Chemistry Unit 4

Unit Overview – Gas Laws

The big picture stuff: Students are introduced to the Periodic table in elementary and middle school. At this stage, students start to understand the motion of gas particles and how they are affected by pressure, temperature and volume. While the gas laws are not an explicit focus of NGSS, they are foundational to implementing the spirit of NGSS.

Next Generation Science Standards – High School (NGSS-HS):

PS1-2. Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

Examples: Limit to chemical reactions involving main group elements and combustion reactions.

Core ideas: The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states. The fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions.

PS1-5. Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

Emphasize: student reasoning that focuses on the number and energy of collisions between molecules. Focus on simple reactions in which there are only two reactants; evidence from temperature, concentration, and rate data; and qualitative relationships between rate and temperature.

Core ideas: Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangements of atoms into new molecules, with consequent changes in the sum of all bond energies in the set of molecules that are matched by changes in kinetic energy.

Science and Engineering:

• Apply scientific principles and evidence to provide an explanation of phenomena and solve design problems, taking into account possible unanticipated effects.
• Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.

Crosscutting concepts:

• Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.

California Science Standards – Chemistry

4a. Students know the random motion of molecules and their collisions with a surface create the observable pressure on that surface.

4b. Students know the random motion of molecules explains the diffusion of gases.

4c. Students know how to apply the gas laws to relations between the pressure, temperature, and volume of any amount of an ideal gas or any mixture of ideal gases.

4d. Students know the values and meanings of standard temperature and pressure (STP).

4e. Students know how to convert between the Celsius and Kelvin temperature scales.

4g.* Students know the kinetic theory of gases relates the absolute temperature of a gas to the average kinetic energy of its molecules or atoms.

h.* Students know how to solve problems by using the ideal gas law in the form PV=nRT.

Investigation and Experimentation Standards:

a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

b. Identify and communicate sources of unavoidable experimental error.

c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.

d. Formulate explanations by using logic and evidence.

e. Solve scientific problems by using quadratic equations and simple trigonometric, exponential, and logarithmic functions.

g. Recognize the usefulness and limitations of models and theories as scientific representations of reality.