Which statement about a chemical reaction is true?

It occurs only at low temperatures.

It occurs only at high temperatures.

It occurs whenever a physical change takes place

It occurs whenever a chemical change takes place.

Gases emitted during volcanic activity often contain high concentrations of hydrogen sulfide and sulfur dioxide.

What are the five main forms of energy

1. How many moles of AgNO3 are in 15.0 g?

What does messenger RNA do during protein synthesis

Warm and cold fronts are formed by the movement of different air masses.

Foods labeled "fat free" can actually contain less than 0.5 grams of fat.

Plants make their own food. The chemical reaction for this process is shown in the equation below. CO2 + H2O + energy → C6H1206 + O2 What are the products in this chemical reaction? O A. C6H1206 + energy O B. H20 + energy O C. CoH1206+02 O D.

Using ohm's law, explain how voltage changes in relation to current, assuming that resistance remains constant.

An average copper penny minted in the 1960s contained about 3.000 g of copper. how much chalcopyrite had be mined to produce 100 pennies?

Which pack has the greatest change in enthalpy, warm packs (such as hand warmers) or cold packs (such as an ice pack) ?