1. Calculate the amount of energy given off when 17 g of vapor at 102C condenses to 87C Did a phase change occur? If so, which one? Is this endothermic or exothermic?

- Amount of energy = -1066.92 J

- Yes, a phase change occurs from gaseous state to liquid state

- It is exothermic

Explanation:

Using Q = m × c × ∆T

Where Q = amount of energy

m = mass = 17g

c = specific heat capacity of water (4.184J/g°C)

∆T = change in temperature (87°C - 102°C = -15°C)

Hence, Q = m × c × ∆T

Q = 17 × 4.184 × (-15°C)

Q = -1066.92 J

- According to this question, vapor condenses i.e. gaseous form of water changes to liquid water, which involves a reduction in temperature. Hence, a change of phase occurs from gaseous state to liquid state.

- Since the change of phase occurs from a less orderly state (gas) to a more orderly state (liquid), there is a release of energy i.e. EXOTHERMIC. The amount of energy or Enthalpy change (∆H) is negative

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.