Session 27 Do Now Open your book to the periodic table. 1.Find five elements with symbols that match (oxygen, O) and list the names and symbols 2.Find five elements with symbols that don’t match (potassium, K) and list the names and symbols 3.What do you think? Which elements were discovered earlier (matching or unmatching) Why?

Session 28 Do Now Give examples of the following and label each one: 1.Element 2.Compound 3.Solution 4.Heterogeneous mixture 5.Physical property 6.Chemical property 7.Physical change 8.Chemical change

Part A—Types of Matter

Matter can be classified Matter Pure Substances Mixtures ElementCompound Homogeneous (Solutions) Heterogeneous

Matter Anything that has mass and takes up space Anything made from atoms Examples:  Molecules  Cells  People  Air  Water

Pure Substances versus Mixtures MixturesPure Substances Every piece of matter is the same More than one type of matter mixed together Matter is classified as either a pure substance or a mixture

Elements versus Compounds CompoundElements Every atom is the same type of atom More than one type of atom chemically bonded together. Every molecule is the same. Pure substances are either elements or compounds

Elements Pure substance Every atom is the same Elements can be found on the periodic table! Element Single Atom Cannot be separated by chemical or physical processes

Compounds Pure substance Every molecule is the same Compound Single Molecule Made of more than one type of atom bonded together Can be separated by chemical reactions only

Mixtures Heterogeneous Homogeneous (aka “solution”) It looks the same throughout Different matter can be seen (chunks, bubbles, floaties, layers, etc.) Mixtures can be classified as homogeneous or heterogeneous

Mixtures Not a pure substance Physical combination of more than 1 type of pure substance Mixture >1 different type of matter Can be separated physically

Let’s Practice Tin foil Example: Determine if each is element, compound, homogeneous or heterogeneous mixtures Copper pipe Concrete Carbon tetrachloride Sports drink

Let’s Practice ElementTin foil Example: Determine if each is element, compound, homogeneous or heterogeneous mixtures Element Copper pipe Heterogeneous mix Concrete Compound Carbon tetrachloride Homogenous mix Sports drink

Part B —States of Matter

Solid Closely packed together particles Vibrate in place Can’t switch places Definite shape Definite volume

Liquid Particles more spread out than solid Particles are free to move past each other Not compressible Definite volume No definite shape – take shape of container

Gas Particles very spread out Rapid, random motion Highly compressible No definite volume—they will fill container No definite shape—take shape of container

Solid Liquid Gas Sublimation Melting Boiling or Evaporating Condensing Freezing Deposition Increasing molecular motion (temperature) Changes in State

Temperature of state changes Freezing point = melting point Boiling point = condensation point

What’s between the particles? ? Nothing! There is absolutely nothing between the particles!

Part C—Properties of Matter

Physical versus Chemical Properties Chemical PropertyPhysical Property Can be observed or tested without changing the atoms or molecules In the process of observing or testing, the atoms or molecules are changed into different substance(s)

Let’s Practice Example: Are the following properties are physical or chemical? Flammability Boiling point Solubility Malleability Reactivity with oxygen

Let’s Practice Chemical Physical Chemical Flammability Boiling point Solubility Malleability Reactivity with oxygen Example: Are the following properties are physical or chemical?

Part D—Density

Definitions How heavy is it for its size? Density- the ratio of mass to volume of a sample Lead = high density…small size is very heavy Air = low density…large sample has very little mass

Density D = m V Mass In grams (g) Volume In liters (L) or mL Density In g/L or g/mL Don’t try to cancel out the units…density has “2 units” – a mass unit over a volume unit!

Example 1—Solving for Density Example: What is the density of a sample with a mass of 2.50 g and a volume of 1.7 mL? D = ? m = 2.50 g V = 1.7 mL

Example 2—Solving for Mass Example: What is the mass of a 2.34 mL sample with a density of 2.78 g/mL? m = ? V = 2.34 mL D = 2.78 g/mL × 2.34 mL 2.34 mL ×

Example 3—Solving for Volume Example: A sample is 45.4 g and has a density of 0.87 g/mL. What is the volume? m = 45.4 g D = 0.87 g/mL V = ? × V V × 0.87 g/mL

Floating Objects float when they are less dense than the substance they are in! Fewer particles in the same space = less dense More particles in the same space = More dense

Let’s Practice 1 Example: If a 22.7 g sample has a volume of 47.8 mL, will it float in water? m = 22.7 g V = 47.8 mL D = ? The density of water is 1 g/mL. This sample’s density is lower. It will float.

Part E—Changes in Matter

Definition Physical Change - n. Change in which the chemical structure of the substances is not changed. Chemical Change - n. Change in which the chemical structures of the substances are changed.

Physical & Chemical Changes Physical changes do not produce new substances  breaking, dissolving, distilling, cutting, etc.  Changes in state are physical changes (boiling, condensing, melting and freezing) Chemical changes do produce new substances  rusting, burning, metabolizing food, oxidation or reduction, reacting with oxygen, etc.

Possible Signs of Chemical Changes Gas production (bubbling) Energy change (getting hot or cold) Color change Light given off Formation of a solid

Physical & Chemical Changes Also…if a change can be un-done by a physical change, then the original change was physical as well. If salt is dissolved in water, it seems to disappear… But if the water is evaporated (a physical change), the salt is left in the container. many people think this is a chemical change. Since the original change was un-done with a physical change, then the original change (the dissolving) was a physical change as well.

Definition Changes a solid into a liquid Reacting with oxygen to produce CO 2 and H 2 O Confusing changes People often use the following terms incorrectly. TermType of Change Melting Physical Burning Chemical Adding one substance to another to form a homogeneous mixture Dissolving Physical Heating a sample to evaporate the water Drying Physical

Part F—Endothermic and Exothermic

Endothermic & Exothermic When the system absorbs energy from the surroundings, it’s an endothermic process When the system releases energy to the surroundings, it’s an exothermic process

Exothermic & You You touch the beaker and it feels hot Energy is being transferred TO YOU You are the surroundings When energy moves from system to surroundings, it’s exothermic

Exothermic If the container feels hot to you, energy is being transferred TO YOU (the surroundings) from the system— exothermic

Endothermic The opposite is also true If the container feels cold to you, energy is being transferred FROM YOU (the surroundings) into the system— endothermic

Let’s Practice Example: Identify the system and surroundings when you hold an ice cube while it melts. Is this endo- or exothermic? System: Water molecules in the form of ice Surroundings: You and the air It feels cold to you…so energy is leaving you (surroundings) When energy goes from surroundings to system it’s endothermic