Complex organic food molecules such as sugars, fats, and proteins are rich sources of energy for cells because much of the energy used to form these molecules is literally stored within the chemical bonds that hold them together. Scientists can measure the amount of energy stored in foods using a device called a bomb calorimeter. With this technique, food is placed inside the calorimeter and heated until it burns. The excess heat released by the reaction is directly proportional to the amount of energy contained in the food.
By diffusion. Letter c.
Diffusion occurs when the smell of the bread "sticks" to the air and if the air travels from a room to another, the smell will go with it.
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Quackery<span> is the promotion of fraudulent or ignorant medical practices. A </span>quack<span> is a "fraudulent or ignorant pretender to medical skill" or</span>"a person who pretends, professionally or publicly, to have skill, knowledge, or qualifications he or she does not possess; a charlatan".
There are about 250 chemicals that are harmful including carbon monoxide and ammonia.