Unit 4: The Nature of Matter Table of Contents 15 Unit 4: The Nature of Matter Chapter 15: Classification of Matter 15.1: Composition of Matter 15.2: Properties of Matter

Substances A substance is a type of matter with fixed, constant composition May be an element or a compound You can write a formula for any substance Examples:

Composition of Matter 15.1 Elements element – Pure Substance- all the atoms in a have the same identity Atoms are the building blocks of elements Examples: ?

Elements 15.1 About 90 elements are found on Earth. Composition of Matter 15.1 Elements About 90 elements are found on Earth. More than 20 others have been made in laboratories, but most of these are unstable and exist only for short periods of time.

Important elements Lead (Pb) has high density, blocks radiation, used in dentist offices in aprons Aluminum (Al) is bendable and resists corrosion. Is strong and lightweight. Used in airplanes, cans, bikes

Composition of Matter 15.1 Compounds Compound- two or more elements combine to form substances. It has a specific chemical composition and you can write a formula for it. Examples?

Compounds 15.1 Composition of Matter Sodium is a silvery metal element chlorine is a green poisonous gas element Chemically combined, they make table salt with formula NaCl which is a compound

Composition of Matter 15.1 Mixtures A mixture- Material made up of two or more substances that can be easily separated by physical means. Examples?

Heterogeneous Mixtures Composition of Matter 15.1 Heterogeneous Mixtures heterogeneous mixture -A mixture in which different materials can be distinguished easily by looking at it. A microscope might be necessary Examples?

Composition of Matter 15.1 Suspensions suspension, a heterogeneous mixture containing a liquid in which visible particles settle. Examples? River water, salad dressing

Composition of Matter 15.1 Colloids colloid –heterogeneous mixture with particles that are larger than those in solutions but not heavy enough to settle out. Kinds of looks homogeneous but is really heterogeneous, especially under a microscope Examples? Paint Whole milk Fog Butter Mayonnaise

Composition of Matter 15.1 Detecting Colloids Tyndall effect- scattering of light by colloidal particles. Laser light works best

Composition of Matter 15.1 Homogeneous Mixtures Homogeneous mixture two or more gaseous, liquid, or solid substances blended evenly throughout. You can only see one thing Examples? Ice tea – sugar, water, tea Air – nitrogen, oxygen Alloys – like brass – made of copper and zinc

Homogeneous Mixtures 15.1 Solution – defined as a homogeneous mixture Composition of Matter 15.1 Homogeneous Mixtures Solution – defined as a homogeneous mixture Particles cannot be seen with a microscope Will never settle to the bottom of their container. May be solid, liquid or gas Made of solvent and solute Substances cannot be separated by filtering

The table summarizes the properties of different types of mixtures. Composition of Matter 15.1 The table summarizes the properties of different types of mixtures.

Concept map – classifying matter

Section Check 15.1 Question 1 A _______ is a type of matter with a fixed composition. A. colloid B. mixture C. substance D. solution

Section Check 15.1 Answer The answer is C. A substance can be either an element or a compound.

Question 2 15.1 How many elements are found on Earth? A. 5 B. 10 C. 30 Section Check 15.1 Question 2 How many elements are found on Earth? A. 5 B. 10 C. 30 D. 90

Section Check 15.1 Answer The answer is D. About 90 elements are found on Earth, and more than 20 have been made in laboratories.

Question 3 15.1 How are compounds different from mixtures? Section Check 15.1 Question 3 How are compounds different from mixtures?

Section Check 15.1 Answer The atoms in compounds are combined in fixed proportions and cannot be separated by physical means. A mixture is made of two or more substances that can be easily separated by physical means.

Properties of Matter 15.2 Physical Properties physical property - characteristic of a material that you can observe without changing the identity of the material. Examples: color, shape, size, density, melting point, and boiling point.

Physical properties Appearance – like color, shape Behavior – like viscosity, magnetism You can use these properties to separate items in a mixture

Behavior 15.2 You can separate a sand/iron mixture by using a magnet Properties of Matter 15.2 Behavior You can separate a sand/iron mixture by using a magnet

The Identity Remains the Same Properties of Matter 15.2 Physical Change The Identity Remains the Same physical change -A change in size, shape, or state (gas, liquid, solid) of matter. Will still have the same formula Examples? Boiling, melting

The Identity Remains the Same Properties of Matter 15.2 The Identity Remains the Same

Using Physical Change to Separate Properties of Matter 15.2 Using Physical Change to Separate Distillation- Separating substances in a mixture by evaporating a liquid and recondensing its vapor Separation occurs due to different boiling points For example, an alcohol/water mixture can be distilled because the alcohol has a lower boiling point than water.

Properties of Matter 15.2 Distillation

Chemical Properties and Changes Properties of Matter 15.2 Chemical Properties and Changes chemical property- any characteristic of a material that you can observe that produces new substances (element or compounds) with new properties and new formulas. Examples? Flammability, rusting

Properties of Matter 15.2 The Identity Changes chemical change - A change from one substance to another. The identity of the substance changes Indications of chemical change: Bubbles Temperature Change Precipitate formation Color change Click image to view movie

Detecting Chemical Change Properties of Matter 15.2 Detecting Chemical Change If you leave a pan of chili cooking unattended on the stove for too long, your nose soon tells you that something is wrong. This burnt odor is a clue telling you that a new substance has formed.

Usefulness of chemical changes Tarnished silver (silver reacted with sulfur) can be cleaned with baking soda and aluminum in hot water. This turns the tarnish (silver sulfide) back into pure silver.

Weathering Physical changes – rocks splitting Chemical changes – acid rain dissolving rocks over time

The Conservation of Mass Properties of Matter 15.2 The Conservation of Mass

The Conservation of Mass Properties of Matter 15.2 The Conservation of Mass Law of conservation of mass, the mass of all substances before a reaction equal the mass of all the substances that remain after the change. Mass of reactants = mass of products no mass is lost during a chemical or physical reaction.

Example of law of conservation of mass If 18 grams of hydrogen (H) reacts with 633 grams of chlorine (Cl), how much hydrochloric acid (HCl) will form? Write words: 18 grams H + 633 grams Cl  651 grams HCl

Another example Methane reacts with oxygen (burning) to form carbon dioxide and water. How many grams of water can be formed if 24 grams of methane reacts with 96 grams of oxygen and 66 grams of carbon dioxide forms? Solve: 24 grams methane + 96 grams oxygen  66 grams carbon dioxide + 54 grams water

Question 1 15.2 Which of the following is a chemical property? Section Check 15.2 Question 1 Which of the following is a chemical property? A. boiling point B. density C. flammability D. melting point

Section Check 15.2 Answer The answer is C. Flammability indicates whether a substance will undergo the chemical change of burning.

Section Check 15.2 Question 2 A characteristic of a material that can be observed without changing the identity of the substances that make up the material is a _______.

Section Check 15.2 Answer The answer is physical property. Examples of physical properties include color, shape, and density.

Section Check 15.2 Question 3 What is the law of conservation of mass?

Section Check 15.2 Answer According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all substances that remain after the change.

15 To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents Click on this icon to return to the previous slide Click on this icon to move to the next slide Click on this icon to open the resources file. Click on this icon to go to the end of the presentation.

End of Chapter Summary File