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Chapter 4 SABIS Grade 10 Part 3

Conservation of Matter and Balancing Chemical Equations

⚖️Lesson 18: ⚖️ Conservation of Matter and Balancing Chemical Equations


Hello there, curious learners! 🌟 Today, we are diving into one of the fundamental laws of the universe - the Law of Conservation of Matter. Plus, we'll learn to balance chemical equations, because, in chemistry, everything should be equal. Let's dive in! ⚖️🔬💡


📘🌟 Prerequisite Material Quiz for Conservation of Matter and Balancing Chemical Equations 🌟📘 Check if you are ready for Lesson 18!

🔹 Question 1: 🧪 Basic Chemistry 🔹

What is the atomic number of an element?

  • A) The number of protons in its nucleus

  • B) The number of electrons in its outer shell

  • C) The sum of protons and neutrons

  • D) The number of neutrons in its nucleus

📝 Answer: A) The number of protons in its nucleus

🔹 Question 2: ⚖️ Law of Conservation of Mass 🔹

The total mass of the reactants in a chemical reaction is __________ the total mass of the products.

  • A) Less than

  • B) Greater than

  • C) Equal to

  • D) Not related to

📝 Answer: C) Equal to

🔹 Question 3: 📘 Chemical Equations 🔹

Which symbol is used to separate reactants from products in a chemical equation?

  • A) ->

  • B) =

  • C) +

  • D) /

📝 Answer: A) ->

🔹 Question 4: 🧮 Basic Math Skills 🔹

When balancing a chemical equation, what can you change to make the equation balanced?

  • A) Subscripts

  • B) Coefficients

  • C) Charges

  • D) Elements

📝 Answer: B) Coefficients

🔹 Question 5: 🧪 Chemical Reactions 🔹

What is a reactant in a chemical reaction?

  • A) A substance that is produced

  • B) A substance that undergoes a change

  • C) A catalyst that speeds up the reaction

  • D) A bond that is broken

📝 Answer: B) A substance that undergoes a change

🔹 Question 6: 📖 Chemical Compounds 🔹

What is the chemical formula for water?

  • A) H2

  • B) CO2

  • C) H2O

  • D) O2

📝 Answer: C) H2O

🔹 Question 7: ⚛️ Atoms and Molecules 🔹

Which of the following is NOT a molecule?

  • A) O2

  • B) H2O

  • C) NaCl

  • D) CO2

📝 Answer: C) NaCl

🔹 Question 8: 🔍 Counting Atoms 🔹

How many oxygen atoms are in 2 molecules of CO2?

  • A) 2

  • B) 4

  • C) 6

  • D) 8

📝 Answer: B) 4

🔹 Question 9: 🔄 Types of Chemical Reactions 🔹

In a synthesis reaction, two or more substances combine to form __________.

  • A) Multiple products

  • B) One product

  • C) No products

  • D) Unstable products

📝 Answer: B) One product

🔹 Question 10: 📊 Molar Mass 🔹

What is the molar mass of oxygen (O)?

  • A) 12 g/mol- B) 16 g/mol

  • C) 32 g/mol

  • D) 1 g/mol

📝 Answer: B) 16 g/mol




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Explanation:

Conservation of Matter & Balancing Equations 🧐👩‍🔬

Law of Conservation of Matter

This law states that matter cannot be created or destroyed. In a chemical reaction, the mass and atoms are conserved, meaning the total number of each type of atom is the same before and after the reaction. However, the number of molecules is not necessarily conserved as a chemical reaction involves a rearrangement of atoms.

Balancing Chemical Equations

This means making sure that the number of atoms of each element in the reactants side is equal to the number of atoms of that element in the products side. To do this, we use coefficients (the number in front of chemical symbols or formulas).

Remember: While balancing, you can change coefficients but not the subscripts. Subscripts tell us the number of atoms of an element in a molecule, while coefficients tell us the number of those molecules.

Examples 🌍🔬🔎

  • Conservation of matter: If you burn a log, the mass of the ash, smoke, and gases produced will equal the original mass of the log and the oxygen consumed.

  • Balancing equations:

    • H2 + O2 → 2H2O (Balanced)

Post-lesson MCQs 📝✅

  1. True or False: In a chemical reaction, the number of each type of atom in the reactants and products is always the same.

  2. A balanced chemical equation obeys the law of ________. A) Gravity B) Conservation of Matter C) Motion D) Energy

  3. What is the role of a coefficient in a chemical equation?

  4. True or False: Ionic compounds are made up of ions, not molecules.

  5. The number of atoms of each element in a chemical reaction can be determined by the ________ in a chemical equation.

Complete the Questions 💡💭

  1. What is the difference between a subscript and a coefficient in a chemical equation?

  2. Balance the following chemical equation: C6H12O6 + O2 → CO2 + H2O

  3. Why can't we change the subscripts while balancing a chemical equation?

  4. Why is the law of conservation of matter important in balancing chemical equations?

  5. What does it mean if a chemical equation is not balanced?

Answers 🎯💡


Post-lesson MCQs:

  1. True,

  2. B,

  3. A coefficient in a chemical equation indicates the number of molecules or units of that compound,

  4. True,

  5. Coefficient and subscript

Complete the Questions:

  1. In a chemical equation, a subscript indicates the number of atoms of that element in a molecule while a coefficient indicates the number of molecules or units of that compound.

  2. C6H12O6 + 6O2 → 6CO2 + 6H2O

  3. We can't change subscripts while balancing a chemical equation because it would change the nature of the substance being represented.

  4. The law of conservation of matter is important in balancing chemical equations because it states that matter cannot be created or destroyed, which means the number and type of atoms must be the same on both sides of the equation.

  5. If a chemical equation is not balanced, it means that the number and type of atoms on the reactant side are not equal to the number and type of atoms on the product side, violating the law of conservation of matter.




4.2.3 |-- Keeping it Real: Atoms & Mass Just Don't Vanish in Reactions, Yo!

Question: Imagine your bike gets rusty - are the iron and oxygen just partying too hard and losing some of their weight? 🤔

Answer: Nah, they don’t lose or gain a pound! It’s like a weight watchers program for atoms; they keep the same mass. That's because the total weight of iron and oxygen before the rust party is the same as after. They just mixed up and turned into iron oxide (which is a fancy way of saying rust). It’s a universal rule, called the law of conservation of mass: no atom gains or loses mass in a reaction. The mass stays the same, just like the coolness of your vintage vinyl collection.

4.3 |-- Chemical Reactions: Like Epic Recipes, But With Atoms

Imagine making a sandwich, you need a certain amount of bread, lettuce, and other stuff. Chemical reactions are kinda like that - but with atoms and molecules.

  1. Example: When hydrogen (think of it as bread) and oxygen (lettuce) get together, they make water (a sandwich). The recipe goes like this: 2H2 + O2 -> 2H2O. Those numbers in front are like saying "two slices of bread and one lettuce make two sandwiches".

  2. Example: Sodium (salt) and chlorine (chlorine, duh!) join the party to make sodium chloride (table salt). The recipe: 2Na + Cl2 -> 2NaCl. Two salty dudes plus a dash of chlorine make two units of table salt.

  3. Example: Calcium carbonate (fancy name for chalk) and hydrochloric acid (nasty stuff!) react to make calcium chloride, carbon dioxide (fizzy gas), and water. The recipe: CaCO3 + 2HCl -> CaCl2 + CO2 + H2O. Kinda like saying, chalk + acid -> salt + fizz + water.

It's like cooking, but instead of delicious food, you're making chemical products! Yum? Maybe not. But super cool.

|-- Writing Equations: The Grammar of Chemistry

  1. Example: Magnesium and oxygen are like Romeo and Juliet. They react to form magnesium oxide. The love letter they write is: 2Mg + O2 -> 2MgO. It's like saying, "two Romeos and one oxygen cloud make two love stories".

  2. Example: Sulfuric acid and potassium hydroxide mix to form potassium sulfate and water. It's like a dance-off where acid and base dance together to make salt and water. The dance move: H2SO4 + 2KOH -> K2SO4 + 2H2O.

  3. Example: Methane burns with oxygen, and they rock the stage as carbon dioxide and water. The rock anthem is: CH4 + 2O2 -> CO2 + 2H2O. Methane and oxygen go full rockstar to become carbon dioxide and water.

Remember, in chemistry grammar, the stuff on the left is like the ingredients, and on the right is the epic meal you’ve made.

|-- Coefficients & Subscripts: The Secret Code of Chemical Reactions

  1. Example: For H2 + O2 -> 2H2O, the “2” in front of H2 and H2O is like saying, “dudes, we need two hydrogens and two waters.” The little 2's (subscripts) in H2 and O2 mean that there are two atoms hanging out together.

  2. Example: In photosynthesis, plants are like, "I'll take 6 of those CO2 and 6 of those H2O, and make some sugar and oxygen!” The equation 6CO2 + 6H2O -> C6H12O6 + 6O2 is just the plants’ shopping list. The subscripts (those little numbers) tell you how many carbons, hydrogens, and oxygens are in each sugar molecule.

  3. Example: When sodium hydroxide and hydrochloric acid are like, “let’s make salt and water,” their secret handshake is: NaOH + HCl -> NaCl + H2O. No coefficients in front mean it’s just one of each. The subscripts tell you how many of each atom are in the club.

4.4.3 |-- Stoichiometry: The Chemistry Chef's Secret Sauce

|-- Balancing Equations: Like Perfectly Level Skateboard Tricks

  1. Example: You’ve got hydrogen gas and oxygen gas, and you’re making water. The unbalanced trick is: H2 + O2 -> H2O. But wait, that’s like a skateboard trick gone wrong! To make it perfectly level, add some style: 2H2 + O2 -> 2H2O. Now both sides are in sync, like a perfectly executed kickflip.

  2. Example: Methane’s about to burn with oxygen to make carbon dioxide and water. But first, we gotta balance this move: CH4 + O2 -> CO2 + H2O. This equation is like a skateboarder trying a trick but not landing it. Let’s add some swagger: CH4 + 2O2 -> CO2 + 2H2O. Now, that’s a balanced, stylish trick.

  3. Example: Iron is chilling with oxygen, and they’re forming iron(III) oxide. The starting move: Fe + O2 -> Fe2O3. Looks off-balance, like trying a grind and slipping off. Let’s fix it: 2Fe + O2 -> 2Fe2O3. Now it’s balanced and ready to impress the crowd.

Remember, balancing equations is like nailing the perfect skateboard trick – you gotta keep both sides level and in sync. You can change the numbers in front (coefficients), but don’t mess with the little numbers (subscripts) – they’re like the DNA of the molecule. Keep it stylish! 🛹






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