WCAS - Washington Comprehensive Assessment of Science Energy Transfer and Conservation Questions and Answers — Questions and Answers
Question 1: A student places a metal spoon in a bowl of hot soup. After a few minutes, the handle of the spoon becomes warm. Which of the following correctly describes the primary method of heat transfer that causes the spoon's handle to warm up?
- Convection, because the heat from the soup circulates up the spoon.
- Radiation, because the soup emits thermal energy in the form of waves.
- Conduction, because heat energy is transferred from particle to particle along the spoon. (Correct answer)
- Insulation, because the metal prevents the heat from escaping the soup.
Correct answer: Conduction, because heat energy is transferred from particle to particle along the spoon.
The correct answer is conduction. Conduction is the transfer of thermal energy through direct contact between particles. In this scenario, the particles of the soup with higher kinetic energy collide with the particles of the spoon, transferring that energy. This process continues up the solid metal spoon from one particle to the next, causing the handle to warm.
Question 2: According to the law of conservation of energy, which of the following statements is true?
- Energy can be created but not destroyed.
- Energy can be lost as heat, reducing the total energy in a closed system.
- The total amount of energy in an isolated system remains constant over time. (Correct answer)
- Energy transformations are always 100% efficient.
Correct answer: The total amount of energy in an isolated system remains constant over time.
The law of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another or transferred from one system to another. Therefore, in an isolated (or closed) system, the total amount of energy is always conserved.
Question 3: A group of students designs a solar oven using a cardboard box, aluminum foil, plastic wrap, and black construction paper. The black paper is placed at the bottom of the box. What is the primary role of the black construction paper in this energy system?
- To reflect sunlight away from the food.
- To absorb radiant energy and convert it into thermal energy. (Correct answer)
- To provide structural support for the oven.
- To create a convection current inside the box.
Correct answer: To absorb radiant energy and convert it into thermal energy.
Dark-colored surfaces, especially black, are excellent absorbers of radiant energy. In the solar oven, the black paper's function is to absorb the maximum amount of incoming sunlight (radiant energy) and transform it into thermal energy (heat), which then cooks the food. The plastic wrap traps this heat inside the oven.
Question 4: An incandescent light bulb is switched on. It produces light and also becomes very hot. This scenario is an example of energy being transformed from:
- Thermal energy into electrical and light energy.
- Light energy into electrical and thermal energy.
- Chemical energy into light and thermal energy.
- Electrical energy into light and thermal energy. (Correct answer)
Correct answer: Electrical energy into light and thermal energy.
An incandescent light bulb works by passing electricity through a filament, causing it to glow. The initial energy input is electrical energy. This electrical energy is then transformed into two main forms: light energy (the intended output) and thermal energy (the heat felt from the bulb), which is often an unintended, less efficient byproduct.
Question 5: In a coastal area, a cool breeze often blows from the sea towards the land during the day. This phenomenon, known as a sea breeze, is primarily caused by which type of energy transfer?
- Convection (Correct answer)
- Conduction
- Radiation
- Advection
Correct answer: Convection
A sea breeze is a classic example of a convection current. During the day, the land heats up faster than the sea. The air over the land becomes warmer and less dense, so it rises. The cooler, denser air over the sea moves in to take its place, creating a breeze. This circulation of fluid (air) due to temperature differences is convection.
Question 6: A student conducts an experiment by placing equal masses of four different materials on a hot plate at the same temperature. After two minutes, the student measures the temperature change for each material. Which property of the materials is most likely being investigated in relation to energy transfer?
- Electrical conductivity
- Density
- Specific heat capacity (Correct answer)
- Malleability
Correct answer: Specific heat capacity
Specific heat capacity is the amount of heat energy required to raise the temperature of a specific mass of a substance by one degree. Materials with a low specific heat capacity will heat up quickly, while those with a high specific heat capacity will require more energy and time to change temperature. By measuring the temperature change of different materials with the same mass and energy input, the student is investigating their specific heat capacities.
WCAS - Washington Comprehensive Assessment of Science Energy Transfer and Conservation Questions and Answers
A student places a metal spoon in a bowl of hot soup.
After a few minutes, the handle of the spoon becomes warm.
Which of the following correctly describes the primary method of heat transfer that causes the spoon's handle to warm up?