kitchen table math, the sequel: Thoughts on teaching Physical Science

Friday, July 24, 2009

Thoughts on teaching Physical Science

As of now, I am preparing to leave Catholic School for Girls and move back to teaching in public high school. I feel sorry for the students who will see another change in the teaching staff (in the last four years, this school saw 3 Biological Science teachers, 3 Chemistry/Physics Teachers, and 4 Principals come and go).

When I got the position there and was assigned to teach Physical Science, Biology, Anatomy, and Environmental Science, I realized that I came to an empty well - there was no curriculum plan (the list of objectives for science courses found in the office binder belonged to another school and was so vague that it could not help me), no teacher manuals for disciplines - nothing except the textbooks and a lab supply room full of 20 -year old "supplies". I knew the curriculum for biology but had no idea what should be taught in physical science (I don't think NY schools teach physical sience at all!), anatomy, or environmental science. So I worked from scratch and created my own curriculum maps. And as I did it, I understood that perhaps the most important course of all in this sequence, the one that required the most effort from me was Physical Science. So I wrote a letter to whoever will take my position to save that teacher some effort and prevent some common (as I saw in upper grades) problems growing from students not knowing the basics.

Here is the excerpt from this letter:

Dear fellow teacher:
As you are getting ready to teach sciences at xxxxx, even if you are a seasoned sciences teacher, please take few minutes to read this - it may help you to understand the major goals of the science courses sequence used in this school as well as to organize your planning and instruction. Also, it is some practical advice based on my experience of teaching here. Even though you will find the curriculum objectives (not really re-worked) and my syllabi, this may be still useful.

The sequence of science courses is as follows:
1) Physical Science – 9th grade
2) Biology – 10th grade
3) Chemistry – 11th grade
4) Physics – elective for juniors/seniors with pre-requisite of 85 in math.
5) Anatomy – elective, no pre-requisites
6) Environmental science – elective, no pre-requisites (not offered in 2009-2010)


Textbook (oldie but goodie!) – Focus on Physical Science by Heimler and Price. It is the best around, with great review exercises and good explanations and examples. I have ordered more through Amazon, but if they don’t come – make photocopies of the units for students. It also has a good lab manual.

As you can see, Physical Science is the first course in the sequence. It lays down the foundation for taking other science courses and, for majority of students, serves as a substitute for the physics course they don’t select to take. In addition, the freshmen come here from a variety of institutions – and many lack basic mathematical and logical reasoning skills not to mention the fuzzy middle school science that leaves them with no clear idea what science disciplines are and how to learn and study for science courses. That simply means that this course will require the most organized, structured, and clear instruction that you can deliver. It must give the students not just an understanding of methods of science, but provide mastery with basic chemistry and physics as well as logical reasoning and mathematics.

Overall, the advice is – leave the “discovery” for later and teach as directly as possible! Use the labs to practice and apply, not to introduce. Based on the attained mastery of Physical Science concepts and skills, the students (and you!) will have it much easier in upper courses from the sequence , where the student-designed and conducted investigations can be used.

Aligning with math.

Physical science involves mathematics. Shall we say that math used is on almost the elementary level, though you will see many students experiencing problems with applying math. And if these problems are not resolved now, they have little chances of experiencing success in chemistry and physics!. Understanding of concepts is absolutely inseparable from the ability to justify the reasoning with mathematics.

So, here are some “obstacles” that require more work on your part. It is also a good idea to ask the math teachers how they explain a particular math concept and skills to students, so you use the same language.

  • In the very beginning, the decimal/fraction/exponent relationship must be reviewed.

Example: 100 = 100/1 = 10² and 1/10 = 0.1 = 1x 10-¹

  • Metric system is based on 10. Ensure the mastery of conversions.
  • Rounding to the nearest tenth, hundredth etc. should be reviewed as necessary (most likely – should)
  • Fractions – basic addition, subtraction, multiplication and division of simple fractions.
  • How to treat proportion as a fraction. (Absolutely essential for stoichiometry and some physics problems! ( If X relates to Y like this, then X1 relates to Y1 like that.)
  • Simple algebraic equations (review before teaching oxidation numbers) as well as adding and subtracting positive and negative numbers.
    Example: x +12 = 24
    x = 12

    12/x = 3
    x= 4

    +5 – 7 = - 2
    Note: have them write fractions in the standard form – with the horizontal line between numerator and denominator.
  • Transforming formulas. a=b/c Find b. Find c. and so on.
  • Practice treating units as numbers in calculations. It helps to see where the units of a variable come from and aids in remembering the formulas (and concepts).

    Critical: Introduce the format for solving problems and stick with it. Require it even for the easy problems – then the students WILL definitely benefit when solving more difficult and multi-step problems in this course and in further courses. The format allows extracting and organizing information from the word problems clearly so the possible solution routs are easily predictable. I followed the format taught in soviet schools, which is this:
    (I do it in the form of a table: divide the page in 3 columns

Column 1:

WHAT IS GIVEN in the problem:

Use appropriate variables and units provided in the texthat is asked (variable, units)

Column 2:
Basic formula(s) connecting what is given and what is asked + necessary derivatives

Column 3:

Solution (complete with units)

Answer, with units

From physics – Find the work done by gravity force when a 2-kg rock falls from the height of 1.5 m to the ground.

m rock = 2 kg
d = 1.5 mg=a = 9.8 m/sec­²


W - ? (J)


W = Fd
(we were not given F, but we can find F if we know mass and acceleration)
F= ma
Substitute ma for FW = mad


W = 2kg x 9.8 m/sec² x 1.5m = 29J

Answer: W=29J

Example 2 (From Chemistry)

Find the masses of salt and water needed to prepare 300g of 10% solution.


V solution =300 g
% Conc. = 10%


m water -? (g)

m salt-? (g)

Formulas (Reasoning)
1)10% means:
10g of salt in 100g of solution
x g of salt are in 300 g of solution

2)m of solution = m of salt + m of water, therefore

m of water = m solution – m salt

1) 10g/x = 100g/300g
x = 3000g/100g = 30g of salt

2) 300g – 30g = 270g of water

Answer: to make 10% solution one should take 30g of salt and 270 g of water

In terms of planning the program, I have found it more useful to clearly separate Chemistry part of the course and Physics part of the course. My syllabus reflects that. Chemistry part (including oxidation states, balancing of chemical reactions and stoichiometry problems) is done in the first semester, and Physics part - in second semester. It correlates with concept sequence taught by math department, so you can arrange the use of problems from your course in math classes and arrange with math teachers to provide more attention to necessary math skills.. It usually works well, and science and math are mutually reinforced.

Of course, you may choose to follow the sequence in the textbook or introduce physics first.

You will find the list of topics to be taught in the syllabus (in the Main Office, Science binder). However, let me emphasize the topics that will require more of your attention – the concepts and skills that usually cause problems for students in biology and chemistry courses if not mastered.

Metric System conversions
Symbols and names of major chemical elements; names of major acids, bases, and salts
Electron configurations and creation of bonds
Calculation and use of oxidation numbers to write the formulas of compounds
Balancing of chemical reactions
Simple stoichiometry – mass to mass problems
Calculation of concentration of solution; preparation of solutions
Properties of water
Neutralization reactions
Reading and creating the graphs - speed, acceleration etc.
Light and Sound – electromagnetic and mechanical waves
Energy transfer, especially heat.

(End of excerpt)


Lsquared said...

Thanks! What a useful letter.

Catherine Johnson said...

Use the labs to practice and apply, not to introduce. Based on the attained mastery of Physical Science concepts and skills, the students (and you!) will have it much easier in upper courses from the sequence, where the student-designed and conducted investigations can be used.

ditto that!

Catherine Johnson said...

I don't know if you're still around - but if so, do you think it's important to teach students the constant of proportionality? (y=kx; k is the constant of proportionality)

I loved ratios when I was in high school; I've spent most of my adult life relying on direct variation ratios to figure things out.

Then, when I worked my way through the Saxon books and discovered the constant of proportionality, it was a revelation.

Here's a confession: until I learned about the constant of proportionality, I had never solved a percent problem through direct multiplication. If I needed to know 'what is 60% of 220?" I had to set it up as:

60/100 = x/220.

I absolutely didn't see that you could simply multiply 220 by .6.