how much does water makes up the human body
60%-70% of the human body
why is water the most critical molecule for life on earth?
it is polar and can form hydrogen bonds which grant water unique emergent properties that are vital for physiological homeostasis
How is water polar (H2O)
the Oxygen has as slightly negative charge and the hydrogens have a slightly positive charge
how does water being polar and can form hydrogen bonds make water the most critical molecule for life on earth
It dissolves things: It can pull apart sugar or salt so our bodies can use them
It stays cool: It doesn’t get hot or cold too fast, which keeps us safe
It sticks: It can climb up tiny tubes in plants to give them a drink
how can water form hydrogen bonds and what is electrical attractions
Since water is like a magnet, the “minus” part of one water piece (oxygen) pulls on the “plus” part of a different water piece (hydrogen). They click together!
It’s just a fancy way of saying “static cling” or “magnet power.” It is the invisible force that pulls a plus and a minus together.
Water is unique due to its structure of
Small size:It is tiny, so it can zip around and squeeze into small spaces
Bent shape: It’s shaped like a “V”. This keeps the plus and minus parts separate so it can act like a magnet
Highly polar covalent bonds
Overall polarity
(it’s a magnet, it is the only thing on Earth that stays as a solid (ice), liquid (water), and gas (steam) all at once in nature!)
Water is the only common substance that exists in all
three physical states in the natural environment (solid, liquid and gas)
4 properties of water
- Cohesive and Adhesive Properties: Water is sticky! It sticks to itself (cohesion) and other things (adhesion), which helps it move through plants
- Temperature Moderator:
(Stays Cool): Water is a great “heat bank.” It takes a lot of sun to make it hot, which keeps our bodies at a safe temperature - Expansion on Freezing:
Unlike most things, water gets bigger and lighter when it freezes. This is why ice floats on top of ponds instead of sinking - Versatility as a Solvent
Water can dissolve almost anything polar or charged. It is the best liquid for mixing things together in our cells
cohesion
is binding between like molecules
Water binds to itself by hydrogen bonding
Results in high surface tension
adhesion
is binding between unlike molecules
Water binds to plastic or glass
This is why water “climbs” up a straw
capillary action
tendency of water to rise
in narrow tubes due to
cohesive and adhesive
forces on water.
surface tension
measure of how difficult it
is to break or stretch the
surface of a liquid.
results from cohesion
Because of surface
tension, light
objects do not
fall through the
water’s surface
A meniscus forms
where water meets a solid surface,
as a result of two forces.
how does adhesion and cohesion work in a glass tube
Adhesion: Water
molecules that
adhere to the glass
pull upward at the
perimeter.
Cohesion: Water
molecules at the
surface form
hydrogen bonds
with nearby water
molecules and resist
the upward pull of
adhesion.
MODERATION OF
TEMPERATURE
Water is a very good heat reservoir. It can absorb and release a large amount of heat with only a slight change in its own temperature.
Heat and Temperature
heat is the sum of the kinetic energy of ALL molecules in the object
Temperature:
Measures average kinetic energy
Tells you how fast molecules are moving on average
- How fast are the molecules moving?
That is temperature.
- How much moving stuff is there in total?
That is heat.
How does the Celsius temperature scale relate to water’s phase changes
The Celsius scale is based on water’s phase transitions at sea level: 0°C is when water changes from liquid to solid, and 100°C is when water changes from liquid to gas.
what are vaporization and evaporative cooling?
Vaporization is the process of liquid turning into gas and can occur at any temperature.
type of vaporization:
boiling
evaporation
Evaporative cooling happens when the highest-energy molecules escape from a liquid’s surface, lowering the temperature of the remaining liquid, such as during sweating.
Your skin releases liquid sweat
The hottest sweat molecules evaporate into the air
They take heat energy with them
Your skin loses heat
You feel cooler
specific heat
amount of energy needed to raise
the temperature of 1 gram of a substance by 1ºC
- Water has a very high specific heat
- Many hydrogen bonds must be broken for water molecules to move faster
Heat of vaporization
energy required to change
1 gram of a substance from liquid to gas
* Water has a very high heat of vaporization
* Explains why sweating is an effective way to
cool off
calorie
unit of heat; the amount of heat needed to raise
the temperature of 1 gram of water 1°C
Density
how much mass is packed into a certain amount of space.
How tightly matter is packed together.
water is denser means
When we say liquid water is denser than ice, we mean:
The water molecules in liquid form are closer together
More mass fits into the same amount of space
Ice → molecules spread out → lower density
Ice is less dense than liquid water
WHY WATER IS LESS DENSE AS A SOLID
In ice, water molecules
form a crystal lattice.
In liquid water, no crystal
lattice forms.
Liquid water is denser than
ice. As a result, ice floats
