2: The Physical and Chemical Properties of Matter
In chapter one, we defined matter as anything that has mass and occupies space. In this chapter, we will look more closely at matter and break it into sub-classes including pure substances and mixtures. We will look at the physical state that matter can adopt (solids, liquids, and gasses) And we will learned how to characterized these using intensive properties such as density. Finally, we will look at changes in these properties and define them in terms of simple physical changes (such as share of physical state) And chemical changes, where one or more substances combine to make new substances.
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- 2.1: Pure Substances and Mixtures
- A compound is a substance that results from the combination of two or more elements in a constant ratio. The chemical formula of which tells us the elements that are present and the ratio of the elements to each other. In a molecule, the atoms are not only bonded together in a constant ratio, but they are bonded in a specific geometric arrangement as well.
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- 2.2: The States of Matter
- At low temperature, water exists as a solid (ice). As the temperature increases, water exists as a liquid, and at high temperature, as water vapor, a gas.These three forms of water represent the three states of matter: solids, liquids and gases. States of matter are examples of physical properties of a substance. Other physical properties include appearance (shiny, dull, smooth, rough), odor, electrical conductivity, thermal conductivity, hardness and density, to name just a few.
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- 2.3: Density, Proportion and Dimensional Analysis
- The physical state of a substance at under a defined set of conditions (like temperature and pressure) is an intensive property of a substance. An intensive property is defined as a property that is inherent to the substance and is not dependent on the sample size. Density, the mass-to-volume ratio of a substance, is another example of an intensive property.
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- 2.4: Chemical and Physical Properties and Changes
- Changes in outward appearances that do not alter the chemical nature of the substance and make no new substance are called physical changes. A chemical change has occurred when the chemical composition of a material changes and a new substance is produced. Chemical properties are simply the set of chemical changes that are possible for that substance.