Substances, Compounds & Mixtures

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 • Are made of molecules and molecules are the smallest particle of a compound • Have properties that are different from the elements that make them up. • Molecules made up of 2 or more atoms chemically bonded together • Examples: Water, salt, sugar • A substance whose smallest unit is made up of atoms of more than one pure element bonded together.

6. Compounds Have Formulas • H2O 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. Water is made of 2 H atoms and 1 O atom. No subscript is used when only one atom of an element is present.

8. Compounds Sugar Carbon, Hydrogen, Oxygen (C12 H22 O12) 12 Carbon atoms + 22 Hydrogen atoms + 12 Oxygen atoms = 1 molecule of sugar

9. Compounds Water Hydrogen, Oxygen (H2 O) Salt Sodium, Chlorine (Na Cl) Hydrogen Peroxide Hydrogen, Oxygen (H2 O2)

10. 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 do not change

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

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

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

14. Mixture Types • MIXTURES MAY BE HOMOGENEOUS OR HETEROGENEOUS

15. Homogeneous Mixtures • Homogeneous Mixtures: • The prefix: "homo"- indicates the same • Have the same uniform appearance and composition throughout • EX. A pile of pennies, iced tea with sugar (sugar has dissolved)

16. Solutions • SOLUTIONS are homogeneous mixtures

17. 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

18. 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

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

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

21. Examples: • Pizza • A pile of coins • Chex Mix

22. 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(l) Notice that the reactants (the substances you start with) combine to form a new substance (the product)

23. 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

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

25. Structure of a Chemical Equation • A chemical equation tells you the substances you start with in a reaction and the substances you get at the end • The substances at the beginning are called the Reactants. • When the reaction is complete, you have new substances call the Products • The number of reactants and products can vary

26. Structure of a Chemical Equation Reactant + Reactant Product + Product Reactant + Reactant yields Product NH3 + HClNH4Cl Ammonia + Hydrogen Chloride yields Ammonium Chloride

27. Structure of a Chemical Equation Reactant Product + Product Reactant yields Product + Product CaCO3CaO + CO2 Calcium Carbonate (heated Limestone- 1,517oF) yields Calcium Oxide + Carbon Dioxide

28. 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

29. 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

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