CHEMISTRY REVIEW

A student observes that a certain metal rusts quickly when left outdoors. Which of the following is the BEST scientific question the student could ask based on this observation?

• Why is metal useful?

• What are the different types of metal?

• What factors affect how quickly this metal rusts?

• Is rust a dangerous substance?

A science textbook states that increasing the temperature of a reaction generally increases the rate of the reaction. To define a problem based on this information, a student might ask:

• What is the fastest reaction?

• How does temperature affect the rate of this specific reaction?

• Are all reactions affected by temperature?

• What are the products of this reaction?

Tags

NGSS.HS-PS1-5

A scientist uses a ball-and-stick model to represent a methane molecule (CH4). What is the primary purpose of this model?

• To show the color of each atom in the molecule.

• To accurately depict the size of the molecule.

• To illustrate the arrangement of atoms and bonds within the molecule.

• To show the movement of electrons in the molecule.

A flowchart is used to represent the steps in a chemical reaction mechanism. This flowchart serves as a:

• Physical model.

• Mathematical model.

• Conceptual model.

• Computational model.

A student performs an experiment multiple times and obtains the following measurements for the density of a substance: 2.71 g/mL, 2.69 g/mL, 2.72 g/mL, and 2.55 g/mL. The value 2.55 g/mL appears to be:

• A precise measurement.

• An accurate measurement.

• An outlier, possibly due to error.

• The average density.

A graph shows that as the concentration of a reactant increases, the rate of the reaction also increases. This represents a:

• Source of error.

• Statistical feature.

• Pattern in the data.

• Limitation of the experiment.

Tags

NGSS.HS-PS1-5

A student collects data on the mass and volume of several aluminum samples. To determine the density of aluminum, the student should:

• Add all the mass values together.

• Subtract the smallest volume from the largest volume.

• Divide the total mass by the total volume.

• Divide the mass of each sample by its corresponding volume and then calculate the average.

A solution has a concentration of 2.0 M and a volume of 0.5 L. The number of moles of solute in the solution is:

• 0.25 moles

• 1.0 mole

• 2.5 moles

• 4.0 moles

Experimental data shows that increasing the concentration of an enzyme increases the rate of a biochemical reaction up to a certain point. This observation is best explained by the scientific idea that:

• Enzymes are consumed in the reaction.

• Enzymes provide an alternative reaction pathway with lower activation energy.

• Increasing concentration always increases reaction rates indefinitely.

• The shape of the enzyme's active site is unaffected by substrate concentration.

A model of gas behavior shows that gas particles are in constant, random motion. This model helps explain the phenomenon of diffusion because:

• It shows that gas particles have no mass.

• It illustrates how particles spread out from an area of high concentration to low concentration through their random movement.

• It demonstrates that gas particles attract each other.

• It proves that gases are less dense than liquids.