📝Lesson 9📝
Chapter 2 Problems and Questions
1️⃣🍀 Easy Questions
🌡 What is the change of a substance from solid to liquid at a definite temperature called?
🌬 Define evaporation in your own words.
🌞 What does the horizontal part of the heating curve represent?
❄️ What does the phase change in the cooling curve signify?
🌡 How does the position of the horizontal part on the heating curve relate to the melting point of the solid?
❄️ What is the physical constant for the temperature at which a solid changes to a liquid at the same temperature and pressure?
🔵 Intermediate Questions
📉 Given a cooling curve of a pure compound, explain the stages in detail.
🎈 Assume the initial volume of a gas is 3L and its pressure is 4 atm. If the pressure is reduced to 2 atm, what will be the new volume, according to Boyle's law?
🎈 What happens to the volume of a gas if the pressure is doubled while the temperature is held constant, according to Boyle's law?
⏳ You have a pure compound, the larger is the amount of solid heated, what happens to the time it needs for the sample to start melting and to melt completely?
📝 Answer: The larger is the amount of solid heated the longer is the time it needs for the sample to start melting and to melt completely.
🌡️ How does the temperature affect the average kinetic energy of the particles during the phase change in the heating curve of a pure compound?
📝 Answer: During the phase change, the temperature remains constant. So, the average kinetic energy of the particles does not change. The added energy is used to change the phase of the substance.
🔴 Difficult Questions
📈 Given a heating curve with the first stage having a slope of 3 and the third stage having a slope of 5, can you justify why the slopes are different?
🎈 If a sample of gas has an initial volume of 100 mL at a pressure of 500 kPa and the pressure is increased to 1000 kPa, what would the final volume of the gas be according to Boyle's law?
🧊 Given a cooling curve of a pure compound, explain the changes in kinetic and potential energy during the phase transitions.
🌡️ How does the phase change represented in the cooling curve differ from the phase change represented in the heating curve?
💠 Advanced Questions
🌡️ Based on a heating curve, describe the kinetic and potential energy changes during each phase transition.
🎈 If the pressure of a gas sample is halved, what will happen to the volume according to Boyle's law?
📈 Draw and explain the stages of a heating curve of a pure compound.
🎈 If a gas has an initial volume of 5L at a pressure of 2 atm and the pressure is increased to 4 atm, what will be the final volume according to Boyle's law?
🌡️ What is the definition of a phase in the context of states of matter?
🏆 Champion-Level Questions
📈 Explain why the heating curve has a flat horizontal part where the solid changes to a liquid and the graph remains horizontal until all the solid melts.
🎈 If a gas initially at 20L and 5 atm is compressed to a volume of 10L, what will the final pressure be according to Boyle's law?
📉 Based on a cooling curve, how does the size of the liquid cooled affect the time it needs to start freezing and to freeze completely?
📈 Given a heating curve, how does the energy added during the phase change from solid to liquid relate to the potential energy of the particles?
🎈 If a sample of gas has a volume of 200 mL at 3 atm, and the pressure is increased to 6 atm, what would be the new volume according to Boyle's law?
🌡️ Describe what happens during the second stage of the heating curve of a pure compound.
🎈 According to Boyle's law, if a gas sample at 300 K with a volume of 2L experiences a pressure increase from 2 atm to 5 atm, what is the new volume?
📈 What determines the melting point of a solid based on the heating curve?
🌡️ Based on a cooling curve, how does the amount of liquid cooled affect the time it takes for the sample to freeze completely?
🎈 According to Boyle's law, if a gas sample at 1 atm and 5L is compressed to a volume of 2L, what will be the new pressure?
🌡️ In a cooling curve of a pure compound, which phase exists in the first stage and which phase in the third stage?📝 Answer: In a cooling curve of a pure compound, the compound exists as a liquid in the first stage and as a solid in the third stage.🎈 According to Boyle's law, what happens to the volume of a gas if the pressure is halved, while the temperature is held constant?📝 Answer: According to Boyle's law, if the pressure is halved, the volume of the gas will double.📈 Given a heating curve of a pure compound, explain why the slopes of the first and third stages are different.📝 Answer: The slopes are different because they represent different heat capacities of the solid and liquid phases of the substance. The steeper slope in the third stage indicates that more energy is needed to raise the temperature of the liquid compared to the solid.🌡️ What physical property determines the position of the horizontal part in a heating curve of a solid compound?📝 Answer: The position of the horizontal part in a heating curve of a solid compound is determined by the melting point of the solid.🎈 A gas has a volume of 10L at a pressure of 3 atm. If the volume is reduced to 5L, what will be the new pressure, according to Boyle's law?📝 Answer: According to Boyle's law, P1V1 = P2V2. So, the new pressure would be (3 atm * 10L) / 5L = 6 atm.🌡️ How does the size of the solid heated affect the time it takes for the sample to start melting and to melt completely, according to the heating curve?📝 Answer: The larger the amount of solid heated, the longer it takes for the sample to start melting and to melt completely.🎈 According to Boyle's law, what will happen to the volume of a gas if the pressure is doubled, while the temperature is held constant?📝 Answer: According to Boyle's law, if the pressure is doubled, the volume of the gas will be halved.📈 Explain the second stage of a cooling curve of a pure compound.📝 Answer: The second stage of a cooling curve represents the phase transition from liquid to solid (freezing). During this stage, the temperature remains constant as the liquid changes to solid.🌡️ What is the melting point of a substance?📝 Answer: The melting point is the temperature at which a solid changes to a liquid at the same temperature and pressure.🎈 If a gas sample has an initial volume of 2L at a pressure of 1 atm and the pressure is increased to 3 atm, what will be the new volume, according to Boyle's law?📝 Answer: According to Boyle's law, P1V1 = P2V2. So, the new volume would be (1 atm * 2L) / 3 atm = 0.67L.🌡️ In the first and third stages of a heating curve, there is a change in temperature, what does this indicate about the average kinetic energy of the particles?📝 Answer: In the first and third stages of a heating curve, there is a change in temperature, which means the average kinetic energy of the particles is increasing.🎈 Boyle's law states that for a given sample of gas (fixed amount) the volume of the gas varies inversely with the pressure at constant temperature. Express this mathematically.📝 Answer: Mathematically, Boyle's law can be expressed as P1V1 = P2V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume.📈 What does the second stage of the heating curve represent when a pure compound changes from solid to liquid?📝 Answer: The second stage of the heating curve represents the phase transition from solid to liquid, often called melting or fusion.🌡️ Explain the significance of the horizontal part of a cooling curve.📝 Answer: The horizontal part of a cooling curve represents the phase transition from liquid to solid (freezing). The temperature remains constant during this phase transition because the heat removed is used to change the phase, not to lower the temperature.🎈 Given a sample of gas with an initial volume of 1L at a pressure of 2 atm, if the volume is reduced to 0.5L, what will be the new pressure according to Boyle's law?📝 Answer: According to Boyle's law, P1V1 = P2V2. So, the new pressure would be (2 atm * 1L) / 0.5L = 4 atm.🌡️ How does the second stage of a heating curve, the plateau, reflect on the average kinetic energy and potential energy of the particles?📝 Answer: In the second stage, the plateau, the average kinetic energy of the particles is constant (hence, the temperature is constant), while the potential energy increases as the heat is used to break intermolecular bonds and change the phase from solid to liquid.🎈 If a gas sample with a volume of 300 mL at a pressure of 5 atm is allowed to expand to a volume of 600 mL, what would be the new pressure according to Boyle's law?📝 Answer: According to Boyle's law, P1V1 = P2V2. So, the new pressure would be (5 atm * 300 mL) / 600 mL = 2.5 atm.📈 Explain how the amount of solid heated affects the time it takes for the sample to start melting and to melt completely based on a heating curve.📝 Answer: The larger the amount of solid heated, the longer it takes for the sample to start melting and to melt completely, because more heat is needed to overcome the intermolecular forces in a larger amount of substance.🌡️ Explain what happens during the first and third stages of a cooling curve.📝 Answer: In the first stage of a cooling curve, the liquid is cooling and the temperature decreases until it reaches the freezing point. In the third stage, the liquid has completely turned into a solid and continues to cool down, with the temperature continuing to decrease.🎈 If a sample of gas has an initial volume of 400 mL at a pressure of 2 atm and the pressure is increased to 4 atm, what would be the new volume according to Boyle's law?📝 Answer: According to Boyle's law, P1V1 = P2V2. So, the new volume would be (2 atm * 400 mL) / 4 atm = 200 mL.