Cooling Rate of Water

1252 WordsAug 20, 20136 Pages
Newton’s Law of Cooling The main purpose of this experiment was to find the positive constant “K” for different liquids in the Newton’s Law of Cooling equation, in order to determine when it was safe to store food products in commercial restaurant after cooking. The high risk temperature for bacteria growth is between 5 and 60 degrees. However putting hot food into your fridge before this point can cause food poisoning especially in deep containers, which is why it is vital that food companies and chiefs are aware of how longer a food, takes to cool down from an approximate temperature. Obviously an exact value is impossible because of varying variables e.g. room temperature, depth of container etc. However by applying newton’s laws you…show more content…
heat capacity); the cooling occurs faster and . The larger the K value the slower the liquid cools, therefore the larger the constant, the steeper the gradient; as reflected in the graph above. k is a constant that depends on several quantities: the masses and specific heat capacities of the two bodies, and the amount of thermal contact between the two bodies. For the most part, k is independent of temperature. Higher heat capacity means higher k value. The heat capacity of water is 4.18 whereas for saltwater (25% salt) and oil it is respectively 3.99 and 1.67. Higher capacity means that it takes much more heat energy to increase the temperature of water by 1°C than it does to cause the same temperature change in other substances Water has such a high heat capacity because when molecules are heated, they move around faster as they gain more energy. Since H2O is a polar molecule where the two H atoms are positively charged and the O is negatively charged. Positive attracts to negative and water molecules stick together. Hence forming stronger intermolecular dipole-dipole bonds and since the molecules are being held tightly in place by these bonds, the H2O molecules don't move much when heated. It takes more and more heat to move the molecules, causing water to have a high specific heat capacity. Water is also able to retain heat better than many substances (i.e., resist cooling), hence results in higher k value. In salt
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