What is Chemistry? Chemistry is the study of the structure, function, and properties of matter and the changes it undergoes.
What are Chemicals? Chemicals are substances with a definite composition.
Matter and its Properties Matter is anything that has mass and volume. Example: A piece of chalk has matter but sunlight does not.
An element is a pure substance made of only one kind of atom. Example: Gold, Silver, Sodium, Fluorine
An atom is the smallest particle of a chemical element that retains its properties.
Compounds are substances composed of atoms of two or more elements chemically bonded in a specific ratio. Example: Water is always H2O.
A molecule is the smallest particle of a chemical compound that retains its properties. Example: A sample of methane is composed of CH4 molecules.
Properties are characteristics of matter that can be observed. Example: Water boils at 1000C and vinegar reacts with baking soda to form carbon dioxide.
Physical propertiescan be observed without changing the composition of the substance. Example: Boiling point, Odor, and Density
Solids • Have a shape that does not change • Cannot be squashed • Do not flow
Solids • Low energy • Particles vibrate • Close together • Regular pattern
Liquids • Take the shape of the container • Cannot be squashed • Can flow
Liquids • Medium energy • Move around • Close together • Not a regular pattern
Gases • Fill the container they are in • Have a volume that can change • Can be squashed • Can flow
Gases • High energy • Move fast • Far apart • Irregular arrangement
song Video Shape of container Fills container Fixed Fixed Fixed Changes No No Yes
No shape, fills containers Definite size, takes shape of container Definite High Medium Low Difficult to squash Changes shape, difficult to squash Easy to squash Streamlined shapes move through easily Things move through easily No
Plasmais a high energy state in which electrons have been knocked off the atoms. Example: Plasma is found in fluorescent light tubes and in the sun.
Physical changesdo not change the identity of the substance. Example: Cutting a board in half is a physical change.
A chemical change usually involves a chemical reaction taking place.
S.I. Base Units The International System (S.I.) is a set of standard unit of measurement for scientists throughout the world.
S.I. prefixesare added to the base units to increase or decrease their value by powers of 10.
Example: 546 µm = .000546 m Example: 0.56 L = 560 ml Example: 1000 g = 1 kg Converting within a specific quantity requires moving the decimal place.
The Metric Number Line We are mostly interested in measurements from the kilo to milli – region of the number line. Use a device to help you remember the order of the prefixes. Kind Hearted Dads Make Dark Chocolate Milk
Mass is a measure of the quantity of matter in an object. Massdoes not change with location. The unit used for mass is the gram (g). The instrument we use to measure mass is a balance.
Weight is a measure of the force of gravity between objects. Weight will vary with location and the unit of measure for weightis the Newton (N). The instrument we use to measure weight is the spring scale.
Length is the distance covered by an object. Unit of measure for lengthis the meter (m). The instrument used to measure length is a ruler, meter stick, etc.
Temperature is a measure of the average kinetic energy of the particles in a sample of matter. The units that can be used for temperature are Kevin (K) or Celsius (0C). The instrument used to measure temperature is the thermometer.
Kinetic energy is the energy an object has due to its motion. Gas molecules move faster than the molecules in solids and liquids, and therefore, have more kinetic energy. Gas molecules Liquid molecules Solid Molecules
Heat is the energy transferred as a result of a temperature difference. Left undisturbed, energy will flow from objects of high temperature to objects of low temperature until the objects have equal temperature. Unit – Joules (J) or Calories (cal) 1 cal – 4.184 J 1000 cal = 1 kcal also called 1 food Calorie
A calorimeter is the Instrument used to measure energy.
Volume is the amount of space occupied by an object. cubic m (m3) = length X length X lengthUnit = cubic centimeter (cm3) = 1 milliliter (mL)The instrument we use most often to measure volume is the graduated cylinder.
Accuracy is how close a measurement is to the actual(accepted) value. Example: Your watch is accurate if it is close to the time kept by the National Institute of Standards and Technology (N.I.S.T.)
Precision is how close a set of measurements are to each other. Example: A field goal kicker is precise if he kicks the ball through the goal posts every time.
Significant Figures or Digits The number of reliable digits in a measurement based on accuracy of the measuring instrument. The last digit in the number may be an estimated one.
Rules for Significant Digits Digits other than zero are significant. Example: 947.3 - 4 significant figures 2. Zeros between other significant digits are significant. The oreo effect! 20,047 has 5 significant figures Leading zeros are NEVER significant. Put numbers with leading zeros into scientific notation Ending zeros are significant if the decimal point is expressd. 500.0 4 sig. fig.
Rule 1: All nonzero digits are significant (they were measured) • Samples • a. 234 m • b. 1678 cm • c. 0.23 g • SD’s and precision • a. 3 sd to the m • b. 4 sd to the cm • c. 2 sd to the g
Rule 2: All zeros between nonzero (or significant) digits are significant Translation: In between 0s must be measured • Samples • a. 202 mm • b. 1003 cm • c. 0.200105 m • SD’s and precision • a. 3 sd to the mm • b. 4 sd to the cm • c. 6 sd to the mm
Rule 3: Zeros to the right of a nonzero digit but to the left of an understood decimal are NOT significant unless otherwise indicated. Translation: 0s at the end of a whole number are NOT measured unless marked. • a. 200 cm • b. 109,000 m • c. 1,000,000 mm • d. 200 cm • e. 200 cm • a. 1 sd to the m • b. 3 sd to the km • c. 1 sd to the km • d. 3 sd to the cm • e. 2 sd to the dm (a bar over a zero indicates the last measured zero)
Significant figures in a measurement include • all of the digits that are known precisely • plus one last digit that is estimated.
2. Non-zero digits are always significant. 103.230002
4. Zeros between two other significant digits are always significant. 10.0 2004 6.000