Activity 7

Activity 7: Acids and Bases

Water is everywhere!  So, lets spend one more activity learning about one of the key aspects of water.  Water has the ability to dissociate (break apart from HOH (or H₂O) into H+ ions and OH- ions).  We refer to solutions with lots of H+ ions as acids and solutions with lots of OH- ions as bases.  By adding chemicals with H+ ions acidic solutions can be made.  By adding chemicals with OH- ions basic solutions can be made.

Activity Tasks:

1. Review the Content Slides Acids and Bases on the D2L site.

2. Complete the Teaching Idea “Concept Questions for Chemistry using PhET”  posted by Trish Loeblein on the pH Scale simulation at PHET (http://phet.colorado.edu/en/simulation/ph-scale). On your blog post the answers with your scientific explanations from the “Clicker Questions pH Scale” posted by Trish.

(If it is highlighted in yellow then it is the answer to the question.) 

Describe image of gases using words and diagrams

1.How gases are distinguishable from a solid or liquid

Gas

A gas is a substance which takes the shape of its container and expands to completely fill it's container. There are several types of gases with slightly different behaviors. These are ideal gasses, real gasses, super critical fluids, plasmas and critical opalescent materials.

Ideal Gas

Ideal gasses (sometimes called perfect gases) refer to the behavior which gasses approach as the pressure nears zero. This behavior is described mathematically by the ideal gas law. Although no gas behaves exactly as an ideal gas, many substances come very close to ideal behavior at atmospheric pressure and most behave ideally at very low pressures.

Real Gas

Most molecules attract one another until they come very close together, when they become repulsive. This attraction is due to the electrostatic interactions between the two molecules. These interactions are often categorized into dispersion forces, van der Waals forces, hydrogen bonding and dipole-dipole interactions. The repulsion between molecules at very close distances is due to the repulsion between the nuclei of the two molecules. These forces give rise to relationships between the pressure, temperature, volume and quantity of a substance which do not exactly obey the ideal gas law. Gasses under physical conditions which give non-ideal behavior are called real gasses.

 

2.How the particle mass and gas temperature affect the image.
Molecular diffusion, often called simply diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, but it is important to note that diffusion also occurs when there is no concentration gradient. The result of diffusion is a gradual mixing of material. In a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing.

3.How the size and speed of gas molecules relate to everyday objects  
It effects how a lot of things react to one another.

1. There are 2 balloons in a room. They are identical in size and material. One balloon is filled with air and the other balloon is filled with Helium. How does the pressure of the air balloon compare to the pressure of the Helium balloon. The pressure in the air balloon is 

A. less  B. equal  C. greater

2. How does the pressure in the Helium balloon compare to the pressure of the air in the room? The pressure in the Helium balloon is  

A. less  B. equal  C. greater

3.  How do the number of air molecules in the air balloon compare to the number of He atoms in Helium balloon?
The number of air molecules is 

A. less  B. equal  C. greater

4. How does the average speed of the Helium molecules compare to that of the air molecules?
The average speed of the He molecules is  

A. less  B. equal  C. greater

Look at the animation of the particles bouncing around in the volume. Describe what visual information you can use to get a sense of the pressure that the gas particles are exerting on the walls. Pressure is also lost with movement.

Why does the pressure reading vary with time?
Pressure can lessen over time and it will do this unless it is in a vacuum.
What visual cues are associated with an increase in pressure?
According to the state equation
pv=nrt
p=pressure
v=volume
n=number of moles
r=gas constant
t=temperature.
This means the volume will be bigger as well and this means it will be bigger.

p and v are inversely proportional; as p increases, v decreases, as v increases, p decreases.

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  5. What will happen to the pressure if temp is held constant and the volume is decreased?

  

A.Pressure goes up because more collisions

B.Pressure goes up because more collisions are happening, but same force per collision

C.Pressure goes up because more collisions are happening, and increased force per collision

D.Nothing because pressure is only related to molecular speed

6. You are flying from Denver to Boston, and you bring along a ½ full bottle of shampoo that was well sealed before you left Denver. You land in Boston and proceed to your hotel. The number of air molecules within the shampoo bottle:

 

A. has decreased  

B. has stayed the same   

C. has increased

7.  If the walls of the shampoo bottle are strong and rigid so that the bottle has the same shape as before you left, how does the pressure of the air inside the bottle compare to the pressure of the air in Denver?

A.less than 

B.equal to  

  c.greater than