Matter is classified as a pure substance or as a mixture of substances. (3.1q)
The three phases of matter (solids, liquids, and gases) have different properties. (3.1kk)
Properties of Solids • Regular geometric pattern in the arrangement of the molecules called a crystal lattice • Molecules are close together and vibrate in place • Molecules do not move from place to place • Solids are not compressible • Definite shape and definite volume
Properties of Liquids • Molecules can move around (fluid) • Molecules are farther apart than in a solid • Liquids take the shape of their container • Not compressible • No definite shape but do have definite volume The forces of attraction between the molecules are weaker in a liquid than they are in a solid.
Properties of Gases • Molecules fill their container (spread out) • Molecules are very far apart • Molecules move in straight lines until they hit something (another molecule or wall of the container) • No definite shape and no definite volume The forces of attraction between the molecules are very weak.
Regents Question: 08/02 #16 Which statement correctly describes a sample of gas confined in a sealed container? (1) It always has a definite volume, and it takes the shape of the container. (2) It takes the shape and the volume of any container in which it is confined. (3) It has a crystalline structure. (4) It consists of particles arranged in a regular geometric pattern. þ
Regents Question: 06/02 #12 Which 5.0-milliliter sample of NH3 will take the shape of and completely fill a closed 100.0-milliliter container? (1) NH3 (s) (3) NH3 (g) (2) NH3(l) (4)NH3 (aq) þ
Regents Question: 06/03 #16 In which material are the particles arranged in a regular geometric pattern? (1) CO2 (g) (2) NaCl(aq) (3) H2O(l) (4) C12H22O11 (s) þ
A pure substance (element or compound) has a constant composition and constant properties throughout a given sample, and from sample to sample. (3.1r) All substances are homogeneous.
Elements are substances that are composed of atoms that have the same atomic number. Elements cannot be broken down by chemical change. (3.1u) There are more than 100 different elements Elements are represented by chemical symbols The first letter of the symbol is always a capital letter the rest are lower case Nitrogen Neon A temporary symbol
Some elements are diatomic. They come in pairs when not combined with other elements. • Diatomic Elements • Hydrogen • Oxygen • Nitrogen • Chlorine • Bromine • Iodine • Fluorine H O N Cl Br I F Neon is a monatomic element Nitrogen is a diatomic element
Compounds are substances that are composed of two or more different elements chemically combined. • The elements in a compound are in fixed proportions • A compound can only be decomposed by chemical means • Compounds are represented by chemical formulas • Compounds are electrically neutral
Using particle diagrams to represent elements, compounds and mixtures. Compound Element Diatomic element Mixture
Regents Question: 08/02 #6 Which species represents a chemical compound? (1) N2 (3) Na (2) NH4+ (4) NaHCO3 þ Compounds are made up of more than one type of element. (Look for more than one capital letter.) Compounds are electrically neutral.
Regents Question: 06/03 #9 Which substance can be decomposed by a chemical change? (1) Co (2) CO (3) Cr (4) Cu þ
Mixtures are composed of two or more different substances that can be separated by physical means.
Regents Question: 08/02 #51 On a field trip, Student X and Student Y collected two rock samples. Analysis revealed that both rocks contained lead and sulfur. One rock contained a certain percentage of lead and sulfur by mass, and the other rock contained a different percentage of lead and sulfur by mass. Student X stated that the rocks contained two different mixtures of lead and sulfur. Student Y stated that the rocks contained two different compounds of lead and sulfur. Their teacher stated that both students could be correct. Draw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms.
Regents Question: 08/02 #51 Answer Draw particle diagrams in each of the rock diagrams provided in your answer booklet to show how Student X’s and Student Y’s explanations could both be correct. Use the symbols in the key provided in your answer booklet to sketch lead and sulfur atoms. Student X Student Y Rock A Rock B
When different substances are mixed together, a homogeneous or heterogeneous mixture is formed. (3.1s) A homogeneous mixture is called a solution A solution in which something is dissolved in water is called an aqueous solution NaCl(aq) means that sodium chloride (table salt) is dissolved in water and is therefore a homogenous mixture. (aq) stands for aqueous An alloy is a solution of metals eg. brass, bronze
Regents Question: 06/03 #15 Which of these terms refers to matter that could be heterogeneous? (1) element (2) mixture (3) compound (4) solution þ
The proportions of components in a mixture can be varied. Each component in a mixture retains its original properties. (3.1t) Two mixtures of Hydrogen (H2) and Neon (Ne)
Particle Size solubility Density and polarity Freezing Point Boiling Point Differences in properties such as density, particle size, molecular polarity, boiling point and freezing point, and solubility permit physical separation of the components of the mixture. (3.1nn) Chromatography, Filtration, Dissolving, Distillation, Crystallization
Regents Question: 01/04 #12 A bottle of rubbing alcohol contains both 2-propanol and water. These liquids can be separated by the process of distillation because the 2-propanol and water (1) have combined chemically and retain their different boiling points (2) have combined chemically and have the same boiling point (3) have combined physically and retain the different boiling points (4) have combined physically and have the same boiling point þ
Density and polarity Particle size Boiling point
A solution is a homogeneous mixture of a solute dissolved in a solvent. The solubility of a solute in a given amount of solvent is dependent on the temperature, the pressure, and the chemical natures of the solute and solvent. (3.1oo) Dissolved particles are too small to be trapped by a filter
Regents Question: 08/02 #7 Which mixture can be separated by using the equipment shown? (1) NaCl(aq) and SiO2(s) (2) NaCl(aq) and C6H12O6(aq) (3) CO2(aq) and NaCl(aq) (4) CO2(aq) and C6H12O6(aq) þ (aq) stands for aqueous which means dissolved in water. Dissolved particles are too small to be trapped by the filter.
Solubility of a nonvolatile solute depends on temperature. • Solubility is the maximum amount of solute that a solvent can hold at a given temperature. • An unsaturated solution is one in which the solvent can dissolve more solute • A saturated solution is one in which the solvent has as much solute as it can hold • A supersaturated solution is one in which there is more solute dissolved than a solvent can normally hold. • Make a supersaturated solution by cooling a saturated solution • Supersaturated solutions are unstable and will precipitate the excess solute when a seed crystal is added. • As temperature increases, solubility of a solid increases.
Table G shows the solubilities of some gases and some solids at various temperatures when dissolved in 100 grams of water.
A solution which is on the line is saturated • A solution below the line is unsaturated • A solution above the line is supersaturated
Add a test crystal to see if a solution is unsaturated, saturated or supersaturated. • Unsaturated – the test crystal dissolves • Saturated – the test crystal settles to the bottom • Supersaturated – a large amount of crystals precipitate from the solution
Regents Question: 06/02 #40 According to Reference Table G, which solution is saturated at 30°C? (1) 12 grams of KClO3 in 100 grams of water (2) 12 grams of KClO3 in 200 grams of water (3) 30 grams of NaCl in 100 grams of water (4) 30 grams of NaCl in 200 grams of water þ
The solubility of a gas depends on temperature and pressure. • As temperature increases, the solubility of a gas decreases • As pressure increases, the solubility of a gas increases
Regents Question: 08/02 #48 One hundred grams of water is saturated with NH4Cl at 50°C. According to Table G, if the temperature is lowered to 10°C, what is the total amount of NH4Cl that will precipitate? (1) 5.0 g (3) 30. g (2) 17 g (4) 50. g þ
Regents Question: 01/03 #65-66 When cola, a type of soda pop, is manufactured, CO2 (g) is dissolved in it. A capped bottle of cola contains CO2 (g) under high pressure. When the cap is removed, how does pressure affect the solubility of the dissolved CO2 (g)? A glass of cold cola is left to stand 5 minutes at room temperature. How does temperature affect the solubility of the CO2 (g)? As the pressure decreases, the solubility decreases. As the temperature increases, the solubility decreases.
Oil and water are not miscible • Like dissolves like (charged solutes dissolve in charged solvents, uncharged solutes dissolve in uncharged solvents) • Nonpolar solutes dissolve in nonpolar solvents • Polar solutes dissolve in polar solvents • Ionic solutes dissolve in polar solvents (Nonpolar) (Polar) Dry cleaners use a nonpolar solvent to get rid of oil and grease Liquids that dissolve each other are called miscible liquids.
Regents Question: 06/03 #42 Hexane (C 6 H 14 ) and water do not form a solution. Which statement explains this phenomenon? (1) Hexane is polar and water is nonpolar. (2) Hexane is ionic and water is polar. (3) Hexane is nonpolar and water is polar. (4) Hexane is nonpolar and water is ionic. þ
Solubility Guidelines • Not all substances are soluble in water • Reference Table F lists solubility rules and exceptions to those rules.
Regents Question: 08/02 #40 Which of the following compounds is least soluble in water? (1) copper (II) chloride (2) aluminum acetate (3) iron (III) hydroxide (4) potassium sulfate þ
Regents Question: 06/03 #14 • According to Table F, which of these salts is least soluble in water? • LiCl • (2) RbCl • (3) FeCl2 • (4) PbCl2 þ
The concentration of a solution may be expressed as molarity (M), percent by volume, percent by mass, or parts per million (ppm). (3.1pp)
Moles Molarity = Liters Regents Question: 06/02 #42 What is the molarity of a solution that contains 0.50 mole of NaOH in 0.50 liter of solution? (1) 1.0 M (3) 0.25 M (2) 2.0 M (4) 0.50 M þ
Regents Question: 08/02 #36 How many moles of solute are contained in 200 milliliters of a 1 M solution? (1) 1 (3) 0.8 (2) 0.2 (4) 200 þ
Molarity = moles liters Na 1 x 23.0 = 23.0 I 1 x 126.9 = 126.9 149.9 g / mole 0.010M = x 1.0 L Regents Question: 08/02 #49 What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution? (1) 0.015 (3) 1.5 (2) 0.15 (4) 15 þ X = 0.010 moles 0.010 moles x 149.9 g/mole =
Regents Question: 01/03 #40 Solubility data for four different salts in water at 60°C are shown in the table below. Which salt is most soluble at 60°C? (1) A (2) B (3) C (4) D Salt Solubility in Water at 60 °C A - 10 grams /50 grams H2O B - 20 grams /60 grams H2O C - 30 grams /120 grams H2O D - 40 grams/80 grams H2O þ
Regents Question: 01/04 #56-58 A student uses 200 grams of water at a temperature of 60°C to prepare a saturated solution of potassium chloride, KCl. Identify the solute in this solution. According to Reference Table G, how many grams of KCl must be used to create this saturated solution? This solution is cooled to 10°C and the excess KCl precipitates (settles out). The resulting solution is saturated at 10°C. How many grams of KCl precipitated out of the original solution? KCl 90 g Hint: 200 g of water was used – table G is for 100 g of water 60 g
The addition of a nonvolatile solute to a solvent causes the boiling point of the solvent to increase and the freezing point of the solvent to decrease. The greater the concentration of particles, the greater the effect. (3.1qq)