This document provides an overview of key chemistry concepts including: 1. Chemistry deals with matter and changes in matter at the macroscopic and microscopic levels. The scientific problem solving process involves stating the problem, formulating a hypothesis, and testing it with experiments. 2. The three states of matter are solids, liquids, and gases which differ in their particle arrangements and ability to change shape or volume. Physical and chemical properties and changes also differ based on whether the chemical composition changes. 3. Common units and measurements in chemistry include the mole, SI units, scientific notation, uncertainty in measurements, and calculating percent error.

2. Chemistry – science that deals with matter and the changes that matter undergoes Macroscopic – all around us Microscopic – air, molecules, etc

3. Scientific Problem Solving 3 Step Process 1. state problem and make observations (qualitative vs. quantitative) 2. formulate a possible solution 3. perform experiments to test hypothesis

4. Theory vs. Law Theory – gives a universally accepted explanation of the problem Law – state what general behavior is observed that occurs normally

5. States of Matter All matter has 2 characteristics Has mass and occupies space 3 types: solid, liquid, gas Solids – definite shape and volume; packed tightly together; vibrate gently around fixed positions Liquids – no shape of own; fill container; definite volume; particles are free to move Gases – no shape or definite volume; particles spread apart; filling all space in container

6. Physical and Chemical Properties and Changes Physical Property: color, odor, density, hardness, solubility, melting point, boiling point Physical Change: chemical composition always remains the same. Ex. Phase changes (2 less known ones are sublimation (solid to gas) and deposition (gas to solid) Chemical Property: reacts with acid, reacts with base, oxidation and reduction Chemical Change: won’t go back to original substance. Ex. combustion

7. E, C, M Element – pure substance that cannot be broken down any further…..single substance from periodic table Compound – pure substance that cannot be broken down by physical means; formed when elements bond together….have fixed composition Mixture – varying composition and is made up of a number of pure substances. Homogeneous – uniform composition Heterogeneous – varying composition

8. Measurement Scientific Notation The number of places the decimal point has moved determines the power of 10 Decimal moves left = positive power Decimal moves right = negative power 42000 = 4.2 x 10 4 0.00012 = 1.2 x 10 -4

9. SI Units and prefixes Base Quantity Unit Symbol Mass Kilogram kg Length Meter m Time Second s Amt. of Substance Mole mol Temperature Kelvin K

10. Prefix Symbol Meaning Giga G 10 9 Mega M 10 6 kilo k 10 3 deci d 10 -1 centi c 10 -2 milli m 10 -3 micro μ 10 -6 nano n 10 -9 pico p 10 -12

11. 3 scales for temperature Celsius Kelvin Fahrenheit Celsius to Kelvin (°C + 273) Kelvin to celsius (K – 273) Celsius to fahrenheit (°C * 9/5) + 32 Fahrenheit to celsius (°F – 32) * 5/9

12. Derived Units All other units can be derived from base quantities Examples: 1. Volume : unit is length 3 Common units are L or mL (how much is a cm 3 ?) 1.00 L = 1000 mL = 1000 cm 3 = 1.00 dm 3 2. Density = mass/volume

13. Uncertainty When reading the scale on a piece of lab equipment, there is always a degree of uncertainty Estimate must be made to record the final digit This “uncertain” digit is recorded by using the +/- scale Rounding – don’t round until the end of a calculation

14. Significant Figures Remember the Atlantic and Pacific rule In Calculations Multiplying and dividing: limit answer to least number of sig figs used Adding and subtracting: limit answer to same number of decimal places that appear in the original data with fewest number of decimal places

15. Accuracy vs. Precision Accuracy – relates to how close the measured value is to the actual value of the quantity Precision – how close 2 or more measurements of the same quantity are to one another

16. Percent Error Data that is derived from experiments will often differ from the accepted, published, actual value Common way of expressing accuracy is: | Actual – Calculated | x 100 Actual