Questions and Answers
Which of the following substances would heat up most slowly?
A 200 g block of a substance requires 1.84 KJ of heat to raise its temperature from 25°C to 45°C. What is the substance?
Iron
Which of the following is an exothermic reaction?
What is the specific heat of a substance if 25 g is heated by 15°C using 915 J of heat?
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Which of the following is true of an exothermic reaction?
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It takes 23.5 kJ of heat energy to raise the temperature of 100 g of a substance by 50°C. What is the substance?
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In the diagram, which letter represents the transition from liquid to gas?
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Two liquids of different temperatures are separated by a barrier. Describe how the molecules move in heat flow.
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A chemical reaction is carried out in a closed container. The energy absorbed by the chemical reaction is 100 kJ. How much thermal energy moves inward from the air or the walls of the container?
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Which of the following is an endothermic reaction?
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In the coffee-cup calorimeter used in the laboratory, which of the following statements is true?
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In a calorimeter, 3.34 kJ of heat was absorbed when 10 g of ice melted. What is the enthalpy of fusion of the ice?
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Which of the following is the abbreviation for a unit of energy?
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How much heat is needed to raise the temperature of 25 g of a substance by 15°C when the specific heat is 0.92 J/g°C?
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A copper block (90°C) is placed in contact with a lead block (20°C). What will happen?
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Which of the following is an endothermic process?
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Which of the following statements is true?
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In a calorimeter, the temperature of 100 g of water decreases by 10°C when 10 g of ice melted. How much heat was absorbed by the ice?
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Where does the energy come from when hydrogen gas explodes when burned with oxygen gas?
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If a warm air mass is located in the northwest United States and a cold air mass is located in the southeast United States, from which direction will the winds blow?
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In the diagram, which letter represents the transition from solid to liquid?
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Study Notes
Heat and Temperature Concepts
- Aluminum heats up most slowly among substances with the same mass and heating conditions.
- A 200 g block requires 1.84 KJ of heat to raise its temperature from 25°C to 45°C, identifying it as iron.
- Oxidation of iron is an example of an exothermic reaction where heat is released.
Specific Heat and Calorimetry
- Specific heat can be calculated: 915 J is needed to raise the temperature of 25 g by 15°C, resulting in a specific heat of 2.44 J/g°C.
- An exothermic reaction has reactants with greater enthalpy than products.
- Ammonia is identified as the substance where 23.5 kJ raises the temperature of 100 g by 50°C.
Heat Transfer and Molecular Movement
- Transition from liquid to gas in a diagram is represented by segment D.
- In heat flow, hot liquid molecules collide, transferring energy to the barrier and subsequently to cold liquid molecules.
Energy Dynamics in Chemical Reactions
- In a closed container, a chemical reaction absorbing 100 kJ also results in 100 kJ of thermal energy moving inward from the surroundings.
- The reaction in a cold pack is categorized as endothermic.
Calorimetry Experiments
- In a coffee-cup calorimeter, water is part of the system impacting energy calculations.
- The enthalpy of fusion for ice is determined as 334 J/g when 3.34 kJ is absorbed by 10 g of ice melting.
Energy Units and Calculations
- The abbreviation for a unit of energy is J (Joule).
- A specific heat of 0.92 J/g°C requires 345 J to raise the temperature of 25 g by 15°C.
Heat Flow Between Materials
- Heat moves from a hot copper block (90°C) to a lead block (20°C) and then to an iron block (70°C) until thermal equilibrium is reached.
- Melting ice in water is categorized as an endothermic process, absorbing heat.
Energy Changes in Reactions
- Energy in an endothermic reaction results in products having greater energy than reactants.
- In a calorimeter experiment, 10 g of ice melting results in a temperature decrease of 10°C in 100 g of water, absorbing 4.18 kJ of heat.
Chemical Bond Energy
- The energy released during the explosion of hydrogen gas with oxygen comes from the breaking of chemical bonds between hydrogen and oxygen atoms.
Air Mass Interactions
- Winds blow from a warm air mass in the northwest United States toward a cold air mass in the southeast due to differences in thermal energy.
Phase Transition Representation
- The transition from solid to liquid in a diagram is represented by segment B.
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Description
Test your knowledge with the Unit 4 Mid Unit Practice Test quiz. It covers various substances and their heat capacities, helping you understand which materials heat up slowly under equal conditions. Perfect for students looking to reinforce their understanding of thermal properties.
