year 10 chemistry
review of atoms physical and chemical change chemical reactions: types, equations, balancing endothermic and exothermic ions: cations and anions ionic bonding and covalent bonding PH: acids and bases acid and base reactions acid and metal reactions photosynthesis and respiration precipitation, neutralization and decomposition radioisotopes nuclear decay carbon dating radiation and nuclear medicine in health
69 flashcards · Other · by Shahd Rawas
3 parts of an atom and the charge
protons - positive electron - negative neutron - no charge
electron configuration
nucleus, 2, 8, 18 electrons in the outer most shell are called valance electrons
what are chemical reactions and the evidence for them
involves the chemical change in the identity of a element involves breaking the bonds and the formation of new bonds evidence: gas formation of solid in solution (precipitate) heat is produced or absorbed color change light is absorbed or emitted changes in electrical and magnetic properties
what is the law of conversation of mass
the law of conservation of mass states that matter cannot be gained or lost in a chemical reaction. mass of reactants = mass of products because atoms are rearranged in new ways in a chemical reactions
chemical equation: composure
reactants (undergoes a reaction) gives products (substances produced at the end of reaction) must be balanced: number of atoms of each element is equal at both stages reactants and products
energy is conserved in chemical reactions, so the total amount of energy in the universe at the end of a reaction is the same as it was before the reaction
energy in chemical reactions
what are the exothermic reactions and examples
when a chemical reaction happens, energy is transferred to the surroundings, temperature of the surrounding increases ex: combustion of fuels, respiration, yeast and hydrogen peroxide
what are endothermic reactions and mention examples
when energy is transferred from surroundings, temperature of surroundings decrease ex: photosynthesis, acetic acid, sodium bicarbonate
in endothermic reactions, energy enters
in exothermic reactions, energy exits
what is activation energy
energy required to break the bonds in reactants for a chemical reaction to occur. it is the minimum energy required for a reaction to take place.
a reaction is exothermic if more energy is released than supplied. if more energy is supplied than released then the reaction is endothermic
energy in exothermic and endothermic reactions
describe the endothermic graph: more energy is taken in to break the bonds in the reactants than released by the bonds being formed in the products. therefore energy is absorbed.
describe the exothermic graph: more energy is released when the products formed than energy was used to break bonds in the reactants. therefore a net release of energy.
recall the Collison theory
reactions take place when particles collide with a certain amount of energy
what are the 2 things the rate of reaction depends on:
frequency of collision between particles the energy which the particles collide with
what happens if particles collide with less energy than activation energy?
they will not react and particles will just bounce off each other.
example of reaction with high rate
wood combustion
example of reaction with low rate
rusting of iron
5 factors affecting reaction rate
temperature agitation catalyst concentration surface area of reactants
how does temperature affect reaction rate? why?
a temperature that takes place at a higher temperature generates more energy than at a lower temp. colliding particles will have the required activation energy at high temp and more Collison's will take place the higher the temp the faster the rate of reaction a rise of 10 deg can cause rate to double
how does concentration affect reaction rate? why?
higher concentration of dissolved reactants, faster rate of reactionas per law of mass: chemical reaction is directly proportional to the concentration of reactants higher concentration means more particles in the same amount of space therefore more particles are likely to collide with each other
stirring reactants can also increase rate of reaction ensure that reactants are kept in contact does this by removing build up of products around reactants
agitation
how does surface area affect reaction rate? why?
reactions can only take place on surface of solid if solid is split, surface area increases means increased area for reactant particles to collide with smaller pieces means larger surface area, means more collisions and greater chance of reacting
catalysts are chemicals that speed up chemical reactions but are not consumed during reaction reduce amount of energy required to convert reactants into products
what are enzymes? mention a example:
enzymes are biological catalysts natural molecules that hold reactants together until they rearrange to form products they can also cut long molecules into smaller pieces ex: amylase brakes down starches in complex carbs so that they can be digested
they have a complex 3d surface to which particular reactants (substrates of that enzyme) fit and enzyme and its substrates bind together forming a enzyme substrate complex. this bring key atoms together as a result, a chemical reaction will occur within the active sites forming a product, the product diffuses again freeing the enzyme to work
how do enzymes work?
how is an ion formed?
when an atom does not have the same number of protons and electrons it looses or gains electron/s and acquires a net electrical charge
positive ions are called cations metal atoms form positive ions, while non metals form negative means the atom is losing an electron has positive charge nearly all metals form cations ex: Na+Na^+Na+ or Al+Al^+Al+ or (Mg2)+(Mg^2)^+(Mg2)+ : has 2 valance electrons so it loses 2 rather than gains 6
cations
negative ions are called anions non metals atoms gain electron/s has negative charge nearly all non metals form anions ex: Cl−Cl^-Cl− or Fl−Fl^-Fl− (O2)−(O^2)^-(O2)− : has 6 valance electrons so it gains 2 rathe than lose 6
anions
explain the process of ionic bonding :
the force of attraction between a positive charge and negative charge to create the ionic bond ( between non metal and metal) in other words: transfer electrons ex: Na+Na^+Na+ has a +1 charge and Cl−Cl^-Cl− has -1 chargetherefore: they bond producing sodium chloride NaClNaClNaCl ex: K+K^+K+ and F−F^-F−
explain the process of covalent bonding :
bonding by sharing electrons to achieve full outer shell want to achieve noble gas configuration (OCTET rule: full outer shell of 8 electrons) ex: chlorine forms a covalent bond with itself : Cl2Cl2Cl2 ex: H2OH2OH2O
what is combustion?
combustion is a type of chemical reaction when a substance burns and reacts with oxygen to produce heat and light energy. combustion reactions are exothermic reaction. ex. wood gives burning wood which gives products of combustion( CO2,H2O,energyCO2, H2O, energyCO2,H2O,energy )
summarize the three things required for combustion:
fuel heat oxygen if one thing is removed from a fire then the fire goes out when fuel burns in combustion, they release useful thermal energy (heat)
what is the equation rule for combustion? give an example:
when a substance burns and reacts with oxygen the new substances formed are called oxides. ex. coal:carbon+oxygen→carbondioxidecoal: carbon + oxygen → carbon dioxidecoal:carbon+oxygen→carbondioxide ex. hydrogen:hydrogen+oxygen→dihydrogen−oxide(water)hydrogen: hydrogen + oxygen → dihydrogen- oxide (water)hydrogen:hydrogen+oxygen→dihydrogen−oxide(water)
what is corrosion?
corrosion is when metals react with substances in the air to produce compounds the metal changes from atom to ion metal atoms loose electrons when they corrode, it is oxidized
tarnish is the result of a chemical reaction between silver and sulfur- containing substances in the air the silver combines with sulfur and forms silver sulfide a thin coating silver sulfide darkens the silver
what is tarnish?
what is rusting?
name given to the corrosion of iron when most metals corrode their surface gets damaged iron corrodes when it is in the presence of water and oxygen
rust vs corrosion: corrosion starts with oxidation where atoms of a metal link up with oxygen followed by a gradual breakdown rusting is a specialized form of corrosion that only iron and steel go through aluminum oxidation occurs faster then steel, because it has strong affinity for oxygen. rather than flaking, aluminum oxide forms a hard coloured surface. the process stops when all aluminum atoms have bonded with oxygen
PH: ph is the special name given to the substance that has acid or base characteristics p stands for potential and h stands for hydrogen hence the potential of a substance to attract hydrogen ions
how does ph paper measure a substance? what are indicators?
the paper is treated with chemicals that change colour the colour determines the acid or base indicators are chemicals that change colour in the presence of an acid or an alkali ex. plants: geranium plants grown in acidic soil have red flowersgeraniums grown in alkali soil have blue flowers
ph scale ranges from 0- 14|0 to 14 ph 7 in neutral eg water low ph 0 - 6.9 | 0 to 6.9 = acid high ph 7.1 - 14 | 7.1 to 14 = base
PH scale
what is an acid, characteristics and examples?
any substance which has the ph value of less than 7 acid turns blue litmus paper red tastes sour can burn skin ex. sulfuric acid H2SO4 (battery), hydrochloric acid HCL (stomach acid), nitric acid HNO3 (fertiliser), carbonic acid H2CO3 (carbonated water.
differentiate between strong vs weak acids
strong acids have high ionizing ability (break cations and anions) all most completely and conduct electricity well ex: sulfuric acid (H2SO4) , hydrochloric acid (HCL), nitric acid (HNO3)weak acids do not completely ionize ex: acetic acid (vinegar), citric acid
what is a base, characteristics and examples?
any substance which has ph value greater than 7 is a base base turns red litmus paper blue tastes bitter can burn skin ex: ammonia NH3 (cleaner), Aluminum hydroxide Al(OH)3 (antacid), sodium hydroxide NaOH
differentiate between strong vs weak bases
strong bases have high ionizing ability (break cations and anions) all most completely and conduct electricity well ex: potassium hydroxide (KOH), sodium hydroxide (NaOH)weak bases do not completely ionize ex: ammonia (NH3)
what happens when a acid and base react? (oxides and hydroxides) give examples
when a acid reacts with a base a neutralization reaction occurs, and produces a chemical called a salt (and water) water is formed because OH- ions from the base react with H+ from acid to produce H2O salts are neutral compounds which means they have no charge involves the transfer of a hydrogen atom from the acid to the base acid+base(oxide,and,hydroxide) →salt+wateracid+base(oxide,and,hydroxide) →salt+wateracid+base(oxide,and,hydroxide) →salt+water ex : sodium hydroxide + hydrochloric acid →…
3 types of bases:
oxides: contain oxide ions with the formula O2- hydroxides: contains hydroxide ions, with the formula OH- carbonates: contains carbonate ions with the formula CO2-
the first part of the salt name comes from base: ex: sodium hydroxide ... sodiumthe second part of the salt comes from the acid: ex: sulfuric acid ... sulfate ∴ sodium hydroxide + sulfuric acid → sodium sulfate
name of salt
what happens when a acid and a carbonate react? give examples
the reaction of an acid with a carbonate produces a salt, water and carbon dioxide 1. acid+carbonate→salt+water+carbonateacid + carbonate → salt + water + carbonateacid+carbonate→salt+water+carbonate acid+carbonate→salt+water+carbondioxideacid+carbonate→salt+water+carbondioxideacid+carbonate→salt+water+carbondioxide 2. acid+hydrogen,carbonate→salt+water+carbondioxideacid + hydrogen, carbonate → salt + water +carbon dioxideacid+hydrogen,carbonate→salt+water+carbondioxide carbon dioxide is presen…
what happens when a acid and a metal react? give examples
acids react with most metals to produces salt metal+acid→salt+hydrogenmetal + acid → salt+ hydrogenmetal+acid→salt+hydrogen the speed of the reaction is dependent on the metal and how high up the reactivity series it is ex: magnesium + hydrochloric acid → magnesium chloride + hydrogen( Mg + 2HCL → MgCl2 + H2
what is the pop test?
a burning wooden splint goes pop if it is put in a test tube of hydrogen. this is because the flame ignites the hydrogen which burns explosively to make a loud sound.
acid reactions in digestion
Chemical digestion involves the secretions of enzymes throughout your digestive tract. These enzymes break the chemical bonds that hold food particles together. This allows food to be broken down into small, digestible parts.
digestion the stomach:
physical churning in the stomach the lining of the stomach secrets acids and enzymes such as pepsin which is responsible to break down protein the stomach
digestion in the duodenum:
stomach acid is used to neutralize the chyme in the duodenum because of its alkaline environment entry of chyme triggers the release of pancreatic juices ( enzymes and bicarbonate) and bile pancreatic enzymes: lipase : breaks down fat protease: breaks down protein amylase: breaks down carbs bile: Dark green or brownish coloured fluid produced by the liver. Bile is passed to the gallbladder and then into the duodenum to help with the digestion of fat.
what is acid rain
Acid rain, is any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.
Acid rain results when sulfur dioxide ( SO2SO2SO2 ) and nitrogen oxides ( NOXNOXNOX ) are emitted into the atmosphere and transported by wind and air currents. The SO2SO2SO2 and NOXNOXNOX react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground causing damage
how does acid rain occur?
explain photosynthesis
naturally occurring occurs in all green plants light+carbon.dioxide+water→glucose+waterlight + carbon.dioxide +water → glucose+waterlight+carbon.dioxide+water→glucose+water Plants are the only photosynthetic organisms to have leaves photosynthesis occurs in the leaves of a plant
explain aerobic respiration
process that transfers energy to cells takes place in the mitochondria of a cell waste products: carbon dioxide and water glucose+water→carbondioxide+waterglucose +water → carbon dioxide + waterglucose+water→carbondioxide+water respiration in plants
The sugar produced by photosynthesis can be converted into the sugar glucose. Thousands of glucose molecules can be linked together to form the complex carbohydrate cellulose. Cellulose is a very tough molecule that is used to build the cell wall of plant cells.
explain the role of sugar in plants
respiration vs photosynthesis
how does respiration occur in humans
The process of respiration in humans also includes the exchange of oxygen and carbon dioxide between the blood and the cells of the body.
what are precipitation reaction
A precipitation reaction is one in which substances in solution are mixed and an insoluble product is made. The insoluble product is called a precipitate and can be seen as a solid forming in the reaction mixture.
If an ion is soluble, then it remains in its aqueous ion form. If an ion is insoluble, then it forms a solid with an ion from the other reactant. If all the ions in a reaction are shown to be soluble, then no precipitation reaction occurs.
what are the solubility rules
mention examples of precipitation reactions
water pipes: magnesium and calcium oxides are found in water pipes as a precipitate formation of kidney stones: Reaction between calcium ions and oxalic acid that are present in food results in calcium oxalate, which is a type of kidney stone.
example of practical use of precipitation reactions
used to determine whether a particular element is present in a solution or not Wastewater treatment: A chemical is added to wastewater so that the pollutants and impurities (e.g., lead) precipitate out from the water, which is then sent for further purification.
what are decomposition reactions
Chemical reaction in which a compound breaks down into two or more substances. It is the opposite of a combination reaction. Sometimes, a complex chemical species breaks down into simple parts. During a decomposition reaction, the bonds between the atoms break down in the starting substance. The atoms then rearrange to form new bonds, resulting in new substances with properties different from the starting material.
examples of decomposition reactions
breakdown of carbonic acid (H2CO3) to carbon dioxide (CO2) and water (H2O) . H2CO3 (aq.) → CO2 (g) + H2O (l)
composition vs decomposition reactions