1. CHEMICAL REACTIONS AND EQUATIONS (S1)

Chemical Reactions and The Magic of Matter Changing! (Class 10 Chemistry) 00040 0 00 Let's explore how elements combine, break apart, and transform our world..

Chemistry is Happening Inside You Right Now! Digestion! Molecular Energy for Life. The Food We Eat. TheBigldea: Elements are the building blocks of all matter. Every second, chemical processes keep you alive! o hatHappens? Molecules rearrange by breaking old bonds and forming new ones. Why It Matters: By looking at how things react, we can figure out exactly what they are made of..

Spot the Difference: Physical vs. Chemical Changes Physical Change Rule: Chemical composition stays the same; only physical traits change. Usually reversible! examples; • Ice melting to water (Solid Liquid) • Dry ice (removing C02 from air using cold temps/high pressure) • Heating solid alloys into gases Chemical Change Original material reacts to produce NEW substances with distinct compositions. Irreversible! • Burning coal • Digestion of food Curdling of milk.

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Meet the Chemical Reaction HEAT Reactants: The starting substances that participate. Products: The new substances formed. Reversing is unfeasible! In a chemical reaction, old chemical bonds break and new ones form. The products have completely different features from the reactants. Energ like heat light, or electricity often drives this! Signs to look for: • Change in colour, temperature, state, evolution of gas, or formation of a precipitate..

Writing the Secret Code: Chemical Equations 1. Word Equation Brief and simple Sodium + water Sodium hydroxide + Hydrogen Fails to conform to the Law of Conservation of Mass! 2. Skeletal Equation Uses symbols, but atoms aren't equal yet Na(s) + HCl(aq) NaCl(aq) + H2(g) Atoms on the Atoms on the 3. Balanced Equation right. Follows the rules! 2Na(s) + 2HCl(aq) 2NaCl(aq) + H2(g).

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The Golden Rule: How to Balance an Equation Step 1: Count Atoms Fea04 has 4 Oxygen atoms on the right, but only 1 on the left! Element Left R ht Step 2: Balance Oxygen Multiply H20 by 4 Fe + 4H20 F%04 + H2 Step 3: Balance Hydrogen We now have 8 H's on the left. Multiply + Step 4: Balance Iron 4 Multiply Feby 3. 3Fe + + Element Left Right.

Identification of Chemical Reactions 1. Change in colour 2. Change in temperature sss 3. Change in state.

Adding Details: Making Equations Informative Physical States% (s) = Solid (l) = Liquid (g) = Gas • (aq) = Aqueous (mixed in water) Cheat Sheet 200 atm cOOC CFe-M0) • (t) = Gas evolving (l) or ppt= Precipitate (insoluble solid) 2NH3(g) + 22400 calories heat + 3H2Cg) pressure $eat Energy;) • (+) on right = Exothermic Cheat given off) • on right = Endothermic Cheat absorbed) Direction: (9) = Irreversible • (e) = Reversible.

Decoding the Secret Math: The Mole Concept 22.4 litres 1 gram atom 1 mole 6.022 x 1023 molecules 1 gram molecule o • • • What the EquationTeIIs Us The big numbers placed before reactants and productsindicate the number of moles! Nature of reactants and roducts through their formulas. Ratio of the number of molecules reacting. Relative masses of the reactants and products. Volume ratios of gases involved. At STP, 1 mole of gas = 22.4 Litres!.

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Chemistry Recipes Part 1: Joining and Breaking Combination / Synthesis Reaction • Two or more substances combine into Example: Burning coal: C(s) + 02(g) —+ C02(g) Decomposition / Analysis Reaction • ONE compound breaks into simpler substances. Requires energy (Heat, Electricity, or Light)! Photochemical: 2AgCl -i 2Ag +.

One element takes the place of another element in a compound. Thread Test Tube Iron nail cuso, solution Chemistry Recipes Part 2: Switching Places o + CuS04 + cu Displacement Reaction A+BC—AC+B Double Displacement (Metathesis) n + CD—AD + CB B Iron nail taken out from CuS04 solution c Mutual exchange of ions to form two new compounds. BaC12 solution 1 1 1 Test tube containing sodium sulphate solution White ppt of Basq Precipitation: Na2S04 + BaC12 —5 BaS04(J) + 2NaCI Also used in Neutralization (Acid + Base Salt + Water).

Think & Answer! Be the Chemist. Reaction Case Files o Challenge 1: Pb + cuC12 -+ PbC12 + cu Question: What type of reaction is this? Challenge 2: 2H O 2H + 02 (using electricity) Question: What type of chemical reaction is this? Lead re laces co er (One substance •nio two).

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The Big Picture: Chapter Mind Map o o o Physical Chemical (new substance) Skeletal o o Changes Equations 0 Balanced (Conservation of Mass) Chemical 00 Reactions Equations Decomposition CAB -i via Heat/Light/Elec) o Decoding Reaction Types Displacement (Switching I) State symbols Moles @QIN Combination CA+B•AB) Double Displacement (Switching 2 — Ppt/ Neutralization).

Quick Revision: Keg Points Concept Reactants & Products Skeletal vs Balanced Exothermic vs Endothermic Mole & GMV Precipitation Reaction Neutralization Reaction Definition / Core Rule Reactants (left side) change into Products (right side, new features). Skeletal is unbalanced; Balanced perfectly follows Law of Conservation of Mass. Exothermic gives off heat (+ sign), Endothermic absorbs heat (- sign). 1 Mole = 6.022 x 1023 molecules. Occupies 22.4 Litres at STP. Double displacement reaction that forms an insoluble solid (l). Acid + Base —Y Salt + Water. Study Smart!.

g Chemistry Pro! Every time you strike a match, cook food, or even take a co o 5 breath, you are a walking, talking chemistry exper- riment! Keep looking for reactions around you. (Hint: Photochemical decomposition leaves grey silver behind!) One Last Ouestion to Ponder: What colour change happens when white Silver Chloride (AgCl) is exposed to sunlight?.