Physical Properties of Water

Title: Physical properties of water

Objectives:
1.To understand factors affecting boiling rate and boiling point of water
2.To determine the effect of varying relative humidity on the water activity of foods.

Part A

Results:

[pic 1]

Figure1. Graph of temperature against time of 200ml, 150ml and 100ml of water.

Discussion Questions:

1. Yes. As water is heated, hydrogen bonds constantly break and form again. Some of the molecules move so rapidly that they overcome their attraction to other molecules of water and escape into the air as vapour or steam. The energy required to do so is called heat of vaporization .The flat section occurs is because the temperature of water ceases to rise, the boiling point is reached because energy is used to meet the high energy required for the change of physical state from liquid to gas.

2. No. The boiling point of water is the same. Boiling point of water will not change no matter the amount is increases or decreases. In fact, the boiling rate of water depend on the amount of water. The lesser the amount of water, the higher the boiling rate.

3. The 100ml of water boils faster. Q=mc∆T , as the mass of water is smaller, the specific heat capacity is also smaller, the heat energy required is lower.

Part B
Result: [pic 2]Figure2. Graph of temperature against time of 200ml of water, sodium chloride solution and sucrose solution.

Discussion Questions:

1. Nacl solution has the highest boiling point. Sucrose that dissolve and NaCl that ionize in water modify vapour pressure. They reduce the vapour pressure, which means that more heat energy must be supplied if the solution is to develop sufficient vapour pressure to overcome the pressure of the atmosphere and boil. Thus, the boiling point of solution is higher than the boiling point of water.

1. NaCl solution increases more on the boiling point of water. NaCl ionize in water as Na+ and Cl- whereas sucrose dissolve in water into smaller particles. As sucrose does not get ionized, it only counts as 'one' added particle, which means it will elevate the boiling point of water by 'one' times the sucrose temperature elevation rate. NaCl on the other hand, will get ionized completely into Na+ and Cl- . So actually NaCl in water counts as 'two'. It will elevate the boiling point of water by 'two' times it's temperature elevation rate. 

Conclusion:

Solutions have higher boiling point than water. Factor that affecting the boiling points including the type of solution or water and factors affecting the rate of boiling point including the volume of solution or water. The lesser the volume, the faster the boiling point reach. The aim is achieved.