Posts Tagged ‘Water’

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 Read 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.

Asked  Deryn

Answer:

The answer is yes.

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.

How does a microwave oven work?

Now, microwave oven is so popular that majority of houses have one. Many use it mainly to reheat food without loss of nutrient. The advantage is that the microwave heats up the food very fast.

Some observations made on microwave oven are,

• It does not heat up the vessels directly
• It is not able to cook food contained inside metal vessels
• If the turn table does not work, cooking will not be even.

So, it is pertinent to ask how the mechanism of heating in a microwave oven is different from other heating devices?

Here the water molecules, which are polar in nature play the magic. (A polar molecule is one in which the centre of mass of positive charges and the centre of mass of negative charges do not coincide and have a net dipole moment.) When microwaves are passed through food materials, the water molecules contained in them tends to turn and this rapid churning of water molecules develops a lot of heat. The turn-table adds to the churning and randomization developing heat more rapidly.

The food materials contained in a closed metal vessel will not be heated up by the microwave oven as they do not allow microwaves to pass through them. The metals are opaque to microwaves.

Why the food materials heated using microwave dry up and become stiff when cool?

In a microwave oven, the water molecules are heated very fats that the water is converted readily into steam. If kept open, the steam will escape and the material will become hard when cooled due to the decrease in the water content.

Related articles

• The History & Inventor Of The Microwave Oven(microwaveexpert.wordpress.com)

  ---

• Microwave, many uses (thehindu.com)

Heat! Heat! Heat!

Thermal vibration of a segment of protein alpha helix. The amplitude of the vibrations increases with temperature. (Photo credit: Wikipedia)

A glass ball at -10 degrees C is placed in 500 ml of water at 20 degrees C. The final temp is 15 degrees C.
A. How much heat is lost by the water
B. what is the heat capacity of the water
C. How much heat is gained by the glass ball
D. What is the heat capacity of the glass ball
E. what is the ratio of the heat capacities of the water and the glass ball
F. What is the ratio of the temp changes of the water and glass ball
G. How are the answers to e and f related