Answer:
They are strong intermolecular forces
Explanation:
Covalent forces are very strong intermolecular forces. In fact, we can say they are the strongest. This is because several big and giant molecules have covalent bonds holding their molecules together. A good example of this is the buckministerfullerence molecule which contains carbon atom to the order of 60 carbon atoms. It is a very giant molecule and it is covalent bond that is holding the molecules together
The strongest substance in the world is diamond. It is so strong that no other substance can cut it asides another diamond. As strong as it is, the molecule is held together by very strong intermolecular forces of covalent bonds which confers the strength it has on it
Reactants are the substances that undergo changes and the new substance created from it is called products.
Answer:
a) 
b) 1657 €
Explanation:
Hola,
a) En este problema, vamos a considerar el millón de litros de agua anuales, ya que con ellos podemos calcular el calor requerido para dicho calentamiento, sabiendo que la densidad del agua es de 1 kg/L:

Luego, usamos la entalpía de combustión del metano para calcular su requerimiento en kilogramos, sabiendo que la energía ganada por el agua, es perdida por el metano:


b) En este caso, consideramos que a condiciones normales de 1 bar y 273 K, 1 metro cúbico de metano cuesta 0,45 €, con esto, calculamos las moles de metano a dichas condiciones:

Con ello, los kilogramos de metano que cuestan 0,45 €:

Luego, aplicamos la regla de tres:
0.715 kg ⇒ 0.45 €
2630 kg ⇒ X
X = (2630 kg x 0.45 €) / 0.715 kg
X = 1657 €
Regards.