How to convert between pH and concentrations.

Aim: How to convert between pH and concentrations.

Activity: Draw the pH scale.

Notes: Sörenson defined pH as the negative logarithm of the hydrogen ion concentration.

pH = – log [H+]

Remember that sometimes H3O+ is written, so

pH = – log [H3O+]

means the same thing.

So let’s try a simple problem: The [H+] in a solution is measured to be 0.010 M. What is the pH?

The solution is pretty straightforward. Plug the [H+] into the pH definition:

pH = – log 0.010

An alternate way to write this is:

pH = – log 10¯2

Since the log of 10¯2 is -2, we have:

pH = – (- 2)

Which, of course, is 2.

How to identify oxidizing and reducing agents Aim: How to identify oxidizing and reducing agents

Notes:

oxidizing agent: the substance that gets reduced

reducing agent: the substance that gets oxidized

An atom gets oxidized when the oxidation number increases.

An atom gets reduced when its oxidation number decreases

Exploring Different Forms of Energy

Aim:  How to connect real world examples of different Forms of Energy to mathematical formulas.

Unitedstreaming.com   “elements of physics: energy work and power”

This video demonstrates how the formula W = Fx is a definition of energy, explains kinetic energy and givesI a number of examples. This is a great review because it also ties in potential energy and gives a number of examples. It illustrates and  explains some of the types of energy such as electromagnetism, nuclear energy, chemical energy, sound energy, and heat energy. Students will see real life examples of energy exchanges and  see how the three laws of thermodynamics apply to real world scenarios. This video also discusses why Einstein’s formula E = mc 2  explains how matter and energy are different aspects of the same thing.This is a great overall review that ties the energy concept together.

Video Quiz follows.

Review for Test(unit study guide)

Notes

1.       Distinguish between electrical, chemical, radiant, and thermal energy.   What do they all have in common?

a)Electrical – energy associated with the movement of charged particles

b)Chemical – energy stored in chemical bonds

c)Radiant – energy carried by electromagnetic waves

d)Thermal – kinetic & potential energy of the particles in an object

e) All of these forms of energy have the ability to do work.

2.      What is kinetic energy?   What is potential energy?   Describe how a swinging pendulum demonstrates the back-and-forth conversion of potential energy to kinetic energy.

Kinetic energy is energy associated with moving objects, no matter how big or how small.   Potential energy is energy stored in an object due to is position and location.

A swinging pendulum demonstrates both kinetic energy and potential energy.   When a swinging pendulum is at the highest point in its swing, it has maximal potential energy and a minimal kinetic energy.   At the bottom or lowest point in its swing, it has maximal kinetic energy and minimal potential energy.

3.      Describe and give an example of the following types of potential energy…

a)      elastic potential energy – energy stored when an object is compressed or stretched, such as a stretched rubber band

b)     chemical potential energy – energy stored in chemical bonds which can be released by a chemical reaction, such as the energy stored in a typical household battery

c)      electrical potential energy – energy due to the position of an electrical charge relative to other electrical charges, such as static electricity

d)     nuclear potential energy –energy stored in the nuclei of atoms and released during nuclear reactions;   the energy produced at nuclear power plants are an example

4.     Calculate the gravitational potential energy of a 500-kg rock resting on the edge of a 200-meter cliff.

Gravitational potential energy   =   mass   x   gravity   x   height

GPE   =   500 kg   x   9.8 m/s2   x   200 meters

GPE   =   980,000 Joule

5.             Calculate the kinetic energy the rock mentioned in question 4 will have just before it hits the ground if it is moving at 10 meters per second.

Kinetic energy   = ½( m   x   v2)

KE   =   ½   x   [500 kg   x (10 m/s)2]

KE   =   2500 Joules

Homework:

Review for Test