Properties and Classification of Matter Section A1.2

Objectives distinguish between physical and chemical properties of substances classify matter as pure substances or mixtures and further into homogeneous or heterogeneous describe evidence for chemical changes

Matter Matter is anything that has a mass and takes up space Desk, humans, Pepsi All matter has both physical and chemical properties

Classifying Substances Use two types of classification: 1) Physical properties Physical appearance and composition of a substance Ex. Boiling point 2) Chemical properties Reactivity of a substance Ex. Reaction with water

Physical or Chemical? For the next properties, classify as physical or chemical and then place into a chart within your notes. Headings on your chart should be property, type, and definition. Color? Physical Solubility? Ability to burn? Chemical (combustion) Reaction to litmus? Chemical

Physical or Chemical? Flash point? State? Ductility? Magnetism? Chemical (temp to ignite flame) State? physical Ductility? Physical Magnetism? Reaction to heat? Chemical (melt or decompose?) Crystal formation? What did we miss on p 13, Figures A1.1 and A1.2? Fill in the rest of your chart with that information

Physical change In a physical change, matter takes on different characteristics by manipulating the properties, but no new substance is produced Physical changes are usually reversible

Chemical change In a chemical change, new substances are produced that have physical and chemical properties that are different from the starting reactants Chemical changes are often non-reversible

There are many ways to produce light A) light bulb (physical change) B) laser (physical change) C) lighter (chemical change) D) burning magnesium (chemical change)

Pure Substances and Mixtures Matter Pure Substances Elements Compounds Mixtures Solutions Mechanical mixtures Suspensions Colloids homogeneous heterogeneous Fig. A1.9 p. 14

Do Now Define each term in the chart (except matter) and provide an example for each

Pure Substances and Mixtures All particles making up substance are identical Physical and chemical properties constant Ex. element/compound Mixtures Combination of pure substances Properties vary with composition Elements Pure substance that cannot be broken down One type of atom (ex. Helium) Compounds Chemical combination of 2 or more elements in specific ratio Ex. water

Continued… Solution Mechanical mixtures Suspension Colloids Separate components not visible (homogeneous) One dissolved into another Ex. Juice Mechanical mixtures Different substances visible (heterogeneous) Ex. Soil Suspension Components in different states Ex. Mud (dirt in water) Colloids Can’t easily separate the suspended substance Ex. milk

Identifying Pure Substances Observe chemical and physical properties Does the physical property change the identity or composition of a substance? Ex. Melting water: does the water itself change when we change states (solid to liquid)? Is this a pure substance or mixture? Ex. Melting a solid produces a gas and a liquid? Is this a pure substance or a mixture?

Chemical Reactions Chemical change/chemical reaction Process that occurs when something reacts to form something new New substance has own physical and chemical properties Energy always absorbed or released How do we know that a chemical reactions has occurred? What signs do we look for?

Homework Answer questions 6-9 on page 17

ACTIVITY A3 – Evidence of chemical change Problem: What observable changes happen when a chemical reaction occurs? Materials, Procedure: see p 16 Observations: Prepare a data table that includes space for the following reactions. For each reactant, record its observable characteristics before the reaction. Also record changes that you observe when you combine the reactants. Give your table a title.