by horse Comment Closed

LARN 116 C29D4

Start the following in class:

1. The required focus question, J116, for today is

a. An ideal gas is one that would obey all the gas laws at every temperature and pressure. To do so such a gas would have to be

  • composed of point molecules which
  • continually undergo random elastic collisions with each other,
  • experience no attractive forces for each other, and
  • sweep out all the volume occupied by the gas by virtue of their motion.

Such an ideal gas exists only in the minds of thinkers such as ourselves.  In full, intelligible sentences, explain why no real gas always behaves ideally.

b. Under what condition of temperature (high or low absolute temperature) would the predicted behavior of the ideal gas and the actual behavior of real gases differ most greatly?  Please make your response longer than one sentence.

c. Under what condition of pressure (high or low gas pressure) would the predicted behavior of the ideal gas and the actual behavior of real gases differ most greatly?  Please make your response longer than one sentence.

2.a.  Use the PQ5R or SQ5R method to prepare study guide for text section 14.2 on The Gas Laws or go to https://socratic.org/chemistry  to research the topics brought up in section 14.2 of your text.  Read section 14.2 in your chemistry text, pages 418 through 425, and as you do, create a study guide using the SQ5R or PQ5R method explained in class and on the distributed handout packet. You may record vocabulary entries in the body of your study guide, or you may check them off on the chapter 14 vocabulary list that was distributed as you think about the meanings of the terms and add any notations to the vocabulary list for clarifications sake.

2. b. Writing in blue or black ink, place your hand in number in a circle followed by your name in the upper right white space of a separate piece of three holed composition paper suitable for handing in that hasn’t been written on.  Place the page reference for the problems to be considered to the left of the red marginal line on the first blue line.  Centered on the first blue line,write a descriptive title for the learning activity such as Section [chapter #.section#] Responses.  Before you write your response to each question or problem listed below, write its designation to the left of the red marginal line as listed below, followed by your response in ink to the right of the marginal line.

This section of the text deals with what are known as gas laws and solving problems using the gas laws mentioned.  A law in physical science is a mathematical statement that is put forth to describe the relationship observed between two or more measurable quantities whose values depend upon each other in some way.  When a law relates two variables according to either a direct or inverse proportion, it is often simplest to solve the problem using the method of comparison ratios. Your assignment is to do one or more of the two problems printed below each of the four boxed sample problems in section C14.2 using the method of thinking about the particular gas law given in terms of direct and inverse proportions and comparison ratios instead of using an algebraic solution such as that exemplified in the test.  The method of comparison ratios is reviewed below.

The steps to use are:

a. Read the problem.

  • Which is the variable that will change its value because one or more other variables are changing?  Only the initial value of this quantity is given in the problem;
  • the final value for this variable will be calculated from the given values of the other variable(s).
  • Which variable(s) are mentioned in the problem as causing the change since it/they has/have an initial and a final value listed?

b. Set up the solution to the problem with the use of the expression □final = □initial x (—-) x (—- ) x ….  The □ variable stands for either the the pressure of an enclosed sample of gas with units of gas pressure in kPa, P;  the volume of the gas in L, V; the amount of gas in moles of gas molecules, n; the absolute temperature of the gas in kelvins, T; or the kinetic energy of the gas in joules, J, Ek.  In the expression, each (—-) stands for a properly written comparison ratio for a variable whose initial and final values are given in the problem.

  •   Write down a law that connects the behavior of the variable that will change to the variable that is causing the change.  So for example, select  Boyle’s law, P·V = k if one of the variables involved in the problem is pressure and the other variable is volume, Charles’ law if one of the variables involved in the problem is volume and the other variable is temperature, V = k·T, Amonton’s law if one of the variables involved in the problem is pressure and the other variable is temperature, P = k·T, …, or, instead, use any two of the variables occurring in the ideal gas law, P·V = n·R·T.
  •   Substitute the symbol for the variable whose value will change for the □final variable in the expression □final = □initial x (—-) x (—- ) x ….  Substitute either the Pfinal, Vfinal, nfinal, Tfinal, or Ek,final for the □final on the left side of the expression.   On the right side of the equation, for □initial substitute the initial numerical value and unit for the quantity that will change when multiplied by one or more comparison ratios.
  •   Recall that two variables both in the numerator on opposite sides of an equal side are directly proportional to each other and that two variables both in the numerator on the same side of an equal side are inversely proportional.
  •   For each variable whose initial and final values have been given in the problem, set up those values as a comparison ratio in the expression □final = □initial x (—-) x (—- ) x …. with the value of the ratio larger or smaller than unity according to the following procedure.  First, use the increase or decrease in the value of the variable that is changing in conjunction with the direct or inverse relationship between the two variables as shown in the mathematical law to predict whether the variable whose value will change increases or decreases, then
    • if the variable whose value will change will increase, arrange the values of the changing variable into a comparison ratio with a numerator that is larger than its denominator.
    • if the variable whose value will change will decrease, arrange the values of the changing variable into a comparison ratio with a numerator that is smaller than its denominator.
    • if a variable has a value of c units and is not changing, its final value is c units and the comparison ratio is c units over c units which is equal to the number “1” and thus can be skipped as a comparison ratio in the setup being written.
  • After all factors have been recorded, find the value of □final by simplifying the solution expression by alternately multiplying and dividing values using a simple five function calculator and canceling numerator units with like units in denominators.  Express your final result to the proper number of significant figures followed by the proper unit of measurement. Then circle or box in your final result! 

After you have written your best effort response for each assigned item, check page R94 of the text and check each of those problems that you can by writing in either a check mark (√) or a correction in green ink as we do in class.

Recommended for those who have time left in their 45 minute study period, but not required of all:

  • Study Sample Problem 14.1 on your handouts page 419 and then show your work including all comparison ratios for practice problems I14-7 (In chapter 14, problem 7) and I14-8.
  • Study Sample Problem 14.2 on your handouts page 421 and then show your work including all comparison ratios for practice problems I14-9 (In chapter 14, problem 9) and I14-10.
  • Study Sample Problem 14.3 on page 423 and then show your work including all comparison ratios for practice problems I14-11 (In chapter 14, problem 11) and I14-12.
  • Study Sample Problem 14.4 on page 424 and then show your work including all comparison ratios for practice problems I14-13 (In chapter 14, problem 13) and I14-14.
  • For the Section Assessment 14.2 on page 425, read, analyze, and answer practice problems I14-15 (In chapter 14, problem 15) and I14-16, I14-17, I14-18, I14-19, I14-21,and I14-22 in full sentences,and show your work including all comparison ratios for practice problem I14-20.

After you have written your best effort response for each assigned item, check page R94 of the text and check each of those problems that you can by writing in either a check mark (√) or a correction in green ink as we do in class.

Also:

1. Review the SI prefixes and their meanings until you can readily explain the meaning of each listed SI prefix as a numerical multiplier.

2. Think about the fifteen properties of covalent molecular substances listed on the Properties to be understood worksheet describing differences in the properties of metals, ionic compounds, covalent network solids, and covalent molecular compounds. Continue to study this handout for understanding and review how the typical properties of members of these classes of compounds depend on whether the compound has localized or delocalized electrons, and upon whether strong metallic, ionic, or covalent bonding or weak van der Waals forces of attraction are predominant between representative particles of the substances. Try to understand how each property of a given covalent molecular substance is related to the groups of covalently bonded atoms that form molecules whose van der Waals attractive forces only weakly attract other molecules.