SOLUTION AND SOLUBILITY

1. Solution is formed when a solute is dissolved in a solvent.

2. Solvent is a substances which dissolves a solute.

3. A solute is a substances which dissolved in a solvent.

4. There are 3 types of solution :

- dilute solution

-concentrated solution

- saturated solution

5. Dilute solution contains small amount of solute.

6. Concentrated solution contains a lot of solute.

7. Saturated solution contains maximum amount of solute.

8. There are 2 ways to dissolve the remaining solute in a saturated solution :

- heat the solution

- add more solvent

9. Solubility the maximum amount of solute which can be dissolved in a certain volume of solvent at specific temperature.

10. Factors that affect the solubility :

- nature of solute

- nature of solvent

- temperature

11. Factors that affect the rate of solubility :

- temperature of solvent

- size of solute

- volume of solvent

- stirring effect

12. When the temperature of the solvent is higher, the rate of solubility is higher.

13. When the size of solute is smaller, the rate of solubility is higher.

14. When the volume of solvent is larger, the rate of solubility is higher.

15. If there is a stirring effect, the rate of solubility is higher.

16. Water is known as UNIVERSAL SOLVENT as it can dissolve almost all the substances in the world.

Comparison Between Evaporation and Boiling

Similarities :

1.Both processes involved the changes from liquid into gases.

2. Both processes absorbed heat.

Differences:

1. Evaporation occurs at any temperature while boiling occurs at boiling point.

2. Evaporation occurs on the surface of a liquid while boiling occurs in the whole liquid.

3. Evaporation is a slow process while boiling is a fast process.

USES OF EVAPORATION

Application of water evaporation in daily life :

i) drying clothes

ii) drying seas products such as dry fishes

iii) drying agriculture products such as coconuts, cocoa

iv) producing evaporated milk

EVAPORATION OF WATER

1. Evaporation of water is a process at which water change into water vapour at any temperature below its boiling point.

2. Factors that affect the rate of evaporation :

- humidity

- surrounding temperature

- exposed surface area

- movement of air

3. Humidity lower, rate of evaporation higher

4. Surrounding temperature higher, rate of evaporation higher

5. Exposed surface area larger, rate of evaporation higher

6. Movement of air exist, rate of evaporation higher.

Composition of Water

Water is a compound.

Water consists of 2 elements which are HYDROGEN and OXYGEN.

2 hydrogen atoms combine with 1 oxygen atom to form 1 molecule of water.

The ratio of hydrogen and oxygen in the water is 2:1

ELECTROLYSIS of water is the process used to determine the composition of water.

How to determine the electrode (anode and cathode) ???

- Look at the battery terminal

- Electrode which is connected to the negative terminal is CATHODE

- Automatically you know ANODE is the electrode connected to the positive terminal of battery.

How to identify the gases collected at the electrode???

- CATHODE : you can find the letter H in the spelling, so remember H for HYDROGEN. ;)

p/s : [ no H in anode]

- So at ANODE, oxygen is collected.

How to test the gas???

- At cathode - HYDROGEN - using burning splinter (kayu uji bernyala). Api akan terpadam dan menghasilkan bunyi "pop".

- At anode - OXYGEN - using glowing splinter (kayu uji berbara). Api akan menyala.

If the volume of hydrogen gas collected is 30cm³ , what is the volume of oxygen collected???

- The ratio of H:O is 2:1 ;- so 15cm³ of oxygen is collected.

How to test the presence of water??

Boiling point and freezing/ melting point is one of the test to determine the presence of water.

Other than that, we can use ;

1. anhydrous cobalt chloride paper - change from BLUE to PINK

2. anhydrous copper sulphate - change from WHITE to BLUE

Boiling Point of Water

Boiling point of water is the temperature at which water boils to form steam.

The boiling point of pure water is 100 ̊C.

Impurities will cause the boiling point of water to increase.

Give one example of impurities????

As we go to higher places such as on the mountain, what happen to the boiling point??? Is it decreases or increases???

Freezing Point of Water

Freezing point of water is the temperature at which water freeze to form ice.

The freezing point of pure water is 0 ̊C

If the water contains impurities such as salt, the freezing point of water will be decrease.

Freezing point of a substances is the same with its melting point.

So, what is the melting point of pure water?

Keadaan Jirim Air

Air wujud dalam tiga keadaan iaitu solid, liquid dan gas.

Proses-proses dalam perubahan keadaaan jirim air :

1. Freezing - from liquid to solid

2. Boiling / evaporation - from liquid to gas

(* p/s : there are differences between boiling and evaporation. we shall discuss this in the next subtopic)

3. Melting - from solid to liquid

4. Condensation - from gas to liquid

There are few substances, which can change from solid directly to gas and vice versa (without liquid state) such as :

i) iodine

ii) dry ice (carbon dioxide in solid form)

The process is known as sublimation.

The process which absorbed heat :

- melting

- boiling

- sublimation (solid to gas)

The process which released heat :

- freezing

- condensation

- sublimation (gas to solid)

Chapter 6 : Water and Solution - Physical characteristics of Pure Water

1. colorless

2. odourless

3. tasteless

4. freezing point is 0 ̊C

5. boiling point is 100 ̊C

6. density 1g/cm³

7. wujud dalam 3 keadaan jirim iaitu solid, liquid and gas

8. poor conductor of heat

9. poor conductor of electric

Welcome

Hari ini tiba2 saya mendapat idea untuk mula menulis nota kepada para pelajar saya khasnya dan pelajar2 lain umumnya. Harap2 usaha ini akan membuahkan hasil. Memandangkan hari ini saya telah mula mengajar kelas 2 Eudora dengan tajuk baru iaitu water and solution, maka saya akan mula menulis nota bermula dari bab 5. Para pelajar sila salin dan baca. Segala penerangan berkaitan akan dijelaskan dengan lebih lanjut dalam kelas. So apabila anda semua masuk ke kelas, anda telah ada sesuatu dan lebih bersedia harapnya ;)