3.1.7 Water Flashcards
What causes the hydrogen bonds between water molecules?
The attraction between the positive pole of one water molecule and the negative pole of another
What is meant by ‘polar molecules’
electrons not evenly distributed- hydrogen atoms are slightly positive and oxygen has a slightly negative charge
What is meant by cohesion?
the attraction of molecules for other molecules of the same kind, and water molecules have strong cohesive forces thanks to their ability to form hydrogen bonds with one another
What does cohesion result in?
more energy being required to seperate molecules so higher boiling point, spec latent heat capac and latent heat of vaporisation
What properties of water affect the structure
High heat capacity, high heat of vaporisation, strong cohesion, the fact that it’s an important solvent and the fact it is a metabolite.
What does high specific heat capacity mean and why is it important to organisms
The heat needed to raise the temperature of 1kg of water by 1°C-, water has a large specific heat capacity, and therefore can absorb large amounts of heat energy before its temperature raises a significant amount. Important because 1) bodies of living organisms are mostly made of water. This water in and around our cells absorbs a lot of heat energy without its temperature increasing much. The water ’buffers’ the heat changes. 2)aquatic organisms as large bodies of water, like seas or lakes, do not techange mperature as quickly as terrestrial environments.
What does latent heat of vaporisation mean and why is it important to organisms
When fast moving molecules evaporate their energy goes with them, leading to the average kinetic energy of the water to decrease. This means the water cools down. The energy that is lost is called the latent heat of vaporisation.
1) Perspiration/sweating in humans- water evaporates off surface of skin and cools us down
2) Cools down plants- when water evaporates from leaves
3) Transpiration
What does strong cohesion between molecules mean and why is it important to organisms
Due to their polarity (charges), water molecules are attracted to each other, and form hydrogen bonds. These hydrogen bonds help hold water together, so they can flow as a continuous stream. This is known as mass flow. 1)In plants, water moves up the xylem vessels as a continuous stream. This allows water to move from the roots to the top of the tallest trees. 2) Water cohesion leads to ‘surface tension’, making water behave as if there is a skin where the water meets air. This allows small animals to live on the surface of water bodies.
What does important solvent mean and why is it important to organisms
A solvent is a liquid that other substances (called solutes) can dissolve. The positive and negative changes of water attract other molecules causing them to separate from each other - dissolve. When substances are dissolved in water they are free to move around and react with other molecules. 1)The metabolic reactions that happen inside all living organisms can only happen when the reactants are dissolved in water. 2)Substances being dissolved in water also allows them to be transported around the bodies of living organisms. E.g. glucose, CO2, urea in blood plasma, also mineral ions and sugars dissolved in water are transported in xylem and phloem in plants.
What does metabolite mean and why is it important to organisms?
Water molecules can also be involved in chemical reactions directly. 1)Hydrolysis reaction are important in digestion of large molecules in animals 2)Condensation reactions are important in synthesis of important molecules such as proteins in living organisms.
