Carbon-14 (14C) is not stable and it spontaneously decays into nitrogen-14 (14N) and an electron by a radioactive beta-decay. Which of these is true about the decay?

What would be the best method to determine the distance to a nearby star? (A star 10 light years away is an example of a nearby star.)

This family (molecules 1, 2, 3, etc) of materials is likely to have what set of properties?

When baking soda is mixed with vinegar it bubbles vigorously and the material gets cold to the touch. What happens to the total entropy of the universe as the products are formed?

The gasoline engine of an automobile is considerably less than 100% efficient. This means that not all of the energy in the gasoline is turned into kinetic energy of the car. Which of these statements best explains why?

Semiconductors can behave like metals when you heat them up. Which of the following best explains how and why that happens?

A divergent plate margin bisects the Red Sea. What will happen to the Red sea as a result of the presence of this diverging plate boundary?   

The elements on the left side of the periodic table above are shaded a greenish tint. Suppose you were to combine the atoms of two of these greenish tinted elements from the fourth row of the periodic table. What characteristics will the product have at room temperature?

When measuring the positions of the lines in the absorption spectrum of stars in a certain galaxy, the lines are all shifted toward the red end of the spectrum. This means

This is the energy diagram for the magnesium–oxygen reaction.    Image Description Graph of the magnesium-oxygen energy curve with energy (y-axis) versus the extent of reaction (x-axis). The energy line starts level then increases before reaching its peak energy around the middle of the reaction, then decreasing in energy and leveling off well below the initial energy level line. Sodium will also react with oxygen. However, unlike magnesium, sodium begins to react as soon as it is exposed to oxygen and produces very little heat and no visible light. Which of these curves best represents the sodium–oxygen reaction compared with the magnesium-oxygen reaction? (The curve for magnesium + oxygen is shown using a dotted line for reference.)    Image Description Five energy diagrams. Diagram A is as follows: The sodium-oxygen energy curve starts by increasing twice as much as the magnesium-oxygen line before reaching its peak and decreasing to below the initial energy line. The final level of sodium-oxygen energy is less than the magnesium-oxygen energy level. Diagram B is as follows: The sodium-oxygen energy curve starts by increasing more than the magnesium-oxygen line, reaching its peak a little after magnesium-oxygen before decreasing and leveling off, with its final energy above the initial energy line. The final level of sodium-oxygen energy is much greater than the magnesium-oxygen energy level. Diagram C is as follows: The sodium-oxygen energy curve starts by increasing a little then going back to the initial energy level by the middle of the reaction. The line keeps decreasing before rounding off and heading back to the initial energy line at the end of the reaction. The final level of sodium-oxygen energy is greater than the magnesium-oxygen energy level. Diagram D is as follows: The sodium-oxygen energy curve starts by increasing, but not as much as the magnesium-oxygen energy line, before rounding off and decreasing to below the initial energy line. The final level of sodium-oxygen energy is above the magnesium-oxygen energy level. Diagram E is as follows: The sodium-oxygen energy curve starts by increasing a little before decreasing a great amount below the initial energy line before rounding back up and increasing in energy back above the initial energy line. It begins to taper back to a decreasing line as the reaction ends. The final level of sodium-oxygen energy is greater than the magnesium-oxygen energy level.