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Published byTrevor Gordon Campbell Modified over 9 years ago
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A chemical reaction is a process. What does this mean? Give some examples of processes Is baking a cake a process? Name some ingredients of baking a cake What is the product of this baking a cake process? The cake – duh! What symbol do we use to show processes?
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In a chemical reaction, the can be read as “produces” or “yields” With a chem. Rx. (chemical reaction) something(s) new is produced from other chemical ingredients. The arrow indicates the process of burning, combining, exploding, disintegrating…. To the left of the arrow is what goes into the reaction: Reactants, separated by + signs On the right: ? Products, also separated by + signs
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Convert baking a cake into a chemical reaction Flour(s) + water(l) + eggs(s) + milk(l), etc cake(s) + good aroma filling the kitchen!(g) Ingredients are reactants Cake + aroma = products = heat (produces, yields) You know a chemical reaction has occurred because you can’t reverse it.
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Elements from periodic table How to write ionic and covalent compound names How to interpret word problems
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(l) = liquid state (s) = solid state (g) = gas (aq) = aqueous (dissolved in water; solution) The BrINClHOF’s Guess what elements these are bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, fluorine
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The BrINClHOF’s Always exist in pairs, when not combined with other elements Gas at room temp. Referred to by their normal chemical name even though they’re combined ie. “chlorine” = Cl 2 (g) “oxygen” = O 2 (g) AKA: “HON and the halogens” Or Hydrogen + 7
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When metals are just named (i.e., “lead”) this is simply the solid pure element (i.e., Pb(s)) When things are “bubbled in” that means a gas form of that element is being added: Ex: “hydrogen is bubbled into a solution of…” Is written as: H2(g) + … … “Solutions” are aqueous. Ex: “ a solution of lead(II)chloride…” = PbCl2(aq) Acids are aqueous
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1. Figure out which are reactants and which are products. 2. Write chemical formulas for all substances, separated by the 3. Add state of matter to each substance 4. Balance equation (to learn Friday)
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Zinc and aqueous lead(II)nitrate are combined in an aqueous solution to produce zinc nitrate and a lead precipitate. 1. zinc and lead(II)nitrate are reactants; zinc nitrate and lead are products 2. Zn + Pb(NO3)2 Zn(NO3)2 + Pb 3. Zn(s) + Pb(NO3)2(aq) Zn(NO3)2(aq) + Pb(s) 4. Balancing Friday
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Carbon tetrachloride may be prepared by the reaction of natural gas, methane, and chlorine in the presence of ultraviolet light. Hydrochloric acid (HCl) is also a product of this reaction. 1. Carbon tetrachloride and hydrochloric acid are the products; methane and chlorine are the reactants 2. CH4 + Cl2 CCl4 + HCl 3. CH4(g) + Cl2(g) CCl4(s) + HCl(aq) 4. To Balance Friday
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Big Idea: Law of Conservation of Matter Matter cannot be created or destroyed Number of atoms of a certain element must be equal on reactant and product side. A balanced chemical equation shows the ratio of elements from one side to other
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Write unbalanced equation Once unbalanced equation is written, NEVER CHANGE THE SUBSCRIPTS Only add coefficients to front of compound Coefficients multiply everything in the compound by that amount Work with most complex molecule first, and save simplest for last If you have an odd # of elements on one side, multiply entire eqn by 2, and continue
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How many oxygen atoms? O2O2 22 H2OH2O 11 PO 4 3- 44 2H 2 SO 4 88 2Ca(OH) 2 44 3Ca 3 (PO 4 ) 2 24
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O3 O2 You need the same number of O’s on both sides 2O 3 3O 2 6 = 6 Balance: H 2 + O 2 H 2 O 2H 2 + O 2 2H 2 O H’s : 4 O’s : 2
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Combustion of ethane C 2 H 6 + O 2 CO 2 + H 2 O Which is most complex? Ethane – so balance those elements first C 2 H 6 + O 2 2CO 2 + 3H 2 O Now you have odd number of O’s Multiply entire eqn by 2 2(C 2 H 6 + O 2 2CO 2 + 3H 2 O) 2C 2 H 6 + 2O 2 4CO 2 + 6H 2 O Balance O’s 2C 2 H 6 + 7O 2 4CO 2 + 6H 2 O Make a T chart to double check balance of all elements on both sides
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SC2 Students will relate how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions. SC2 a. Identify and balance the following types of chemical equations: Synthesis Decomposition Single Replacement Double Replacement Combustion
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Combustion - “burning” (but not necessarily with flames) to release energy from a compound The energy is stored in the bonds of the compound being “burned” Oxygen is almost always one of the reactants Produces carbon dioxide and water Ex: cellular respiration Glucose + oxygen water + carbon dioxide + ENERGY
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Synthesis: Putting things together 2H2 + O2 2H2O (releases energy) Can you think of another example from biology? Decomposition Breaking compounds down 2H2O 2H2 + O2 (requires much energy) What other rx type is also decomposition? combustion
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Single replacement: One element “steals” partner from another 3SrO(s) + 2Al(s) Sr(s) + Al 2 O 3 (s) Double replacement: like “Wife Swap” CaF 2 + H 2 SO 4 CaSO 4 + 2HF
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Soluble dissolves (in water) Insoluble doesn’t dissolve (in water) Precipitate solids that form when two ions react in water to form an Insoluble compound Precipitation/ing forming a solid
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