Thermal Energy in Chemical Reactions

Which event indicates an endothermic chemical reaction?

• Decrease in temperature

• Release of heat

• Production of light

• Increase in thermal energy

Tags

NGSS.HS-PS1-4

Which statement is true about the reaction shown by this chemical equation?

HCl + NaOH → NaCl + H₂O

• It is endothermic.

• It is exothermic.

• It is a combustion reaction.

• It is a synthesis reaction.

Tags

NGSS.HS-PS1-4

Which type of reaction is represented by this graph?

• Exothermic

• Decomposition

• Endothermic

• Synthesis

Tags

NGSS.HS-PS1-4

Which bonds form in the reaction shown in the diagram?

• The bonds between the two hydrogen atoms

• The bonds between the oxygen and hydrogen atoms

• The bonds between the two oxygen atoms

• The bonds between the two hydrogen atoms and between the two oxygen atoms

Tags

NGSS.HS-PS1-7

This chemical equation represents one of the reactions that form acid rain. Which two options list the bonds that break in the reaction?

• The bonds between N and O in NO₂

• The bonds between H and O in H₂O

• The bonds between N and O and between H and O in HNO₃

• The bonds between N and O and between H and O in HNO₂

Which part of this chemical process requires energy?

NaOH + HCl → NaCl + H₂O

• Breaking bonds in NaCl and H₂O

• Forming bonds in NaOH and HCl

• Forming bonds in NaCl and H₂O

• Breaking bonds in NaOH and HCl

Tags

NGSS.HS-PS1-4

The energy diagram shows the changes in energy during a chemical reaction. Which statement best describes the total energy change of the system?

• The reactants have higher potential energy, and energy is absorbed.

• The reactants have higher potential energy, and energy is released.

• The products have higher potential energy, and energy is released.

• The products have higher potential energy, and energy is absorbed.

Tags

NGSS.HS-PS1-4

How do collisions between molecules transfer energy from a system of reacting substances to its surroundings?

• They cause molecules to flow into the system from the surroundings.

• They cause the thermal energy of the surroundings to decrease.

• They cause heat to flow from the system to the surroundings.

• They cause the potential energy of the system to increase.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

Based on the diagram, which statement explains how energy is conserved during this chemical reaction?

• The potential energy lost by the reaction system (C) is also lost by the surroundings.

• The potential energy lost by the reaction system (B) is gained by the surroundings.

• The potential energy gained by the reaction system (A) is also gained by the surroundings.

• The potential energy changes indicated by C and B involve energy lost by the surroundings.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

The bonds of the products store 27 kJ more energy than the bonds of the reactants. How is energy conserved during this reaction?

• The reaction system absorbs 27 kJ of energy from the surroundings.

• The reaction creates 27 kJ of energy when bonds form.

• The reaction uses up 27 kJ of energy when bonds break.

• The surroundings absorb 27 kJ of energy from the reaction system.

Tags

NGSS.HS-PS1-4