Chapter 2 Section 1
Describing Matter Properties used to describe matter can be classified as extensive or intensive Extensive property - depends on the amount of matter in a sample. Ex. Mass and Volume Intensive property - depends on the type of matter in a sample, not the amount Ex. hardness or type of material
Identifying Substances A substance is matter that has a uniform composition. copper, aluminum, or silver Every sample of a given substance has identical intensive properties because every sample has the same composition When comparing two substances you need to examine the properties of that substance. Identify 3 differences between copper and gold
Identifying Substances A physical property is a quality or condition of a substance that can be observed or measured without changing the composition of the substance. Examples include: Hardness Color Conductivity Malleability Melting Point Boiling Point
States of Matter There are 3 states of matter 1. Solid definite shape and volume not easily compressed particles are very tightly packed 2. Liquid definite volume take the shape of the container particles are close together but not rigid not easily compressed
States of Matter States of matter cont. 3. Gas take the shape of the container easily compressed can expand to fill any container Vapor describes a gaseous state of a substance that is generally a liquid or solid at room temperature
Physical Changes During a physical change some properties of a material change but the composition of the material does not Physical changes can be classified as reversible or irreversible Ex. Boiling, freezing, melting, condensing, cutting, breaking, or crushing.
Section 2 Notes Mixtures
Classifying Mixtures A mixture is a physical blend of two or more components Ex. Air, vegetable soup, pop Two categories: Heterogeneous Mixtures - the composition is not uniform throughout Every sample will have a different composition Ex.?
Classifying Mixtures Homogeneous Mixtures -composition is uniform throughout AKA solution Most solutions are liquids, but some are gases (air) or solids (stainless steel) Homogeneous mixtures contain a single phase Any part of a sample with the same composition and properties Heterogeneous mixtures often have more then one phase. Ex. How many different phases would oil and water have?
Separating Mixtures Mixtures can be easy or difficult to separate Therefore, we can use the differences in physical properties to separate mixtures Ex. Oil and Vinegar 1 st method, pour off the oil layer 2 nd method, cool the mixture until the oil layer solidifies Each method takes advantage of the difference in physical properties of the oil and vinegar
Separating Mixtures Filtration - process that separates a liquid from a solid in a heterogeneous mixture Filter has holes that can be very tiny or very large, depending on the material. Ex.? Distillation - separates water from a liquid mixture Mixture is boiled to produce a vapor that then condenses into a liquid The solid substances in the mixture boil at a higher temperatures then water therefore the water will turn to vapor first and allow it to separate
Section 3 Elements and Compounds
Distinguishing Elements and Compounds Element- the simplest form of matter that has a unique set of properties Ex. Hydrogen, Carbon, Polonium, Zinc Compound- substance that contains more then one element Ex. Glucose (C 6 H 12 O 6 ), Salt (NaCl), baking soda (NaHCO 3 ) The proportion of elements in the same compound is fixed
Breaking Down Compounds Compounds can only be broken down chemically, not physically A chemical change is a change that produces matter with a different composition then the original matter Chemical changes include: burning a material - glucose sending electricity through the material - water
Properties of Compounds Properties of compounds are very different then the element that make them up. Sodium is a gray metal. Chlorine is a pale yellow-green poisonous gas. When combined they form a white crystal called?
Distinguishing Substances and Mixtures If the composition of a material is fixed, the material is a substance If the composition of a material can vary, the material is a mixture
Symbols and Formulas Each element is represented by a one or two letter chemical symbol The First letter is always capitalized The Second letter is always lowercase Ex. Hydrogen H Copper Cu Symbols are based off of chemical name. Either the English form or the Latin name. Examples of each?
Section 4 Chemical Reactions
Chemical Changes The ability of any substance to undergo a change is a chemical property Ex. Rust is a chemical property of Iron Chemical properties can only be observed when a substance undergoes a chemical change. During a chemical reaction, one or more substances (called?) will change into one or more new substances (called?) Reactants Products
Recognizing a Chemical Change Possible clues to chemical change include: 1. A transfer of energy true of all chemical changes Ex. When natural gas reacts with oxygen energy is given off in the form of heat and light and transferred to the food you are cooking 2. The production of a gas Ex. Bathroom cleaners often form bubbles when reacting with soap scum Are bubbles forming always a sign of a chemical change? No: Water boiling causes bubbles to form but no chemical change is occurring
Recognizing a Chemical Change Possible clues cont. 3. A change in color 4. The formation of a precipitate A precipitate is a solid that forms and settles out of a liquid mixture The only way to know for sure is a chemical change has taken place is to test the composition of the sample before and after the change.
Conservation of Mass The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved Mass of the products = mass of the reactants. When wood burns it forms ash, water vapor and carbon dioxide. The mass of the wood = the mass of the ash, water vapor and carbon dioxide