A model showing that gases are made from the matter of particles that are too small to see and are moving freely around in space can explain many observations.
The material needed to stop a beta particle is c. thin pieces of wood.
The attraction of inter-molecular forces between molecules is defined by a general term "Van der Waals forces". It is the weak interactions caused by momentary changes in electron density in a molecule.
Inter-molecular forces that are present between hydrogen atom which is bonded to highly electronegative atom (
) and the lone pair electrons present in the other molecule on these electronegative atoms is known as hydrogen bonding.
The type of interactions between methane, 
is Van der Waals interactions whereas in water, 
is hydrogen bonding.
Since, the hydrogen bond is stronger than the Van der Waals forces so, it results in higher strength between the molecule possessing hydrogen bonding. Thus, molecules possessing hydrogen bonds will have higher boiling point than the molecules which possess Van der Waals forces.
Hence, water () have a significantly higher boiling point than methane ( ) because water molecules are attracted to one another by hydrogen bonds.
Hello!
The greatest negative impact of a new hydroelectric dam is the changes in the surrounding landscape.
Hydroelectric dams are among the cleanest energy sources, they don't generate waste, pollutants or atmospheric emissions. The negative impact is given by the landscape transformation needed to take advantage of the natural conditions of the dam. They stand out wherever they are, so it is important to consider the aesthetic aspect when building a dam.
Have a nice day!
