Chem 1 - Exothermic/Endothermic & Entropy

You observe a combustion reaction (like a campfire burning) and feel warmth. This is because...

(choose TWO correct answers)

• the system (the burning wood) is releasing energy toward you (in the surroundings)

• the system (the burning wood) is absorbing energy from you (in the surroundings)

• the combustion process is exothermic

• the combustion process is endothermic

What is true of an endothermic reaction?

• The substances in the reaction will release energy

• The substances in the reaction will absorb energy

This is a model of the combustion of propane. Which is the best description of what will happen?

(Choose TWO correct answers)

• When the propane burns, the propane will release energy and the surroundings will absorb energy

• When the propane burns, the propane will absorb energy and the surroundings will release energy

• When the propane burns, the entropy (disorder) of the surroundings will increase

• When the propane burns, the entropy (disorder) of the surroundings will decrease

Imagine you are conducting a chemical experiment in a lab. If the reaction you are observing is ENDOTHERMIC, what would happen to the temperature on your thermometer?

• The temperature will stay the SAME because of equilibrium

• The temperature will DECREASE because the reaction will absorb energy away from the thermometer and the particles of the thermometer will slow down.

• The temperature will DECREASE because the reaction will release energy and chemical particles will collide more with the thermometer. Therefore the particles of the thermometer will speed up.

• The temperature will INCREASE because the reaction will release energy and chemical particles will collide more with the thermometer. Therefore the particles of the thermometer will speed up.

As someone is running on the track their body begins to release heat and they begin to perspire. If we consider the runner's body to be the "system," then the processes in their body represent a(n)...

(Choose TWO correct answers)

• Endothermic process because their body is gaining energy

• Exothermic process because their body is losing energy

• transfer of energy since stored chemical energy is being converted to mechanical and thermal energy

• transfer of energy since kinetic energy is being converted into stored chemical energy

The ice is the "system." The cup of ice is sitting an warm room. Which is true?

(Choose TWO correct answers)

• Thermal energy is being transferred from the ice to the surroundings. The ice is losing energy while the glass and air around it are gaining energy.

• Thermal energy is being absorbed into the ice from the surroundings. The ice particles are gaining energy and the glass and the air around it are losing energy.

• If you touch the glass, it will "feel" cold because the cold is moving from the ice particles to the glass particles and into your hand.

• If you touch the glass, it will "feel" cold because thermal energy is moving from your hand to the glass particles to the ice particles.

Tags

NGSS.HS-PS3-4

Which of these is an exothermic process?

When substances change from solid, to liquid, to gas, entropy increases. Why?

• The molecules become more randomly arranged and move more chaotically

• The molecules spread out and take up more space

• The molecules become more reactive

• The molecules become more compact and organized

The natural tendency and progress of systems in nature over time is toward

• lower energy and less disorder

• lower energy and more disorder

• higher energy and less disorder

• higher energy and more disorder

Which are synonyms for entropy?

(Check TWO correct answers)

• disorder

• organization

• randomness

• structure