Colored Solutions—The color of a solution will sometimes indicate which
chemicals are present. For instance, the colors of solutions containing
transition metals will vary depending on the element present.
Gas Evolution—When we want to measure the amount of gas that is evolved in
a reaction, we use a device called a manometer. The reaction takes place in
an Erlenmeyer flask, which is hooked up to a U-shaped tube filled partially
with mercury. As the reaction proceeds and the gas is produced, the
pressure increases. This causes the mercury in the tube to rise. We can tell
what the change in pressure inside the flask is by how much the mercury in
the tube rises. Remember: Pressure is how we measure amounts of gases.
Calorimetry—This is how we determine how much heat is produced by or
absorbed by a reaction, i.e., ΔH. A calorimeter consists of a very well
insulated container in which the reaction of known amounts of reactants
occurs. A thermometer measures the temperature change of either the
compounds involved in the reaction, or some other substance, which
absorbs/provides the heat for the reaction. The temperature change of this
substance, along with its mass and specific heat, allows us to calculate the
amount of heat produced or absorbed by the reaction:
Q = mc∆T