The Kelvin temperature scale is used extensively in theoretical and applied chemistry work.

a. Find out how closely scientists have approached a temperature of zero kelvins $(0 \mathrm{~K})$ in a laboratory setting.

b. Results from research in cryogenics have suggested intriguing applications of low-temperature chemistry and physics concepts. Report on activities in this field.

Scientists use deep-ice samples from the Antarctic to estimate the atmospheric carbon dioxide concentrations many thousands of years ago. Research and prepare a report on how such ice samples are analyzed to obtain this information .

Given what you now know about the ideal gas law, consider an investigation to determine the identity of an unknown pure gas.

a. What would be an appropriate beginning question for this investigation?

b. What variables would you need to measure?

c. What variables, if any, would you need to control?

d. How could you measure each of the variables?

In what ways is an analogy involving an "ocean of gases"

a. useful in thinking about the atmosphere?

b. not an accurate representation of the atmosphere's observed behavior?

Think about the investigations you have completed throughout this unit. Why is it important to :

a. Compare your results to those of your classmates?

b. Compare your results to published data, when available?

c. Discuss your ideas with your classmates?

d. Reflect upon how your ideas have changed?

Considering the identity of the criteria pollutants and the sources of air pollutants in the United States where should air-qualit y monitoring devices be located? Explain .

What evidence would be needed to support a claim that human activity has not influenced global climate?

Consider Investigating Matter B.8, Phase Changes.

a. What would be an appropriate beginning question for this investigation?

b. What are the variables of interest?

What pattern would you expec t to find among pH readings taken of preci pit ation in the immedia te vicinity of an acid -rain producing smokestac k and at regular intervals downwind and upwind from the site? Sketch a graph of what you would expec t to find.

Collision theor y states that molecules can break bonds and form new substances when they collide with sufficient energy and suitable orientation . What types of evidence could support each of the following aspects of collision theory?

a. Formation of new substances.

b. Requirement for sufficient energy.

c. Requirement for suitable orientation

Heat is often described as "lost energy." For instance, automobile engines release about $75 \%$ of the energy from gasoline combustion as heat. Explain this idea of energy loss in terms of your understanding of heat.

If air at $25^{\circ} \mathrm{C}$ has a density of $1.28 \mathrm{~g} / \mathrm{L}$ and your classroom has a volume of $2.0 \times 10^5 \mathrm{~L}$,

a. what mass of air is contained in your classroom?

b. assume that the room temperature is increased. How would that affect the total mass of air contained in the room,

i. if the room were tightly sealed?

ii. if the room were not sealed?

Consider the data you graphed in Developing Skills C.2.

a. List two scientific claims you could make based on the data or the graph.

b. For each claim, cite evidence for making that claim.

Why is the presence of ozone regar ded as a problem at ground leve l, whil e the absence of ozone is regarded as a prob lem in the stratosphere?