Matter, Energy and Measurement Bettelheim, Brown, Campbell and Farrell Chapter 1

Introductory Material Definitions Review of basic ideas and skills Some examples and practice problems

Matter: Anything that has mass and takes up space (has volume) –Mass: measure of amount of matter Does not change with location –Weight: measure of pull of gravity on matter Can change with location

Chemistry is the science that deals with matter: the structure and properties of matter and the transformations of matter from one form to another –Chemical change: Matter changes its identity (formula) Also called chemical reaction Old substances used up and new ones formed –Physical change: Matter keeps its identity Ex: Dissolving substance or changing state (phase) between solid, liquid and gas

Scientific Method Law is summary of observations Theory explains those observations –Hypothesis is preliminary statement of theory) –Model uses pictures or everyday objects to explain observation –Always subject to revision as needed

Exponential (Scientific Notation) Used to represent very big or very small numbers – uses “powers of 10” Examples –Large number:1234 = x 10 3 (positive exponent) –Small number: = 4.56 x (negative exponent)

Write the following in exponential form:

Write the following in decimal form 1.4 x x 10 3

Significant Digits (Figures) Can only have as many digits in measurement as can be read with measuring device –Last digit is “uncertain” (estimated) Calculations can only have number of digits justified by measurements See Appendix II to review rules for sig figs

Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit.

How many sig figs are there in: 1.The number The number The product of 12.2 x The sum of The sum of 1.2 x x 10 -2

Table 1.1, p.7

Table 1.2, p.8

Metric System Unit Prefixes

Conversions factors between English and Metric Systems Taken from Table 1.3, BBM

Table 1.3, p.8

Unit Conversions Factor-Label Method Conversion factorConversion factor –Ratio, including units, used as a multiplier to change from one system or unit to another –For example, 1 lb = g –Example: –Example: convert 381 grams to pounds –Example: –Example: convert gallons to milliliters

Unit Conversions Factor-Label Method 27 cm = ? in 1 in = 2.54 cm Which unit goes on top? –The unit you want to end up with Which unit goes on bottom? –The unit you start with

Temperature Scales Fahrenheit (F):Fahrenheit (F): freezing point of water is 32°F and the boiling point of water is 212°F Celsius (C):Celsius (C): freezing point of water is 0°C and boiling point of water is 100°C Kelvin (K):Kelvin (K): zero is the lowest possible temperature; also called the absolute scale –degree is the same size as Celsius degree –K = °C + 273

Fig. 1.6, p.11

Convert the following: 25 o C to K 25 o C to o F 67 o F to o C

The Three States of Matter GasGas –has no definite shape or volume –fills whatever container it is put into –is highly compressible LiquidLiquid –has no definite shape but a definite volume –is slightly compressible SolidSolid –has a definite shape and volume –is essentially incompressible

Density Density:Density: the ratio of mass to volume –Commonly used units are g/mL for liquids, g/cm 3 for solids, and g/L for gases. –Example: –Example: If 73.2 mL of a liquid has a mass of 61.5 g, what is its density in g/mL?

Specific Gravity Specific gravity:Specific gravity: the density of a substance compared to water as a standard –because specific gravity is the ratio of two densities, it has no units (it is dimensionless) –Example: –Example: the density of copper at 20°C is 8.92 g/mL. The density of water at this temperature is 1.00 g/mL. What is the specific gravity of copper?

Energy Energy:Energy: the capacity to do work –may be either kinetic energy or potential energy –the calorie (cal) is the base metric unit Kinetic energy:Kinetic energy: the energy of motion –KE increases with velocity –KE increases with mass Potential energy:Potential energy: the energy an object has because of its position; stored energy

Energy Kinetic energy –Mechanical energy, light, heat, and electrical energy Potential energy is –Chemical energy Stored in chemical substances Energy released in chemical reactions The law of conservation of energy –Energy cannot be created or destroyed Energy can only be converted from one form to another

Heat and Temperature Heat is a form of energy –Heating refers to the energy transfer process when two objects of different temperature are brought into contact –Heat always flows from the hotter object to the cooler one until the two have the same temperature

Energy Units 1 calorie (cal) is the amount of heat needed to raise 1 g of water 1 o C I kcal = 1000 cal (calorie) 1 cal = J(joule)

Specific Heat Specific heat:Specific heat: the amount of heat necessary to raise the temperature of 1 g of a substance by 1°C.

Specific Heat The amount of heat change when matter is heated or cooled is given by the following equation Example:Example: how many calories are required to heat 352 g of water from 23°C to 95°C?