What is a controlled experiment? a. one variable is changed at a time b. none of the variables are changed c. all variables are kept constant d. two variables are changed at a time

Listen base your answer to the question on the information below. propane is a fuel that is sold in rigid, pressurized cylinders. most of the propane in a cylinder is liquid, with gas in the space above the liquid level. when propane is released from the cylinder, the propane leaves the cylinder as a gas. propane gas is used as a fuel by mixing it with oxygen in the air and igniting the mixture, as represented by the balanced equation below. c3h8(g) + 5o2(g) → 3co2(g) + 4h2o() + 2219.2 kja small amount of methanethiol, which has a distinct odor, is added to the propane to consumers detect a propane leak. in methanethiol, the odor is caused by the thiol functional group (–sh). methanethiol, ch3sh, has a structure that is very similar to the structure of methanol. what is the correct structural formula for a molecule of methanethiol

What causes different colors to appear in the sky? the absorption of light by air molecules the reflection of light by bodies of water the greenhouse effect in earth's atmosphere the scattering and reflection of light by dust particles

Asubstance is held in an open container. its particles move past one another at random speeds but do not leave the container. heat is removed from the system, and the particles slow down. when enough heat is removed, the particles no longer have enough speed to overcome the weak attractive forces between them. when this happens, the substance enters its solid state. the process described above is known as .