If food is kept in the fridge, the food will keep longer because the low temperature will slow down the rate of the chemical reaction which destroys food.
Cooking food in a pressure cooker
- In a pressure cooker, the high pressure causes the water in the cooker to boil at a temperature of more than 100°C.
- At a higher temperature, the time for the food to get cooked is decreased.
Cooking Food in Small Pieces
Food in the shape of big pieces has a surface area per volume which is small, so the heat takes a longer time to reach the inside of the food. So, to cook faster, the food needs to be cut into smaller pieces.
- Vegetable oil is an organic compound that is not saturated and exists in liquid state at room temperature.
- Through investigation and continuous development, vegetable oil can be changed to margarine through the process of hydrogenation using nickel as catalyst at a temperature of 180°C.
Breakdown of Petroleum
- Big molecules of hydrocarbon obtained during fractional distillation of petroleum have been found to be less useful than small molecules of hydrocarbon.
- The breakdown process with the use of the catalyst alumina produces smaller hydrocarbons.
Burning of Coal
- Coal contains the element carbon. Burning of coal in air that is in excess will produce carbon dioxide, water, and heat energy.
- A big piece of coal takes a long time to burn because the total surface area that is touched by the fire is small.
- The rate of burning pieces of coal which are small is higher because the total surface area is bigger. With this, it provides a lot of heat energy in a short period of time.