Matter and Energy. Chapter 3

Transcription

1 Matter and Energy Chapter 3

2 Matter Anything that has mass and takes up space Two categories Pure substances Mixtures

3 Pure Substances Matter with a fixed composition Either an element or compound Element - only one type of atom Compound - two or more elements chemically combined

4 Mixtures Two or more different substances are physically mixed Can vary the composition Two types Homogeneous Heterogeneous

5 Classification of Matter

6 Classification of Matter Practice 1. Classify as a mixture or pure substance: a. soft drink b. propane [C 3 H 8 ] c. cheese sandwich d. iron [Fe] nail e. salt substitute [KCl]

7 Classification of Matter Practice 2. Classify each of the following mixtures as homogeneous or heterogeneous: a. nonfat milk b. chocolate-chip ice cream c. gasoline d. peanut butter sandwich e. cranberry juice

8 States of Matter 1. Solid 2. Liquid 3. Gas

9 Physical Properties and Changes Physical property Characteristics that can be observed or measured without affecting the identity Examples: Physical change State or appearance changes, but the composition does not Examples:

10 Chemical Properties and Changes Chemical property Describe the ability of a substance to change into a new substance Examples: Chemical change Original substance is changed into new substance Examples:

11 Properties of Matter Practice 1. Describe each of the following properties as physical or chemical: a. neon is a color gas at room temperature b. apple slices turn brown when exposed to air c. phosphorus will ignite when exposed to air d. at room temperature, mercury is a liquid e. propane gas is compressed to a liquid for placement in small cylinder.

12 HOMEWORK page , 3.3, 3.5 page , 3.9, 3.11, 3.13

13 Temperature

14 Temperature Conversions T F = 1.8(T C ) + 32 T c = (T F - 32) / 1.8 T K = T C + 273

15 Temperature Practice 1. Make the following temperature conversions: a o C to o F b. -27 o C to K c. 15 o F to o C d o F to o C e. 224 K to o C

16 Energy Ability to do work Classified as: Kinetic energy Potential energy

17 Heat Energy associated with the motion of particles Flows from object with higher temperature to object with lower temperature Units Joule (J) calorie (cal) 1 cal = J

18 HOMEWORK page page , 3.27 Lab 3 Pre-Lab

19 Specific Heat All substances have own ability to absorb heat Definition: amount of heat required to change the temperature of exactly 1 g of the substance by exactly 1 o C

20 Heat Equation

21 Specific Heat Practice 1. Determine the amount of energy, in joules, required to heat 25.0 g of water from 12.5 o C to 25.7 o C. The specific heat of water is J/g o C.

22 Specific Heat Practice 2. Calculate the specific heat for tin if a 18.5 g sample of the element absorbs 183 J as it increases in temperature from 35.0 o C to 78.6 o C.

23 Specific Heat Practice 3. Calculate the change in temperature for 115 g of copper that loses 2.45 kj. The specific heat of copper is J/g o C

24 HOMEWORK page , 3.33, 3.37, 3.41

25 Atoms and Elements Chapter 4

26 The Periodic Table

27 The Periodic Table Family/Group Vertical column Elements in a family have similar chemical properties Period Horizontal row Physical and chemical properties change somewhat regularly across a period.

28 The Periodic Table Names of Different Groups: Group 1: Alkali Metals Group 2: Alkaline Earth Metals Group 17: Halogens Group 18: Noble Gases Groups 1-2, 13-18: Representative Elements Groups 3-12: Transition Metals

29 The Periodic Table Types of Elements Metals Mostly shiny solids [Hg is only liquid] Good conductors of heat/electricity Ductile and Malleable Left side of periodic table

30 The Periodic Table Types of Elements [cont d] Nonmetals Dull in appearance Not conductive Low melting points Low densities Right side Metalloids Characteristics of both Zigzag down middle B, Si, Ge, As, Sb, Te, Po, At

31 HOMEWORK page , 4.9, 4.13

32 The History of the Atom Aristotle vs Democritus BC

33 The History of the Atom John Dalton 1808 Atomic Theory All matter is composed of tiny particles called atoms All atoms of a given element are the same; atoms of different elements are different Atoms of two or more elements combine to form compounds A chemical reaction involves the rearrangement, separation or combination of atoms

34 Modern Atomic Theory Not all aspects of Dalton s theory have proven to be correct. Atoms are divisible into smaller particles. A given element can have atoms with different masses Some remain unchanged: All matter is composed of atoms. Atoms of any one element differ in properties from atoms of another element.

35 Structure of the Atom Atom Smallest part of an element that retains the chemical properties of that element. Two regions: 1. The nucleus: a very small region located at the center of the atom 2. The large region surrounding the nucleus

36 Subatomic Particles Electron Negatively charged In the region surrounding the nucleus Proton Positively charged In the nucleus Neutrons Neutral charge In the nucleus

37 Discovery of the Electron J.J. Thomson 1897 Studied cathode rays Called the particles electrons Measured charge to mass ratio of an electron Plum pudding model of the atom

38 Discovery of the Nucleus Ernest Rutherford Gold Foil Experiment Shot alpha particles at thin gold foil Results Most passed through Some deflected at sharp angles Conclusions Atom mostly empty space Nucleus - dense, small, positive

39

40

41 Mass of the Atom Atoms are so small, scientists use a unit called atomic mass unit to talk about their masses 1 amu = 1.66 x g

42 HOMEWORK

43 Atomic Number Specific for each element Same for all atoms of an element Equal to the number of protons in an atom

44 Mass Number Represents the number of subatomic particles in the nucleus Equal to the sum of protons and neutrons Not found on the periodic table

45 Atomic Number and Mass Number Practice 1. An atom of zinc has a mass number of 65. a. How many protons are in a zinc atom? b. How many neutrons are in a zinc atom? c. What is the mass number of a zinc atom that has 37 neutrons? 2. An atom has 14 protons and 20 neutrons. a. What is its atomic number? b. What is its mass number? c. What is this element?

46 Isotopes Atoms of the same element that have different masses Have same number of protons Differ in number of neutrons

47 Isotopes Hyphen notation Mass number is written after the name of the element Hydrogen-3 Carbon-14 Oxygen-18 Nuclear symbol Superscript is the mass number; subscript is the atomic number

48 Isotopes Practice 1. What are the number of protons, neutrons, and electrons in the following isotopes? Then give the symbol notation each. a. strontium-89 b. chromium-52 c. sulfur-34 d. bromine-81

49 HOMEWORK Giant chart

50 Average Atomic Mass Gives the mass of an average atom of each element compared to C-12. Not the same as the mass number. Calculated using a weighted average.

51 Average Atomic Mass

52 Average Atomic Mass Average Atomic Mass Equation: Avg mass = (abundance of isotope 1) x (mass of isotope 1) + (abundance of isotope 2) x (mass of isotope 2)+

53 Average Atomic Mass Examples 1. The atomic mass of chlorine is amu. Based on this information, which of the isotope of chlorine is more abundant - chlorine-35 or chlorine-37?

54 Average Atomic Mass Examples 2. Copper consists of 69.15% copper-63, which has an atomic mass of amu, and 30.85% copper-65, which has an atomic mass of amu. Calculate the average atomic mass of Copper to two decimal places.

55 Average Atomic Mass Examples 3. Three isotopes of argon occur in nature. Calculate the average atomic mass of argon to two decimal places, given the following relative atomic masses and abundances of each of the isotopes: argon-36 (35.97 amu; 0.337%), argon-38 (37.96 amu; 0.063%), and argon-40 (39.96 amu; %).

56 HOMEWORK page , 4.35, 4.40, 4.41, 4.42, 4.43, 4.44