Chapter 3: Matter and Energy Chemistry 1020: Interpretive chemistry Andy Aspaas, Instructor

What are properties? Characteristics of a substance under observation Can be directly observable Indirectly observable: observe the way it interacts with other substances

Matter and energy 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 –Properties of matter –Behavior of matter under influence of other matter and/or energy

Properties of matter Physical properties: characteristics that can be changed without changing the composition of the matter –These are directly observable Chemical properties: determine how the composition of matter changes when matter interacts with other matter or energy –These describe the behavior of matter

States of matter StateShapeVolumeCompressFlow Solid Keeps shape Keeps volume No Liquid Takes shape of container Keeps volume NoYes Gas Takes shape of container Takes volume of container Yes

Changes in matter Physical changes: change the form of a substance but not what it’s made of –State changes –Shape changes –Dissolving Chemical changes: the fundamental components of a substance are changed –A new substance is formed –Chemical reaction takes place

Elements and compounds Element: substance that cannot be broken down into other substances by chemical means –Contains a single type of atom –Ex. Aluminum contains only aluminum atoms Compound: substance consisting of different elements chemically combined together –Can be broken down into pure elements by chemical methods –Ex. Water consists of H 2 O molecules, can be broken down into hydrogen and oxygen

Mixtures and pure substances Mixture: something with variable composition –Coffee can be strong or weak –Can be separated into 2 or more pure substances Pure substance: always has the same composition –Pure water always has the exact same composition

Types of mixtures Homogeneous mixture: the same throughout –Also called a solution –Ex. Air, saltwater, brass Heterogeneous mixture: contains regions with different properties than others –Ex. Sand in water, a casserole

Separation of mixtures Distillation: separation of a solution by boiling one compound away from the other –Purification of seawater Filtration: separation of heterogeneous mixtures by trapping solids in a filter –Purification of sand in water

Energy, temperature, and heat Energy is the capacity to do work Energy can change the temperature of substance –Heat: a flow of energy due to a temperature difference –Heat is transferred from warm areas to cool areas Exothermic process: heat is given off Endothermic process: heat is absorbed

Calculating energy changes Calorie: amount of heat energy required to raise the temperature of 1 g water by 1 °C Joule: SI unit of heat 1 cal = J Specific heat capacity: amount of energy required to raise the temperature of 1 g of any substance by 1°C –Water: J / g °C –Aluminum: 0.89 J / g °C –Gold: 0.13 J / g °C

Specific heat capacity calculations Q = s x m x ΔT –Q = heat energy required –s = specific heat capacity –m = mass of sample in grams –ΔT = change of temperature required in °C