How are chemical and physical changes different on a molecular level?

Chemical changes involve the breaking of bonds in molecules.

Physical changes do not involve molecules.

Physical changes cause new molecules to form.

Roger poured water over a pile of sand. Some of the sand washed away. This process is similar to which of the following?

State one reason for the color change in beaker A

How hydrogen is usually obtained in the laboratory?

Jamal wants to make a model of a hill near his house to test the way the slope affects how rain runs down the hill. Which type of model would be best for what he needs?

Scientific notation is___ A) used to communicate the level of precision B) used to keep track of very small and very large numbers during mathematical calculations C) used to accurately measure volumes D) used to measure length with precision

A gas occupying a volume of 25 ft3 weighs 3.5 lbf on the moon, where the acceleration of gravity is 5.47 ft/s2. determine its weight, in lbf, and density, in lb/ft3, on mars, where g = 12.86 ft/s2.

What's the physical state of hydrogen and zinc in 2HCl+Zn=ZnCl2+H2

H2O (s) ⇒ H2O What would be the best argument against writing this in the form of a chemical equation?

What effect does an increase in products have on the reaction rate of a mixture at equilibrium?

Explain the basic principles of a distillation unit operation