Chapter 14-1 Objectives: Distinguish between chemical and physical changes of matter Identify characteristics properties of matter and explain their uses Compare mixtures and a pure substances and describe elements and compounds.

Key Terms: Characteristics property Boiling point Melting point Physical change Chemical change Chemical activity Mixture Solution Pure substance Element Compound

What is Matter? In Science, however, the word “matter” has a specific meaning. Matter is the “stuff” that makes up everything in the universe. But what is matter exactly? This question is not so easy to answer! You can begin by looking at some of its properties.

Properties Matter might be hard or soft, rough or smooth, round or square, hot or cold. Can matter change properties? The answer is yes. For example, water is a clear liquid at room temperature. At cold temperature, however, water is in its solid form—ice—which is hard and frosty. Solids, Liquids and gases are three principle states of matter.

Characteristic Properties Some properties of matter, such as size or amount, are true only for a given sample of matter. For example, a piece of ice can be as small as an ice cube or as big as a glacier. In both cases, the substance is still ice. However, some properties hold true for a particular kind of substance not matter what the sample. These properties are called characteristic properties. Since characteristics properties for a given substance never change, they can be used to identify unknown matter.

Interpreting Data Look at the melting points and boiling points of the five substances listed in the table. Identify each substance’s physical state at room temperature (approximately 20 degree Celsius). Is it a gas, liquid, or a solid? Explain how you arrived at your conclusion.

Interpreting Data Substance Melting Point Boiling Point Water 100 100 Chloroform -64 61 Ethanol -117 79 Propane -190 -42 Table Salt 801 1465

Boiling Point The temperature at which a liquid boils is called its boiling point.

Boiling Point

Boiling Point

Boiling Point Continue… Boiling point is an example of a characteristic property of a substance. For this reason, comparing boiling points can be an excellent way to tell one liquid from another. For example, consider three different liquids: water, chloroform, and ethanol. Chloroform once was used to put people to sleep in operating room, and ethanol is one of a group of substance called alcohols. All three liquids are clear and colorless—you would not be able to tell them apart from their looks alone, but you can see that each liquid boils at a different temperature.

List the three principal states of matter. Give two examples of each. Homework for Today Answer the Questions List the three principal states of matter. Give two examples of each. 2. Liquid A and Liquid B both boil at 100 degree Celsius. Using what you know about characteristic Properties, explain why the liquids may not be the same.

Changes in Matter Physical Change---Changes in the state of matter , such as boiling or melting , are example of physical changes. Physical changes alter the form of a substance, but not its identity. Example: boil away water; crushing a soda can; tearing a piece of paper; mixing sugar into iced tea or breakfast cereal. In each of examples, the form or appearance of the substances changed, but the substances themselves remained.

Chemical Changes Chemical changes, however, one or more substances combine or decompose to form new substances. Example: heating sugar and changing it into caramel. When the process is complete, the original sugar particles no longer exist. Burning wood is another example of a chemical change. When the wood burns, it combines with oxygen in the air to produce changes the wood into ash and gases that are no longer wood.

Chemical Activity The ability of a substance to undergo a chemical change is another example of a characteristic property. The property is called the chemical activity of the substance.

Types of Matter Matter can be classified into 2 general categories: Mixtures and pure substances. The pure substances include elements and compounds.

Diagram of matter Solution The best mixed of all possible mixtures.

1. Mixture- Consists of two or more substances that are mixed together but not chemically combined. 2. Element- It is made of one kind of matter and has definite properties. 3. Compound- It is a pure substance formed from chemical combinations of two ore more different elements

Homework Answer List the three principals state of matter. Give two examples of each. Solid—rocks, desk; Liquid—water, blood; Gas—air, pure oxygen 2. Liquid A and Liquid B both boil at 100 degree Celsius. Using what you know about characteristic properties, explain why the liquids may not be the same. Many substances may share a single characteristic property, and so you may have to study three or four properties to distinguish between the two liquids.

Homework for Today What is meant by a characteristic property of a substance? Answer: A characteristic property is property that every sample of a substance has. Compare physical changes and chemical changes. Use examples in your answer. Answer: In a physical change, such as melting ice to get water, only the form of the substance changes. In a chemical change, such as rust forming on iron, a new substance is formed. Describe how matter is classified into mixtures, pure substances, elements and compounds. Answer: See the diagram

Diagram of matter

Project Comparing Brand X The project of this chapter

Introduction Every object you see in this world is an example of matter. In this chapter, you will explore the properties of matter, the changes that matter can undergo, and the particles that make up matter.

Your Goal: Compare a property of matter in three different brands of a consumer product.

To complete the project you will… Design a comparison test on the project and collect data. Provide a procedure for your partner to follow Conduct the comparison test designed by your partner Compare the data you and your partner obtained Follow the safety guidelines. Safety guideline needs to be address.

Get started As a class, brainstorm a list of different products to compare. For each product, write down several properties that could be compared. For example, paper towels may absorb different amounts of water or adhesive bandages may have different strengths. You will be working on this project as you study this chapter. To keep your project on track, look for the following pages: section 1 review—page 445; section 3 review—page 457; section 4 review—page 462