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How supercooled water is prevented from turning into ice?

Water below zero degree celsius is called super cooled water. liquid water does not become completely unstable as it becomes supercooled, prior to turning into ice crystals. an energy barrier for crystal formation exists throughout the region in which supercooled water’s compressibility continues to rise.

Air and Liquid Pressure

Does air pressure in a capped bottle is different as that of open bottle??

If not and the atmospheric pressure in a closed container is same as that of the surroundings let 1bar at sea level, if i consider a
tube both end open and dip one end in water (like pipette in chemistry lab) and close the other by thumb, water remain
hanged in the tube..  if we say it is because the atmosphere that pushes up on the water in the tube is same as that of remaining air in tube pushing down on the water..won’t the water fall out due to its own weight as the upward and downward pressure is balanced…

Please explain the whole process and compare weight of water with up and down pressure by atmosphere..

Again would liquid ‘ll flow out of a container through a hole in vacuum??

The Air Pressure in an open bottle is equal to the atmospheric pressure. The pressure inside a closed bottle can be different.

In the experiment described, when the tube is partially filled and the upper end is closed, the water tries to fall down creating a lower pressure above it inside the tube. This creates a pressure difference, the outside pressure greater than the pressure inside and the water can fall only upto the level where the weight of water column is balanced by the force due to difference in pressure created.
See one live demonstrations here

• A guide into hydraulics – Part 1

Why does a heavier solid float on water?

Why does a heavier solid i.e. a plastic float on water?

An object floats or sinks in water depending upon the weight of the body and the weight of water displaced by the immersed part of the body. If the weight of the body is greater than the weight of water displaced by it, then it will sink.

If you feel that the weight of the body must be greater than an equal volume of water, and it does not sink, there must be a reason. This is what happens in the case of a ship. The ship is made up of steel. If you put a steel ball or a nail, it sinks. But when the steel is flattened and then shaped in to a boat, it floats. Why?

Because here the average density, which includes the cavity of the boat,  becomes less than the weight of water displaced. You can easily see that the ship will sink if water is allowed to enter into the cavity.

You can experiment with a steel bowl too. The bowl will float on water, it water is not allowed to enter the cavity.

So, it’s not just the density of the material, it is the average density that counts.

If the object is made in the shape of a bowl or a ship, water is not allowed to enter inside, and the weight of the ship is maintained less than the weight of water displaced by it.

Also refer to

http://en.wikipedia.org/wiki/Buoyancy

Why to drink water if it is produced during the chemical reactions during respiration?

Why to drink water if it is produced during the chemical reactions during respiration?

The formula for respiration is:

Glucose + Oxygen –> water + Carbon dioxide + Energy (ATP)

Asked a group of students of class VII, KV AFS Bidar

Water is just a product during respiration. The amount of water obtained during respiration is not sufficient to carry out all the functions. Water has a multitude of functions in human body. See the picture below.

FUNCTIONS OF WATER IN HUMAN BODY

About 78% of human body is water.

The water:

• Transports nutrients and oxygen into cells
• Moisturizes the air in lungs
• Helps with metabolism
• Protects our vital organ
• Helps our organs to absorb nutrients better
• Regulates body temperature
• Detoxifies
• Protects and moisturizes our joints

For all the above functions we require more water than produced as a byproduct of respiration.

More details on the role of water in human body can be read from:

How is electricity made from water and coal?

Tazim asked: “How is electricity produced from coal and water?”

The question is whether

• “How is electricity produced from water and how is electricity produced from water?
• or
• How is electricity produced from coal and water TOGETHER?

Whatever,
Electricity can be produced from water using hydel (hydroelectric) power stations.

Water is also used in almost all power stations like thermal and nuclear where the heat produced is used to boil water to convert it into steamwhich is then used to rotate turbines to produce electricity.

Coal is often used as a fuel in thermoelectric power statiuons. the heat obtained by the burning of coal is used to boil water and to produce staem. the steam at high pressure is then utilized to rotate turbines and thus to produce lectricity in generators.

Class VI Science Question Bank

HIGHER ORDER THINKING SKILLS
FOOD: Where does it come from.
1. You are the manager of a restaurant, make a list of food items you would serve in lunch.
2. What measures are to be taken to avoid wastage of food.
3. Why are humans considered omnivores?
4. List the ingredients of any five food items you relish.
5. Form pairs of words in group A with words in group B.
A—Mustard plant, Nectar, Beetroot, carnivore, omnivore.
B– Honey, sugar, oil, humans, tiger.
6. Name two aquatic plants eaten as food.
COMPONENTS OF FOOD
1. Why is it necessary to have fresh and un-cooked vegetables and fruits in our diets.
2. Doctors advice us to drink atleast two litres of water daily why?
3. What happens (more…)

Water content in our body helps to regulate temperature stable.

Does the presence of large amounts of water in the body help keep body temperature stable? exp

lain.

Here, the high value of specific heat capacity of water helps.

Drinking water helps regulating the body temperature during winter (extreme cold) as well as during summer.

I remember, schools had made it mandatory for students to dring water after every period during a summer time when the atmospheric temperature was too high and students used to faint often. The water treatment was very effective and the no. of students fainting due to high surrounding temperature decreased significantly.

If we consider the earth system also. it can be seen that the climate is moderate near water bodies.

Further, it is the abundance of water on earth which makes it a planet suitable for the existence of life.

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