W2: Chemical Principles Lecture (8/29-8/31-9/02)
W2: Chemical Principles Lecture (8/29-8/31-9/02) sch 100 01
Seton Hill University
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This 4 page Class Notes was uploaded by Olivia Lange on Monday September 12, 2016. The Class Notes belongs to sch 100 01 at Seton Hill University taught by Professor Flowers in Fall 2016. Since its upload, it has received 16 views. For similar materials see Chemical Principles in Chemistry at Seton Hill University.
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Date Created: 09/12/16
● SI units are related to metric units, with a few differences. ○ Metric unit of mass is the gram (g) ○ Metric unit of volume is the liter (L) rather than cubic meter (1L = 1/1000 ○ Metric unit of temperature is Celsius ( degrees C ) rather than Kelvin. ● Derived units: ○ Speed: meters per second (m/s) ○ Density: grams per cubic centimeter (g/cm^3) ● 1.7 Physical Quantities graph Measuring Mass, Length, Volume ● Mass amount of matter in an object ● Weight a measure of gravitational force that the earth or other large body exerts on an object. ● The mass of an object can be determined by comparing the weight of the object to the weight of a known reference standard. 1.8 Units of Mass graph (Table 1.7) ● The meter is the standard measure of length or distance, in the SI and metric systems. ● Volume amount of space occupied by an object ● SI unit for volume cubic meter, m^3 ● So large that the liter (1 L = 0.001 m^3 = 1 dm^3) is more commonly used. Significant Figures the number of meaningful digits used to express a value. Experimental Measurements Recorded Value 54.07 g, 7 is uncertain, a mass between 54.06 and 54. 08 (+/ 0.01 g) Rules for significant figures Rule 1: zeros in the middle of a number are like any other digit; always significant Rule 2: zeros at the beginning of a number are not significant; act only to locate the decimal point. Scientific notation a number expressed as the product of a number between 1 and 10, times 10 raised to a power. 215 = 2.15 x 100 = 2.15 x (10 x 10) = 2.15 x 10^2 The exponent on the 10 tells how many places the decimal point was moved to position just after the first digit. For a number smaller than 1, the decimal point is moved to the right until it follows the first digit. The number of places moved is the negative exponent of 10. 0.000 000 015 6 = 1.56 x 10^ 10 1.11 Rounding Off Numbers A procedure used for deleting nonsignificant figures. Rule 1: Multiplication or division answer cannot have more significant figures than the original numbers. Rule 2: Addition or subtraction answer cannot have more digits after the decimal point than the original numbers. 1.12 Problem Solving: Unit Conversions and Estimating Answers Calculations involving different units: Factorlabel method: Problem solving procedure Equations are set up so that unwanted units cancel and only the desired units remain. Conversion factor: Expression of the numerical relationship between two units. Conversion factors are numerically equal to one. Units are treated like numbers and can thus be multiplied and divided. Think through a rough estimate, or ballpark estimate your work. Steps 1, 2, 3, 4 and ballpark check graph in book. 1.13 Temperature, Heat, and Energy Energy the capacity to do work or supply heat. Temperature the measure of the amount of heat energy in an object. Commonly reported either in Fahrenheit (*F) or Celsius (*C) units SI unit for temp. Is the kelvin (K). Not “degrees Kelvin”. The kelvin and the Celsius degree are the same size. Change in temp. Of 1*C is equal to a change of 1 K. Celsius scale assigns a value of 0 *C to the freezing point of water. Kelvin scale assigns a value of 0 K to the coldest possible temperature, absolute zero, 273.15 *C 0 K = 273.15 *C and +273.15K = 0 *C. Fahrenheit scale defines freeing point of water as 32 *F and the boiling point of water as 212 *F It takes 180 Fahrenheit degrees to cover the same range encompassed by 100 Celsius degrees. A change in temp. Of 1.0 *C is equal to a change of 1.8 *F. TemperatureSensitive Materials Thermochromic materials change color as their temperature changes. These “liquid crystals” can be incorporated into plastics or paints, and can be used to monitor the temperature of the products or packages in which they are incorporated. SI units for energy is joules (J) Metric unit calorie (cal) is still widely used. A kilocalorie (kcal), called a large calorie (Cal) or food calorie by nutritionists, equals 1000 cal. 1.13 Temp, heat, energy One calorie Raises the temp. of 1 g of water by 1 *C Raises the temp. of 1 g of iron by 10 *C The amount of heat needed to raise the temp. of 1 g of a substance by 1 *C is called specific heat. Knowing the mass and specific heat of a substance makes it possible to calculate how much heat must be added or removed to accomplish a given temperature change. 1.14 Density and Specific Gravity Density is the physical property that relates the mass of an object to its volume; mass per unit volume. Most substances contract when cooled, and expand when heated. Water expands when it freezes, so ice floats on liquid water. Specific Gravity Density of a substance divided by the density of water at the same temperature. At normal temps/ room temperature... Density of water is very close to 1 g/mL Specific gravity of a substance is numerically equal to its density.
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