# Fundamentals A - Matter and Energy + Signficant Figures

## Chemistry 1a with Arasasingham, R. at University of California - Irvine *

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- Fundamentals A - Matter and Energy + Signficant Figures

Gianna C.

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Chemical Principles: The Quest for Insight by Atkins and Jones 5th Edition Study Guide by Gigi :) Fundamentals A Matter and Energy Significant Figures Key Concepts: types of properties (physical, chemical, intensive, extensive) the use of density in calculations energy, kinetic and gravitational significant figures the nature of volume the properties and base units of matter Matter ξmatter: anything that has mass and takes up space ξsubstance: a single, pure form of matter ξstates of matter: 1. solid: matter retains shape and does not flow 2. liquid: matter is fluid with a well-defined surface, takes the shape of the container it occupies 3. gas: matter is fluid and fills any vessel containing it 4. vapor: the gaseous form of a substance that is normally solid or liquid (water vapor) Physical Properties ξphysical property: a characteristic of a substance that can be observed or measured without changing the substances' identity 1. melting point 2. boiling point 3. color 4. mass 5. temperature 6. color 7. state (solid, liquid, or gas) 8. density ξphysical change: the identity of the substance does not change, only its physical properties 1. melting 2. freezing 3. boiling 4. crystallization 5. sublimation (from solid directly to gas) 6. deposition (from gas directly to solid Chemical Properties ξchemical property: any of the properties of matter that may only be observed and measured by performing a chemical change or reaction 1. reactivity with other chemicals 2. toxicity 3. flammability ξchemical change: the process by which a substance is transformed into a different substance Physical Quantities: ξSI Units are internationally accepted 1. meter – length 2. kilogram – mass 3. second – time 4. temperature – Kelvin (not “degrees Kelvin”) 5. electric current – ampere 6. amount of substance – mole 7. luminous intensity – candela ξPrefixes: 1. centi – 1/100 (centimeter = 1/100 m) 2. milli – 1/1000 (milliliter = 1/1000 L) 3. kilo – 1000 (kilogram = 1000 g) ξderived units are used to express more complicated properties 1. volume (V) – meters cubed (m^3) 2. density – kilograms/meter^3 3. force – kg x meters/seconds^2 (Netwon N) 4. energy – kg x meters^2/seconds^2 (Joule J) ξCommon unit conversions: 1. 1.000 kilogram = 2.205 lb (pounds) 2. 1.000 pound = 453.6 g (grams) 3. 1.000 ounce = 28.35 g 4. 1 ft = 30.48 cm 5. 3 ft = yard 6. 1.094 yard = 1.000 meter 7. 1.000 km = 0.6214 miles 8. 1 cm = 0.3937 in 9. 1 in = 2.54 cm 10. 1 min = 60 seconds 11. 1 hour = 3600 s 12. 1 day = 86400 s 13. 1 Liter = 10 cm^3 or 1 decimeter^3 (dm^3) ξconversion factor = units required / units given ξinfo required = info given / conversion factor ξExample: 1. Snow White is 5.0 feet tall. How tall is she in centimeters? 1. y is Snow White's height 2. conversion factor: 30.48 cm/1.000 ft 3. y = 5.0 x (30.48 cm / 1.000 ft) 4. y = 152.4 cm 5. Snow White is 152.4 cm tall. ξWhen converting a unit raised to a power (including negative powers), raise the conversion factor to the same power. ξExample: express density of 11600 kilograms/meters^-3 in grams/centimeter^-3 1. 1 kg = 10^3 g and 1 cm = 10^2 m 2. Density = 11600 kg/m^3 x (10^3 g/1 kg) x (1 cm/10^-2 m)^-3 3. 11600 kg/m^3 x (10^3 g/1 kg) x (10^-6 m^3/1cm^3) 1. REMINDER: because the exponent is negative, the numerator and denominator of the expression are switched 4. 11.6 g/cm^3 Intensive and Extensive Properties ξintensive property: a property independent of the size of the sample of a particular substances 1. temperature 2. density 3. hardness 4. melting point 5. boiling point 6. malleability 7. ductility (ability of a solid to deform under tensile stress) 8. viscosity (ability to deform under compressive stress) ξextensive property: a property dependent of the size of a sample 1. energy 2. mass 3. volume 4. weight 5. number of moles 6. electrical charge 7. length ξdensity = mass / volume (d = m/V) ξdensity of a substance is independent of the size of the sample because the ratio of mass to volume remains the same ξIt is usually given in g/cm^3 ξmost properties depend on the state of matter and conditions such as temperature and pressure ξExample: The density of gold is 19.30 g/cm^3 What is the volume occupied by 5.0 g of gold? 1. V = m/d 2. V = 5.0 g/19.30 g/cm^3 3. V = 5.0/19.30 cm^3 4. V = 0.25 cm^3 Significant Figures ξthe number of significant figures is the number of digits in a value that can be justified by the data. ξRules for identifying sig figs: 1. any nonzero digits (1 to 9) are significant (example: 9875 has 4 sig figs) 2. any zeroes (regardless of how many) between two significant digits are significant (200004 has 6 sig figs) 3. any zeroes found to the right of both a significant digit and a decimal place are significant (6.00 has 3 sig figs) ξbe careful: many texts (and teachers) consider numbers such as 500 to be ambiguous examples. How to avoid ambiguous zeroes: 1. use scientific notation (5.00 x 10^2 has 3 sig figs) 2. place a zero after the last zero to show significance (500. shows 3 sig figs) 3. place a bar over the final zero to show significance ξRules for determining number of sig figs in a given operation: 1. Addition and subtraction 1. Answer must show the same number of decimal places as the measurement in the problem with the least number of decimal places 2. Example: 12.3 (3 sig figs) + 1.302938 = 13.6 (3 sig figs) 3. Multiplication and division 1. Answer must show the same number of sig figs as the measurement in the problem with the least number of sig figs 4. Example: 4.333 x 23.4 (3 sig figs) = 101 (3 sig figs) Force ξforce (F): an influence that changes the state of motion of an object. An object accelerates when it experiences a force ξacceleration (a): the rate of change of the velocity of an object ξacceleration is proportional to force ξForce = mass x acceleration or F = ma ξVelocity: rate of change of position, has both magnitude and direction ξspeed (v): the magnitude of the velocity of an object Energy ξenergy: the capacity to do work ξwork: motion against an opposing force ξEnergy = force x distance ξSI unit for energy is the joule (J). ξ1 J = 1 kg x m^2 x s^-2 ξthree kinds of energy – kinetic, potential, and electromagnetic ξKinetic energy: 1. E(k) = ½mv ^2 2. Example: how much energy does it take to accelerate a biker 70 kg to 20 mph (8.9 m/s) in one direction, starting from rest? 3. ½ x 70 kg x (8.9 m/s)^2 4. 2722.35 J 5. to account for sig figs, represent as kJ 6. 2722/1000 = 2.722 kJ 7. to show 2 sig figs, round to 2.7 kJ ξpotential energy: the energy an object has on account of its position in a field of force ξtwo types of potential energy: gravitational and Coulomb 1. gravitational – E(p) = mgh 2. m is mass, g is acceleration of free fall, h is height 3. the greater the altitude of an object, the greater its gravitational potential energy ξCoulomb – to find the potential energy of two charged particles: 1. E= (1/4πε0)(q1q2/r) 2. where “vacuum permitivity” epsilon zero ε0 = 8.854x10-12 C^2/ Jm 3. where C is a “Coulomb”, the SI unit of charge 4. r is distance 5. Q1 and Q2 are charged particles 6. J is joules, m is meters ξTotal energy E = kinetic energy + potential energy Helpful Resources Tutorial on the use of significant figures: http://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.html Potential Energy on UC Davis ChemWiki: http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Pot ential_Energy The Properties of Matter: http://www.files.chem.vt.edu/RVGS/ACT/notes/Properties_of_Matter.html Converting and Canceling Units: http://www.purplemath.com/modules/units.htm Force and Acceleration: www.Neevia.com, Document Converter Pro, Convert to PDF or Image in batches!

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