CP Chemistry THHS

Section 2.1 Matter Objectives Identify the characteristics of matter and substances Differentiate among the three states of matter Define physical property and list several common physical properties of substances

Properties of Matter Matter anything that has mass and takes up space. Mass The amount of matter the object contains. Note mass ≠ weight. Substance Pure substances contain only one kind of matter. Question – is lemonade a substance?

Physical Properties Physical Property – a quality or condition of a substance that can be observed without changing the substance’s composition. Examples of physical properties are color, solubility, odor, hardness, density, melting point, and boiling point.

Properties of the States of Matter - Solid, Liquid and Gas PropertySolidLiquidGas or vapor ShapeDefiniteIndefinite VolumeDefinite Indefinite Expansion on heating Very slightModerateGreat CompressibilityAlmost incompressible Readily compressible

Properties of Solids, Liquids, Gases Solid Has a definite shape and volume Does not depend on the shape of its container Almost incompressible Liquid Particles are in close contact but not rigidly packed Can flow and take the shape of the container it is in A fixed volume can take a variety of shapes Almost incompressible

Properties of Solids, Liquids, Gases Gas or vapor “ Gas” is limited to those substances who are in a gaseous state at room temperature. “Vapor” describes the gaseous state of a substance that is a liquid or a solid at room temperature. An example is steam. Gases take the shape of the container they are in. Particles are spaced far apart. Gases expand without limit to fill any space, so its volume changes with the container, unlike liquids. Gases tend to expand when heated.

Physical Changes A change which alters a given material without changing its composition is called a physical change Examples are cutting, grinding, bending Melting a metal, melting ice, boiling water Boil, freeze, dissolve, melt, condense, break, split, crack – all examples of physical changes

Section Mixtures Objectives Categorize a sample of matter as a substance or a mixture Distinguish between homogeneous and heterogeneous samples of matter

Classifying Mixtures A mixture is a physical blend of two or more substances. Salad with lettuce, tomatoes, carrots Blood – with water, cells, chemicals Each of these mixtures can vary in composition Heterogeneous mixture – if you were to sample the mixture in two different places the composition wouldn’t be the same (salad) Homogeneous mixture – if you were to sample the mixtures in two different places, the composition would be the same (salt water) Homogeneous mixtures are called solutions.

Phases in Mixtures SystemExamples Gas- gasCarbon dioxide and oxygen in nitrogen (air) Liquid – gasWater vapor in air (moist air) Gas – liquidCarbon dioxide in water (soda water) Liquid- liquidAcetic acid in water (vinegar) Solid – liquidSodium chloride in water (salt water or brine) Solid – solidCopper in silver (sterling silver, an alloy) Phase – any part of a system with uniform composition and properties is a phase. Homogeneous mixtures are one phase. Heterogeneous mixtures are two or more phases. Oil and vinegar separates into two phases

Separating Mixtures Some mixtures can be separated by physical methods. Magnet to separate iron filings from sulfur. Distillation can be used to separate pure water from impurities.

Section 2.3 – Elements and Compounds Objectives Explain the difference between an element and a compound. Identify the chemical symbols of common elements, and name common elements given their symbols

Elements vs. Compounds Elements are the simplest forms of matter that can exist under normal laboratory conditions. This statement does not include the subatomic level (protons, neutrons, etc.) Elements cannot be separated into simpler substances by chemical means. Examples: Oxygen, carbon, nitrogen Compounds are made when two or more elements combine chemically, like H 2 O or CO 2. Compounds can be separated into simpler substances by chemical means.

Compounds Example: Sodium chloride NaCl (table salt) Composed of Chlorine (which is the gas Cl 2 as an element) and Sodium (which is the solid Na as an element) Anyone know why sodium (solid) is normally stored in oil?

Quick Quiz Do you think gasoline is an element, a compound or a mixture? If you had a uniform blue solid and heated it up in the absence of air, and it formed a colorless gas and a white solid – was the blue solid an element, a compound or a mixture? A clear liquid is allowed to evaporate for 3 days and at the end you find a solid residue – was the liquid an element, compound or mixture?

Chemical Symbols Some chemical symbols are easy to remember Carbon = C, Oxygen = O, Nitrogen = N Others are not so easy, and come from Latin or other sources Sodium = Na (from Natrium) Potassium = K (from Kalium) Gold = Au (from Aurum) Lead = Pb (from Plumbum) A list of more unusual symbols is on page 40 and on my website for you to review! You will need to know at least the top 4 rows of the periodic table - name and symbol

Section 2.4 – Chemical Reactions Objectives Differentiate between physical and chemical changes in matter Apply the law of conservation of mass

Changing reactants to products Chemical reactions - one or more substances react and change into a new substance Example: iron + oxygen = rust (iron oxide) The starting substances are called reactants The ending substances are called products Words that convey that a chemical change has occurred include: burn, rot, rust, decompose, ferment, explode, corrode, etc.

Chemical Properties Chemical properties tell you something about the ability of a substance to undergo a chemical reaction to form new substances Rusting is a chemical property of iron Rotting is a chemical property of waste organic material Burning is a chemical property of wood

Examples of chemical reactions

Chemical reactions How can you tell if a reaction has taken place? Energy is always given off or absorbed during a reaction Change in color or odor – silver chromate forms when yellow sodium chromate is added to clear silver nitrate (above right) Production of gas or solid from a liquid zinc + hydrochloric acid releases H 2 gas >>> Most chemical changes are not easily reversed, like many physical changes are.

Conservation of Mass – Key concept When you burn wood at a beach bonfire, the reaction produces carbon dioxide gas (CO 2 ), water vapor (H 2 O) and some ash. It may seem that the amount of matter has been reduced when you look at the ash pile. However, if you could carefully measure the mass of the reactants and the mass of the products, you would find they are the same. This is the law of conservation of mass – mass is neither created or destroyed in a chemical reaction.

Conservation of Mass

Chapter Review: Quick Quiz 2.1 Contrast the characteristics of the three states of matter. Solids have a definite shape and volume and are nearly incompressible. Liquids have a definite volume but no definite shape, and are nearly incompressible. Gases have neither definite shape nor volume and are easily compressed, and expand without limit when heated.

Quick Quiz 2.2 Explain the difference between a homogeneous and heterogeneous mixture. Homogeneous mixtures have a uniform composition throughout the sample. Heterogeneous mixtures have a non-uniform composition consisting of two or more phases.

Quick Quiz 2.3 What are the chemical symbols for the following elements? Copper, oxygen, silver, sodium, phosphorus, helium. Cu, O, Ag, Na, P, He What are the chemical elements that have the following symbols? Sn, Ca, S, Cd, K, Cl Tin, Calcium, Sulfur, Cadmium, Potassium, Chlorine

Quick Quiz 2.4 Classify the following changes as physical or chemical: Cookies are baked chemical Water boils physical Soap dissolves in water physical A firefly emits light chemical Milk spoils chemical A metal chair rusts chemical

What is the definition of a substance? Matter that has a uniform and definite composition. A physical blend of two or more substances is called what? Mixture Substances that can be separated into simpler substances only by chemical reaction are called what? Compounds Any part of a system with uniform composition and properties is called what? A phase