4.1 Atoms
Alchemy is an ancient tradition that predated the modern science of chemistry. One goal of the alchemist was to change base metals, such as iron or lead, into valuable metals such as gold or silver. Explain, using Dalton's theory, why alchemists were unable to do this.
Atoms of one element cannot be changed into atoms of a different element as a result of a chemical reaction.
Describe the contribution of Democritus to modern atomic theory.
He was a Greek philosopher that lived 400 years BC and was the first known person to suggest the idea that all matter consisted of tiny, indestructible particles called atoms. Atom is a Greek word that means indivisible.
What happens to the total mass of a system during a chemical reaction?
One of these is called the law of conservation of mass, which states that during a chemical reaction, the total mass of the products must be equal to the total mass of the reactants. In other words, mass cannot be created or destroyed during a chemical reaction, but it must always be conserved.
What does "fixed composition" mean with regard to chemical compounds?
Joseph Proust discovered, "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound." This became known as the law of constant composition. For example, a sample of pure water has the same properties and same ratio of hydrogen to oxygen whether the sample is isolated from a river (and then purified) or produced by a chemical reaction in a laboratory.
What law explains the relationships between different chemical compounds that contain only the elements carbon and oxygen?
Law of multiple proportions. Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. (for example Carbon monoxide, contains 1.333 g of oxygen for every 1 g of carbon. Carbon dioxide, contains 2.666 g of oxygen for every gram of carbon. The ratio of oxygen in these two compounds is 1:2, which is a ratio of small whole numbers.)
What are the four essential points of Dalton's atomic theory?
o All Matter is composed of extremely small particles called atoms o Atoms of the same element are identical in terms of size, mass, and other properties. Atoms of one element are different from the atoms of any other element. o Atoms of different elements can chemically combine with one another in simple whole-number ratios to form chemical compounds. o Chemical reactions can be described as the separation, combination, or rearrangement of atoms. Atoms of one element cannot be changed into atoms of a different element as a result of a chemical reaction.
