<< Chapter < Page Chapter >> Page >

Why does snow remain on mountain slopes even when daytime temperatures are higher than the freezing temperature?

Snow is formed from ice crystals and thus is the solid phase of water. Because enormous heat is necessary for phase changes, it takes a certain amount of time for this heat to be accumulated from the air, even if the air is above C . The warmer the air is, the faster this heat exchange occurs and the faster the snow melts.

Got questions? Get instant answers now!

Summary

  • Most substances can exist either in solid, liquid, and gas forms, which are referred to as “phases.”
  • Phase changes occur at fixed temperatures for a given substance at a given pressure, and these temperatures are called boiling and freezing (or melting) points.
  • During phase changes, heat absorbed or released is given by:
    Q = mL, size 12{Q= ital "mL"} {}

    where L size 12{L} {} is the latent heat coefficient.

Conceptual questions

Heat transfer can cause temperature and phase changes. What else can cause these changes?

Got questions? Get instant answers now!

How does the latent heat of fusion of water help slow the decrease of air temperatures, perhaps preventing temperatures from falling significantly below 0ºC size 12{"0°C"} {} , in the vicinity of large bodies of water?

Got questions? Get instant answers now!

What is the temperature of ice right after it is formed by freezing water?

Got questions? Get instant answers now!

If you place 0ºC size 12{"0°C"} {} ice into 0ºC size 12{"0°C"} {} water in an insulated container, what will happen? Will some ice melt, will more water freeze, or will neither take place?

Got questions? Get instant answers now!

What effect does condensation on a glass of ice water have on the rate at which the ice melts? Will the condensation speed up the melting process or slow it down?

Got questions? Get instant answers now!

In very humid climates where there are numerous bodies of water, such as in Florida, it is unusual for temperatures to rise above about 35º C ( 95º F ) . In deserts, however, temperatures can rise far above this. Explain how the evaporation of water helps limit high temperatures in humid climates.

Got questions? Get instant answers now!

In winters, it is often warmer in San Francisco than in nearby Sacramento, 150 km inland. In summers, it is nearly always hotter in Sacramento. Explain how the bodies of water surrounding San Francisco moderate its extreme temperatures.

Got questions? Get instant answers now!

Putting a lid on a boiling pot greatly reduces the heat transfer necessary to keep it boiling. Explain why.

Got questions? Get instant answers now!

Freeze-dried foods have been dehydrated in a vacuum. During the process, the food freezes and must be heated to facilitate dehydration. Explain both how the vacuum speeds up dehydration and why the food freezes as a result.

Got questions? Get instant answers now!

When still air cools by radiating at night, it is unusual for temperatures to fall below the dew point. Explain why.

Got questions? Get instant answers now!

In a physics classroom demonstration, an instructor inflates a balloon by mouth and then cools it in liquid nitrogen. When cold, the shrunken balloon has a small amount of light blue liquid in it, as well as some snow-like crystals. As it warms up, the liquid boils, and part of the crystals sublimate, with some crystals lingering for awhile and then producing a liquid. Identify the blue liquid and the two solids in the cold balloon. Justify your identifications using data from [link] .

Got questions? Get instant answers now!

Problems&Exercises

How much heat transfer (in kilocalories) is required to thaw a 0.450-kg package of frozen vegetables originally at C size 12{0°C} {} if their heat of fusion is the same as that of water?

35.9 kcal

Got questions? Get instant answers now!

Questions & Answers

full meaning of GPS system
Anaele Reply
how to prove that Newton's law of universal gravitation F = GmM ______ R²
Kaka Reply
sir dose it apply to the human system
Olubukola Reply
prove that the centrimental force Fc= M1V² _________ r
Kaka Reply
prove that centripetal force Fc = MV² ______ r
Kaka
how lesers can transmit information
mitul Reply
griffts bridge derivative
Ganesh Reply
below me
please explain; when a glass rod is rubbed with silk, it becomes positive and the silk becomes negative- yet both attracts dust. does dust have third types of charge that is attracted to both positive and negative
Timothy Reply
what is a conductor
Timothy
hello
Timothy
below me
why below you
Timothy
no....I said below me ...... nothing below .....ok?
dust particles contains both positive and negative charge particles
Mbutene
corona charge can verify
Stephen
when pressure increases the temperature remain what?
Ibrahim Reply
remains the temperature
betuel
what is frequency
Mbionyi Reply
define precision briefly
Sujitha Reply
CT scanners do not detect details smaller than about 0.5 mm. Is this limitation due to the wavelength of x rays? Explain.
MITHRA Reply
hope this helps
what's critical angle
Mahmud Reply
The Critical Angle Derivation So the critical angle is defined as the angle of incidence that provides an angle of refraction of 90-degrees. Make particular note that the critical angle is an angle of incidence value. For the water-air boundary, the critical angle is 48.6-degrees.
dude.....next time Google it
okay whatever
Chidalu
pls who can give the definition of relative density?
Temiloluwa
the ratio of the density of a substance to the density of a standard, usually water for a liquid or solid, and air for a gas.
Chidalu
What is momentum
aliyu Reply
mass ×velocity
Chidalu
it is the product of mass ×velocity of an object
Chidalu
how do I highlight a sentence]p? I select the sentence but get options like copy or web search but no highlight. tks. src
Sean Reply
then you can edit your work anyway you want
Wat is the relationship between Instataneous velocity
Oyinlusi Reply
Instantaneous velocity is defined as the rate of change of position for a time interval which is almost equal to zero
Astronomy
Practice Key Terms 3

Get the best College physics course in your pocket!





Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics' conversation and receive update notifications?

Ask