When placed in a freezer, liquid water turns into solid ice. Why is this considered a physical change?

If a research paper appeared reporting the structure of a new molecule with formula C2H8, most chemists would be highly skeptical. Why?

Do nonmetals form ions by gaining electrons?

Which two cases can be solved using the law of sines? (select all that apply.) ?

What is the density of a substance that weights 3.45 pounds and occupies a volume of 1.63 liters? Express answer in g/ml.

A * Blank * reaction occurs when one compound reacts and is broken down into different elements or simpler compounds

Calculate the ΔHrxn for the following reaction: CH4 (g) + 2Cl2 (g) - - > CH2Cl2 (g) + 2HCl (g) Use the following reaction and given ΔH's: CH4 (g) + Cl2 (g) - - > CH3Cl (g) + HCl (g), ΔH = - 99.

Select all that apply to diffusion. A solid cannot diffuse in to another solid. Solids can diffuse in liquids. Liquids can diffuse in liquids. It is the process of intermingling atoms from one substance into another.

We are all familiar with the general principles of operation of an internal combustion engine: the combustion of fuel drives out the piston.

A first order reaction has a rate constant of 0.816 at 25 oC. Given that the activation energy is 22.7 kJ/mol, calculate the rate constant at 34 oC. (enter answer to 3 decimal places)

Part b select the ester that is formed when propanoic acid reacts with isopropyl alcohol in the presence of heat and an acid catalyst.