8th Grade ScienceMr. Monson’s Class

Change of State is the change of a substance from one state to another

Melting Freezing

Evaporation Condensation

Sublimation – the process in which a solid changes directly into a gas

◦Example Dry Ice (CO2)!

Changes of state is the change of a substance from one physical form to another

All Change of states are physical changes

Why is a change of state a physical change?

Particles of a substance move differently depending on the state of a substance

Particles have different amounts of energy in different states

Solid least energy

Liquid more energy

Gas most energy

To change from one state to another you must add energy or remove energy

Change of State Triangle

Add energy to a solid can cause melting

Melting is the change of state from a solid to a liquidThere are two changes taking place in this picture can you identify them?

Melting Point -the temperature a solid changes to a liquid

to melt particles must overcome some of the attraction to each other

Melting is an endothermic reaction (energy is gained)

◦As energy is gained the temperature rises

Example: gallium Is a metal Melting point 30oC Human temperature 37oC

Why would gallium make a bad ring?

Salt’s (NaCl) melting point is 801oC Salt will not melt in your hand

Melting Salt in Vats in China

Freezing: change of state from liquid to solid

Freezing is the reverse process of melting

Because freezing is the reverse process of melting . . .

Freezing and melting occur at the same temperature

Water & ice 0oC

Add more energy – melting will continue

Remove the energy and freezing will increase

Exothermic

Change Energy is removed from a substance to freeze it

Evaporation is the change of substance from a liquid to a gas

Boiling is the change of a substance from liquid to vapor

◦ Occurs when pressure inside Bubbles equals pressure Outside bubbles.

Boiling point is affected by where you are at in comparison to sea level.

◦ The lower or closer to sea level the higher the boiling temperature

◦ The higher up from sea level the lower the boiling temperature

Comparing Altitude & Boiling Point

Condensation is Gas going to a liquid Condensation point is temperature gas

turns into a liquid Exothermic reaction because energy is

removed (the temperature goes down) Example: Dew

Solid going to a gas Endothermic

because there is an increase in energy (temperature)

Example Dry Ice

Both the temperature and state are affected by the energy/ movement of particles

Temperature of a substance is related to the speed of the substance particles

Note: the change of temperature does not take place until the state has completely changed

100 oC

Remember. . . . Change of state has concurrent changes

http://www.ewart.org.uk/science/structures/states.jpg 10/12/09 http://www.all-water.org/H2O_Images/800px-DryIceSublimation.JPG 10/12/09 https://tas-ms-8sci-go-p7.wikispaces.com/file/view/state.gif/32513769 10/12/09 http://misterguch.brinkster.net/energydiagram3.gif 10/12/09 http://202.114.88.54/g/web18/wangluo/webelements/webelements/properties/media/tables/intensity/melt

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http://www.periodictable.ru/031Ga/slides/Ga1.jpg 10/12/09 http://media.rd.com/rd/images/rdc/mag0805/cutting-back-on-salt-01-af.jpg 10/12/09 http://www.cringel.com/files/images/adia_2007_03_15_DSC_5503_salt_farm_worker_vietnam_ninh_hoa_cri

ngel.com.jpg 10/12/09

http://www.cbc.ca/gfx/images/news/photos/2009/01/16/full-watermain090116.jpg 10/12/09 http://www.andybrain.com/sciencelab/wp-content/uploads/2008/04/ice-water-volume.jpg 10/12/09 http://away.com/gifs/states/wy/yel_icef.jpg 10/27/09 http://aaronandsarah.files.wordpress.com/2008/09/canyon-waterfall-2.jpg 10/27/09 http://www.gsaclt.com/customers/106082309312252/images/delta_therm_snow_picture.jpg 10/27/09 http://www.fakefoodonline.com/i/Ice%20Cream/product_image_13.jpg 10/27/09 http://www.clipartguide.com/_thumbs/0060-0502-2515-5358.jpg 10/27/09 http://www.its.caltech.edu/~atomic/snowcrystals/icespikes/icespike.jpg 10/27/09 http://blog.hotelclub.com/wp-content/uploads/2008/04/chile_hot_springs.jpg 10/27/09 http://www.clickandlearn.org/images/water_cycle.gif 10/27/09 http://www.epicurious.com/images/articlesguides/howtocook/primers/

highalt_illustration1.gif 10/27/09 http://farm1.static.flickr.com/61/189332042_a25deba877.jpg 10/28/09 http://www.quantumtheatre.co.uk/BigDrip%20ks1_files/image008.jpg 10/28/09 http://rachellekoch.com/blog/wp-content/uploads/2009/07/Bumpass-Hell-Steam.jpg

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