Which of these indicate that a chemical reaction has occurred?

A.) Formation of a gas.

B.) Boiling of a substance.

C.) Melting of a substance.

D.) Freezing of a substance.

In general, should atmospheric pressure increase or decrease as altitude increases?

Which of the following correctly describes a property of an atom? it has more protons than neutrons it has a negative or positive charge it has an equal number of protons and electrons it has an equal number of neutrons and electrons

24. Is the following nuclear equation balanced? 2Pb →He + 290Hg a. yes b. no

What is a magnetic field

What is the formula for CO3 2 - and Al3 + ?

What element is represented by the following electron configuration: 1s22s22p63s23p64s23d4 Question 2 options: Cr Ca Ge Ar

He substance, cocl2, is useful as a humidity indicator because it changes from pale blue to pink as it gains water from moist air. What is its name?

The weighted average atomic mass of an element depends upon the a. relative abundance of protons in the element b. mass and relative abundance of each isotope of that element c. mass and relative abundance of each neutron of that element d.

What part of an atom do we change for isotopes

The Safe Drinking Water Act (SDWA) sets a limit for mercury-a toxin to the central nervous system-at 0.002 mg/L. Water suppliers must periodically test their water to ensure that mercury levels do not exceed 0.002 mg/L.