Objective 4

1. Objective 4 • The student will demonstrate an understanding of the structures and properties of matter.

2. 3 overarching TEKS • IPC(7) The student knows relationships exist between properties of matter and its components. • IPC(8) The student knows that changes in matter affect everyday life. • IPC(9) The student knows how solution chemistry is a part of everyday life.

3. 7(A) • Density: The amount of matter per given space (volume). The formula to calculate density is D = mass/volume and is found on the formula chart. The density of an object does not change by changing the volume. Solids are more dense than liquids and liquids are more dense than gases. • Viscosity: The resistance of fluids to flow. Thick fluids flow slower than thin ones do. Oil flows more slowly than water, thus, oil is more viscous than water. • Buoyancy: The force with which a more dense fluid pushes a less dense substance upward. The student will have to compare the densities of two substances and will need to know that the more dense substance will be below the less dense. You will have to know that the density of water is 1 g/cm3 .

4. 1) A sample of an element has a volume of 78.0 mL and a density of 1.85 g/mL. What is the mass in grams of the sample? Record your answer to the nearest tenth. • a.What does 78.0 represent? • Mass volume density temperature • b. What does 1.85 represent? • Mass volume density temperature • c. What is the question asking you to calculate? • Mass volume density temperature

5. Cont. problem 78.0 mL • 1) A sample of an element has a volume of 78.0 mL and a density of 1.85 g/mL. What is the mass in grams of the sample? Record your answer to the nearest tenth. • d. What formula will you use from the formula sheet? • e. Substitute numbers from the problem into the formula? • f. Calculate the unknown to the nearest tenth. 1.85 g/mL mass Mass volume D = = 144.3 g

6. Another question 6) The picture shows the results of pouring a blue liquid into a clear liquid and allowing the mixture to settle for 25 minutes. Compared to the clear liquid, the blue liquid is more — • A massive • B dense • C viscous • D soluble See buoyancy notes.

7. 7(D) • The periodic table organizes the elements into a grid of horizontal rows (left to right) called periods and vertical columns (up and down) called groups or families. • – there are 18groups • - groups 1,2,13,14,15,16,17,18 have the pattern of representing the number of valence (outermost)electronsan atom of that element has; 1,2,3,4,5,6,7,8 electrons, respectively. • - groups 1 & 2 want to lose their total valance electrons. • - groups 13-17 nonmetals want to gain or accept extra electrons to have a total of 8 valence electrons. • - group 18 does not loose or gain electrons, thus becoming non reactive. • -elements in the same group have similar chemical and physical properties because they have the same number of valance electrons.

8. 7(D) • The zigzag line on the periodic table separates metals from nonmetals – elements to the right of the line are nonmetals and elements to the left of the line are metals. • The metals want to react with the nonmetals, except group 18. • -The formulas for these compounds are written by balancing charges. The total positive charge has to cancel the total negative charge. This can be accomplished by the drop and swap method – drop the charge and swap the number of the charge as a subscript of the other element or ion.

9. Ex Problems 1 Which of the following groups contains members with similar chemical reactivity? A Li, Be, C B Be, Mg, Sr C Sc, Y, Zr D C, N, O 2 According to this information, what is the chemical formula for aluminum sulfate? A AlSO4 B Al2(SO4)3 C Al3(SO4 )2 D Al6 SO4 All in group 2 Drop and Swap

10. 7(E) • Element: is a pure substance that can not be broken down into simpler substances. • Symbol form - “C” for carbon, “Ni” for nickel *notice one capital letter. • Word form – nitrogen, magnesium *words found on the periodic table • You will need to be able to identify an atom from its model. Atomic number represents number of protons (+ charge)

11. 7(E) • Compound: a combination of 2 or more elements that are combined chemically. There are two common compounds to memorize; water (H2O) and table salt (NaCl). • Symbol form – CaBr2; Mg(NO3)2 *notice two or more capital letters. • Word form – calcium bromide; magnesium nitrate *notice two elements names from the periodic table.

12. 7(E) • Mixture: two or more compounds and/or elements together that are not chemically combined. • stainless steel – exact words not found on the periodic table. • Air – exact words not found on the periodic table.

13. Ex Questions • 1 An unknown silvery powder has a constant melting point and does not chemically or physically separate into other substances. The unknown substance can be classified as — A an element B a compound C a mixture D an alloy • 2 The picture shows a model of the element — A fluorine B helium C beryllium D oxygen 4 protons so look at atom number 4

14. 8(A) • Chemical Change: A process that involves one or more substances changing into new substances. • Key words: explode, rust, oxidize, corrode, tarnish, ferment, burn, rot, reacts • Physical Change: A process that alters a substance without changing its composition. • Key words: bend, grind, crumple, split, crush, melt, condense, evaporate, boil, freeze. • The questions on TAKS will be about the rock cycle, digestive system, changes in state (water freezing, evaporating, condensing), and oxidation (rusting, burning, decomposing). You will have to decide if the change is chemical or physical.

15. Ex. Questions • 1) Which of the following is an example of a chemical change? A Combustion of gasoline B An apple being bitten C An ice cube being swallowed D Absorption of a water molecule • 2 Which of the following processes is an example of a physical change associated with an oak tree? A Decomposition of bark by bracket fungi B Starches and sugars being broken down during energy production C Water and carbon dioxide being converted to glucose D Evaporation of water from the surfaces of leaves

16. O H H 8(C) Law of conservation of mass • There are two basic questions on TAKS on this TEK: 1) choosing a balanced equation or balance one. 2) making sure the mass of reactants equal the mass of products. • BALANCING EQUATIONS: • Let’s first review counting atoms in a chemical formula. • The numbers to the lower right of each chemical symbol, called the subscript, tells how many of those atoms make up the compound. • If no number appears, then there is considered only one of those atoms. H2O

17. O O H H H H 8(C) • The numbers in front of the chemical formula are called coefficients and tell how many compounds are represented. So 4 hydrogens and 2 oxygens. You multiply the coefficients by the subscripts for counting. 2H2O 2 water molecules

18. Ex. Problem What are the coefficients that will balance this chemical equation? A 2, 1, 1 B 3, 4, 2 C 2, 2, 1 D 4, 3, 2

19. Cont. 8(C) Law of conservation of mass • MASSES OF REACTANTS EQUAL TO MASSES OF PRODUCTS • Remember that reactants are on the left side of the arrow and products are on the rightside of the arrow.

20. Ex. Problem According to the law of conservation of mass, how much zinc was present in the zinc carbonate? A 40 g B 88 g C 104 g D 256 g 64g + 192g = 152g + ?

21. 9(A) Relate the structure of water to its function [as a universal solvent]. • The water molecule (H2O) is a polar molecule – meaning that one end of the molecule is slightly (δ+) positive and the other end is slightly (δ-) negative. • -the difference in charges allows the water molecule to surround charged particles and thus dissolve them. • The water molecule is also important because its solid form (ice) is less dense than its liquid form. Thus, ice floats on water to form a protective insulation to prevent further freezing.

22. Water molecules surrounding ions. Positive end of water (H) Negative end of water (O)

23. Ex. Problem Fish survive through severe winters because of the property of water that allows water to — F form chemical bonds as it freezes, raising the water temperature below the ice G increase in density while it freezes, dissolving more oxygen from the air H expand when it freezes, creating a floating and insulating layer of ice J precipitate vital nutrients when it freezes, increasing the food supply Water acts as a solvent of ionic compounds because — F water is liquid over a wide range of temperatures G water molecules are polar H water is found in three states of matter J water takes the shape of its container

24. 9(B)relate the concentration of ions in a solution to physical and chemical properties such as pH, electrolytic behavior, and reactivity. • Concentration of ions is the amount of ions per given volume. Concentration can be expressed as percent(%) solution. • pH is the measure of H+ ions in water. The “p” in pH means power, so, pH means power of H+ ions in solution. We have the pH scale that is used to measure the acidity of solutions. The higher concentration of [H+] the greater the acidity, but can be confusing when looking at the pH scale because lower pH means more acidity. • One cause of Acid rain is by burning fossil fuels.

25. This is pH. Notice as pH decreases, [H+] increases and becomes more acidic.

26. Electrolytic behavior • Electrolytic behavior of a solution is its ability to conduct electricity. The more ions are dissolved in water the greater the conduction of electricity. In the picture below, seawater has lots of salt dissolved in water making electricity flow through it. The greater the concentration of ions the brighter the light.

27. Ex. Problem The table shows data from an investigation designed to find a liquid solution that is both an acid and a strong electrolyte. Based on the data, a solution that is both an acid and a strong electrolyte is — A Solution 1 B Solution 2 C Solution 3 D Solution 4

28. Bathwater normally has electrolytic behaviors even though distilled water does not. This is because bathwater — • F contains isotopes of hydrogen • G has been heated • H is separated into H+ and OH– ions • J contains dissolved minerals

29. 9(D) demonstrate how various factors influence solubility including temperature, pressure, and nature of the solute and solvent. • In most cases the solvent will be water and the solute will be what ever is being dissolved. Some things do not dissolve and are thus called insoluble. Some substances, compounds or elements, are more soluble than others. There are Solubility Rules that scientist follow but is not required to memorize for TAKS. • Several factors affect solubility for solids and gases. • These are the factors for solids: • increasingtemperature of solvent (water) increases solubility. • crushing or increasing surface area increases solubility. • stirring or agitation increases solubility. • pressure does not affect solubility of solids.

30. 9(D) cont. Notice the trend between solubility and temperature.

31. 9(D) continue • Gases: • increasing temperature of solvent decreases solubility of gases. (heating a can of soda makes it fizz) • stirring or agitation of solvent decreases solubility of gases. (shaking a soda) • increasing pressure of gas above solvent increases solubility – pushes gas into water. • *Notice the relationship between temperature and solubility of gases in the table.

32. Ex. Problems Pain medications can be made as powders or tablets. The powders tend to work faster than tablets with the same ingredients because powder — F dissolves faster in solution than a single tablet G has more total mass than a single tablet H travels through the bloodstream more easily than a tablet J is easier to swallow than tablets Over time an open soft drink will lose carbonation (dissolved CO2). Which of these allows the CO2 to remain in solution the longest? A Reduced air pressure B Exposure to direct sunlight C Increased air currents D Cooler temperatures