Which of the following is not a phase change?
melting of snow
evaporation of water from the ocean
condensation of water vapor to form clouds
hydrogen and oxygen gas combining to form water vapor

Answer : The correct option is hydrogen and oxygen gas combining to form water vapor.

Explanation :

Phase change : It is a change from one state to another state without changes in chemical composition.

Phase change such as solid to liquid, liquid to vapor, vapor to liquid, liquid to solid, vapor to solid, solid to vapor.

the answer is a. co2, this would be colder than the : )

explanation:

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.