Hon Bio Notes Review - Water Polarity And Properties

Water is considered the most abundant chemical in organisms because it is essential for life and is found in large quantities in all living organisms. It makes up a significant portion of cells, tissues, and fluids in the body, playing a crucial role in various biological processes. Water is involved in maintaining temperature, transporting nutrients and waste, lubricating joints, and facilitating chemical reactions. Its abundance and importance in sustaining life make it the most abundant chemical in organisms.

Water molecules have an uneven distribution of electrons due to the oxygen atom being more electronegative than the hydrogen atoms. This causes the oxygen atom to pull the shared electrons closer to itself, creating a partial negative charge. In contrast, the hydrogen atoms have a partial positive charge. This separation of charges within the molecule makes water polar, as there is an asymmetrical distribution of charge.

Many chemical reactions require water because water is a versatile solvent that can dissolve many substances. It can participate in hydrolysis reactions, where a compound is broken down by reacting with water molecules. Additionally, water can act as a reactant or a product in certain chemical reactions. For example, in the process of photosynthesis, water is used as a reactant to produce oxygen and glucose. Overall, water plays a crucial role in facilitating and enabling various chemical reactions to occur.

In a covalent bond, electrons are shared between atoms. This means that both atoms involved in the bond contribute electrons to form a shared electron pair. This sharing of electrons allows both atoms to achieve a more stable electron configuration, fulfilling the octet rule. Therefore, the correct answer is "shared".

Electrons spend more time around atoms that have a stronger attraction for them because the attraction between the negatively charged electrons and the positively charged nucleus is stronger. This stronger attraction causes the electrons to be pulled closer to the nucleus and spend more time in its vicinity. On the other hand, atoms that are larger in size have more electron shells and a greater distance between the nucleus and the outermost electrons. As a result, the attraction between the electrons and the nucleus is weaker, causing the electrons to spend less time around the atom.

A polar molecule is a molecule that has a positive charge in one part and a negative charge in another part. This occurs when there is an uneven distribution of electrons, causing one end of the molecule to be slightly positive and the other end to be slightly negative. Therefore, in a polar molecule, both positive and negative charges are present.

This statement is false. All organisms require water for survival, even those living in desert environments. While desert organisms have adaptations that allow them to conserve and utilize water efficiently, they still need water to carry out essential biological processes. Without water, organisms would not be able to maintain their metabolic functions, transport nutrients, eliminate waste, or regulate their body temperature. Therefore, water is a fundamental requirement for all living organisms, regardless of their habitat.

Covalent bonds are stronger than hydrogen bonds. Covalent bonds involve the sharing of electrons between atoms, creating a strong bond. On the other hand, hydrogen bonds are a type of intermolecular force that occurs when a hydrogen atom is attracted to an electronegative atom in a different molecule. While hydrogen bonds are important for various biological processes, they are weaker than covalent bonds. Therefore, the statement that hydrogen bonds are stronger than covalent bonds is false.

In molecules, opposites attract refers to the concept of electronegativity, which states that atoms with different electronegativities will attract each other. This attraction occurs because one atom has a stronger pull on the shared electrons, causing a partial positive charge on one atom and a partial negative charge on the other. This phenomenon is essential for the formation of chemical bonds and the stability of molecules. Therefore, the statement "In molecules, opposites attract" is true.

Water has a high specific heat capacity, meaning it requires a large amount of energy to change its temperature. This is because the hydrogen bonds between water molecules are strong and require a lot of energy to break. As a result, water can absorb or release a large amount of heat energy without experiencing significant temperature changes. Therefore, it is true that it takes a lot of energy for water to change its temperature.

Water molecules are polar, meaning they have a slightly positive charge on the hydrogen atoms and a slightly negative charge on the oxygen atom. This polarity allows for hydrogen bonding, where the slightly positive hydrogen of one water molecule is attracted to the slightly negative oxygen of another water molecule. This attraction between the positive and negative ends of different water molecules is responsible for many of the unique properties of water, such as its high boiling point and surface tension. Therefore, the statement is true.

Cohesion refers to the attraction between water molecules. This attraction is caused by hydrogen bonding, where the positive end of one water molecule is attracted to the negative end of another water molecule. This cohesive force allows water molecules to stick together, creating surface tension and enabling water to form droplets or be drawn up through narrow tubes, such as in plants. Therefore, the statement that cohesion is the attraction between water molecules is true.

In this scenario, sugar is being dissolved in water. The substance that does the dissolving is called the solvent. Since water is the substance that dissolves the sugar, it is considered the solvent in this case.

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Hydrogen bonds occur between water molecules due to its polarity, not its lack of polarity. Water is a polar molecule, meaning it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This polarity allows the hydrogen atoms of one water molecule to attract the oxygen atom of another water molecule, forming hydrogen bonds. Therefore, the correct answer is False.

Adhesion is actually the attraction between water molecules and other substances, not between two water molecules themselves. This attraction allows water to stick to other surfaces, such as when water forms droplets on a glass surface. Therefore, the correct answer is false.

Water actually becomes less dense when it freezes. This is because the water molecules arrange themselves in a hexagonal lattice structure when freezing, which creates open spaces between the molecules. As a result, the solid ice takes up more volume than the same amount of liquid water, making it less dense. This is why ice floats on water.

A polar molecule is formed when there is an unequal sharing of electrons between atoms in a covalent bond. This unequal sharing results in a partial positive charge on one side of the molecule and a partial negative charge on the other side, creating a dipole moment. Therefore, the statement "When a molecule has covalent bonds that do not share electrons equally, that molecule is called a polar molecule" is true.

In a polar water molecule, oxygen is actually a little bit negative and hydrogen is a little bit positive. This is because oxygen is more electronegative than hydrogen, meaning it has a greater ability to attract electrons towards itself. As a result, the oxygen atom in a water molecule pulls the shared electrons closer to itself, giving it a partial negative charge, while the hydrogen atoms have a partial positive charge. Therefore, the correct answer is False.

Salt is dissolved in water, which means that it is the substance being dissolved. In a solution, the solute is the substance that is dissolved, while the solvent is the substance that does the dissolving. In this case, water is the solvent, and salt is the solute. Therefore, the correct answer is solute.