Which of these is an indication that a chemical reaction has occurred?

A. melting of a substance

B. boiling of a substance

C. formation of a precipitate

D. freezing of a substance

Methane and carbon dioxide gas are two harmful greenhouse gases. Identify two sources of these gases and discuss what society can do to reduce their impact on the environment.

Trimix is a general name for a type of gas blend used by technical divers and contains nitrogen, oxygen and helium. In one Trimix blend, the partial pressures of each gas are 55 atm oxygen, 90 atm nitrogen, and 50 atm helium.

An atom has 18 protons and 8 valence electrons which statement would best identify this element

Why is chemistry flexible a. it is biased b. it cannot be verified c. it adds new evidence d. it cannot be reproduced

How many cubic centimeters (cm3) of olive oil have the same mass as 1.10 L of gasoline? Olive oil. 92g/mL Gasoline. 66g/mL

The standard enthapy of combustion of solid urea co (nh2) 2 is - 632kjmol-1 at 298k

What happens to an isotopes during radioactive

Why does the effective nuclear charge increase across a row of the periodic table?

Iodine-131 decays to form xenon-131. the half-life of this reaction is 8.07 days. from a 200-g sample of iodine-131, how much of the sample is xenon-131 after 16.14 days?

Complete the following statement by checking all that apply Creativity allows scientists to develop multiple approaches to solving problems. adapt to changes in scientific knowledge. look at old problems in new ways.