A state of matter similar to gas in which a certain portion of the particles is ionized. You just studied 20 terms! Kinetic Molecular Theory states that gas particles are in constant motion and exhibit perfectly elastic collisions.
The average kinetic energy of a collection of gas particles is directly proportional to absolute temperature only. Kinetic energy is the energy of motion. All moving objects have kinetic energy. When an object is in motion, it changes its position by moving in a direction: up, down, forward, or backward.
Kinetic and potential energies are found in all objects. If an object is moving, it is said to have kinetic energy KE. The classic example of potential energy is to pick up a brick. The different types of energy include thermal energy, radiant energy, chemical energy, nuclear energy, electrical energy, motion energy, sound energy, elastic energy and gravitational energy.
Energy sources are categorized as renewable or non-renewable. A source of energy is considered renewable if it comes from natural sources or processes that are constantly replenished. Examples are solar from the sun , wind, water, geothermal from the earth and biomass from organic materials.
Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on.
Each form can be converted or changed into the other forms. The Georgia Performance Stand- ards name five types: heat, light, electricity, mechanical motion and sound. Promote reflection on and clarification of existing ideas The initial meanings that students form for the particle model are rarely truly particulate.
Provide opportunities for students to articulate the meanings they have and refine these in what is an iterative process. Thought experiments such as imagining a tiny person as small as a needle sticking a needle into a particle of a gas can help students formulate views about particles. Would the gas leak out? Would the gas burst out and make a hissing sound?
Ask students to predict how much a syringe full of air can be compressed by one person. Call for justifications, perform the experiment and call for explanations in terms of the particle model. Then repeat with the syringe full of water. Practise using and build the perceived usefulness of a scientific model or idea Students come to see the particle model as more useful than a continuous model only gradually, therefore they should observe a range of phenomena which require the particle model to help explain them.
Some examples:. Students can then demonstrate what happens as a substance changes from a solid to a liquid to a gas using the play dough particles. Role playing different phenomena such as perfume particles when the bottle is open or the particles in melting ice requires students to build a concrete meaning for propositions about particles. Videoing these and debriefing helps pick up ideas not yet assimilated. Group activities where students construct posters in groups to explain phenomena and present their posters to the class and creative writing where students imagine they are particles in different situations can both provide opportunities for students to discuss and modify their prior views.
Such a learning log is best achieved by creating questions that students can respond to. Our website uses a free tool to translate into other languages. This tool is a guide and may not be accurate. For more, see: Information in your language. You may be trying to access this site from a secured browser on the server. Please enable scripts and reload this page. Skip to content. Lavoisier mixed the two gases, phlogiston and the newly renamed oxygen, in a closed glass container and inserted a match.
He saw that phlogiston immediately burned in the presence of oxygen, and afterwards he observed droplets of water on the glass container.
After careful testing, Lavoisier realized that the water was formed by the reaction of phlogiston and oxygen, and so he renamed phlogiston hydrogen , from the Greek words for 'water maker'. Lavoisier also burned other substances such as phosphorus and sulfur in air, and showed that they combined with air to make new materials. These new materials weighed more than the original substances, and Lavoisier showed that the weight gained by the new materials was lost from the air in which the substances were burned.
From these observations , Lavoisier established the Law of Conservation of Mass , which says that mass is not lost or gained during a chemical reaction. Elements are used up when they fuel chemical reactions, so resulting substances have less mass. Priestley, Lavoisier, and others had laid the foundations of the field of chemistry.
Their experiments showed that some substances could combine with others to form new materials, other substances could be broken apart to form simpler ones, and a few key "elements" could not be broken down any further.
But what could explain this complex set of observations? John Dalton , an exceptional British teacher and scientist, put together the pieces and developed the first modern atomic theory in To learn more about Priestley's and Lavoisier's experiments and how they formed the basis of Dalton's theories , try the interactive experiment Dalton's Playhouse , linked to below.
Dalton made it a regular habit to track and record the weather in his hometown of Manchester, England. Through his observations of morning fog and other weather patterns, Dalton realized that water could exist as a gas that mixed with air and occupied the same space as air.
Solids could not occupy the same space as each other; for example, ice could not mix with air. So what could allow water to sometimes behave as a solid and sometimes as a gas?
Dalton realized that all matter must be composed of tiny particles. In the gas state, those particles floated freely around and could mix with other gases, as Bernoulli had proposed. But Dalton extended this idea to apply to all matter — gases, solids, and liquids.
Dalton first proposed part of his atomic theory in and later refined these concepts in his classic paper A New System of Chemical Philosophy which you can access through a link under the Resources tab. Dalton's theory had four main concepts: All matter is composed of indivisible particles called atoms. Bernoulli, Dalton, and others pictured atoms as tiny billiard-ball-like particles in various states of motion. While this concept is useful to help us understand atoms, it is not correct as we will see in later modules on atomic theory linked to at the bottom of this module.
All atoms of a given element are identical; atoms of different elements have different properties. Dalton's theory suggested that every single atom of an element such as oxygen is identical to every other oxygen atom; furthermore, atoms of different elements, such as oxygen and mercury, are different from each other. Dalton characterized elements according to their atomic weight ; however, when isotopes of elements were discovered in the late s, this concept changed.
Chemical reactions involve the combination of atoms, not the destruction of atoms. Atoms are indestructible and unchangeable, so compounds , such as water and mercury calx, are formed when one atom chemically combines with other atoms. This was an extremely advanced concept for its time; while Dalton's theory implied that atoms bonded together, it would be more than years before scientists began to explain the concept of chemical bonding. When elements react to form compounds, they react in defined, whole-number ratios.
The experiments that Dalton and others performed showed that reactions are not random events; they proceed according to precise and well-defined formulas. This important concept in chemistry is discussed in more detail below. Some of the details of Dalton's atomic theory require more explanation. Elements: As early as , Robert Boyle recognized that the Greek definition of element earth, fire, air, and water was not correct. Boyle proposed a new definition of an element as a fundamental substance, and we now define elements as fundamental substances that cannot be broken down further by chemical means.
Elements are the building blocks of the universe. They are pure substances that form the basis of all of the materials around us. Some elements can be seen in pure form, such as mercury in a thermometer; some we see mainly in chemical combination with others, such as oxygen and hydrogen in water.
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