The Law of Definite Composition states that compounds will have a definite composition. Ex. H2O will always remain as H2O anywhere. The compound will always have 2 Hydrogens and 1 Oxygen.
The Law of Multiple Proportions is when 2 or more compounds that contain different proportions of the same element can be made. EX. CO2 x2= C2O4.
Matter
Pages 25-34 and 36-39 of the Heath Chemistry Textbook allows us to refresh our brains on matter.
2.1 What we know about matter
Basically matter is anything that takes up space. We know that matter can take any shape or form, in the three states known as liquid, gas, and solid. Physical/Chemical chnages occur to change the substance's form. We can also identify matter through color, taste, and boiling or melting points. A prime example is water. Water can be different. If we compare distilled water to muddy water, we will see huge differences.
2.2 Purifying Matter
There are two types of matter. Pure substances only have one set of properties while mixtures have more than one set of properties and a substance. We can purify substances to separate the mixture and the substance. E.g. alum and lime can trap impurites. Salt and sugar will change the taste but will blend in with the substance. These are called substances. Distillation is the process where the components are seprated from the mixture; however, some solutions cannot be seperated. When there is no way to seperate matter into components, it means that the substance is pure.
2.3 Characteristics of Pure Substances
The freezing point and melting points of both pure substances and mixtures are quite similar. However pure substances have a constant boiling point, while mixtures do not, but some do have a constant boiling point. For example Grain Alcohol is comprised of 95.6% of ethanol and 4.4% of water. Together they have a constant boiling point of 78.2 degrees C. Any other mixture of ethanol and water will not have a constant boiling point. The freezing point and melting points of both pure substances and mixtures are quite similar. Electrolysis is when matter decomposes to form new kinds of matter. Decomposition is the process when a pure substance are seperated into components.
2.4 Physical and Chemical Changes.
Physical changes do not produce a new substance . That being said, chemical composition does not change and is reversible. Chemical changes on the other hand produce a new substance and are irreversible.
2.5 Compounds and Elements
Elements are pure substances that cannot be broken down by decomposition. Elements can change to different states, from liquid to solid and to gas. The increase and decrease of temperatures is what makes the elements change form. Compounds on the other hand can be decomposed into new kinds of matter. Compunds are formed together by simpler substances, they are also comprised of 2 or more atoms.
2.7 Atoms
Atoms happen to be the smallest part of an element.Atoms are closely packed in thier solid state. In liquid form, atoms are some what close together. When they are in the gas state, the atoms are far apart.
The Heating/Cooling Curve
Point A - Solid State, Paticles packed together
Point A-B - Molecules vibrate faster
Point B - Molecules start to melt or remain frozen
Point B-C - Temperature remains contant, exist in both liquid and solid states.
Boint C - Everything is melted, liquid form
Point C-D - Particles are heated and they move faster and faster, due to the kinectic energy increasing. In Liquid state
Point D - Still exists in liquid state, molecules start to move freely
Point D-E - Liquid turns into gas. Temperature remains the same.
Point E - All liquid is now gas
Point E-F - Gas absorbs energy, molecules move freely . Temperature increases.
For more information on matter, here is a Youtube video from the Discovery Channel.
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