Chapter 1 

• chemistry is the study of the composition, properties, and interactions of matter.
• Scientific laws are statements that summarize a vast number of scientific observations and

  describe or predict some aspect of the natural world.

• Theories are well-substantiated, comprehensive, testable explanations of a particular aspect of nature.
• The Law of Conservation of Mass states that matter cannot be created or destroyed in chemical processes.
• Matter is anything that has mass and occupies space (has volume). Matter may take one of

  three forms (phases or states) of interest to chemists: solids, liquids, and gases. (but in some cases, plasma can be the fourth phase/form.)

• solid- the shape and volume of the material are definite (the material is rigid) \n liquid- the volume is definite, but takes the shape of its container \n gas - both the shape and volume follow that of the container (the material is compressible)
• Mass is the quantity of a substance that is present. (Note that mass and weight are different.
• Weight is the force that gravity exerts on an object.
• The Law of Conservation of Matter states that the sum of the masses of the reacting species in a chemical reaction equals the sum of the masses of the products.
• A pure substance is composed of a single component and cannot be divided into parts by physical processes.
• Elements are pure substances that consist of only one type of atom and cannot be broken into simpler substances.
• Compounds are pure substances made up of atoms of two or more different elements chemically bonded together. Compounds can be broken up into their constituent elements by chemical processes.
• A mixture is a substance that is composed of two or more pure substances that can be separated by physical processes. Mixtures can further be broken down into two categories: homogeneous and heterogeneous.
• Homogeneous is distributed uniformly throughout and visibly appears uniform. Example: a cup of coffee
• Heterogeneous mixtures would then be those whose compositions vary throughout the mixture. Example: trail mix
• Physical properties do not change the identity of a substance. (color, length, volume, opacity)
• chemical properties (usually chemical reactions or classes of chemical reactions) can change the identity of a substance. (acidity, reactivity, flammability, toxicity)
• Extensive properties depend on the amount of the material present, while intensive properties don’t. extensive example (mass, energy) intensive example (color, melting point)
• Density is the ratio of the mass of an object to its volume and is measured in g/mL for liquids and solids and g/L for gases.
• Significant digits (also referred to as significant figures) are those digits in a number that have physical meaning.
• Exact numbers have an infinite number of significant digits.
• Accuracy is a measure of how close a measured value is to the “real” or “true” value.
• Precision is a measure of how reproducible measurement is.