U2-T5 Flashcards
The main properties of water
- Change of state
- Anomalous expansion
- Solvent properties
- High heat capacity
Water is polar. What does it means?
It means that the positive and negative electrical charges are unevenly distributed
Why is water polar ?
Because of the bent shape of the molecule
Why a water molecule has is bent shape?
Because the negative charge from oxygen is on a side of the molecule and the positive charge of the hydrogen atoms is on the other side of the molecule. So the reason the shape of the molecule is because of its electronegativity between hydrogen(2.1) and oxygen(3.5)
Qu’est éléctronégativité d’un élément?
L’éléctronégativité d’un élément est une grandeur qui caractérise sa capacité à attirer les éléctrons lors de la formation d’un liaison chimique avec un autre élément
For most material, the solid form is more heavy or more weak than the liquid form
More heavy, but it is not the case for water
What happens when water freezes?
The molecules space one from the other forming a large cristal lattice. There is less particles in an equal volume, this structure is denser and so weaker than in a liquid state
Why does ice float?
Because water is denser in its solid form, so in an equal volume of water, there is less molecule in the solid form than in the liquid so it’s weaker and float.
What happens to most material when they are warm up and when they are cooled down?
Most material expands when heating and narrows when cooled down. Water react like that between 4 and 100 degrees C
What happens to water between 0 and 4 degrees C?
Water expand cooling down under 4 degrees C until 0 degree.
What happens to water while cooling down, but above degrees?
Water narrows
Why water is also called “general physiological solvent”?
Because most biological reactions occur with solutés dissolved in water
What does “high heat capacity” mean?
It means that water heats up and cool down slowly
Why is it important (in climate change) that water has a high heating capacity?
Because it helps to maintain climatic stability by moderating temperature changes
How often occur hydrogen bonds?
They are ubiquitous
Why does hydrogen bonds happen?
This happens because the hydrogen is attracted to both, it’s own oxygen and the oxygen of other molecules that come close enough.
What is the total number of hydrogen bonds formed between 1 water molecule ?
It’s 4
Water molecules are naturally attracted to one another. How does this affect the biking point of water?
Water molecules tend to bond together in group of 4, acting like a single larger molecule that would normally have a higher boiling point than the small individuals molecules
Does pression increase or decrease with altitude?
Decrease
Will the boiling point of water be higher or lower at the top of a mountain compared to sea level?
As pressure decreases with altitude, it would be lower in the mountains so the boiling point of water will therefore be lower in mountains
What property of water is important when considering how ocean currents affect climate and why?
For ocean currents to affect climate, the water must be able to remain at a stable temperature so it is important that it has a heat capacity
What is responsible for driving the hydrological cycle?
Solar energy
Named 2 main thyme of energy involved in the hydrological cycle (appart from solar energy)
Kinetic energy and potential energy
Which objects posses potential energy
Objects that are not in motion posses potential energy, which is converted to kinetic energy when some force, such as gravity, acts upon the object to sell it in motion
When occur the 3 main thyme of energy in hydrological cycle?
Solar energy is responsible for driving the hydrological cycle but once water vapour is in the air, it has potential energy. This is transformed once it Starr’s to fall as precipitation and then flow downwards on and in the ground
Formula to find the average transfer rate in or out the reservoir
= volume of water / residence time
Can warm or cold ai hold the most water vapour?
Warm air
Explain the difference between percolation and infiltration
Infiltration is the movement of surface water down into the ground whereas percolation is the flow of the water down through spaces between soil and rock particles
How does groundwater flow helps to recharge aquifers?
Precipitation falls on the ground and infiltrates the soil. It percolates down through the soil and rock and then moves by the groundwater flow through permeable rock to an aquifer
Why water evaporates in lakes for exam,e, at less than 100 degrees C?
The hydrogen bonds between water molecules are constantly being broken and reformed, so individual water molecules at the surface can escape and move away. As the temperature of the air above the body water gets warmer, or moist is blown away and dry air takes its place, it can hold more of these escaped molecules, so more water evaporates - even if the temperature of the water is well below boiling point
What are the main reservoirs of water?
1. Ocean 2 atmosphere 3 lakes and rivers 4. Land ice 5. Groundwater 6. Soil 7. Living organisms
