CHEM-UA 125 Chapter 2.1: Chapter 2 part 1
11 Aug 2016
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2. 1 elements, compounds, and mixtures: an atomic overview. Matter with a fixed composition is called a substance: elements and compounds are substances but mixtures are not because they are not of one fixed composition but rather a mixed one. Mixture- 2 or more substances that are physically intertwined, they are not chemically combined: the components of the mixture can vary in mass and has similar properties of its components, mixtures can be separated by physical changes. 2. 2 the observations that led to an atomic view of matter. Mass conservation: law of mass conservation- the total mass of a substance does not change during a chemical reaction. The energy changes of chemical reactions are so small that practically, mass is conserved. Mass fraction= (mass of element x in compound a)/ (mass of compound a) Each element in a compound has a fixed mass fraction and mass percent. The mass fraction is fixed no matter what the size of the sample.
