Unlike most other solvents, water is unique in that its solid form is actually less dense than its liquid form. This is precisely the reason why ice floats in water. Water does indeed participate in many biochemical reactions and can form hydrogen bonds with other water molecules to allow for great cohesion. Also, the specific heat capacity of water is , which is the amount of heat required to raise the temperature of one mole of substance by 1 Kelvin. This value is much higher than the specific heat capacities of many other solvents. For example, the specific heat capacity for hexane is .

The partial negative and positive charges on a water molecule allow it to be attracted to other polar water molecules, which creates the cohesive nature of water and contributes to its high surface tension and heat capacity. London dispersion and Van der Waals forces are significantly weaker than hydrogen bonding. Additionally, ionic bonding only occurs intramolecularly, so it has little effect on the intermolecular properties of water.

Water is an amphipathic molecule, meaning that it can act as both an acid and a base. In some situations, water can act as a Bronsted-Lowry base (defined as a species which accepts a proton). Here is an example of water acting as a base:

As you can see,  accepted a hydrogen atom (proton) to become .

In other situations, water can act as a Bronsted-Lowry base (defined as a species which donates a proton). Here is an example of water acting as an acid:

As you can see,  donated a hydrogen atom (proton) to become .

Thus, water can act as both an acid and a base. 

 (benzene) is the least soluble in water because it is a non polar substance. Polar compounds are soluble in water because like dissolves like. Water is polar and therefore dissolves other polar substances. The more polar or ionic a substance is, the more soluble it is in water. , ,  are polar compounds because of the uneven electron distribution within these compounds.

In this question, we're asked to identify an answer choice that describes something that is not a characteristic of water.

Remember that water molecules consist of a single oxygen atom with single bonds to two hydrogen atoms. There are also two lone pairs of electrons on the oxygen atom, giving the overall molecular structure of water a bent shape. This bent shape is important, because it results in an overall net dipole moment of the water molecule, where the two hydrogen atoms have a partial positive charge and the oxygen atom has a partial negative charge.

The significance of this partial charge separation is that it allows water to be excellent at forming hydrogen bonds. Recall that hydrogen bonds occur when a partially positive hydrogen atom participates in a non-covalent bond to another electronegative atom on some other molecule (though can also be intramolecular in bigger compounds, like enzymes). These intermolecular interactions between individual water molecules results in an overall strong force of attraction between them.

As a consequence of these strong hydrogen bonds between the water molecules, many unique properties of water result. For instance, liquid water has an unusually high heat capacity. Due to the strong intermolecular forces of attraction, it takes a relatively large amount of energy in order overcome the attractive forces that hold water molecules together. Another very unique property of water is that its solid phase is actually less dense than its liquid phase. Thus, when water freezes into ice, it will float to the top surface in a body of water, which is important for sustaining life in certain environments.

Finally, these strong intermolecular hydrogen bonds give water a high surface tension. Once again, the reason for this is due to the fact that it takes a relatively greater amount of energy in order to break these bonds apart. Thus, water does not have low surface tension, making this the correct choice.

By definition, isotopes of a given element have the same number of protons and electrons, but differ in the number of neutrons. This causes a difference in the mass number (protons + neutrons) as well. Neither the number of protons nor the number of electrons changes with different isotopes of the same element.

Isotopes are versions of an element with different numbers of neutrons. Hydrogen has three naturally occurring isotopes. , sometimes called protium, contains one electron, one proton, and no neutrons. , called deuterium, contains one electron, one proton, and one neutron. , called tritium, contains one electron, one proton, and two neutrons. Hydrogen has no such isotope that contains three neutrons.

In order to find the molar mass of an atom from its isotopes and their natural abundances, use the following equation:

 for all the given isotopes.

Since chromium has four isotopes, we will write the following equation to find its atomic mass:

Each element is defined by the number of protons its atoms contain. For example, hydrogen has one proton, helium has two protons, and lithium has three protons. Each element also has a characteristic number of neutrons. For example, hydrogen has zero neutrons, helium has two neutrons, and lithium has four neutrons.

Some elements, however, also have different "versions" of themselves: atoms which have a different number of neutrons, called isotopes. For example, there are three isotopes of hydrogen.  has one proton and zero neutrons.  has one proton and one neutron. Lastly,  has one proton and two neutrons. Carbon is another such element that has different isotopes. 

Recall that when a particle undergoes alpha decay, the particle is emitting an alpha particle, which is the same as .

Now, write the following equation of the alpha decay:

Thus,  is the daughter nucleus.