WCAS - Washington Comprehensive Assessment of Science Science and Engineering Practices Questions and Answers — Questions and Answers
Question 1: A student builds a model of the solar system using foam balls of different sizes and places them at varying distances from a central lamp representing the Sun. What is the primary scientific purpose of this type of model?
- To prove that the Sun is the center of the solar system.
- To help visualize and understand the relative sizes and positions of celestial bodies. (Correct answer)
- To perfectly replicate every detail of the solar system.
- To calculate the exact gravitational forces between the planets.
Correct answer: To help visualize and understand the relative sizes and positions of celestial bodies.
Scientific models are simplified representations of complex systems or phenomena. Their main purpose is to help scientists and students visualize, understand, and predict how these systems work. This model, while not perfectly to scale, effectively demonstrates the basic structure of the solar system, making a complex concept easier to grasp.
Question 2: A student wants to investigate how the color of light affects the growth rate of bean plants. She places three identical bean plants in separate containers with the same type of soil and gives them the same amount of water. One plant is exposed to red light, one to green light, and one to white light for 12 hours a day. She measures the height of each plant every day for two weeks. What is the independent variable in this investigation?
- The height of the bean plants.
- The amount of water given to each plant.
- The color of the light. (Correct answer)
- The type of soil used.
Correct answer: The color of the light.
The independent variable is the factor that the experimenter intentionally changes or manipulates to observe its effect on the dependent variable. In this case, the student is systematically changing the color of the light to see how it impacts plant growth. The growth (height) is the dependent variable, and factors like water, soil, and light duration are controlled variables.
Question 3: 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?
- As the water temperature increases, the time it takes for salt to dissolve decreases. (Correct answer)
- The rate of dissolving is unrelated to the water temperature.
- As the water temperature decreases, the time it takes for salt to dissolve decreases.
- Salt dissolves fastest in the coldest water.
Correct 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.
Question 4: A student claims, "Plants require sunlight to grow." Which of the following statements provides the strongest scientific evidence to support this claim?
- My friend told me that her plant died when she kept it in a dark closet.
- It is a well-known fact that all plants need sunlight.
- Plants look healthier and greener when they are outside in the sun.
- An experiment was conducted where one plant was placed in sunlight and an identical plant was placed in a dark room; the plant in the sun grew 5 cm while the plant in the dark did not grow. (Correct answer)
Correct answer: An experiment was conducted where one plant was placed in sunlight and an identical plant was placed in a dark room; the plant in the sun grew 5 cm while the plant in the dark did not grow.
A scientific argument requires a claim supported by evidence and reasoning. The strongest evidence comes from controlled, repeatable investigations that produce measurable data. The statement describing a controlled experiment provides specific, empirical evidence that directly supports the claim that sunlight is necessary for growth, while the other options are anecdotal, assertions, or uncontrolled observations.
Question 5: A student is curious about rainfall in their city. Which of the following is a scientifically testable question that the student could investigate for a school project?
- Does the amount of rainfall affect the growth of grass on the school lawn? (Correct answer)
- Is rain good or bad for the city?
- Why does it feel so sad when it rains?
- What is the most beautiful cloud formation that produces rain?
Correct answer: Does the amount of rainfall affect the growth of grass on the school lawn?
A scientifically testable question is one that can be answered by collecting and analyzing measurable data. The question about rainfall affecting grass growth allows for the measurement of two variables (amount of rain and height/health of grass) to find a relationship. The other questions are based on opinion, emotion, or subjective values and cannot be answered through a scientific investigation.
Question 6: A student observes that the grass is wet on a cool, clear morning, even though it did not rain. Which of the following statements best represents a scientific explanation for this observation, rather than just another observation?
- The grass is wet, and so is the top of my mailbox.
- The air cooled overnight, causing invisible water vapor in the air to condense into liquid water on the cool blades of grass. (Correct answer)
- The water on the grass will probably evaporate when the sun comes out.
- The sprinkler system must have turned on by accident during the night.
Correct answer: The air cooled overnight, causing invisible water vapor in the air to condense into liquid water on the cool blades of grass.
A scientific explanation provides a mechanism for why a phenomenon occurred based on established scientific principles. The statement about water vapor condensing due to cooling explains the process (condensation) that caused the observation (wet grass). The other options are an additional observation, a prediction, or an alternative hypothesis that doesn't explain the common phenomenon of dew formation.
WCAS - Washington Comprehensive Assessment of Science Science and Engineering Practices Questions and Answers
A student builds a model of the solar system using foam balls of different sizes and places them at varying distances from a central lamp representing the Sun.
What is the primary scientific purpose of this type of model?