Chapter 1 Introduction to Chemistry

What you’ll learn… You will describe the relationships between chemistry and matter You will recognize how scientific methods can be used to solve problems You will distinguish between scientific research and technology

Chemistry and Matter Chemistry is the study of matter and the changes that it undergoes Matter is anything that has a mass and takes up space Mass is a measurement that reflects the amount of matter Is air matter?

Weight is a measurement not only of the amount of matter but also the effect of the Earth’s gravitational pull on that matter Why would scientists use “mass” instead of “weight”?

Macroscopic vs. Microscopic Macroscopic matter does not need a microscope to see it whereas microscopic matter needs a microscope Submicroscopic= atoms FYI: 1 million million atoms could fit onto the period at the end of a sentence

Scientific Methods Observations Qualitative Data- information that describes Examples: color, odor, shape Quantitative Data- numerical information Examples: how tall, how fast, how much

Experiments Independent variable- variable that you plan to change Dependent variable- variable that changes in response to a change in the independent variable

Chapter 3 Matter- Properties and Changes What about Chapter 2??? (We’ll come back to that…)

Pure Substance Substance- matter that has a uniform and unchanging composition Examples: Table Salt, water, sugar

Physical Properties of Matter A physical property can be observed or measured without changing the sample’s composition Examples: Density, Color, Odor, Taste, Hardness, Melting Point, Boiling Point

Extensive vs. Intensive Properties Extensive Properties are dependent upon the amount of substance present Example: Mass Intensive Properties are independent of the amount of substance present Example: Density, Color

Chemical Properties of Matter Chemical property -the ability of a substance to combine with or change into one or more other substances Example: The ability of iron to form rust when combined with oxygen

States of Matter Solid Liquid Gas Definite shape Definite volume Flows Constant volume Takes the shape of its container Gas Flows to conform to the shape of its container Fills entire volume of container Vapor- refers to the gaseous state of a substance that is a solid or a liquid at room temperature

Physical Change Physical changes alter a substance without changing its composition Example: cutting a sheet of paper Indicating words: bend, grind, crush, split, melting, freezing, condense

Chemical Changes AKA Chemical Reaction A process that involves one or more substances changing into new substances

Conservation of Mass The law of conservation of mass states that matter is neither created nor destroyed (it is conserved) WOOD + OXYGEN  ASH + WATER VAPOR + CARBON DIOXIDE

Chemical or Physical Change? wind eroding rocks _________________________ dead leaves decaying __________________________ rain puddle drying up __________________________ mixing flour and baking powder__________________________ gasoline evaporating __________________________ hydrogen peroxide decomposing__________________________ bread baking in an oven __________________________ instant tea dissolving in water __________________________ milk souring __________________________ gasoline burning __________________________

ANSWERS wind eroding rocks – PHYSICAL CHANGE dead leaves decaying – CHEMICAL CHANGE rain puddle drying up – PHYSICAL CHANGE mixing flour and baking powder- PHYSICAL CHANGE gasoline evaporating – PHYSICAL CHANGE hydrogen peroxide decomposing- CHEMICAL CHANGE bread baking in an oven – CHEMICAL CHANGE instant tea dissolving in water – PHYSICAL CHANGE milk souring – CHEMICAL CHANGE gasoline burning- CHEMICAL CHANGE

Mixtures A mixture is a combination of two or more substances in which each pure substance retains its individual chemical properties

Heterogeneous Mixture- one that does not blend smoothly throughout and which the individual substances remain distinct Examples: Sand and Water, Oil and Water, Cement Homogeneous Mixture (Solutions)- has constant composition throughout; it always has a single phase Examples: salt water, vinegar, alloys

Separating Mixtures Filtration- technique that uses a porous barrier to separate a solid from a liquid Distillation- technique that is based on differences in the boiling points of substances Crystallization- technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance Chromatography- separates the components of a mixture on the basis of the tendency of each to travel or be drawn across the surface of another material

Elements and Compounds Element- a pure substance that cannot be separated into simpler substances Located on the periodic table in rows and periods Periods= Horizontal Rows Groups= Vertical Columns Compound- a combination of two or more different elements that are combined chemically

Law of Definite Proportions Elements comprising compounds combine in definite proportions Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass Percent by Mass- the ratio of the mass of each element to the total mass of the compound as a percentage

Practice Problem 15.9% Hydrogen A 78.0g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound? 15.9% Hydrogen

Pure Substance or Mixture Material Pure Substance or Mixture Element, Compound, Homogeneous, Heterogeneous Limestone (CaCO3) Soil Bronze Aluminum Sugar + water Concrete Sterling Silver Caffeine

ANSWERS Material Pure Substance or Mixture Element, Compound, Homogeneous, Heterogeneous Limestone (CaCO3) PURE SUBSTANCE COMPOUND Soil MIXTURE HETEROGENOUS Bronze HOMOGENOUS Aluminum ELEMENT Sugar + water Concrete Sterling Silver HOMOGEN Caffeine

 Homework  Page 9 Page 13 Page 60 Page 69 Page 76 Page 77 #6-8,10 #12 Page 60 #1-5 Page 69 #15-17 Page 76 #21-23 Page 77 #25-30 SKIP #28