1. To comprehend and learn about the factors that affects the boiling rate and the boiling point of water. 2. To evaluate the moisture content of foods.
3. To observe the relationship of different relative humidities of the surroundings towards the sensory properties of foods. Results
Table 1: Part a(i) – Heating 200ml of Water
Time (s)| Temperature (⁰C)|
Table 2: Part a(ii) – Heating 150ml of Water Table 3: Part a(iii) – Heating 100ml of Water
1. The curves in part a(i), a(ii) and a(iii) do have a flat section. These indicate that the boiling point has been reached, as the temperature remains constant until the volume of the water decreases by 50ml. This indicates that the vapour pressure has reached the external pressure thus resulting in water boiling (Vaclavik & Christian, 2008). The temperature remains constant because the excess energy put in is used to meet the energy requirement for the change between liquid and gaseous state, in which the process is called the latent heat of vaporization (McWilliams, 2008) 2. The boiling point of water does not depend on the amount of water, but in fact remains constant for all volumes. This is due to the fact that the liquid used is the same (water) therefore the particles present in the liquid is the same. Boiling point can only be influenced by exerting external pressure, or adding substances that decreases vapour pressure hence able to increase boiling point. (Vaclavik & Christian, 2008) 3. The sample with 100ml of water (Part a(iii)) is the sample that boils at the highest speed. This is because with lesser volumes of water and a constant heating temperature, there are fewer particles to heat up; therefore managing to infuse enough energy to each water particle at a higher rate, therefore it is able to boil faster. As water has a high specific capacity, that is, the energy required to raise 1g of water by 1⁰C (Vaclavik & Christian, 2008), less energy is needed to raise a lesser volume of water up to the boiling point. Table 4: Part b(i) – 200ml 10g NaCl Table 5: Part b(ii) – 200ml 10g Sucrose
1. The sample that has the highest boiling point is the 200ml NaCl solution(Part b(i)) because NaCl is an ionic compound that deionises in water, forming equal proportions of Na+ and Cl- ions, hence making it difficult for molecules to vaporize as the salt dilutes the water, leaving fewer molecules of water, decreasing vapour pressure. (Vaclavik & Christian, 2008) From this theory, a conclusion can be drawn by which the boiling point of water is lower than the boiling point of a solution. 2. The solute NaCl increases more on the boiling point of water. This is due to the fact that NaCl is ionized, and when in presence of water, it deionises into Na+ and Cl- ions, and for every mole of NaCl, there is one mole of sodium ions and one mole of chloride ions in water. Sucrose on the other hand does not deionise in water, hence only one mole of sucrose is present in water when mixed. (Vaclavik & Christian, 2008)
Table 6 – Determination of the moisture content of cream cracker Sample| Cream Cracker|
Empty Crucible + lid (g)| 44.0680g|
Crucible + Sample + lid (g)| 46.1155g|
Sample (g)| 2.0475g|
Crucible + Sample + lid after 30 minutes (g)| 45.9532g|
Crucible + Sample + lid after 60 minutes (g)|...