Commercially available cold packs are simple in design: a pouch with water on one side, isolated by a barrier from a specific salt on the other side. When the barrier is broken, the salt and water mix and the solution turns cold. Select which of the statements is true about the reaction occurring in cold packs. O The reaction between the salt and water is endothermic. O The reaction between the salt and water is exothermic. O The reaction between the salt and water is neither endothermic nor exothermic. The cold pack releases heat into the environment. #8

The reaction between the salt and water is endothermic.

Explanation:

The reaction is endothermic because the reaction absorbs heat and causes the surroundings to become cooler.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.