Chemistry 1 Chang/Goldsby Chapter 1 Outline/Summary

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Chemistry and Biochemistry
CHM 1045
Mark Kearley

1.1 Chemistry: A science for the 21 century  Chemistry is the study of matter and the changes it undergoes.  Called the central science 1.3 The Scientific Method  Scientific method: a systematic approach to research.  1) Carefully define the problem  2) Performing experiments, making careful observations, and recording information/data about the system.  3) Interpretation, meaning the scientist attempts to explain the observed phenomenon.  4) Based on the data, the researcher formulates a hypothesis ( a tentative explanation for a set of observations).  5) Further experiments are devised to test the validity of the hypothesis in as many ways as possible.  6) After a large amount of data is collected, it is desirable to summarize the information in a concise way, as a law. (law- a concise verbal or mathematical statement of a relationship between a phenomena that is always the same under the same conditions)  Qualitative- consisting of general observations about the system  Quantitative- comprising numbers obtained by various measurements of the system  Isaac Newton’s second law of motion: force equals mass time acceleration (F = ma).  Theory- a unifying principle that explains a body of facts and/or those laws that are based on them.  Theories are constantly being tested. If a theory is disproved by an experiment, then it must be discarded or modified so that it becomes consistent with experimental obsercations. 1.4 Classifications of Matter  Matter- anything that occupies space and has mass  Chemists distinguish among several subcategories of matter based on composition and properties. The classifications of matter include substances, mixtures, elements, and compounds, as well as atoms and molecules.  SUBSTANCES AND MIXTURES  Substance- a form of matter that has a definite (constant) composition and distinct properties.  Ex: water, ammonia, table sugar (sucrose), gold, and oxygen.  Substances differ from one another in composition and can be identified by their appearance, smell, taste, and other properties.  Mixture- a combination of two or more substances in which the substances retain their distinct identities.  Ex: air, soft drinks, milk, and cement.  Mixtures do not have constant composition.  Mixtures are either homogeneous or heterogeneous.  Homogeneous mixture: the composition of the mixture is the same throughout. Ex: spoonful of sugar dissolved in water.  Heterogeneous mixture: the composition is not uniform. Ex: sand mixed with iron filings, the sand grains and the iron filings remain separate.  Any mixture, whether homogeneous or heterogeneous, can be created and then separated by physical means into pure components without changing the identities of the components  ELEMENTS AND COMPOUNDS  Substances can either be elements or compounds.  Element: a substance that cannot be separated into simpler substances by chemical means.  118 elements.  Atoms of most elements can interact with one another to form compounds.  Compound: a substance composed of atoms of two or more elements chemically united in fixed proportions. Ex: water.  Unlike mixtures, compounds can be separated only by chemical means into their pure components. 1.5 The three states of matter  All substances, at least in principle, can exist in three states: solid, liquid, gas.  Solid: molecules are held close together in an orderly fashion with little freedom of motion.  Liquid: molecules are held close together but are not held so rigidly in position and can move past one another.  Gas: the molecules are separated by distances that are large compared with the size of the molecules.  The three states of matter can be interconverted without changing the composition of the substance.  Melting point: solid to liquid  Boiling point: liquid to gas 1.6 Physical and chemical properties of matter  Substances are identified by their propertied as well as by their composition.  Color, melting point, and boiling point are all physical properties.  Physical property- can be measured and observed without changing the composition or identity of a substance.  Ex: melting ice and helium gas being lighter than air.  Chemical property- to observe this property we must carry out a chemical change. Ex: “hydrogen gas burns in oxygen gas to form water”.  After the change, the original chemical substance (the hydrogen gas), will have vanished, and all that will be left is a different chemical substance (water).  Ex: hard-boiling an egg= chemical change  All measurable properties of matter fall into one of two additional categories: extensive properties and intensive properties.  The measured value of an Extensive property- depends on how much matter is being considered.  Mass – the quantity of matter in a given sample of a substance (extensive property).  Values of the same extensive property can be added together.  Volume – length cubed. (extensive property).  The value of an extensive quantity depends on the amount of matter.  The measured value of an intensive property- does not depend on how much matter is being considered.  Density- the mass of an object divided by its volume (intensive property).  Example of intensive property: temperature.  Unlike mass, length, and volume, temperature and other intensive properties are not additive 1.7 Measurement  Meterstick- measures length or scale  Buret, pipet, graduated cylinder, volumetric flask- measures volume  Balance – measures mass  Thermometer- temperature  Macroscopic properties- can be determined directly.  Microscopic properties- on the atomic or molecular scale, must be determined by an indirect method.  SI UNITS (International System of Units)  Metric units: related decimally by powers of 10. Base quantity Name of unit Symbol Length Meter
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