C974 - Science Methods—Middle Grades General Science

Explanation:

The dependent variable is the outcome measured in an experiment to determine the effect of changes in the independent variable. It responds to manipulation and provides data to test the hypothesis. By observing and recording changes in the dependent variable, researchers can analyze cause-and-effect relationships.

Correct Answer:

The outcome that is measured to assess the effect of changes

Why Other Options Are Wrong:

The variable that is manipulated by the researcher

This is incorrect because the variable manipulated is the independent variable, not the dependent variable.

The conditions that are kept constant throughout the experiment

This is incorrect because constants are maintained to ensure fair testing, but they are not the dependent variable.

The initial hypothesis being tested

This is incorrect because the hypothesis is a prediction, not the variable being measured in the experiment.

Explanation:

Fossils provide multiple types of information that help scientists reconstruct ancient ecosystems and understand evolutionary processes. They offer direct observations of species that lived in the past, reveal the geographical distribution of organisms over time, and can provide evidence of interactions between species, such as predator-prey relationships. Collectively, these insights allow scientists to piece together the structure and dynamics of ancient ecosystems and track evolutionary changes.

Correct Answer:

All of the above

Why Other Options Are Wrong:

By providing direct observations of ancient species

This is incomplete because, while true, it does not account for the information fossils provide about distribution or species interactions.

By indicating the geographical distribution of species

This is incomplete because distribution alone does not fully explain interactions or evolutionary patterns.

By showing the interactions between different species

This is incomplete because fossils also provide data on species themselves and their locations, not only interactions.

Explanation:

The observation of fizzing, a color change, and heat production indicates a chemical change. These signs show that new substances are being formed, and energy is being released during the reaction. Chemical changes result in a transformation of the original substances into products with different chemical and physical properties, which is evident in this experiment.

Correct Answer:

This is a chemical change because new substances are being formed that have new physical properties.

Why Other Options Are Wrong:

This is a physical change because the color changed, and color is a physical property

This is incorrect because the formation of gas (fizzing) and heat release are indicators of a chemical change, not just a physical change.

This is a chemical change because an energy change is observed

This is partially correct but incomplete; the reaction also produces new substances, which is a critical characteristic of a chemical change.

Explanation:

Both higher temperature and agitation increase the rate at which a solid dissolves in a liquid. Higher temperature provides particles with more kinetic energy, allowing solute particles to break apart faster. Agitation, such as stirring, helps distribute the solute and solvent more effectively. However, temperature generally has a more significant impact on the dissolution rate than agitation, making it the dominant factor.

Correct Answer:

Higher temperature and agitation both increase the rate of dissolution, but temperature plays a more critical role.

Why Other Options Are Wrong:

Higher temperature significantly enhances the rate of dissolution, while agitation has a minimal impact

This is incorrect because agitation does contribute to the dissolution rate, though less critically than temperature.

Both higher temperature and agitation equally contribute to the rate of dissolution

This is incorrect because temperature has a stronger influence than agitation on how quickly a solid dissolves.

Agitation alone is sufficient to increase the rate of dissolution, regardless of temperature

This is incorrect because agitation alone cannot overcome the kinetic limitations that lower temperatures impose on particle movement.

Explanation:

An increase in temperature is evidence of a chemical reaction in the decomposition of hydrogen peroxide. The reaction is exothermic, releasing energy in the form of heat. Physical changes, such as phase changes or color remaining clear, do not indicate a chemical reaction, and the mass of the solution staying the same follows the law of conservation of mass, which is true for both chemical and physical changes. The heat release is a direct indicator that a chemical transformation is occurring.

Correct Answer:

Temperature of the solution increases

Why Other Options Are Wrong:

Mass of the solution stays the same

This is incorrect because conservation of mass occurs in both physical and chemical changes; it does not specifically indicate a chemical reaction.

Phase changes are observed

This is incorrect because phase changes are physical changes and do not necessarily indicate that a chemical reaction has occurred.

Color of the solution remains clear

This is incorrect because the solution remaining clear does not indicate a chemical change; some chemical reactions do not produce visible color changes.

Explanation:

If wax melts fastest on aluminum, it indicates that aluminum transfers heat more efficiently than lead or steel. Thermal conductivity measures a material’s ability to conduct heat, and a higher thermal conductivity results in faster heat transfer. Therefore, aluminum having the fastest melting of wax demonstrates that it has the highest thermal conductivity among the materials tested.

Correct Answer:

Aluminum has the highest thermal conductivity

Why Other Options Are Wrong:

Aluminum has the lowest thermal conductivity

This is incorrect because if aluminum had the lowest thermal conductivity, it would transfer heat slowly, and the wax would melt more slowly, not fastest.

Lead has the highest thermal conductivity

This is incorrect because the wax did not melt fastest on lead, indicating that lead conducts heat less efficiently than aluminum.

Steel has the highest thermal conductivity

This is incorrect because the wax melted fastest on aluminum, not steel, so steel’s thermal conductivity is lower than aluminum’s.

Explanation:

A material with high thermal conductivity transfers heat quickly. Therefore, when heat is applied, such a material will exhibit a rapid increase in temperature. This is because thermal energy moves efficiently through the material, allowing it to warm up faster than materials with lower thermal conductivity. Observations like slow heating or no change in temperature indicate poor thermal conductivity.

Correct Answer:

A rapid increase in temperature

Why Other Options Are Wrong:

A slow increase in temperature

This is incorrect because a slow temperature rise indicates low thermal conductivity, meaning the material does not transfer heat efficiently.

No change in temperature

This is incorrect because no temperature change suggests the material is insulating heat or has extremely low thermal conductivity.

A decrease in temperature

This is incorrect because a decrease in temperature does not indicate thermal conductivity; it may simply reflect a cooling process rather than heat transfer properties.

Explanation:

Scientific evidence is the foundation of validating or refuting claims. By collecting data through observations and experiments, scientists can determine whether a claim is supported or contradicted by empirical results. Reliable evidence increases the credibility of a scientific claim and ensures that conclusions are based on objective, reproducible findings rather than opinion or assumption.

Correct Answer:

Evidence provides support or refutation for a claim, helping to establish its credibility

Why Other Options Are Wrong:

Evidence is irrelevant to the scientific process and does not affect claims

This is incorrect because evidence is central to the scientific method; without evidence, claims cannot be verified or disproved.

Evidence is primarily anecdotal and does not require rigorous testing

This is incorrect because anecdotal evidence is insufficient in science; rigorous testing and reproducibility are required for validity.

Evidence is only useful if it confirms existing theories without question

This is incorrect because scientific evidence must be evaluated objectively, whether it supports or challenges existing theories; confirmation bias undermines scientific credibility.

Explanation:

Quantitative data involves numerical measurements that can be counted or calculated, such as height, weight, or temperature. Qualitative data, on the other hand, describes characteristics, qualities, or attributes that are not inherently numerical, such as color, texture, or shape. The distinction is important because it determines the methods of analysis and interpretation in scientific research.

Correct Answer:

Quantitative data is based on numerical values, while qualitative data is based on descriptions and characteristics

Why Other Options Are Wrong:

Quantitative data is subjective, while qualitative data is objective

This is incorrect because quantitative data is generally objective, and qualitative data can include subjective observations.

Quantitative data is always collected through surveys, while qualitative data is collected through experiments

This is incorrect because both types of data can be collected through a variety of methods, not strictly surveys or experiments.

Quantitative data cannot be measured, while qualitative data can be measured

This is incorrect because quantitative data is defined by its measurability, while qualitative data is descriptive rather than measurable.