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Substances, Compounds & Mixtures

Substances, Compounds & Mixtures. How everything is put together. Substances. Matter that has the same composition and properties throughout is called a substance . When different elements combine, other substances are formed. Substances. Contains only one particle

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Substances, Compounds & Mixtures

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  1. Substances, Compounds & Mixtures How everything is put together.

  2. Substances • Matter that has the same composition and properties throughout is called a substance. • When different elements combine, other substances are formed.

  3. Substances • Contains only one particle • Can exist in 3 states of matter • Can be elements or compounds Picture from http://www.ilpi.com/msds/ref/gifs/statesofmatter.gif

  4. What is a Pure Substance? A pure substance is a classification of matter that includes both elements and compounds Pure substances cannot be separated by physical means such as distillation, filtration, or chromatography

  5. Compounds • A compound is a substance whose smallest unit is made up of atoms of more than one element bonded together. • Compounds often have properties that are different from the elements that make them up. • Examples: Water, salt, sugar

  6. Compounds Have Formulas • H20 is the chemical formula for water, and H2O2 is the formula for hydrogen peroxide. • The formula tells you which elements make up a compound as well as how many atoms of each element are present.

  7. How to read a formula H20 This is a subscript. It tells us how many atoms of that element exist in one unit of that compound. Hydrogen is made of 2 H atoms and 1 O atom. No subscript is used when only one atom of an element is present.

  8. Compound Review •  A pure compound has the same elements and the same amount of elements all of the time • Elements are chemically combined • Compound properties are different from the properties of the elements • They cannot be separated physically • Physical properties such as boiling point or melting point of pure substances are do not change

  9. Mixtures • A mixture is a combination of two or more substances where there is no chemical combination or reaction.

  10. A mixture is a combination of two or more substances where there is no chemical combination or reaction.

  11. Mixtures combine physically in no specific proportions. They just mix.

  12. Solids, liquids and gases can be combined to create a mixture.

  13. Mixture Types • MIXTURES MAY BE HOMOGENEOUS OR HETEROGENEOUS

  14. Homogeneous Mixtures • Homogeneous Mixtures: • The prefix: "homo"- indicates the same • Have the same uniform appearance and composition throughout

  15. Solutions • SOLUTIONS are homogeneous mixtures

  16. What is a solution? • A solution is a mixture of two or more substances. • At least two substances must be mixed in order to have a solution

  17. A solution has two parts • The substance in the larger amount is called the SOLVENT - it does the dissolving • IN most common instances water is the solvent • The substance in the smallest amount and the one that DISSOLVES is called the SOLUTE

  18. Examples of solutions • Salt water • Clean Air • Vinegar

  19. Heterogeneous Mixtures: • The prefix: "hetero"- indicates difference • A heterogeneous mixture consists of visibly different substances or phases • Two or more parts can be seen

  20. Examples: • Pizza • Sandwich • Chex Mix

  21. How Can We Change Matter Into New Substances? • Chemical reaction (also known as a chemical change) is a change in a substance or substances that results in a totally new substance • Ex: 2H2(g) + O2(g)  2H2O(g) Notice that the reactants (the substances you start with) combine to form a new substance (the product)

  22. How Do I Know If A Chemical Reaction Has Occurred? • There are 5 indicators of a chemical reaction • Evolution of a gas • Evolution of light • Evolution of heat • Color change • Evolution of a precipitate Precipitate: an insoluble substance that is produced as result of a chemical reaction

  23. Why Do Chemical Reactions Occur? • Chemical reactions occur to produce a more stable product than the existing reactants

  24. Where Does The Matter Go? • It is important to understand that when matter undergoes a chemical reaction (ie a chemical change) it does not disappear or appear • The atoms are rearranged and form new bonds, but no matter is lost nor gained • This is called the Law of Conservation of Matter

  25. Compounds vs Mixtures Mixtures Compounds Not chemically combined Combine chemically forming molecules Can combine in any proportion Combine in set proportions Separated chemically Separated physically

  26. Classifying Matter Matter Pure Substances Mixtures Elements Homogeneous Compounds Heterogeneous Fe, O H2O, CO2 milk, tea Rocky Road ice cream, muddy water

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