Dalton's theory was used to explain the law of constant composition and the law of conservation of mass.
The law of constant composition says that any given compound always consists of the same atoms and the same ratio of atoms. For example, water always consists of oxygen and hydrogen atoms, and it is always 89 percent oxygen by mass and 11 percent hydrogen by mass. This Applet from the IrYdium Project at Carnegie Mellon University allows for an interactive demonstration of these principles.
The law of conservation of mass says that the total mass of materials before and after a chemical reaction must be the same. For example, if we combine 89 grams of oxygen with 11 grams of hydrogen under the appropriate conditions, 100 grams of water will be produced—no more and no less.
In addition to explaining these two well-known laws, Dalton used his atomic theory to predict another law : the law of multiple proportions
Gases can be studied by considering the small scale action of individual molecules
or by considering the large scale action of the gas as a whole. We can directly
measure, or sense, the action of the gas. But to study the action of the molecules,
we must use a theoretical model. The model, called the kinetic theory of
gases, assumes that the molecules are very small relative to the distance
between molecules. The molecules are in constant, random motion and frequently
collide with each other and with the walls of any container.
The individual molecules possess the standard physical properties of mass, momentum,
and energy. The density of a gas is simply the sum of the mass of the molecules
divided by the volume which the gas occupies. The pressure of a gas is a measure
of the linear momentum of the molecules. As the gas molecules collide with the
walls of a container, the molecules impart momentum to the walls, producing
a force that can be measured. The force divided by the area is defined to be
the pressure. The temperature of a gas is a measure of the mean kinetic energy
of the gas. The molecules are in constant random motion, and there is an energy
(mass x square of the velocity) associated with that motion. The higher the
temperature, the greater the motion.
This interactive experiment is designed to demonstrate the properties of the ideal gas law.
The second law of thermodynamics is concerned with entropy (S), which is a measure of disorder. The second law says that the entropy of the universe increases. An increase in disorder (overall) is therefore spontaneous. If the volume and energy of a system are constant, then every change to the system increases the entropy. If volume or energy change, then the entropy of the system can actually decrease. However, the entropy of the universe does not decrease. The molecules in one's body exist in great order; this only happens because the entropy of the rest of the universe is increased to a greater amount than the entropy of the body is decreased.
To understand how the kinetic theory of gases explains the second law click here
In 1827 the English botanist Robert Brown noticed that pollen grains suspended
in water jiggled about under the lens of the microscope, following a zigzag
path. In 1889 G.L. Gouy found that the "Brownian" movement was more
rapid for smaller particles (we do not notice Brownian movement of cars, bricks,
or people). In 1900 F.M. Exner undertook the first quantitative studies, measuring
how the motion depended on temperature and particle size. The first good explanation
of Brownian movement was advanced by Desaulx in 1877: "In my way of thinking
the phenomenon is a result of thermal molecular motion in the liquid environment
(of the particles)." This is indeed the case. A suspended particle is constantly
and randomly bombarded from all sides by molecules of the liquid. If the particle
is very small, the hits it takes from one side will be stronger than the bumps
from other side, causing it to jump. These small random jumps are what make
up Brownian
motion.
The first mathematical theory of Brownian motion was developed by Einstein in
1905. For this work he received the Nobel prize.
The scanning tunneling microscope (STM) was the first of several "proximal probes" that in the past decade have revolutionized our ability to explore, and manipulate, solid surfaces on the size scale of atoms. At its heart, the STM is little more than a pointed electrode scanned over a conducting surface (or "specimen") of interest, via electronic control of a piezo-electric crystal's shape. Gerd Binnig and Heinrich Rohrer of IBM's Zurich Research Center were awarded the 1986 Nobel Prize in Physics for discovering the STM. Excitement about this instrument, and its "atomic force microscope" cousin, remains high. One reason is that scanning probe microscopes continue to open new doors, while serving as our eyes and hands in the exploration of solid surfaces on submicron size scales. In fact, the 1996 Nobel Prize in Chemistry was awarded to Richard E. Smalley of Rice University (a scanning probe microscope enthusiast) for his role in the joint discovery of fullerines. Named after geodesic dome inventor R. Buckminster Fuller, fullerines are spherical carbon molecules whose cousin (the carbon nanotube or "Bucky tube") promises to make scanning tunneling microscopes even more powerful (in a microscopic way) in days ahead.