List four observation that suggest a chemical change is occuring

Which element is present in all organic compounds? (1) nitrogen (2) oxygen (3) carbon (4) sulfur

Hich element is likely to be the most brittle? a. selenium b. cobalt c. platinum d. zinc

Which of the following will most likely increase the amount of erosion that occurs on the banks of a river? A. Heavy rains on the mountain that is the river's water source B. High winds over the ocean to which the river flows C.

Consider the following cyclic process carried out in two steps on a gas. Step 1: 50. J of heat is added to the gas, and 20. J of expansion work is performed.

Elliptical galaxies often appear reddish due to an abundance of

Discuss why two objects of made of the same type of matter at the same starting temperature with different masses increase in temperature at different rates when the same amount of thermal energy is transferred to each object.

An isotope contains 56 protons, 54 electrons, and 74 neutrons. What is the identity of the isotope?

How many ozone particles are needed to form 24 particles of oxygen gas?

Calculate the molality of a 27.0% (by mass) aqueous solution of nitric acid.

What is the percent of carbon-14 remaining after two half-lives?