The Science of Chemistry

Chapter 1, part B

I. What is chemistry?

A. Deals with the properties of matterB. Physical states

1. Solid2. Liquid3. Gas

C. Chemical reactions1. Describe how matter behaves

1. NaOH + HCl H2O + NaCl

reactants products2. Energy in reactions

1. Endothermic – energy is absorbed, and the reaction feels cold

2. Exothermic – energy is released, and the reaction feels warm

D. Properties1. Physical – can be observed without

changing the substance2. Chemical – can only be observed by

chemical change

E. Changes1. Physical – does not change the

properties of the substance2. Chemical – changes the substance

both chemically and physically

Signs of chemical change

1. Evolution of a gas 2. Formation of a precipitate 3. The evolution of or absorption of

heat 4. The emission of light5. A color change

II. What is matter?

A. Anything that has mass and volumeB. How do mass and weight differ?

1. mass is the amount of material in an object2. weight is the pull of gravity on the mass of an object.

III. What is the nature of matter?

A. Atoms1. Microscopic particles of which all

things are made2. It would take nearly 4 million to form

a line 1 mm long!

B. Elements1. The more than 110 types of atoms2. Each has a unique set of chemical and

physical properties

3. Each has a unique symbola. this symbol may be 1, 2 or 3

letters in lengthb. the first letter is always

capitalized.C. Molecules

1. Two or more atoms combined in a definite ratio

2. Atoms may be of the same element or different elements

D. Allotropes1. One of a number of different

molecular forms of an elementEx. Oxygen: O2 is the oxygen we breathe

O3 is ozone, a toxic, pale blue gas

IV. How is matter classified?

A. Compounds – pure substances composed of atoms of 2 or more different elements

1. Covalent compounds – smallest particle is a molecule

2. Ionic compounds – composed of ions1. 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

B. Organic or inorganic1. Organic – contains carbon2. Inorganic – does not contain carbon

C. Formulas1. Molecular – C9H8O4

a. Shows the #of atoms but not how they’re bonded

2. Structural – shows the # of atoms and how they’re bonded

3. Ball and stick – shows geometric arrangement

4. Space-fill - also shows geometric arrangement and most closely represents the actual shape

Formulas

structural

Ball and stick

Space-fill

molecular

D. Mixtures – a collection of two or more pure substances physically mixed together

1. Alloy – solid mixture (18-karat gold, bronze)

2. Homogeneous – components are evenly distributed (a solution is the best example of this type of mixture)

3. Heterogeneous – components are not evenly distributed

Matter

Pure Substance

Element Compound

Mixture

Homogeneous

Alloy Solution

Heterogeneous

E. How to distinguish mixtures and compounds

A. The properties of a mixture maintain properties of the substances of which it is composed.

B. Compounds often have no resemblance to the elements of which they are composed.

C. Compounds have a definite composition by mass

D. Mixtures have varying composition

Mixtures

Homogeneous

Components are evenly distributed

Properties are the same

throughout

Heterogeneous

Components are NOT

evenly distributed

Properties are NOT the same

throughout

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?