Chemistry – Unit 2 Review and Study Guide DUE Monday 11/10/14
To prepare for the unit 2 test, you should assemble your notes, worksheets and quiz and review them,
preferably in a small group where you can draw from each other’s understanding.
Energy:
When a substance gets hotter or colder, energy is either transferred into or out of the system. One
way energy is stored in a system is in the motion of the particles. As particles move faster, their
thermal energy increases. As the particles move faster, they tend to move farther apart from one
another. Temperature is a measure of the average motion of the particles in the system.
1.Use words and diagrams to explain why the alcohol level in a thermometer rises when it is placed in a warmer fluid and falls when it is placed in a cooler fluid.2.Explain how the Celsius scale was devised and why we can’t use it when we describe the behavior of gases.
3. Describe the difference between temperature and heat. Give an example that illustrates your answer.
4. What causes particles to spread apart when they get warmer? What causes particles to get closer together when they get cooler?
Kinetic Molecular Theory
This theory describes all matter as being composed of tiny particles in endless random motion. In
a solid, the particles vibrate, but are locked into an orderly array. In a liquid, the particles are still
touching but are free to move around past one another. In a gas, the particles are moving very
rapidly and are widely separated.
- Draw particle diagrams to represent a solid, liquid and gas. List properties or characteristics of each state of matter and explain how the arrangement and movement of particles determine these properties.
- Explain with words and particles diagrams how particles travel from one point in the room to another point? (Think of the orange smelly particles).
- Draw particle diagrams to represent samples of a cold gas and a hot gas.
Pressure (1 atm = 760 mm Hg = 101.325 kPa = 14.7 psi = 760 torr)
- Set up proportions to convert the following units. Show the appropriate sig figs in the answers.
b. Convert 125.3 kPa to atm.
c. Convert 25.6 psi to torr
10. Determine the pressures of these gases in the
manometers. Explain your reasoning for deciding
where pressure is greatest.
11. Draw diagrams and explain how differences in pressure cause at least 3 of the following:
a. how you breathe.e. why water rises in the upended flask
b. how water rises in a straw when you drinkf. why the Cartesian diver falls and rises
c. why the can crushes g. why the balloon is pushed into the flask
d. why mercury in a barometer rises or falls when the weather changes:
Gas behavior
Gas pressure is a measure of the collisions of the molecules with the sides of the container. A
barometer is used to measure atmospheric pressure; a manometer is used to measure the pressure
in a container. (review ws 3) The 3 variables P, V, T and n are interrelated. Any factor that
affects the number of collisions has effect on the pressure. You should be able to:
12. Predict the effect of changing P, V, T or n on ANY of the other variables. For example:a. The temperature of a gas in a sealed container increases; the pressure of the gas ____.
b. The temperature of a gas increases; the volume of the gas______.
13. Fill in the table below:
Dependent vs. Independentvariable / Graph / Relationship
(as one changes, what happens to the other?) / Explain relationship in terms of particle motion.
P vs. T
P vs. V
V vs. T
P vs. n
14.Explain why one must use the absolute temperature scale (Kelvin scale) to solve gas problems.
15.Use a PVTn table and factors to calculate the new P, V, T or n in gas problems:
Standard temperature and pressure (STP): 1 atm and 273 K
Kelvin = Celsius + 273
- Suppose that you lowered the temperature of a gas from 100˚C to 50 ˚C. By what factor do you change the volume of the gas? (remember to use Kelvin!)
- Suppose that 25.0 mL of a gas at 725 mm Hg and 20˚C is converted to standard pressure and temperature. What would be the new volume?
Modeling Chemistry1U2 review v2.1