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Chapter 2 sec 1 - Classifying Matter. Pg 38-44. Classifying Matter. Gold Cookie Dough Based on their compositions, materials can be divided into pure substances and mixtures.
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Chapter 2 sec 1 - Classifying Matter Pg 38-44
Classifying Matter Gold Cookie Dough • Based on their compositions, materials can be divided into pure substances and mixtures http://www.google.com/url?source=imglanding&ct=img&q=http://2.bp.blogspot.com/_J17OlUgCsE4/SLAbz66A7fI/AAAAAAAABkM/lhtNEs1ZhyA/s400/ChocCHip+3.jpg&sa=X&ei=7mwrT5C3A8mC2wWMuZD0Dg&ved=0CAwQ8wc47QE&usg=AFQjCNHTWGGIAkJYkrKTI8FZw5L5ijfOlg
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Pure Substances • Pure substance - matter that always has exactly the same composition • Every sample of a given substance has the same properties because a substance has a fixed, uniform composition • Substances can be classified into two categories - elements and compounds
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Elements • An element is a substance that cannot be broken down into simpler substances • Example- if you cut up a copper wires into smaller and smaller pieces, it would still be copper. Very small pieces of copper. • Atom- is the smallest particle of an element • Example- if you could cut up the copper wire into extremely tiny particles you would eventually get copper atoms
Elements • An element has a fixed composition because it contains only one type of atom. No two elements contain the same type of atom • At room temperature, 20OC or 68OF, most elements are solids. • Oxygen and Nitrogen are the main gases in the air you breathe • Mercury and bromine are liquids at room temperature and are extremely poisonous http://periodictable.com/Elements/020/index.html
Symbols for Elements • Symbols for elements are either one or two letters • The first letter is always capitalized and the second letter is not • Symbols allow scientists from different countries to communicate without confusion • Examples: • Aluminum = Al • Hydrogen = H • Calcium = Ca • Silver = Ag
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Compounds • A compound is a substance that is made from two or more simpler substances and can be broken down into those simpler substances • A compound always contains two or more elements joined in a fixed proportion
Compounds • Water is a compound because it is made up of 2 hydrogen atoms and 1 oxygen atom, H2O • Oxygen and hydrogen are gases at room temperature but water is a liquid at room temperature
Mixtures • Salsa is an example of a mixture, you can adjust the amount of each ingredient until it suits your taste • Mixtures tend to retain some of the properties of their individual substances but those properties are less constant than the properties of a substance • The properties of a mixture can vary because the composition of a mixture is not fixed
Heterogeneous Mixtures • Sand is a heterogeneous mixture • Hetero and genus mean “different” and “kind” • In a heterogeneous mixture, the parts of the mixture are noticeably different from one another
Homogeneous Mixtures • Water from the deep end of a pool and water from the shallow end of a pool will appear the same • Water in a swimming pool is a homogeneous mixture of water and substances that are dissolved in it • In a homogeneous mixture, the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another
Solutions, suspensions, and Colloids (Solution, colloid, suspension) • The size of the particles in a mixture have an effect on the properties of the mixture • Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid • You would need to observe the properties of a mixture before you can decide if it is homogeneous or heterogeneous
Solutions • When substances dissolve and form a homogeneous mixture, the mixture that forms is called a solution • Liquid solutions are easy to recognize • They do not separate into distinct layers over time • If poured through a filter none of the substances get trapped • You can see through them because light can pass through them without being scattered in all directions • The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light.
Suspensions • “Shake well before using” is a clue that the material in the bottle is a suspension • A suspension is a heterogeneous mixture that separates into layers over time • Suspended particles settle out of a mixture or are trapped by a filter (larger particles than that in the solution) • Suspensions are cloudy because the larger particles can scatter light in all directions
Colloids • A colloid contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension • Do not separate into layers • Cannot filter to separate parts of a colloid • Light is scattered when going through a colloid • The scattering of light is a property that can be used to distinguish colloids and suspensions from solutions
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The End http://www.google.com/url?source=imglanding&ct=img&q=http://www.warrentboe.org/images/homework/pics/Science/j0321055.jpg&sa=X&ei=H0gwT-enHYONigLc46CNAw&ved=0CA0Q8wc4-QI&usg=AFQjCNFSmaRtnGGrpMyryFfi03G2TfWYpA