A1.1 Water

How did water become part of a cell?

Water and solutes became trapped in a membrane, and more reactions within them began occuring, leading to the evolution of cells

What elements make up a water molecule and how are they bonded together?

A water molecules is made up of a negative oxygen atom, covalently bonded with 2 positive hydrogen atoms

How did water become part of a cell?

Water and solutes became trapped in a membrane, and more reactions within them began occuring, leading to the evolution of cells

What elements make up a water molecule and how are they bonded together?

A water molecules is made up of a negative oxygen atom, covalently bonded with 2 positive hydrogen atoms

Why is the water molecule polar?

The hydrogen atoms are positive, and the oxygen atom is negative

How do different water molecules bond together?

There are intermolecular hydrogen bonds between the positive hydrogen atom of one water molecule, and the negative oxygen atom of another

Are the intermolecular hydrogen bonds between water molecules permanent?

No, they can break and reform.

What are the chemical properties of water?

-Cohesive

-adhesive

-solvent

What are the physical properties of water?

-Buoyant

-high specific heat capacity

-thermal conductivity

-viscosity

What is cohesion of water?

The intermolecular forces between water due to hydrogen bonds cause them to be attracted to each other, pulling them together.

What is an example of cohesion of water in plants?

Water travels from the roots, up the xylem, to the leaves in plants, in order to evaporate from them. The water counteracts gravity by moving upwards

What is adhesion of water?

Water is polar, so it bonds to other surfaces that are charged (e.g., this is how water droplets hang from a leaf)

What is an example of adhesion of water in plants?

Water moves up the capillary in plants by bonding to the surface. Capillary action occurs

What is capillary action?

The movement of water upwards, counteracting gravity, using adhesive and cohesive forces. It occurs when adhesion causes the liquid to stick to the surface of a narrow tube, while cohesion pulls the other molecules along

How does water act as a solvent?

Water can dissolve polar molecules, as water molecules disrupt the forces between molecules, resulting in dissasociation of atoms

What is the name for molecules that are attracted to water?

Hydrophillic

How is the property of water as a solvent important for blood plasma?

Blood plasma consists of 95% water, so it can dissolve important nutrients such as glucose needed to be transported in it

How is the property of water as a solvent important for carrying nutrients in xylem and phloem?

Mineral ions are dissolved in water and carried up the phloem, and sucrose is dissolved in water and carried in the xylem

How is oxygen carried in the blood, if it is non-polar?

Because oxygen is non-polar, it cannot be transported in the blood plasma, so it is carried in haemoglobin in red blood cells

How is water buoyant?

Bouyancy is the force that counteracts gravity. Water is bouyant, so it is quite dense and allows less dense materials to float on it. The upward force which water exerts onto a floating object is equal to the amount of water displaced by it.

How are living organisms (especially fish) adapted to floating in water?

Fish have swim bladders, and they can use the gas in them to ascend or descend. As it gets deeper, the pressure of water increases, so this bladder helps them to adjust to it.

Pond skaters can sit on water due to its cohesion properties and surface tension.

What is viscosity?

Resistance to flow

Does water have high or low viscosity?

Water has quite low viscosity, meaning it is not that resistant to flow, however it is more viscous than air

What happens to the viscosity of a fluid when solutes are added to it?

It becomes more viscous (more resistant to flow). This is why blood has a higher viscosity than water

Does water have high or low thermal conductivity?

Water has high thermal conductivity, meaning it can easily transfer heat from one medium to another

How is good thermal conductivity of water useful to the body?

It helps with thermoregulation (keeping the body at right temperatures through high-water content blood)

What is specific heat capacity?

How much energy is needed to raise the temperature of a substance

Why does water have a high specific heat capacity?

Water has a high specific heat capacity, because a lot of energy is needed to raise its temperature and to break the strong intermolecular forces of hydrogen bonds between water molecules

Which property of water allows a pond skater to walk on it?

Cohesion, as the water molecules at the surface of a lake, have no water molecules above them, so they tend to stick more to each other, forming a layer across the surface called surface tension

Describe the properties of water and the consequences for living organisms

High specific heat capacity → aquatic animals don’t have to suffer from constantly changing temperatures

Plants can use capillary action from adhesion and cohesion

Solvent → transport minerals in blood in animals

Ice floats on water as it is less dense → provides habitiat for polar animals such as ice bears