Chapter 8 SABIS Grade 10 Part 2

Chapter 8 Second Lesson :

🔥 Demonstration: Measuring the Heat of Reaction and Calculations

Part 1: 🔍 The Measurement of Reaction Heat

8.1.4 Calorimetry🧪 Exploring Calorimetry Calorimetry is like using a special scale to weigh the heat exchanged during a reaction! ⚖️ It helps us measure reaction heats by observing temperature changes.

Sample Question 8 🧠

Finding the True Meaning Calorimetry is: a) measuring reaction heats by observing changes in color. b) using a calorie meter to measure calories. c) determining the rate of reaction by measuring how quickly the temperature rises. d) the measurement of reaction heats. e) the measurement of heat content of a compound.

Part 2: 🔍 Detailed Explanation

8.1.5 Expressing the Heat of Reaction in Chemical Equations

🔥 Heat Expressed in Equations Let's learn how to express the heat of reaction in different formats. It's like using different languages to describe the same fascinating story of energy changes!

📖Sample Question 10 🧠

Recognizing Different Formats Which of the following equations is equivalent to: N2(g) + 2O2(g) + 68 kJ → 2NO2(g) a) N2(g) + 2O2(g) → 2NO2(g) ΔH = +68 kJ b) N2(g) + 2O2(g) → 2NO2(g) ΔH = -68 kJ c) ½N2(g) + O2(g) → NO2(g) ΔH = + 34 kJ d) N2(g) + 2O2(g) → 2NO2(g) ΔH = +68 kJ/mol N2 e) ½N2(g) + O2(g) → NO2(g) ΔH = −34 kJ f) N2(g) + 2O2(g) → 2NO2(g) ΔH = +34 kJ/mol NO2

8.1.6 Predicting the Heat of a Reaction

🔮 Predicting Reaction Heat Let's use the heats of formation to calculate the heat of reaction! It's like solving a puzzle to discover the hidden energy changes in a chemical transformation.

🧩Sample Question 12

🧠 Simple Application of Heats of Formation Given: C(diamond) + O2(g) → CO2(g) ΔH = −395.4 kJ C(graphite) + O2(g) → CO2(g) ΔH = −393.5 kJ a) Find ΔH for the manufacture of diamond from graphite: C(graphite) → C(diamond) ΔH = -393.5 + 395.4 = +1.9 kJ b) Is heat absorbed or evolved as graphite is converted to diamond? 🎯 Correct Answer: Absorbed

Part 3: 🔍 Energy Stored in a Molecule8.2.1 Conservation of Energy in a Chemical Reaction🔌 Understanding Electrical Work In chemistry, when we talk about electrical work, we refer to: a) The energy supplied by an electric current. b) The force supplied by an electric current. c) The energy stored in a battery. d) The power supplied by an electric current. e) The current that can produce a chemical reaction.

Sample Question 14 🧠 Calculating Energy Supplied by Electric Current A current is used to electrolyze water. The voltage across the terminals is 6.00 volts (J/Coulomb). If the current was 0.500 A (Coulomb/sec) and the time was 80.0 seconds, the energy supplied is: 🎯 Correct Answer: 240 J Explanation: W = I × V × t = 0.500 × 6.00 × 80.0 = 240 J

8.2.2 Kinetic and Potential Energy in Molecules🚗

Kinetic and Potential Energy in Molecules Just like a roller coaster ride has kinetic and potential energy, molecules have their unique energy dance! 🎢

Sample Question 15

🧠 Recalling Expressions for Gravitational Potential and Kinetic Energy of an Object An object of mass m is moving at a velocity of v at a height of h meters above the ground. Its kinetic and gravitational potential energies with respect to the ground are respectively: 🎯 Correct Answer: c) mgh and ½ mv^2

.8.2.3 Chemical Bond Energy

🔗 Exploring Chemical Bond Energy As atoms get closer, their potential energy changes. It's like feeling the energy between two friends as they get closer for a high-five!

🙌Sample Question 16

🧠 Variation of Potential Energy as Two H Atoms Approach As two hydrogen (H) atoms approach each other to form an H2 molecule: 🎯 Correct Answer: The potential energy decreases.

Part 4: AnswersSample Question 8: Correct Answer: d) The measurement of reaction heats.

Sample Question 9: Correct Answer: c) ΔH for the substance at constant pressure.

Sample Question 10: Correct Answer: a) N2(g) + 2O2(g) → 2NO2(g) ΔH = +68 kJ.

Sample Question 11: Correct Answer: C2H6(g) → 2C(s) + 3H2(g) ΔH = +84.5 kJ.

Sample Question 12a: Correct Answer: +1.9 kJ.

Sample Question 12b: Correct Answer: Absorbed.

Sample Question 13: Correct Answer: a) The energy supplied by an electric current.

Sample Question 14: Correct Answer: 240 J.

Sample Question 15: Correct Answer: c) mgh and ½ mv^2.

Sample Question 16: Correct Answer: The potential energy decreases.Congratulations! 🎉 You've completed Lesson 2 and learned how to measure and predict the heat of reaction, explore electrical work, and understand kinetic and potential energy in molecules. Great job! 🚀 Stay curious and ready for more chemistry adventures ahead! 🧪