Introduction and Basic Concepts of Chemistry PDF

Introduction and Basic Concepts of Chemistry Instructor: Dyanne Jane C. Duldulao, RCh., MSc. 1 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes...

Introduction and Basic Concepts of Chemistry Instructor: Dyanne Jane C. Duldulao, RCh., MSc. 1 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes ❏ Basic concepts of energy 2 What is CHEMISTRY? - the study of matter, its properties, changes that matter undergoes, energy associated with those changes - provides a background for understanding the properties of matter in terms of atoms, the almost infinitesimally small building blocks of matter 3 Fundamental Definitions Matter - the physical material of the universe; - it is anything that has mass and occupies space. Property - any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types 4 Fundamental Definitions Atoms - the almost infinitesimally small building blocks of matter Molecules - two or more atoms are joined together in specific shapes Substance - is a form of matter that has a definite (constant) composition and distinct properties 5 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes ❏ Basic concepts of energy 6 Classification of Matter 7 Classification of Matter Element - a substance that cannot be separated into simpler substances by chemical mean Compound - a substance composed of atoms of two or more elements chemically united in fixed proportions Mixture - a combination of two or more substances in which the substances retain their distinct identities. Mixtures do not have constant composition 8 Classification of Matter Homogeneous Mixture - The composition of the mixture is the same throughout - Also called solutions Heterogeneous Mixture - The composition is not uniform 9 Classification of Matter Molecular comparison of elements, compounds, and mixtures. Adapted from Chemistry: the central science (12 th ed.) (page 8), by T. L. Brown et al., 2012, Pearson Education, Inc 10 Activity: Element, Compound or Mixture (Homogeneous or Heterogeneous)? 1. Water - H2O 2. Carbon - C 3. Carbon dioxide - CO2 4. Baking soda 5. Acetic acid 6. Sand 7. Gasoline 8. Air 9. Iron 10. Oxygen - O2 11 States of Matter The three states of matter. Adapted from Chemistry: the molecular nature of matter and change (5 th ed.) (page 7), by M. S. Silberberg, 2009, McGraw-Hill 12 States of Matter 13 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes ❏ Basic concepts of energy 14 Properties of Matter Physical properties - can be observed without changing the identity and composition of the substance. These properties include color, odor, density, melting point, boiling point, and hardness Chemical properties - describe the way a substance may change, or react, to form other substances. A common chemical property is flammability, the ability of a substance to burn in the presence of oxygen. 15 Properties of Matter 16 Properties of Matter Intensive properties - They do not depend on the amount of sample being examined and are particularly useful in chemistry because many intensive properties can be used to identify substances (temperature and melting pt) Extensive properties - depend on the amount of sample, with two examples being mass and volume. Extensive properties relate to the amount of substance present. 17 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes ❏ Basic concepts of energy 18 Changes of Matter 19 Changes of Matter Physical change - substance changes its physical appearance but not its composition. All changes of state (for example, from liquid to gas or from liquid to solid) are physical changes Chemical change - also called a chemical reaction - substance is transformed into a chemically different substance. When hydrogen burns in air, for example, it undergoes a chemical change because it combines with oxygen to form water 20 Activity: Physical or Chemical Change (a) Frost forms as the temperature drops on a humid winter night. (b) A cornstalk grows from a seed that is watered and fertilized. (c) A match ignites to form ash and a mixture of gases. (d) Perspiration evaporates when you relax after jogging. (e) A silver fork tarnishes slowly in air. 21 Outline ❏ Fundamental definitions ❏ Classification of matter ❏ Physical and chemical properties ❏ Physical and chemical changes ❏ Basic concepts of energy 22 Energy - physical and chemical changes are accompanied by energy - often defined as the ability to do work - total energy an object possesses is the sum of its potential energy and its kinetic energy Potential energy - the energy due to the position of the object Kinetic energy - the energy due to the motion of the object 23 Energy Total Energy = Potential Energy + Kinetic Energy - Lower energy states are more stable and are favored over higher energy states. - Energy is neither created nor destroyed - it is conserved - and can be converted from one form to another 24 Potential Energy is Converted to Kinetic Energy - A gravitational system. The potential energy gained when a weight is lifted is converted to kinetic energy as the weight falls. - A lower energy state is more stable. 25 Potential Energy is Converted to Kinetic Energy (2) - A system of two balls attached by a spring. The potential energy gained by a stretched spring is converted to kinetic energy when the moving balls are released. - Energy is conserved when it is transformed 26 Potential Energy is Converted to Kinetic Energy (2) - A system of oppositely charged particles. The potential energy gained when the charges are separated is converted to kinetic energy as the attraction pulls these charges together. 27 Potential Energy is Converted to Kinetic Energy (2) - A system of fuel and exhaust. A fuel is higher in chemical potential energy than the exhaust. As the fuel burns, some of its potential energy is converted to the kinetic energy of the moving car. 28 References 29 Thank you! -end of discussion- 30