Why is sea water salty?

Hi 5J,

Ever wonder why sea water is salty?

Sea water has been defined as a weak solution of almost everything. Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter. Most of the ocean's salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth's crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea. Some of the ocean's salts have been dissolved from rocks and sediments below its floor. Other sources of salts include the solid and gaseous materials that escaped from the Earth's crust through volcanic vents or that originated in the atmosphere.

In the beginning the primeval seas must have been only slightly salty. But ever since the first rains descended upon the young Earth hundreds of millions of years ago and ran over the land breaking up rocks and transporting their minerals to the seas, the ocean has become saltier. It is estimated that the rivers and streams flowing from the United States alone discharge 225 million tons of dissolved solids and 513 million tons of suspended sediment annually to the sea. Recent calculations show yields of dissolved solids from other land masses that range from about 6 tons per square mile for Australia to about 120 tons per square mile for Europe. Throughout the world, rivers carry an estimated 4 billion tons of dissolved salts to the ocean annually. About the same tonnage of salt from the ocean water probably is deposited as sediment on the ocean bottom, and thus, yearly gains may offset yearly losses. In other words, the oceans today probably have a balanced salt input and outgo.

Salts become concentrated in the sea because the Sun's heat distills or vaporizes almost pure water from the surface of the sea and leaves the salts behind. This process is part of the continual exchange of water between the Earth and the atmosphere that is called the hydrologic cycle. Water vapor rises from the ocean surface and is carried landward by the winds. When the vapor collides with a colder mass of air, it condenses (changes from a gas to a liquid) and falls to Earth as rain. The rain runs off into streams which in turn transport water to the ocean. Evaporation from both the land and the ocean again causes water to return to the atmosphere as vapor and the cycle starts anew. The ocean, then, is not fresh like river water because of the huge accumulation of salts by evaporation and the contribution of raw salts from the land. In fact, since the first rainfall, the seas have become saltier.

Cheers:)

Ms Tay

Confirmation of SA1 topics

Hi all,

Here is the confirmation of SA1 topics:

P3:
1. Plants
2. Life Cycles of Plants.

P4:
1. Matter
2. Light
3. Heat

P5:
1. Energy
2. Water
3. Plant Transport System

Thanks!

Remember to study for all topics covered!

Good luck!

Ms Tay

Plant Transport System Powerpoint Available

Hi 5J,

Please login to slideshare to download the powerpoint slides on plant transport system.

Please right click, the "save target us" to download. Do not open it directly.

Please print the handouts and file it in your science file. Thanks!

:)
Ms Tay

Why do you feel cool after your perspiration dries off?

Hi 5J,

A question for you:

After your p.e. lesson, you will be persipiring. After a while, when your perspiration dries off, you feel cooler. Why is that so?

Please comment.

Cheers
:) Ms Tay

SA1 topics

Hi 5J,

These are the topics that are tested in the coming SA1. They are from p3, p4 and p5 topics.

P3 topics:
1. Life cycle

P4 topics:
1. Heat
2. Light
3. Matter (Not sure. Need to check. Will confirm later.)

P5 topics:
1. Energy
2. Water cycle
3. Plant system

Coming lesson tomorrow, I will be revising all p5 topics. Next week, will be revising p4 topics. Expect homework over the weekend...:)

Enjoy studying.. Hee..

Cheers!

Ms Tay

Another diagram on the cross section of the stem.

xy·lem : A tissue in vascular plants that carries water and dissolved minerals up from the roots through the stem to the leaves and provides support for the softer tissues. Xylem consists of various elongated cells that function as tubes. In a tree trunk, the innermost part of the wood is dead but structurally strong xylem, while the outer part consists of living xylem, and beyond it, layers of cambium and phloem. See more at cambium, photosynthesis.

Movement of food and water in the stem

As you can see, movement in the xylem is one way, upwards from the roots to the leaves.

Movement in the phloem is two way, from the leaves to all parts of the plants.

Cross section of the stem

Dear 5J,

This is a picture of the cross section of the phloem and xylem of the stem of the plant. Phloem is in the outside and xylem is in the inside.

Hi 5J,

Check out these websites to find out more about about the plant transport system. You may want to print it out and keep it in your file.

http://www.biology4kids.com/files/plants_xylemphloem.html

Hi 5J,

This is a photo I took of Stumpy this afternoon...caught him yawning...Hee.

This is a more decent photo of Stumpy enjoying himself on bed.

Powerpoint slides on Water

Dear 5J,

I can't upload the widget on the blog.

So, please click on the link to go to slide share.

login: stumpy2878
pw: stumpy

Once you are there, click on My Slidespace. You may then download it and print. Put it into your science file.

Thanks!

Ms Tay

Dear 5J,

Can you do the following:
1) summarize what are the factors that affect the rate of evaporation of water and how they affect the rate of evaporation of water?

2) Does evaporation take place in the fridge?

Type your contributions in the chat box...Thank you!!!

Enjoy your long weekend!!!

Hi all,

Here is another version of water cycle song...Please do click on the link..

http://vimeo.com/1594826

Reminder: Pls contribute to the findings for the effect of salt on the melting point of ice and the boiling point of water.

Thanks,

Ms Tay

Effect of salt on melting point of ice and boiling point of water

Dear 5J,

By now, you should have done some research on the effect of salt on the melting point of ice and the boiling point of water.

Please contribute your findings on this blog.

Thanks.

You may also comment on your friends' inputs.

Water Cycle image

Water Cycle Song

Hi all,

Here is a link to an an interesting song about water cycle. It helps to understand the processes in the water cycle in an interesting manner.

Hope you enjoy it...

http://www.youtube.com/watch?v=Yw275056JtA

5J Science (2009)

Hi 5J,

This blog is setup in order to extend our learning beyond the four walls of our classroom. Between us, we can share our findings with one another. I will use this blog as a platform for our discussions on science. I will upload the powerpoint that has been used in the classroom. You may download them if you want to. However, this is not meant to replace your scrape book. Hee.

I will also include links to websites that might be interesting for your exploration. I may include videos too.

If you have any doubts, we may also clarify via this blog. Please do not hesitate to share and suggest any other useful links or resources that you find interesting and useful.

However, a word of caution... please do not post rude comments on this blog... It is not very nice... Hee

Hope you find this blog useful.

Ms Tay