Chapter 3: Matter and Energy

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

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

3. 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

4. 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

5. States of matter

6. 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

7. 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 H2O molecules, can be broken down into hydrogen and oxygen

8. 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

9. 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

10. 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

11. 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

12. 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 = 4.184 J • Specific heat capacity: amount of energy required to raise the temperature of 1 g of any substance by 1°C • Water: 4.184 J / g °C • Aluminum: 0.89 J / g °C • Gold: 0.13 J / g °C

13. 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