Law of Definite Composition
Compunds will have a definite composition
Ex. H
2O will be H
2O anywhere (It will always have 2 H's and 1 O)
Law of Multiple Preportions
When 2 or more compunds with different proportions of the same element can be made
Ex. CO
2 -> C
2O
4 -> C
4O
6
The Heating/ Cooling Curve of a Pure Substance
Picture made with Firworks
A: It is now in a solid state ( any temperature below melting point ). The particles are packed very close and neatly together and the forces between the particles are very strong. The particles can only vibrate at a fixed position.
A-B: As the particles are heated, the heat energy is converted to kinetic energy. The Kinetic energy increases and the molocules vibrate faster around their fixed position. This also increases the temperature
B: By here the solid will change into a liquid or a liquid turned into a solid (Frozen)
B-C: In Both solid and liquid states ( Ice and water ), the temperature remains constant because the heat supplied is used to overcome the forces of atractiong between particles. This constant temperature is called the melting point.
C: All melted, solid has now become liquid
C-D: It is still a liquid, as it is heated the molocules hgain more heat energy and the temperature increases. The particles move faster as the kinetic energy increases.
D: It still exists in a liquid state. The molocules have recieved enough energy to overcome forces of attraction between particles and they start moving freely. The liquid starts becoming gas.
D-E: The liquid is changing into a gas (Is both a liquid and gas at the moment). The temperature remains unchanged which we call the boiling point. The absorbed heat is being used to overcome the forces of atraction instead is raising the temperature.
E: all liquid is now gas
E-F: The gas particles continue to absorb energy and move faster. The temperature increases as the heating continues.
Matter in the Macroscopic World
When you look at anything, you will see that you have used the tools of science to observe and order observations through classification. For example you could say that from what you've seen, people are happy and are preparing to eat. Science uses the same skills as looking except you make much more precise and detailed observations requiring much time and effort to specialize in something. Chemists specialize in matter with questions asking what is it, how does one differ from another, what different things have in common, and how matter can be kept the same?
What we know about Matter
We've learned a lot about matter as we've grown up like water when cooled turns into ice and the water can be freely poured to fill any solid container. But if you took water from a muddy stream and water from a river you could say their different right? Properties can help us identify things in many ways including touch and taste. Part of the study of science is learning of all the ways you can distinguish one piece of matter from another like the temperature at which liquid changes into gas is which called the
Boiling Point
Purifying Matter
There are 2 classifications of matter. Mixtures which are 2 or more kinds of matter that have separate identities or Pure substances which cannot be separated. Understanding which samples can be separated and which samples can be not is something that comes with experience. If you have dirty water then put it in the light, it will scatter the light. If you check with clean water, it won't scatter the light. That means you should be able to separate the mud from the water by how? If you go to a water processing plant, clean the water, and then see if it scatters the light which it doesn't, is it pure water? If we check the water there could be salt or sugar added to the water that do not scatter light which is when we call the water a
Solution. This is still a mixture though so you should be able to separate it right? Then if we boil the water so that we still will have the water and a white solid of sugar or salt separate, this procedure is what we call
Distillation. After you have boiled the water you can conlude that the water and the sugar or salt is pure. Many mixtures are too difficult to separate thus are considered pure for years until a way is found to separate them.
Characteristics of Pure Substances
An easy way to detect an important difference between mixtures and pure substances is that pure substances have a CONSTANT boiling point unlike mixtures that ordinarily do not. The problem is nature likes to defy our simple definition of saying the mixtures never have a constant boiling point. The reason the mixture of water and grain alchohol cannot be separated is that it has a constant boiling of 78.2 degrees celcius. The temperature when a liquid changes to a solid is call the
Freezing Point. The temperature at which a solid becomes a liquid is called the
Melting Point.
Chemecal and Physical Changes
Density is the property of matter that describes its mass per volume unit. A
chemical change when a new kind of matter with different properties is formed. When a new substance is formed, thats a good way to tell if a chemical change occurred.
Decomposition is a chemical change where one kind of matter come apart to for 2 or more kinds of matter. Changes that are easy to reverse or reversable are called
Physical Changes. Physical changes do not produce new kinds of matter.
Compunds & ElementsElectrolysis is when a passing electric current throught a substance causes it to decompose into new kinds of matter. Usually electrolysis represents a chemecal change in the form of decomposition.
Distillation is a physical change that separates two or more things that already exist like separated components that are still in the original mixture as separate substances. Pure substances that can be decomposed into new kinds of matter are called
Compounds. The word comes from the fact that they appear to be "compunded" or put together from simpler substances. Pure substances that cannot be decomposed are called
Elements. There are 109 known elements, 85 exist in nature and the others have been made in atomic reactors(they do not exist in nature).
Compunds have a Definite Composition
Not all combinations of elements are compounds. The important difference between mixtures of elements and compunds of elements is that the mixtures can have almost any composition desired but the compounds will have a definite composition which is called
The Law of Definite Composition. The fact of 2 or more compunds with different amounts of the same elements is called
The Law of Multiple Proportions.
Matter is made of Atoms
When you have made an observation using feel, touch, or etc... is is called a
Macroscopic Observation. Macro means large and scopic means viewing or observing. Melting point, boiling point, heat of fusion, temperture, etc... are properties of many parts of matter which we call
Macroscopic Properties.
Atoms
Atom means the smallest possible piece of something like saying you take a iron nail and you break it again and again. It only seams reasonable that what you get from the broken nail is to obtain the "smallest possible piece" of iron. Atoms are usually represented by spheres of various shapes and sizes. There are as many atoms as there are elements. Elements should be made of only one atom as if was made of 2 different atoms, the thought of we should be able to separate it would occur. Atoms vibrate even though stay in the shape they hold. As the temperature increases, they start vibrating more and they should vibrate with such force that they overcome the forces of attraction. Since atoms vibrate, they are able to move past each other from one side of a container to another. Particles made up of more then one atom is called a
Molocule. Elements have different melting points and boiling points from the fact the atoms vary in size and mass which means more energy is required to get large atoms to break the forces of attraction.
CompundsAll compunds are made by combining elements in definite proportions which means all compunds must be made of 2 or more kinds of atoms. Since compunds are made of 2 or more kinds od atoms, if enough energy is supplied, you can break the compund apart. Heat and electricity supply the energy needed to do that. Not all compunds are made of molocules. Ions are particles that have an electrical charge. Compounds that melt to form ions conduct an electric current and compunds that don't melt to for ions do not conduct electricity.
