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The Science of Chemistry. Chapter 1, part B. I. What is chemistry?. Deals with the properties of matter Physical states Solid Liquid Gas. Chemical reactions Describe how matter behaves NaOH + HCl H 2 O + NaCl reactants products Energy in reactions
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The Science of Chemistry Chapter 1, part B
I. What is chemistry? • Deals with the properties of matter • Physical states • Solid • Liquid • Gas
Chemical reactions • Describe how matter behaves • NaOH + HCl H2O + NaCl reactants products • Energy in reactions • Endothermic – energy is absorbed, and the reaction feels cold • Exothermic – energy is released, and the reaction feels warm
Properties • Physical – can be observed without changing the substance • Chemical – can only be observed by chemical change • Changes • Physical – does not change the properties of the substance • Chemical – changes the substance both chemically and physically
Signs of chemical change Evolution of a gas Formation of a precipitate The evolution of or absorption of heat The emission of light A color change
II. What is matter? • Anything that has mass and volume • How do mass and weight differ? 1. mass is the amount of material in an object 2. weight is the pull of gravity on the mass of an object.
III. What is the nature of matter? • Atoms • Microscopic particles of which all things are made • It would take nearly 4 million to form a line 1 mm long! • Elements • The more than 110 types of atoms • Each has a unique set of chemical and physical properties
3. Each has a unique symbol a. this symbol may be 1, 2 or 3 letters in length b. the first letter is always capitalized. • Molecules • Two or more atoms combined in a definite ratio • Atoms may be of the same element or different elements • Allotropes • One of a number of different molecular forms of an element Ex. Oxygen: O2 is the oxygen we breathe O3 is ozone, a toxic, pale blue gas
IV. How is matter classified? • Compounds – pure substances composed of atoms of 2 or more different elements • Covalent compounds – smallest particle is a molecule • Ionic compounds – composed of ions • Ion is an atom or group of atoms w/ an electrical charge
3. Acids – a group of compounds w/ certain chemical properties taste sour, turn blue litmus red, have pH < 7, react w/bases to form salts 4. Bases - a group of compounds w/ certain chemical properties (mostly opposite those of an acid) taste bitter and feel slippery, turn red litmus blue, pH > 7, reacts w/ acids to form salts
Organic or inorganic • Organic – contains carbon • Inorganic – does not contain carbon • Formulas • Molecular – C9H8O4 • Shows the #of atoms but not how they’re bonded • Structural – shows the # of atoms and how they’re bonded • Ball and stick – shows geometric arrangement • Space-fill - also shows geometric arrangement and most closely represents the actual shape
Mixtures – a collection of two or more pure substances physically mixed together • Alloy – solid mixture (18-karat gold, bronze) • Homogeneous – components are evenly distributed (a solution is the best example of this type of mixture) • Heterogeneous – components are not evenly distributed
How to distinguish mixtures and compounds • The properties of a mixture maintain properties of the substances of which it is composed. • Compounds often have no resemblance to the elements of which they are composed. • Compounds have a definite composition by mass • Mixtures have varying composition
Science Starter You have 10 bags with 1000 coins each. In one of the bags, all coins are forgeries. A true coin weighs 1 gram; each counterfeit coin weighs 1.1 gram. If you have an accurate scale, which you can use only once, how can you identify the bag with the forgeries? And what if you didn't know how many bags contained counterfeit coins?
