Absolutely. This looks like a **huge amount**, but it is actually built around a few simple ideas. I’ll explain it like a Year 10 study guide, with **what you need to understand + what you need to memorise + easy examples**. # 🧪 YEAR 10 REACTIONS — SIMPLE EXPLANATION ## PART 1: LAW OF CONSERVATION OF MASS ### ⭐ The most important sentence to memorise: > **Matter cannot be created or destroyed during a chemical reaction. Atoms are only rearranged.** Think of LEGO. If you have: * 5 red LEGO pieces * 3 blue LEGO pieces You can rearrange them into something completely different, but you still have **5 red + 3 blue**. A chemical reaction works the same way. ### Before reaction: **Reactants → Products** The atoms in the reactants get rearranged to make the products. --- ## 🔵 Reactants vs Products **Reactants = what you START with** **Products = what you END with** Example: **Hydrogen + Oxygen → Water** * Hydrogen = reactant * Oxygen = reactant * Water = product The **arrow →** means "produces" or "makes". ### Memorise: **Reactants → Products** --- # 🔒 Closed vs Open Systems This is VERY important for your experiment. ### Closed system 🔒 Nothing can escape. For example, you react vinegar and sodium bicarbonate inside a sealed container. The gas produced stays inside. Therefore: **Mass before = Mass after** because nothing has escaped. --- ### Open system 🔓 Something can escape. For example: **Vinegar + sodium bicarbonate → carbon dioxide gas** If you do this in an open container, the CO₂ gas escapes into the air. So your scales might show: **Mass before: 50 g** **Mass after: 48 g** It looks like 2 g disappeared. But it didn't disappear! 👉 **The 2 g of mass left the container as CO₂ gas.** ### ⭐ Exam sentence: > In an open system, the mass may appear to decrease because gaseous products escape into the surroundings. --- # ⚖️ Why do we balance equations? Because atoms **cannot magically appear or disappear**. Example: ❌ H₂ + O₂ → H₂O Let's count: Left: * H = 2 * O = 2 Right: * H = 2 * O = 1 There is an oxygen atom missing! So we balance it: ✅ **2H₂ + O₂ → 2H₂O** Now: Left: * H = 4 * O = 2 Right: * H = 4 * O = 2 Perfect! ### ⭐ Memorise: > **A balanced equation has the same number of each type of atom on both sides.** --- # 🔢 SUBSCRIPT vs COEFFICIENT This is a common test question. ### Subscript The little number **inside** a formula. Example: **H₂O** The ₂ means there are **2 hydrogen atoms**. You **cannot change the subscript when balancing** because that changes the substance. --- ### Coefficient The big number **in front**. Example: **2H₂O** This means there are **2 water molecules**. Each H₂O has: * 2 H * 1 O So 2H₂O has: * 4 H * 2 O ### Easy way to remember: **Subscript = inside the formula** **Coefficient = in front** --- # ⚛️ PART 2: ATOMS AND IONS ## Atom An atom is electrically **neutral**. It has equal numbers of: * protons (+) * electrons (-) --- ## Ion An ion has an electrical charge. It happens when an atom **loses or gains electrons**. ### Loses electrons → positive ion (+) ### Gains electrons → negative ion (-) Why? Electrons are negative. So if you **lose negative electrons**, you become more positive. --- # 🧠 Common ion charges You need to know the common patterns from the Periodic Table. | Group | Common charge | | -------- | ------------- | | Group 1 | +1 | | Group 2 | +2 | | Group 13 | +3 | | Group 15 | -3 | | Group 16 | -2 | | Group 17 | -1 | | Group 18 | 0 | For example: **Na → Na⁺** **Mg → Mg²⁺** **Al → Al³⁺** **Cl → Cl⁻** **O → O²⁻** --- # 🧪 MAKING IONIC COMPOUNDS The total charge must equal **0**. Example: ### Sodium chloride Na⁺ + Cl⁻ +1 + -1 = 0 Therefore: **NaCl** --- ### Magnesium chloride Mg²⁺ + Cl⁻ You need TWO Cl⁻: +2 + (-1) + (-1) = 0 Therefore: **MgCl₂** --- ### Aluminium oxide Al³⁺ + O²⁻ You need: * 2 Al³⁺ = +6 * 3 O²⁻ = -6 Therefore: **Al₂O₃** ### ⭐ Main rule: > **The total positive charge must equal the total negative charge.** --- # 🧩 POLYATOMIC IONS These are groups of atoms that act as **one ion**. Some important ones: | Ion | Charge | | --------- | -----: | | Nitrate | NO₃⁻ | | Hydroxide | OH⁻ | | Sulfate | SO₄²⁻ | | Carbonate | CO₃²⁻ | For example: **Na⁺ + NO₃⁻ → NaNO₃** And: **Ca²⁺ + OH⁻ → Ca(OH)₂** The brackets are needed because there are **two whole OH groups**. --- # 🧪 COMMON FORMULAS TO KNOW You should recognise these: | Substance | Formula | | ----------------- | ------- | | Water | H₂O | | Carbon dioxide | CO₂ | | Hydrochloric acid | HCl | | Sulfuric acid | H₂SO₄ | | Sodium chloride | NaCl | | Sodium hydroxide | NaOH | --- # 🧪 PART 3: CHEMICAL EQUATIONS There are three levels. ### 1️⃣ Word equation **Hydrogen + oxygen → water** ### 2️⃣ Formula equation **H₂ + O₂ → H₂O** ### 3️⃣ Balanced chemical equation **2H₂ + O₂ → 2H₂O** So you're basically going: **words → formulas → balance** --- # 💧 STATES OF MATTER You might need these symbols: | Symbol | Meaning | | ------ | ------------------ | | (s) | solid | | (l) | liquid | | (g) | gas | | (aq) | dissolved in water | Example: **H₂O(l)** = liquid water **CO₂(g)** = carbon dioxide gas **NaCl(aq)** = sodium chloride dissolved in water --- # ⚗️ PART 4: TYPES OF CHEMICAL REACTIONS There are several patterns you need to recognise. --- ## 1. SYNTHESIS ### Think: **put together** Two or more substances combine to make **one product**. ### Pattern: **A + B → AB** Example: **2H₂ + O₂ → 2H₂O** Two substances combine to form one substance. ### Memory trick: **Synthesis = Single product** --- # 2. DECOMPOSITION ### Think: **break apart** One compound breaks into two or more substances. ### Pattern: **AB → A + B** Example: **2H₂O → 2H₂ + O₂** One substance becomes multiple substances. ### Memory trick: **Decomposition = Divide** --- # 3. DISPLACEMENT One element **kicks out** another element. Example: **Mg + 2HCl → MgCl₂ + H₂** Magnesium replaces the hydrogen. Think: 🏃 **"Get out! I'm taking your place!"** ### Reactivity matters A more reactive metal can displace a less reactive metal. For example, a very reactive metal can push out a less reactive metal from its compound. --- # 4. DOUBLE DISPLACEMENT Two compounds swap partners. ### Pattern: **AB + CD → AD + CB** Example: **AgNO₃ + NaCl → AgCl + NaNO₃** The ions swap partners. Think: 💃 **Everybody switches partners.** --- # ☁️ PRECIPITATION Sometimes a double displacement reaction produces a **solid**. That solid is called a: ### **PRECIPITATE** If two clear solutions are mixed and suddenly a solid forms, that solid is the precipitate. --- # 5. NEUTRALISATION This one is VERY important. ### ⭐ Memorise: **ACID + BASE → SALT + WATER** Example: **HCl + NaOH → NaCl + H₂O** Hydrochloric acid + sodium hydroxide → sodium chloride + water. That's neutralisation. --- # 6. ACID + METAL An acid reacting with a metal usually produces: ### ⭐ **SALT + HYDROGEN GAS** Example: **Hydrochloric acid + magnesium → magnesium chloride + hydrogen** You can test hydrogen using a **lit splint**; hydrogen gives a characteristic **"pop"**. You don't need to memorise complicated details—just remember: **Acid + metal → salt + hydrogen** --- # 7. ACID + METAL CARBONATE This is another one you should memorise. ### ⭐: **ACID + METAL CARBONATE → SALT + WATER + CARBON DIOXIDE** Example: **Hydrochloric acid + calcium carbonate → calcium chloride + water + carbon dioxide** You can test carbon dioxide using **limewater**; it turns **milky/cloudy**. ### Memory: **Acid + carbonate = SWC** **S**alt **W**ater **C**arbon dioxide --- # 🧪 PART 5: ACIDS, BASES AND pH ## Acids Acids have a **pH below 7**. Examples: * Hydrochloric acid * Sulfuric acid * Vinegar --- ## Neutral pH = **7** Pure water is approximately neutral. --- ## Bases Bases have a **pH above 7**. Examples: * Sodium hydroxide * Soap * Some cleaning products --- # 📏 THE pH SCALE Memorise this: **1 — 2 — 3 — 4 — 5 — 6 | 7 | 8 — 9 — 10 — 11 — 12 — 13 — 14** 🔴 **1–6 = ACIDIC** 🟢 **7 = NEUTRAL** 🔵 **8–14 = BASIC/ALKALINE** ### Important: The **lower the pH → stronger/more acidic** The **higher the pH → more basic/alkaline** --- # 🌈 INDICATORS Indicators tell you whether something is acidic or basic. For example, universal indicator changes colour depending on pH. You don't necessarily need to memorise every colour unless your teacher specifically requires it. The important idea is: **Indicator → tells you about pH** --- # ⚖️ NEUTRALISATION AND pH If you mix an acid and a base: **acid + base → salt + water** The pH moves **towards 7**. For example: pH 2 acid + base → pH might move toward 7. If you add too much base, it can eventually become **basic**, so the pH can go past 7. --- # ⚡ PART 6: RATE OF REACTION This connects directly to your vinegar experiment. ## What is rate of reaction? ### ⭐ Memorise: > **Rate of reaction is how quickly reactants are converted into products.** Basically: **How FAST is the reaction happening?** --- # 💥 COLLISION THEORY This is probably the most important idea for explaining reaction rates. Imagine particles as tiny balls constantly moving around. For a reaction to happen: ### 1. Particles must collide. BUT... ### 2. They must collide with enough energy. This is called: ### **Activation energy** So: **Collision + enough energy → successful reaction** --- # 🧠 ACTIVATION ENERGY Activation energy is the **minimum energy needed for a successful reaction**. Think of it like a hill. The particles need enough energy to get **over the hill**. --- # 🔥 FACTORS THAT CHANGE REACTION RATE There are four main ones: ### **C**oncentration ### **S**urface area ### **T**emperature ### **C**atalyst Think: # **CSTC** --- # 🧪 1. CONCENTRATION Higher concentration = **more particles in the same amount of space.** More particles means: **more collisions** More collisions means: **faster reaction** ### Chain to memorise: **Higher concentration → more particles → more collisions → faster reaction** --- # 🧊 2. SURFACE AREA Imagine a big block of chalk versus chalk powder. The powder has much more surface exposed. More exposed surface = more particles available to collide. Therefore: **Higher surface area → more collisions → faster reaction** ### Easy example: Powder reacts faster than a large lump. --- # 🌡️ 3. TEMPERATURE Higher temperature gives particles **more kinetic energy**. That means: * particles move faster * collisions happen more often * collisions are more energetic * more collisions have enough energy to react Therefore: **Higher temperature → faster reaction** ### ⭐ Exam explanation: > Increasing temperature increases the kinetic energy of particles, causing them to move faster and collide more frequently and with greater energy, increasing the rate of reaction. --- # 🧪 4. CATALYST A catalyst makes a reaction happen faster. It does this by providing an: ### **alternative pathway with lower activation energy** The catalyst is **not used up** in the reaction. ### ⭐ Memorise: > **Catalyst = faster reaction + lower activation energy + not used up.** --- # 📈 PART 7: REACTION-RATE GRAPHS You might get a graph and have to explain it. Imagine: ```text Amount of product | | _______ | __/ | __/ | __/ |___/________________ Time ``` At the beginning, the graph rises steeply. That means: ### **Fast reaction** Then it starts becoming less steep. That means: ### **Reaction is slowing down** Eventually it becomes flat. That's called a: # PLATEAU A plateau means **no significant additional product is being formed**. The reaction has essentially stopped/progressed to completion. --- # 📊 HOW TO DESCRIBE A GRAPH Don't just say: ❌ "The reaction was faster." Instead explain **why** using Collision Theory. For example: > Increasing the concentration increased the rate of reaction because there were more reacting particles in the same volume, resulting in more frequent collisions and therefore more successful collisions per second. That's the type of explanation your teacher wants. --- # 🧠 THE BIGGEST THINGS TO MEMORISE If you are overwhelmed, focus on these first: ### ⚖️ Conservation of Mass **Matter is not created or destroyed. Atoms are rearranged.** ### 🔒 Closed system **Nothing escapes → mass stays the same.** ### 🔓 Open system **Gas can escape → measured mass can decrease.** ### 🧪 Equation **Reactants → Products** ### ⚖️ Balancing **Same number of each atom on both sides.** ### ⚛️ Ions **Lose electrons → positive** **Gain electrons → negative** ### 🧪 Ionic compounds **Total positive charge = total negative charge.** ### 🔥 Reaction types **Synthesis:** A + B → AB **Decomposition:** AB → A + B **Displacement:** one element replaces another **Double displacement:** compounds swap ions **Neutralisation:** **Acid + Base → Salt + Water** **Acid + Metal:** **Salt + Hydrogen** **Acid + Carbonate:** **Salt + Water + CO₂** ### 📏 pH **1–6 = acid** **7 = neutral** **8–14 = base** ### 💥 Collision Theory **Particles must collide + have enough energy.** ### ⚡ Rate factors **Concentration ↑ → collisions ↑ → rate ↑** **Surface area ↑ → collisions ↑ → rate ↑** **Temperature ↑ → kinetic energy ↑ → successful collisions ↑ → rate ↑** **Catalyst → lower activation energy → faster reaction** --- ## 🎯 One simple way to remember the entire topic Think of a chemical reaction as a **particle rearranging game**: **Atoms rearrange → new substances form → mass is conserved.** Then ask: **What are the particles doing?** If they're colliding more often or with more energy, the reaction is faster. That's basically the connection between **Conservation of Mass + Chemical Reactions + Collision Theory + Rate of Reaction**.