Select the correct answer.

The chemical composition of most stars usually has which element in the highest concentration?

A. oxygen

B. hydrogen

OC. chromium

OD. lead

A climate-control heat pump can both heat and cool a building by A. moving heat energy from a low-temperature source to a high-temperature sink. B. moving heat energy from a high-temperature source to a low-temperature sink. C.

Which of the following should be represented in ionic form in aqueous solution? 1) HClO4 2) HNO2 3) HF 4) HCN

Describe porosity and how that affects groundwater infiltration.

Which property is a measure of the average kinetic energy of the particles in a sample or matter? (1) mass (2) density (3) pressure (4) temperature

What is the relationship between. chemicals and cancer?

Gasoline has a density of 0.749 g/mL. How many pounds does 19.2 gallons of gasoline weigh? Use significant figures. Do not enter "pounds" as part of your answer.

Which of these changes involved a physical change and not a chemical change?

Which of the following statements is true? Running an electric current through a magnet can create a magnetic field. Electric engines change electricity into magnetism. The strength of a magnetic field increases with distance.

valancy of x is 3 while that of y is 1. write a formula of the compounds when each of the seperaty combines with oxygen

The elements that contain electrons in an F sublevel near the highest occupied energy level are referred to as? A. Alkali metals B. Alkali earth metals C. transition metals D. inner transmission levels