Today is Friday (!), September 4 th, 2015 Pre-Class: You know, I really like to save money whenever I can. This year, I’m hoping to stop paying so much for salt at the grocery store. So, the next time I’m at the beach, I’m going to take some of the salt out of the salt water. Is that possible? How? In This Lesson: Mixtures (Lesson 2 of 6)

Today’s Agenda Types of matter Properties of matter Interactions of matter – Also known as mixtures Where is this in my book? – P. 44 and following…

By the end of this lesson… You should be able to classify matter based on its composition. You should be able to determine the error of measurements taken during a laboratory process.

Types of Matter As you can imagine, having a definition as broad as “has mass, takes up space” leads to an awfully large amount of matter in the world. More than just the phases of matter, chemists have ways of classifying matter by its composition.

Classifying Matter MATTER Pure Substance Mixture Element Compound Homogeneous Mixture Homogeneous Mixture Heterogeneous Mixture Heterogeneous Mixture

Substances and Mixtures Mixtures can be separated by physical means. – You’ll do this in a lab! MATTER Pure Substance Mixture Physical Separation

MATTER Substance Mixture Element Compound Substances Substances have: – Uniform compositions – Distinctive characteristics – Examples: NaCl (Salt) Al (Aluminum) O 2 (Oxygen)

MATTER Substance Mixture Element Compound Elements and Compounds Elements are substances that cannot be broken down into components. Elements are composed of only one type of atom. – Example: Hydrogen Oxygen Uranium

MATTER Substance Mixture Element Compound Elements and Compounds Compounds are composed of two or more elements. Compounds can be broken down chemically. – Example: Glucose (C 6 H 12 O 6 ) Water (H 2 O) Carbon Dioxide (CO 2 ) Chemical Separation

Mixtures MATTER Substance Mixture Homo- geneous Mixture Homo- geneous Mixture Hetero- geneous Mixture Hetero- geneous Mixture Mixtures are physical blends of two or more substances. – Examples: Salt water Sand and water Blood Air Vegetable soup

Substances and Mixtures MATTER Substance Mixture Homo- geneous Mixture Homo- geneous Mixture Hetero- geneous Mixture Hetero- geneous Mixture Homogeneous mixtures are also called solutions. They have a “single state” – in other words, it all looks the same. – Examples: Salt water Crystal Light Apple juice

Substances and Mixtures MATTER Substance Mixture Homo- geneous Mixture Homo- geneous Mixture Hetero- geneous Mixture Hetero- geneous Mixture Heterogeneous mixtures are not uniform. They have more than one state – in other words, it doesn’t all look the same. – Examples: Cookies and cream ice cream Fruit salad Vegetable soup

Closure It’s time for the “Mixture or Substance” game! – [cue 70’s game show music] I’ll show you a picture of a substance or mixture, you tell me which one it is. – Imaginary bonus points if you can identify whether it’s an element or compound, or a heterogeneous or homogeneous mixture. That sentence had many uses of the word “or.”

Salt Salt Water AirSoilBlood Classification of Matter Is it a mixture or a substance? Substance Mixture Compound Homogeneous Heterogeneous Homogeneous

Sand Water Gasoline IronSteel Classification of Matter Mixture SubstanceMixtureSubstanceMixture Is it a mixture or a substance? Heterogeneous Compound Homogeneous Element Homogeneous [Alloy]

Aluminum Sand & Salt Sand & Water Raisin Bread Brass (copper & zinc) Classification of Matter Substance Mixture Is it a mixture or a substance? Element Heterogeneous Homogeneous [Alloy]

Wood Carbon Dioxide Cement Candle Wax Sugar Classification of Matter SubstanceMixture Substance Is it a mixture or a substance? Mixture Heterogeneous Compound Homogeneous Compound

Physical and Chemical Properties In addition to physical and chemical reactions, like we learned about previously, there are also physical and chemical properties. – They work mostly the same way.

Physical and Chemical Properties Physical properties are those that can be observed without actually causing a chemical reaction. Examples: – Density – Hardness – Melting/boiling points – Color – Smell

Important Physical Properties of the States of Matter

Important Physical Properties of the States of Matter Solids: – Definite shape/definite volume – Not easily compressed Liquids: – Indefinite shape/definite volume – Not easily compressed Gases: – Indefinite shape/indefinite volume – Easily compressed

Physical and Chemical Properties Chemical properties are those that cannot be observed without actually causing a chemical reaction. Examples: – Flammability – Corrosion (or rust-ability)

Intensive and Extensive Properties There are also properties considered intensive and extensive. Intensive properties are those that apply to any amount of a substance. Examples: – Color – Melting/boiling point – Combustibility

Intensive and Extensive Properties Extensive properties are those that vary based on the amount of a substance. Examples: – Volume – Length – Mass – Weight

Closure Part Deux Now let’s separate a mixture ourselves. – Separation of a Mixture Lab There’s just one more thing you need…

Percent Error Today will be our first lab with a considerable amount of calculations. Because we will all have slightly different numbers, it’s important for us (and for chemists) to be able to measure the accuracy of the measurements we’ve taken.

Accuracy When measuring anything, there is usually some error on the part of the scientist or the equipment. – The value calculated in the experiment is thus called the experimental value. There is, of course, the “true” value; the one we would expect to get if everything went perfectly. This is called the accepted value because scientists have agreed that it is correct. – Accepted value is sometimes called theoretical value, ideal value, or expected value.

Percent Error Therefore, to find how far off we are from what we should have gotten, we need to calculate a statistic called percent error. Here’s the formula – be careful of order of operations:

Percent Error Example You calculate the mass of an object to be 57.3 grams. However, your teacher tells you the object is actually 59 grams. What is your percent error?

Closure You collect 23 mL of liquid in a graduated cylinder. Unfortunately, the reaction you did was only supposed to make 21.4 mL. What is your percent error?