Enthalpy and Entropy

In a chemistry experiment, Liam, Maya, and Mason are trying to make a reaction happen between two chemicals to create a new compound. What factor can influence the reaction to occur?

• Enthalpy

• Entropy

• Both enthalpy and entropy

• Neither enthalpy nor entropy

Answer explanation

In a chemical reaction, both enthalpy and entropy play significant roles. Enthalpy is the heat content in a system and its change can drive a reaction. Entropy, on the other hand, is a measure of disorder or randomness. A reaction tends to occur if it leads to an increase in entropy. Therefore, both factors can influence the reaction to create a new compound in the chemistry experiment conducted by Liam, Maya, and Mason.

Tags

NGSS.HS-PS1-5

Grace, Noah, and Abigail were baking a cake together. They noticed a change in the energy of the system during the chemical reaction between the ingredients. What is this change called?

• A decrease in energy during a chemical reaction

• An increase in energy during a chemical reaction

• The randomness of a chemical

• The stability of a chemical

Answer explanation

The change in energy during a chemical reaction, as observed by Grace, Noah, and Abigail, is called an increase in energy. This occurs when the energy of the system increases as the ingredients interact and form new bonds, resulting in the formation of the cake.

Tags

NGSS.HS-PS1-4

Benjamin and Charlotte are working on a chemistry project together. They observe an endothermic reaction when they mix two chemicals. What is the result of this endothermic reaction?

• An increase in energy

• A decrease in energy

• An explosion

• An increase in randomness

Answer explanation

In an endothermic reaction, energy is absorbed from the surroundings, causing an increase in energy. When Benjamin and Charlotte mix the two chemicals, they observe this type of reaction, which results in an increase in energy, making it the correct choice.

Tags

NGSS.HS-PS1-4

In a chemistry experiment, Noah, Daniel, and Luna are trying to determine the entropy of a substance in a real-world scenario. They are analyzing the melting of ice in a glass of water. What does entropy measure in this context?

• The randomness of a chemical

• The stability of a chemical

• The energy flow in a reaction

• The heat released in a reaction

Answer explanation

In this chemistry experiment, entropy refers to the degree of randomness or disorder in a system. As ice melts in a glass of water, it transitions from a more ordered state (solid) to a less ordered state (liquid), increasing the system's entropy. Therefore, the correct answer is 'The randomness of a chemical'.

Which tendencies favor a spontaneous reaction?

• decreasing enthalpy and decreasing entropy

• increasing enthalpy and increasing entropy

• increasing enthalpy, and decreasing entropy

• decreasing enthalpy and increasing entropy

Predict the sign (+, -, or 0) of ∆G_f°, ∆H_f°, ∆S_f°, respectively, for the deposition of carbon dioxide (CO₂) at room temperature and atmospheric pressure. CO₂ (g) → CO₂ (s)

• -, +, +

• 0, +, +

• -, +, -

• +, -, -

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

What is true about thermodynamically favorable reactions?

• They need outside energy to be put in

• They always increase entropy

• They always have a negative ΔH

• ΔG is positive

Tags

NGSS.HS-PS3-1

In terms of entropy, why is it easier to mix two substances than to separate them once mixed?

• Mixing increases the energy of the system

• Mixing decreases the energy of the system

• Mixing increases the disorder of the system

• Mixing decreases the disorder of the system

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DOK Level 2: Skill/Concept

Anika, Hannah, and William are helping Zoe in her science lab. They noticed that when Zoe increased the entropy of a system, something happened. What does Zoe observe when she increases the entropy in a real-world scenario like making a cup of hot chocolate?

• The reactions in her experiment start to happen

• The reactions in her experiment stop

• The reactions in her experiment become more stable

• The reactions in her experiment start to release energy

Answer explanation

In a real-world scenario like making a cup of hot chocolate, when Zoe increases the entropy of a system, the reactions in her experiment start to happen. Entropy is a measure of disorder, and an increase in entropy typically leads to a higher likelihood of reactions occurring, as the system becomes more disordered and less stable.

Tags

NGSS.HS-PS3-4

During a chemistry class, Abigail, Maya, and Zoe observed that the room got warmer when their teacher, Henry, mixed two chemicals together. What does this scenario illustrate?

• An exothermic reaction releasing energy into the surroundings

• An exothermic reaction drawing energy from the surroundings

• An exothermic reaction releasing energy into the reactants

• An exothermic reaction drawing energy from the reactants

Answer explanation

In this question, the observation of the room getting warmer when two chemicals are mixed together indicates an exothermic reaction. An exothermic reaction releases energy into the surroundings, which is why the room's temperature increased. This matches the correct choice provided.

Tags

NGSS.HS-PS1-4