Unit 2: Matter and Energy. Regents Chemistry

Transcription

1 Unit 2: Matter and Energy Regents Chemistry Essential Questions: What is stuff made of? What is energy? How are energy and matter related? How are matter and energy inter-related? Aims to the Unit: To understand what makes up everything in the physical world. Determine the laboratory techniques to isolate and purify components homogenous and heterogeneous mixtures. Know the signs of a chemical reaction. Know the difference between a physical and chemical change. Understand the definition of energy, the different forms of energy, and the concept that energy is conserved. To learn how to convert between different units of temperature. Know the difference between reactions that release heat and those that absorb hear and understand why energy flows the way it does.

2 (I) Definition and forms of Matter Matter Lesson Objective: To understand what makes up everything in the physical world. Matter Occupies and has Phases of Matter: Particle Vibration/Speed: Particle Vibration/Speed: Particle Vibration/Speed: Spacing: Spacing: Spacing: Shape: Shape: Shape: Phase Changes: Element Contains only type of atom. Can be broken down by chemical means. Monatomic Diatomic (Br, I, N, Cl, H, O, F) Page 2

3 Compound Contains or more atoms that are chemically. Requires chemical means (a chemical ) to separate. (Note: chemical reactions do not automatically separate compounds, many reactions create new compounds by recombining the atoms in different way). Substance One type of material --can *not* be physically separated, so can be either an or a Mixture Has at least parts which can be Two Types of Mixtures: : All parts of a mixture are evenly distributed (same everywhere). : Mixture has different composition and ratios of components in different regions of the mixture. *** Important Note: Mixtures do NOT follow the Law of Definite Proportions, which states that a chemical compound always contains exactly the same proportion of elements by mass *** Page 3

4 Matter Word Bank: Homogeneous, Heterogeneous, Pure Substance, Element, Compound No Is it uniform throughout??? Yes Mixture Homogeneous Does it have a variable composition? No Yes Mixture No Can be separated into simpler substances Yes Practice: Classify each of the following as either a substance (S) or mixture (M) 1. chlorine 3. sugar water 5. air 7. Soil 2. water 4. oxygen 6. rocky road ice cream 8. CO2 Page 4

5 (II) Separation Techniques Lesson Objective: Determine the laboratory techniques to isolate and purify components homogenous and heterogeneous mixtures. In chemistry, we often need to isolate specific compounds for research purposes. There are several general methods of separation in particular that are particularly useful in a laboratory. Some separate homogenous mixtures while others separate heterogeneous mixtures. A few are listed below: Filtration A process used to separate objects by their and. Source: blog.khymos.org Source: chemistryland.blogspot.com Chromatography A broad range of separation techniques which use a stationary phase and mobile phase to separate complex mixtures. Separation is based on the and of the particles being separated. Page 5

6 Separator Funnel Used for extraction liquids. Two layers form called the and layer. The layers form because the liquids have different densities. Image Source: wikipedia.org Used to separate liquids based on different of liquids. Specifically, separation happens by boiling one out while keeping the other in a liquid form then condensing the separated liquid and recollecting it in a separate flask Distillation Evaporation Separates by heating materials to to remove liquids from a mixture. Image source: Question: Which techniques of separation would be best for homogenous solutions and which would be better for heterogeneous solutions? Page 6

7 (III) Chemical Reactions and Physical vs. Chemical Changes Lesson Objective(s): Know the signs of a chemical reaction. Know the difference between a physical and chemical change. Chemical Reaction Ex- 2Zn(s) + 2HCl(aq) 2ZnCl(aq) + H 2 (g) (1) What are the signs of a chemical reaction? (2) (3) (4) Law of Conservation of Matter: a fundamental principle of classical physics that matter cannot be or in an isolated system. This will become important when we discuss chemical reactions in further detail. Physical Properties and Changes Chemical Properties and Changes Page 7

8 Extensive Property: A property that depends on the of something Ex: Intensive Property: A property that does not depend on the of something. Ex: Identify each of the following as a physical (P) or chemical (C) change. Provide a rational for your thinking. A.) A carrot broken in half B.) The entire carrot is eaten and digested by Sadie C.) A puddle of water evaporates D.) Ice cream melts E.) Milk is left out of the fridge and turns sour F.) A cake is baked G.) A campfire burns H.) H 2 and O 2 make water Page 8

9 Energy: Important Terminology Potential Energy Kinetic Energy Exothermic Endothermic is often referred to as Energy or "ENERGY OF POSITION". For example. a rock resting at the top of a hill has greater,energy than one which is on the side. is referred to as "ENERGY OF. Particles which are moving possess kinetic energy. The FASTER the particles are moving. the the KINETIC ENERGY Energy is transferred from the SYSTEM to the SURROUNDINGS. Examples include burning and the dissolving of calcium chloride. The temperature will. It feels hot! Energy is ultimately transferred from the SURROUNDINGS to the SYSTEM and STOERED as energy. Examples include melting and the dissolving of ammonium chloride. Heat. is the form of energy which flows from a object (higher temperature) to a one (lower temperature). is measured using the unit called CALORIE. A calorie is defined as the amount of heat needed to raise the temperature of gram of WATER by ºC Temperature. is a measure of the energy of the particles in a sample. This means that as the TEMPERATURE INCREASES. the particles MOVE and have GREATER KINETIC ENERGY. is generally measured in the lab in degrees Celsius (ºC) or Kelvins.. You need to be able to convert from one scale to another by using the equation: *** Temperature is NOT the same thing as heat!!!*** Page 9

10 (I) Energy Concepts: Potential & Kinetic Energy Objective: Understand the definition of energy, the different forms of energy, and the concept that energy is conserved. ENERGY Potential Energy: Kinetic Energy: Heat (aka energy) How heat moves: Explain why you want to be careful how close your face is to the oven when you open it up to check on the cookies you are baking. Page 10

11 Law of Conservation of Matter and Energy Energy cannot be created nor. Energy can only be transferred from one type to another or from one object to another. Example: burning paper converts stored (chemical) energy in paper to heat Example: Holding ice to a burn transfers the kinetic energy of overheated skin to melting the ice Exercise: Energy Classification: Classify the type of energy in the examples below and indicate whether the potential and kinetic energy decrease/increase or stay the same. 1. A sunbather lies on a beach. Answer: The sunbather s K.E. (kinetic energy) increases (the skin warms) and the P.E. (potential energy) of the sun decreases as its nuclear energy decreases. 2. A gas stove is lit. 3. A deer eats lettuce 4. A student tugs on a frozen car door with bare hands 5. An athlete runs a mile 6. A housekeeper plugs in a vacuum cleaner 7. A mother warms up her child s cold hands 8. Water freezes 9. A girl winds up the spring on an alarm clock (hint: if there is no heat involved, then the situation involves transfer between two forms of P.E) Page 11

12 (II) Temperature Scales and Heat Measurements Celsius Motion Temperature Kelvin 0 (zero) 32 Fahrenheit Higher 37 Heat Lower 100 Kinetic The particles making up any sample of matter are in random motion. In other words, they have energy, which is defined as the energy of. The of a body is a measure of the average energy of the particles making up the body. The form of energy called flows from a body at a temperature to a body at a temperature. (We say that the hotter body heats up the cooler body.) Bodes that have the same are composed of particles that have the same average energy. A thermometer is the instrument used to measure. The Celsius scale has been adopted for most scientific uses. It has two fixed points. The temperature ºC is the freezing point of water. The temperature ºC is the boiling point of water. Another temperature scale sometimes used in chemistry is the (Absolute) scale. One Kelvin degree represents the same difference in as one degree. There is only one fixed point on the Kelvin scale, the socalled absolute. At this point, the energy of the particles would theoretically become zero. This temperature is approximately degrees below zero on the scale. It is convenient to use the relationship: K = ºC + to change from one scale to the other. The Fahrenheit scale has little use in chemistry. Its fixed points are defined as ºF for the freezing point of water and ºF for the boiling point of water. Supply the correct numerical values for each temperature on three different scales on the next page Page 12

13 Celsius Scale Kelvin Scale Fahrenheit Scale Boiling Point of Water ºC K ºF Freezing Point of Water ºC K ºF Absolute zero K ºF (III) Temperature Conversions: Objective: To learn how to convert between different units of temperature. Units of Temperature and Temperature Conversions Use your Reference Table to help you make the following temperature conversions: 25 o C to K -150 o C to K 0K to o C (there is something special about this value) 100K to o C Page 13

14 (IV.) Exothermic and Endothermic Reactions Objective: Know the difference between reactions that release heat and those that absorb hear and understand why energy flows the way it does. Endothermic Reactions -Definition -Flow of energy Demo: Sodium bicarbonate is added to acetic acid: Record your observations: NaHCO3 (s) + CH3COOH CH3COONa + H2O + CO2(g) Since the bag feels to the touch, energy is being by the reaction. Therefore, this is a(n) reaction. Draw a diagram in the box at right and indicate the direction of heat flow between the bag and your hand with arrows. Page 14

15 Exothermic Reaction -Definition -Flow of energy Demo: Calcium chloride is added to water: CaCl2 (s) + H2O (l) 2HCl(aq) + CaO (s) 1. Record your observations: 2. Since the bag feels to the touch, energy is being by the reaction. Therefore, this is a(n) reaction. 3. Draw a diagram in the box at right and indicate the direction of heat flow between the bag and your hand with arrows. Page 15

16 Supplemental Materials Practice Regents Questions Physical and Chemical Properties 1. Which statement describes a chemical property of hydrogen gas? (A) hydrogen gas is colorless (B) hydrogen gas burns in air (C) hydrogen gas has a boiling point of 20. K at standard pressure (D) hydrogen gas has a density of g/cm 3 at STP. 2. Which of the following statements describes a chemical property of bromine? (A) bromine is soluble in water (B) bromine changes from a liquid to a gas at 332 K and 1 atm (C) bromine combines with aluminum to produce AlBr 3 (D) bromine has a reddish-brown color 3. A large sample of solid calcium sulfate is crushed into smaller pieces for testing. Which two physical properties are the same for both the large sample and one of the smaller pieces? (A) solubility and volume (B) mass and volume (C) mass and density (D) solubility and density 4. Solid ZnCl 2 and liquid ZnCl 2 have different (A) empirical formulas (B) physical properties (C) ion ratios (D) formula masses Practice Regents Questions Separation of Mixtures 1. Which mixture can be separated by using the equipment shown below? (A) NaCl(aq) and SiO 2(s) (C) CO 2(aq) and NaCl(aq) (B) NaCl(aq) and C 6H 12O 6(aq) (D) CO 2(aq) and C 6H 12O 6(aq) 2. When a mixture of water, sand, and salt is filtered, what passes through the filter paper? (1) water, only (2) water and sand, only (3) water and salt, only (4) water, sand, and salt Page 16

17 3. Which physical property makes it possible to separate the components of crude oil by means of distillation? (1) melting point (2) conductivity (3) solubility (4) boiling point 5. 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 their different boiling points (4) have combined physically and have the same boiling points Practice: Physical vs. Chemical Changes REMEMBER! In a physical change, the original substance still exists, it has only changed form. In a chemical change, a new substance is produced. Energy changes always accompany chemical changes. Classify the following as being a physical or chemical change- a. Sodium hydroxide dissolves in water. b. Hydrochloric acid reacts with potassium hydroxide to produce a salt, water, and heat. c. A pellet of sodium is slice in two. d. Water is heated and changed to steam. e. Potassium chlorate decomposes to potassium chloride and oxygen gas. f. Iron rusts. g. Evaporation h. Ice melting i. Milk sours j. Sugar dissolves in water k. Wood rotting l. Pancakes cooking on a griddle m. Grass growing on a lawn n. A tire is inflated with air Page 17

18 o. Food is digested in the stomach Physical vs. Chemical Properties Classify the following properties as either chemical or physical by putting a check in the appropriate column. 1. blue color 2. density 3. flammability 4. solubility 5. reacts with acid to form hydrogen gas [H2 (g)] 6. supports combustion 7. sour taste 8. melting point 9. reacts with water to form a gas 10. reacts with a base to form water 11. hardness 12. boiling point 13. can neutralize a base 14. luster 15. odor 16. rust 17. freezing point 18. malleability 19. ductility Physical Property Chemical Property Page 18

19 Practice Regents Questions Energy & Temperature 1. Solid A at 80 C is immersed in liquid B at 60 C. Which statement correctly describes the energy changes between A and B? (A) A releases heat and B absorbs heat. (C) Both A and B absorb heat. (B) A absorbs heat and B releases heat. (D) Both A and B release heat. 2. Which change in the temperature of a 1-gram sample of water would cause the greatest increase in the average kinetic energy of its molecules? (A) 1 o C to 10 o C (B) 10 o C to 1 o C (C) 50 o C to 60 o C (D) 60 o C to 50 o C 3. An increase in the average kinetic energy of a sample of copper atoms occurs with an increase in (A) concentration (B) temperature (C) pressure (D) volume 4. The average kinetic energy of water molecules is greatest in which of these samples? (A) 10 g of water at 35 C (C) 10 g of water at 55 C (B) 100 g of water at 25 C (D) 100 g of water at 45 C 5. Which form of energy is converted to thermal energy when propane burns in air? (A) Electromagnetic (B) nuclear (C) electrical (D) chemical Practice Regents Questions Phases of Matter 1. Which 5.0-milliliter sample of NH 3 will take the shape of and completely fill a closed milliliter container? (A) NH 3(s) (B) NH 3(l) (C) NH 3(g) (D) NH 3(aq) 2. Which statement correctly describes a sample of gas confined in a sealed container? (A) It always has a definite volume, and it takes the shape of the container. (B) it takes the shape and the volume of any container in which it is confined. (C) It has a crystalline structure. (D) It consists of particles arranged in a regular geometric pattern. 3. In which material are the particles arranged in a regular geometric pattern? (A) CO 2 (g) (B) NaCl(aq) (C) H 2O(l) (D) C 12H 22O 11(s) 4. Which grouping of the three phases of bromine is listed in order from left to right for increasing distance between bromine molecules? (A) gas, liquid, solid (B) liquid, solid, gas (C) solid, gas, liquid (D) solid, liquid, gas Page 19