Matter and Energy. Introductory Chemistry: A Foundation FOURTH EDITION by Steven S. Zumdahl University of Illinois. Properties. Universe Classified

Transcription

1 Introductory Chemistry: A Foundation FOURTH EDITION by Steven S. Zumdahl University of Illinois Matter and Energy Chapter Properties Universe Classified Characteristics of the substance under observation Properties can be either directly observable or the manner something interacts with other substances in the universe Matter is the part of the universe that has mass and volume Energy is the part of the universe that has the ability to do work Chemistry is the study of matter The properties of different types of matter The way matter behaves when influenced by other matter and/or energy 3 4 Properties of Matter Physical Properties are the characteristics of matter that can be changed without changing its composition Characteristics that are directly observable Chemical Properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy Characteristics that describe the behavior of matter Classify Each of the following as Physical or Chemical Properties The boiling point of ethyl alcohol is 78 C. Diamond is very hard. 5 6

2 Classify Each of the following as Physical or Chemical Properties The boiling point of ethyl alcohol is 78 C. Physical property describes inherent characteristic of alcohol boiling point Diamond is very hard. Physical property describes inherent characteristic of diamond hardness Chemical property describes behavior of sugar forming a new substance (ethyl alcohol) solid, liquid, gas States of Matter State Shape Volume Compress Flow Solid Liquid Gas Keeps Shape Keeps Volume Takes Keeps Shape of Volume Container Takes Takes Shape of Volume of Container Container No No Yes No Yes Yes 7 8 Figure 3.1: Liquid water takes the shape of its container Figure 3.2: The three states of water 9 10 Changes in Matter Figure 3.3: Electrolysis Physical Changes are changes to matter that do not result in a change the fundamental components that make that substance State Changes boiling, melting, condensing Chemical Changes involve a change in the fundamental components of the substance Produce a new substance Chemical reaction Reactants Products 11 12

3 Classify Each of the following as Physical or Chemical Changes Classify Each of the following as Physical or Chemical Changes Iron metal is melted. Iron combines with oxygen to form rust. Iron is melted. Physical change describes a state change, but the material is still iron Iron combines with oxygen to form rust.. Chemical change describes how iron and oxygen react to make a new substance, rust Chemical change describes how sugar forms a new substance (ethyl alcohol) Elements and Compounds Classification of Matter Matter Substances which can not be broken down into simpler substances by chemical reactions are called elements Most substances are chemical combinations of elements. These are called compounds. Compounds are made of elements Compounds can be broken down into elements Properties of the compound not related to the properties of the elements that compose it Same chemical composition at all times Pure Substance Constant Composition Homogeneous Mixture Variable Composition Homogeneous = uniform throughout, appears to be one thing pure substances solutions (homogeneous mixtures) Heterogeneous = non-uniform, contains regions with different properties than other regions Figure 3.4: Table salt is stirred into water (left), forming a homogeneous mixture called a solution (right) Figure 3.5: Sand and water do not mix to form a uniform mixture 17 18

4 Pure Substances vs. Mixtures Pure Substances All samples have the same physical and chemical properties Constant Composition all samples have the same composition Homogeneous Separate into components based on chemical properties Mixtures Different samples may show different properties Variable composition Homogeneous or Heterogeneous Separate into components based on physical properties All mixtures are made of pure substances Identity Each of the following as a Pure Substance, Homogeneous Mixture or Heterogeneous Mixture Gasoline A stream with gravel on the bottom Copper metal Identity Each of the following as a Pure Substance, Homogeneous Mixture or Heterogeneous Mixture Gasoline a homogenous mixture A stream with gravel on the bottom a heterogeneous mixture Copper metal A pure substance (all elements are pure substances) Separation of Mixtures Separate mixtures based on different physical properties of the components Physical change Different Physical Property Boiling Point State of Matter (solid/liquid/gas) Adherence to a Surface Volatility Technique Distillation Filtration Chromatography Evaporation Figure 3.6: Distillation of a solution consisting of salt dissolved in water Figure 3.7: No chemical change occurs when salt water is distilled 23 24

5 Figure 3.8: Filtration separates a liquid from a solid Figure 3.9: Separation of a sand-saltwater mixture Figure 3.10: The organization of matter Energy and Energy Changes Capacity to do work chemical, mechanical, thermal, electrical, radiant, sound, nuclear Energy may affect matter e.g. raise its temperature, eventually causing a state change All physical changes and chemical changes involve energy changes Figure 3.11: In ice, the water molecules vibrate randomly about their positions in the solid Units of Energy One calorie is the amount of energy needed to raise the temperature of one gram of water by 1 C kcal = energy needed to raise the temperature of 1000 g of water 1 C joule = 1 cal In nutrition, calories are capitalized 1 Cal = 1 kcal 29 30

6 Example - Converting Calories to oules Convert 60.1 cal to joules 1cal = joules 60.1cal cal = 251 Energy and the Temperature of Matter The amount the temperature of an object increases depends on the amount of heat added (Q). If you double the added heat energy the temperature will increase twice as much. The amount the temperature of an object increases depends on its mass If you double the mass it will take twice as much heat energy to raise the temperature the same amount Specific Heat Capacity Specific Heat (s) is the amount of energy required to raise the temperature of one gram of a substance by one Celsius degree By definition, the specific heat of water is g C Amount of Heat = Specific Heat x Mass x Temperature Change Q = s x m x T 33 Example Calculate the amount of heat energy (in joules) needed to raise the temperature of 7.40 g of water from 29.0 C to 46.0 C Specific Heat of Water = g- C C Mass = 7.40 g Temperature Change = 46.0 C 29.0 C = 17.0 C Q = s x m x T Heat = g 17.0 C = 526 g C 34 Example A 1.6 g sample of metal that appears to be gold requires 5.8 to raise the temperature from 23 C to 41 C. Is the metal pure gold? Q = s m T Q s = m T T = 41 C - 23 C = 18 C 5.8 s = = g x 18 C g C Table 3.2 lists the specific heat of gold as 0.13 g C Therefore the metal cannot be pure gold. 35