Unit 12 Thermochemistry Review

Which law states that energy cannot be created nor destroyed, but it can be transformed or transferred?

• Dalton's Law

• law of conservation of energy

• Hess's Law

• E=mc^2

Answer explanation

The law of conservation of energy states that energy cannot be created or destroyed, only transformed or transferred. This principle is fundamental in physics, distinguishing it from other laws like Dalton's or Hess's.

Tags

NGSS.HS-PS3-3

What happens when kinetic energy increases?

• Temperature increases.

• Temperature decreases.

• Temperature is not affected by kinetic energy.

Answer explanation

When kinetic energy increases, particles move faster, leading to an increase in temperature. This is because temperature is a measure of the average kinetic energy of particles in a substance.

A liquid has _________ temperature than a solid.

• Higher

• Lower

Answer explanation

A liquid has a higher temperature than a solid because, in general, liquids have more kinetic energy due to increased molecular movement compared to solids, where molecules are more tightly packed and less mobile.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A gas has ________ kinetic energy than a liquid.

• more

• less

Answer explanation

A gas has more kinetic energy than a liquid because the particles in a gas move more freely and rapidly, while in a liquid, the particles are closer together and have less energy.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

• 309.6 J

• -309.6 J

• 465 J

• -465 J

Answer explanation

To find the heat released, use q=mcΔT. Here, m=30 g, c=0.258 J/g°C, and ΔT=-40°C. Thus, q=30*0.258*(-40) = -309.6 J. The negative sign indicates heat is released, confirming the correct answer is -309.6 J.

Tags

NGSS.HS-PS3-4

NGSS.HS-PS3-1

• -3.48 J

• 3.48 J

• 1704 J

• -1704 J

Answer explanation

To find the heat added, use the formula q=mcΔT. Here, m=77 g, c=0.885 J/g°C, and ΔT=25°C. Thus, q=77*0.885*25=1704 J. Therefore, the correct answer is 1704 J.

Tags

NGSS.HS-PS3-4

NGSS.HS-PS3-1

When water evaporates, the process is...

• endothermic

• exothermic

Answer explanation

When water evaporates, it absorbs heat from the surroundings, making the process endothermic. This means energy is required for the water molecules to transition from liquid to gas.

Tags

NGSS.HS-PS1-4

When wood is burned in a campfire, the process is...

• endothermic

• exothermic

Answer explanation

When wood burns in a campfire, it releases energy in the form of heat and light, indicating that the process is exothermic. This means it gives off energy rather than absorbing it.

Tags

NGSS.HS-PS1-4

• negative

• positive

Answer explanation

In an exothermic reaction, energy is released to the surroundings, resulting in a decrease in enthalpy. Therefore, the change in enthalpy, \( \Delta H \), is negative, indicating that the reaction releases heat.

Tags

NGSS.HS-PS1-4

• negative

• positive

Answer explanation

For an endothermic reaction, heat is absorbed from the surroundings, resulting in a positive change in enthalpy (δH). This means that the energy of the products is higher than that of the reactants, making δH positive.

Tags

NGSS.HS-PS1-4