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Chapter 1

Chapter 1.docx

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Lydia W.L.Chen

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Chapter 1: Chemistry the Study for Change Chemistry: The study of matter and the changes it undergoes. Macroscopic World: The things we can see touch and measure directly o Ex: desk, chairs, phone,… Microscopic World: The things we cannot see or experience without modern technology o Ex: atoms, molecules,… 1.3 – The Scientific Method Scientific Method:Asystematic approach used when researching. • Define the problem o What is it that you are trying to determine? • Then, perform an experiment. Make observations, and record data about the system. o Data obtained from the system may be qualitative or quantitative. o Qualitative data includes general observations of the system. Quantitative data includes the numbers obtained from measurements of the system. • Generate a hypothesis and perform tests to check the validity of the hypothesis. o Ahypothesis is a set of explanations for the observations and data obtained in the experiment. • If the hypothesis is not valid, more experiments are performed. However, if it is valid, the hypothesis can develop into a law or theory. o Alaw is a verbal/mathematical statement of a relationship that stays the same under the same conditions. (Ex: F = ma) o Atheory is a principle that can be used to explain multiple facts and/or laws. 1.4 – Classifications of Matter • Matter is anything that has mass and volume. • Its main classifications are substances, mixtures, elements and compounds. Substances and Mixtures • Asubstance is a form of matter that has uniform composition and definite properties. o Ex: H O, NH , C H O ,Ag and O . 2 3 6 12 6 2 • Substances with different compositions have different properties. • Amixture is a combination of two or more substances in which the substances retain their properties. o Ahomogeneous mixture has uniform composition (ex. NaCl dissolved in H O). 2 o Aheterogeneous mixture does not have uniform composition (ex. a mixture of sand and iron fillings). • Any mixture can be separated back into the original substances that made it through physical means. o Ex: Salt water can be heated until the water evaporates, leaving the salt behind. This separates the mixture into salt and water. Elements and Compounds • An element is a substance that cannot be separated into simpler substances by chemical means. o Al, Cu, Hg,… • Acompound is a substance composed of atoms from more than one element chemically bonded in specific proportions. o Ex: H 2, HCl, NaCl,… • Compounds can be separated into the substances that made them by chemical means. 1.5 – The Three States of Matter • All matter exists as a solid, liquid, or gas. o In a solid, the molecules are held very close to one another in highly ordered arrangement. They have very little freedom of motion. o In a liquid, the molecules are close to one another. However, they are not held rigidly in place and can slide past one another. o In a gas, the molecules are very far apart from one another and can move freely. • In water, the molecules in liquid state are closer than that in a solid state (ice is less dense than liquid water). o This is because there are large empty spaces when water molecules are strongly bonded to one another in solid state. These empty spaces are not present between the molecules in the liquid state. 1.6 – Physical and Chemical Properties of Matter • Physical properties can be observed without changing the chemical composition of a substance o Ex: boiling point, melting point, colour, temperature, …. • Chemical properties are observed by changing the chemical composition of a substance. o Ex: Formation of water from hydrogen gas and oxygen gas. • The measured value of an extensive property depends on the amount of matter o Ex. of Extensive Properties: mass, volume,….. o The more matter, the greater the mass and volume. o Values of the same extensive property can be added. • The measured value of an intensive property does not depend on the amount of matter o Ex. of Intensive Properties: density, temperature,….. o Density and temperature do not increase if more matter is being considered. o Values of the same extensive property cannot be added. 1.7 – Measurement • Macroscopic properties can be measured by using a variety of instruments. o The buret, pipet, graduated cylinder and volumetric flask all measure volume. o The balance measures mass. o The thermometer measures temperature. • Units must be provided when stating measurements. • Measurements can be stated in metric units or SI units (International System of Units). o The SI system is a revised form of the metric system SI Base Units Base Quantity Name of Unit Symbol Length Meter m Mass Kilogram kg Time Second s Electrical Current Ampere A Temperature Kelvin K Amount of substance Mole mol Luminous Intensity Candela cd Prefixes Used with SI Units Prefix Symbol Meaning 12 tera- T 10 giga- G 109 mega- M
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