goes first 2. The name of the non-metal or negative ion comes next 3. Change its ending to “ide” Writing ionic compound formulas 1. Print the elements symbols for each with its ionic charge Ca​+2 Cl​ ​ -1 2. Balance the ion charges Ca​+2 ​Cl​-1 ​Cl​-1 3. Write the formula showing the number of atoms (not ionic charges) CaCl​2(s) Naming molecular compounds 1. All compounds have a name & a formula -> the name describes the composition of elements in the compound. The formula indicates the number of atoms in each element 2. A set of rules is followed when naming compounds & writing their formula 3. A chemical formula indicates the number of atoms of each element by a subscript number 4. After each compound, the state of the compound at room temperature is indicated in subscript parentheses: (s) (l) (g) (aq) Molecular compounds When non-metals combine, they produce a pure substance called a molecule or molecular compound. They can be solids, liquids or gas at room temperature. A compound formed when 2 non-metals combine Writing formulas for molecular compounds It is similar to the way ionic compounds are written, except that no ions are present and the ion charge is not used in the formulas. This makes it difficult to predict how the non-metals will combine. The formulas do tell how many of each atom is present in the molecule. Properties of molecular compounds -> a ​low ​boiling and melting point -> poor conductor of electricity, therefor a ​good insulator -> distinct crystal shape Rules for naming compounds 1. The first element uses its name 2. The second element changes it ending to “ide” 3. When there is more than one atom of an element a ​prefix​ is used 4. Do not use mono in the first element 1 2 3 4 5 6 7 8 9 10 mono di tri tetra penta hexa hepta octa nona deca Topic 4-Substances undergo a chemical change when they interact to produce different substances. Chemical reactions A chemical reaction takes place when two or more substances combine to form new substances. Reactants -> a substance that reacts with another substance or substances in a chemical reaction to create a new substance with different products or properties -> found on the left side of the chemical word equation -> left side of arrow -> plus signs separate the reactants from each other Products -> a new substance produced in a chemical reaction between reactants -> found on the right side of the chemical word equation -> right side of arrow -> plus signs separate the products from each other Alka-seltzer + H​2​O → CO​2 Chemical change -> a chemical change results from a chemical reaction. Evidence that a chemical change has occurred include: - change in colour - formation of an odour - formation of a solid or gas (bubbles) - release or absorption of energy (heat) Reactions - “exo” or “endo” A chemical change, which ​releases ​heat energy, is called ​exothermic.​ Eg. fire A chemical change, which ​absorbs​ heat energy, is called e ​ ndothermic​. Eg. cold pack Chemical reactions involving oxygen Combustion​ is a chemical reaction that occurs when oxygen reacts with a substance to form a new substance & gives off energy. Corrosion​ is a slow chemical change that occurs when oxygen in the air reacts with metal. Corrosion is a chemical reaction in which the metal is decomposed (eaten away), when it reacts with other substances in the environment. Cellular respiration​ is a chemical reaction that takes place in the cells in your body. Food (glucose) reacts with oxygen to produce energy, water & CO​2​. Conservation of mass in chemical reactions The ​law of conservation of mass​: in a chemical reaction, the total mass of the reactants is ​always​ equal to the total mass of products. This law ties in well with the atomic theory, which states that atoms are never created or destroyed. In a chemical reaction the atoms & molecules are simply rearranged. Closed system vs open system Closed systems​: an experiment in which all reactants & all products of the chemical reaction are accounted for. Is also one in which the reaction occurs in a given area. Open systems​: an experiment in which one or more products of a chemical reaction can escape. Is also one in which the reaction occurs can escape. Factors affecting the rate of a chemical reaction The speed of chemical reaction is called the ​reaction rate​. There are 4 factors that affect the reaction rate. 1. The presence of a ​catalyst -> catalysts are substances that help a reaction proceed faster -> catalysts are not consumed in reactions. Types of reactions involving catalysts can be found in living & non-living things -> ​enzymes (organic catalyst)​ help in the reactions in the body, which break down food -> they also get rid of poison in the body. Catalase (an enzyme found in plant & animal cells) speeds up the breaking down of hydrogen peroxide into harmless oxygen & water. 2. The ​concentration​ of the reactants -> the greater or higher the concentration, the faster the reaction rate 3. The ​temperature​ of the reactants -> the higher the temperature the faster the reaction rate 4. The ​surface area​ of the reactants -> the more surface in contact, the faster the reaction rate. Increasing the surface area of the reactants will increase the reaction speed.