AP CHEMISTRY Unit 1 Topics: Classifying matter: S, L, G, pure substance, element, compound, mixture (ho/he) Law of Definite Proportion; Law of Multiple Proportion; Conservation of Mass Chemical vs. physical changes/properties Ways to separate mixtures (filtering, distillation, chromatography) Precision and Accuracy: Significant Figures Density Conversion problems… (You won’t have “notes” on this topic, only practice problems.)
Classifying Matter What is matter? How are solids liquids, and gases different from one another on an atomic or molecular level? How are the macroscopic properties of each state of matter related to these differences? What is a pure substance? What makes something an element vs. compound vs. mixture? What is the difference between a homogeneous mixture and a heterogeneous mixture?
Three States of Matter
Here are some basic properties of the 3 phases of matter… Three States of Matter Here are some basic properties of the 3 phases of matter…
Classification of Matter
Classification of Matter
Heterogeneous Mixtures
Homogeneous Mixtures
Classification of Matter
Classification of Matter
Chemical Symbols of Elements, Compounds, and Mixtures Element: 1 capital letter H2 N2 Br2 Ne S8 Cu C Ba K P4 Compound: 2 or more capital letters H2O NaCl CuSO4 Ba(OH)2 C6H12O6 CO2 Mixture: You will see a “plus sign” separating the components of the mixture or the symbol “(aq)” meaning an aqueous solution. H2 + O2 Li + NaCl NaOH(aq) Other symbols: Ions: They have a charge on the atom or group of atoms… Na+ NO3− Hydrates: They have water attached to the crystal… CuSO4 ∙ 5H2O
The Creation of Chemistry – The Fundamental Laws: Crash Course Chemistry https://www.youtube.com/watch?v=QiiyvzZBKT8&list=PLJHzWdNHnihpV-XXnkBKqIssToRlSfA13 This episode of Crash Course Chemistry takes a historical perspective on the creation of the science, which didn't really exist until a super-smart, super-wealthy Frenchman put the puzzle pieces together - Hank Green tells the story of how we went from alchemists to chemists, who understood the law of conservation of mass as proposed by a decapitated aristocrat, and explains how we came to have a greater understanding of how chemical compounds work and eventually a complete understanding of what atoms and molecules are.
Law of Definite Proportion (This is a way to tell if something is a compound or a mixture.) The law of definite proportions, sometimes called Proust's Law, states that a chemical compound always contains exactly the same proportion of elements by mass. This observation was first made by the French chemist Joseph Proust, based on several experiments conducted between 1798 and 1804. At the time, the distinction between pure chemical compounds and mixtures had not yet been fully developed. For example, oxygen makes up 8/9 of the mass of any sample of pure water, while hydrogen makes up the remaining 1/9 of the mass. Deviations from this ratio would mean that the sample is not pure. Along with the law of multiple proportions, the law of definite proportions forms the basis of stoichiometry.
Law of Definite Proportion
Law of Multiple Proportions It is sometimes called Dalton's Law after its discoverer, the English chemist, John Dalton. The statement of the law is: If two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers. For example, Dalton knew that the element carbon forms two oxides by combining with oxygen in different proportions. A fixed mass of carbon, say 100 grams, may react with 133 grams of oxygen to produce one oxide, or with 266 grams of oxygen to produce the other.
Law of Multiple Proportions The ratio of the masses of oxygen that can react with 100 grams of carbon is 266:133 ≈ 2:1, a ratio of small whole numbers. Dalton interpreted this result in his atomic theory by proposing (correctly in this case) that the two oxides have one and two oxygen atoms respectively for each carbon atom. In modern notation the first is CO (carbon monoxide) and the second is CO2 (carbon dioxide). The law of multiple proportions is best demonstrated using simple compounds (as opposed to large hydrocarbons.) John Dalton first expressed this observation in 1804 and published it in 1808.
Another Example of the Law of Multiple Proportions
Law of Multiple Proportions Humor H2O vs. H2O2