Chemistry TAKS Review

1. Chemistry TAKS Review

2. Let’s get started with… Differences between elements, mixtures, and compounds

3. - Elements, Mixtures, and Compounds - 1. Element - a pure substance made up of one type of atom. - organized on periodic table - each element has a unique number of protons…its atomic number Examples: Hydrogen (H), Oxygen (O), Carbon (C), and Sodium (Na)

4. TIME OUT! • Atomic Structure Reminder: • Atoms contain three subatomic particles… • 1. Protons…positive charge • 2. Neutrons…no charge • 3. Electrons…negative charge These are located in NUCLEUS! Electrons surround the nucleus in orbitals

5. - Elements, Mixtures, and Compounds - 2. Mixture - made up of more than one type of substance - physically combined Examples: mixture of sugar and salt, salad dressing, solutions, and your blood!

6. - Elements, Mixtures, and Compounds - 3. Compound - made up of more than one type of substance - chemically combined - always combined in same RATIO… that’s the chemical formula! Examples: water (H2O), glucose (C6H12O6), and salt (NaCl)

7. Let’s practice… Try questions 1- 4 on your review packet

8. Now let’s talk about physical properties of matter…

9. - Physical Properties of Matter - Density amount of mass per volume Density = mass / volume Remember! Look at the Formula Chart for equations!

11. - Physical Properties of Matter - Density amount of mass per volume Density = mass / volume You will also have a calculator to use! Remember! Look at the Formula Chart for equations!

12. - Physical Properties of Matter - Example: What is the density at 20°C of 12.0 milliliters of a liquid that has a mass of 4.05 grams? A. 0.338 g/mL B. 2.96 g/mL C. 16.1 g/mL D. 48.6 g/mL X D = m / v D = 4.05 g / 12.0 mL D = 0.338 g/mL Does the density equation include temperature? NO! Ignore extra information!

13. Things to know about Density • Density of water = 1 • Objects with a density • greater than 1 sink in water • Objects with a density • less than 1 float in water • When you cut a large object into pieces, density remains the same

14. Let’s practice… Try questions 5-9 on your review packet

15. - Physical Properties of Matter - Buoyancy the force that fluids exert UPWARD on an object The buoyant force on an object is EQUAL to the weight of the fluid DISPLACED by the object.

16. - Physical Properties of Matter - Buoyancy the force that fluids exert UPWARD on an object The buoyant force on an object is EQUAL to the weight of the fluid DISPLACED by the object. When the density of a fluid is INCREASED, the buoyant force the fluid exerts on an object INCREASES too!

17. - Physical Properties of Matter - Viscosity property of a fluid when it RESISTS the tendency to flow So…fluids with a LOW viscosity flow easily like water and fluids with a HIGH viscosity flow slowly (like thick syrup)

18. Let’s practice… Try questions 10-12 on your review packet

19. - Physical Properties of Matter - Solubility ability of a substance to be dissolved in another The substance that is dissolved is called the SOLUTE. The substance that is dissolving the other is called the SOLVENT. Water is the universal SOLVENT!

20. Things that affect Solubility • Size of solute • The smaller the solute, the faster it dissolves! • Temperature of solvent • The higher the temperature, the faster the solute dissolves! • Stirring, swirling, or shaking • All of these speed up how fast a solute dissolves!

21. Things that affect Solubility Gases are more soluble in a liquid that is colder! Ex. a warm soda will contain less fizzy carbon dioxide, than a cold soda!

22. Let’s practice… Try questions 13-22 on your review packet

23. Do you remember physical vs. chemical changes?

24. Physical vs Changes Changes Physical Change alters the form of a substance, but does not change the substance into another substance Chemical Change a change in which one or more new substances with new properties are formed

25. Physical vs Changes Changes Physical Change Chemical Change Paper burning Water freezing Erosion of rocks Rust forming on a bridge Fermenting Wine Salt dissolving

26. Let’s practice… Try questions 23-32 on your review packet

27. When chemical reactions do occur, they must follow the Law of Conservation of Mass!

28. - Law of Conservation of Mass - This law means that the total mass of the reactants must equal the total mass of the products in a chemical reaction. What are reactants? What are products?

29. - Law of Conservation of Mass - How much Zinc (Zn) is produced in this reaction?

30. - Law of Conservation of Mass - PRODUCTS REACTANTS 35 g + 55 g = 74 g + ??? g 90 g = 74 g + ??? g 90 g - 74 g = 74 g - 74 g + ??? g 16 g = ??? g So 16 g of Zn were produced!

31. Something to remember… Sometimes the products of a chemical reaction include a gas. The mass of the gas is included in the total mass of the products.

32. Let’s practice… Try questions 33-38 on your review packet

33. - Balancing Equations - Because of the Law of Conservation of Mass, when we write chemical equations, they have to be BALANCED! Hint: That means that the same number of ATOMS have to be on BOTH sides of the chemical equation!

34. - Balancing Equations - What process is this the chemical equation for? PHOTOSYNTHESIS! Here’s an example… CO2 + H2O = C6H12O6 + O2 Is this equation BALANCED? NO!

35. - Balancing Equations - PHOTOSYNTHESIS! CO2 + H2O = C6H12O6 + O2 The little numbers in a chemical formula are called subscripts. When balancing equations, you CANNOT change subscripts…that would change the formula for the compound!

36. - Balancing Equations - If the coefficient is not written, then it is equal to 1. PHOTOSYNTHESIS! _ CO2 + _ H2O = _ C6H12O6 + _ O2 You can put big numbers called coefficients in front of the chemical formulas. The coefficients multiply by the subscripts of all atoms in chemical formula for the total number of atoms.

37. - Balancing Equations - Now let’s balance… _ CO2 + _ H2O = _ C6H12O6 + _ O2 6 How many carbons are on both sides? What coefficient goes here to balance the carbons?

38. - Balancing Equations - Now let’s balance… _ CO2 + _ H2O = _ C6H12O6 + _ O2 6 6 Now how many hydrogens are on both sides? What coefficient goes here to balance the hydrogens?

39. - Balancing Equations - Now let’s balance… _ CO2 + _ H2O = _ C6H12O6 + _ O2 6 1 6 6 Now how many oxygens are on both sides? What coefficient goes here to balance the oxygens? Now it’s balanced!

40. Let’s practice… Try questions 39-45 on your review packet

41. This is the Periodic Table of Elements that you will be using on the TAKS Test!

42. The rows are called PERIODS

43. The columns are called GROUPS The elements in each group have the same number of valence electrons…so they react in the same way.

44. These groups are MOST reactive

45. This group is LEAST reactive

46. The atomic number is the number of PROTONS Each element is described with its name and symbol

47. The atomic mass is the number of PROTONS plus the number of NEUTRONS

48. So an atom of silicon has how many neutrons? 28 – 14 = 14 neutrons

49. Let’s practice… Try questions 46-50 on your review packet

50. Acids and Bases • Properties of Acids • Taste sour (don’t try this at home). • Conduct electricity. • React with metals. • Change the color of indicators. • React with bases to form water and a salt. • Donate H+ ions • Ex: HCl, H2SO4