Please solve the following chemistry problems: Describe Salt P and Q, the effect of heating blue hydrated copper (II) sulphate, the systematic name of But-2-ene, and its reaction with HBr.

Salt P turned into liquid after being left open. This indicates that it absorbed enough moisture from the atmosphere to dissolve and form a solution.
This property is called $\boxed{\textbf{deliquescent}}$.

Salt Q became sticky after being left open. This indicates that it absorbed moisture from the atmosphere but did not dissolve to form a solution.
This property is called $\boxed{\textbf{hygroscopic}}$.

When blue hydrated copper (II) sulphate is heated:

• The blue solid turns into a $\boxed{\textbf{white solid}}$.
• $\boxed{\textbf{Colourless liquid droplets}}$ are observed on the cooler parts of the test tube.

Compound A has the formula $\text{CH}_3\text{CH}=\text{CHCH}_3$. This is an alkene with four carbon atoms and a double bond between the second and third carbon atoms.
The systematic name is $\boxed{\textbf{But-2-ene}}$.

Compound A (But-2-ene) reacts with hydrogen bromide (HBr) in an addition reaction. The double bond breaks, and hydrogen and bromine atoms add across the carbons that were part of the double bond. Since But-2-ene is a symmetrical alkene, only one product is formed.
The reaction is:

The product formed is $\boxed{\textbf{2-bromobutane}}$.