Mixed Deck — All WCAS Topics Flashcards

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?

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.

When a wave passes from one medium into another, which wave property always remains unchanged?

Answer: Frequency

Frequency is determined by the source of the wave and does not change when the wave enters a new medium.

Many different energy sources are used to produce electricity. The Amount of Carbon Dioxide Released graph shows the amount of carbon dioxide gas released by some energy sources, in grams per kilowatt hour (g/kWh). Which change in energy sources would cause the greatest decrease in the amount of carbon dioxide released?

Answer: Increasing hydroelectric and reducing coal

Explanation: Hydroelectric power also produces electricity with very low carbon dioxide emissions, whereas coal is one of the highest emitters of carbon dioxide among energy sources. Thus, increasing hydroelectric power and reducing coal would likely result in the greatest decrease in carbon dioxide emissions.

A student conducts an experiment by mixing 50 grams of vinegar with 5 grams of baking soda in a sealed plastic bag. The bag inflates due to gas production, and the substances turn into a new liquid. According to the law of conservation of mass, what should be the total mass of the contents inside the bag after the reaction?

Answer: Exactly 55 grams.

The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. [4, 19] Therefore, the total mass of the reactants (vinegar and baking soda) must equal the total mass of the products (the new liquid and the gas). Since the initial mass was 50g + 5g = 55g, the final mass will also be 55g, as long as the system is closed (sealed bag) and no mass escapes. [17, 30]

When thermal energy is added to a pure substance in its solid state, the particles within the substance begin to vibrate more rapidly. If enough thermal energy is added, what change will most likely occur?

Answer: The substance will melt into a liquid state.

Adding thermal energy increases the kinetic energy of particles in a substance. In a solid, this causes increased vibration. When the vibrations become strong enough to overcome the forces holding the particles in a fixed lattice, the solid melts and transitions into the liquid state. This is a physical change, not a chemical reaction. Condensation is the process of a gas turning into a liquid. Breaking particles into individual atoms would require a chemical reaction, not just a phase change.

The ozone layer is a critical component of Earth's atmosphere that absorbs the majority of the Sun's harmful ultraviolet (UV) radiation. In which atmospheric layer is the ozone layer primarily located?

Answer: Stratosphere

About 90% of the Earth's ozone is found in the stratosphere, which is the layer of the atmosphere located from approximately 10 to 50 kilometers above the surface. This concentration of ozone forms the protective ozone layer. [14, 18, 20, 21, 25]

A city located in a seismically active region of Washington State is updating its building codes to improve safety during an earthquake. Which engineering strategy would be most effective at mitigating damage to a new skyscraper?

Answer: Installing a base isolation system with lead-rubber bearings to absorb seismic energy.

Base isolation is a modern engineering technique designed to 'decouple' a building from its foundation during an earthquake. Flexible bearings, often made of lead and rubber, are installed in the foundation to absorb the seismic waves and allow the ground to move without transmitting the full force to the structure above. This significantly reduces shaking and mitigates damage.

A geologist studying the rock cycle finds a sample of shale, a sedimentary rock, that has been subjected to intense heat and pressure deep within the Earth's crust, transforming it into slate. Which of the following geological processes is responsible for this change?

Answer: Metamorphism

Metamorphism is the process where existing rocks are altered by heat, pressure, or reactive fluids. The transformation of shale into slate is a classic example of metamorphism, where the original rock changes form without melting. [1, 3, 22, 24]

What property of a wave is defined as the number of complete wave cycles that pass a given point per second?

Answer: Frequency

Frequency is the number of complete wave cycles passing a point per second, measured in hertz (Hz).

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?

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.

A team is developing a device to purify water in remote areas. They have built an initial prototype. What is the primary purpose of building and testing this first prototype?

Answer: To identify flaws and gather performance data to inform the next design iteration.

A prototype is an early model of a product built to test a concept or process. [2, 5] Its main purpose is to allow engineers to test functionality, identify weaknesses, and collect data that will guide improvements in the next version of the design. [3, 6] It is a key part of the iterative process of refining and optimizing a solution.

A group of students collected the following data to determine the effect of water temperature on the time it takes for 5 grams of salt to dissolve completely. | Water Temperature (°C) | Time to Dissolve (seconds) | | :--- | :--- | | 20 | 125 | | 40 | 80 | | 60 | 45 | | 80 | 20 | Based on the data in the table, which conclusion is best supported?

Answer: As the water temperature increases, the time it takes for salt to dissolve decreases.

The data table clearly shows a trend: as the temperature in the first column increases (from 20°C to 80°C), the time it takes for the salt to dissolve in the second column decreases (from 125 seconds to 20 seconds). This demonstrates that salt dissolves faster at higher temperatures.

According to the law of conservation of energy, which of the following statements is true?

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.

Which term describes the characteristics that help organisms survive or reproduce in their environment?

Answer: Adaptation

Explanation: Adaptation refers to the traits or characteristics that enable organisms to thrive in their environment by increasing their chances of survival and reproduction.

A student group has identified a problem: the classroom's recycling bin is often contaminated with non-recyclable trash. They have brainstormed several potential solutions. According to the engineering design process, what is the most logical next step?

Answer: Establish criteria and constraints to evaluate the potential solutions.

After brainstorming, the next critical step in the engineering design process is to develop a clear set of criteria (measures of success) and constraints (limitations) for a solution. [1, 10] This framework is essential for systematically and objectively evaluating the brainstormed ideas to determine which one is most likely to be successful before committing resources to prototyping or implementation.

In a population of rock pocket mice, most individuals have light-colored fur, which provides camouflage on sandy soil. A volcanic eruption covers the area in dark lava rock. Over many generations, the frequency of mice with dark-colored fur increases significantly in the population. This scenario is an example of:

Answer: Natural selection

This is a classic example of natural selection. The change in environment (dark lava rock) made dark-colored fur an advantageous trait for survival, as it provided better camouflage from predators. Mice with this heritable trait were more likely to survive and reproduce, passing the trait to their offspring, which led to an increase in its frequency in the population over time.

A model of a water molecule (H₂O) is shown to a student. Which statement accurately describes the atomic composition of this molecule?

Answer: It is composed of two hydrogen atoms and one oxygen atom.

The chemical formula H₂O indicates the atomic composition of a water molecule. The subscript '2' applies to the element symbol preceding it (H for Hydrogen), and the absence of a subscript for Oxygen (O) implies '1'. Therefore, a water molecule consists of two hydrogen atoms and one oxygen atom bonded together. [25] It is a simple molecule, not an extended structure like a crystal. [25]

Which of the following best defines a 'trade-off' in the context of engineering design?

Answer: A design choice where improving one desired feature necessitates worsening another.

A trade-off is a fundamental concept in engineering design where a decision must be made to sacrifice one benefit to gain another. [7, 14] For example, making a product stronger (a benefit) might require using heavier materials, thus increasing its weight (a drawback). Engineers must constantly balance these competing criteria to find an optimal solution.

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?

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.

What type of eclipse occurs when the Moon passes directly between the Earth and the Sun?

Answer: Solar eclipse

Explanation: A solar eclipse occurs when the Moon blocks the Sun's light from reaching Earth.