Chapter 4 Elements, Compounds, and Mixtures

Section 2: Objectives Explain how elements make up compounds. Describe the properties of compounds. Explain how a compound can be broken down into its elements. Give examples of common compounds.

Compounds A compound is a pure substance composed of 2 or more elements that are chemically combined. Elements combine by reacting or undergoing a chemical change, with one another. Example: Coke and mentos lab.

Compounds A particle of a compound is a molecule. Molecules of compounds are formed when atoms of 2 or more elements join together. Compounds have different properties than the elements that make them up. Examples: Salt, Water, Vinegar, Baking soda, Carbon dioxide

Compounds Elements do not randomly join to form compounds. Elements join in a specific ratio according to their masses to form a compound. Example: The ratio of masses from hydrogen to oxygen in water is 1 to 8. Every sample of water has a 1:8 ratio. If the ratio is different, the compound is not water.

Compounds Each compound has its own physical property. Physical properties include melting point, density, and color. Compounds can also be identified based on their chemical properties. Some compounds react with acids while other may react with light.

Compounds A compound has different properties than elements do. Example: Sodium chloride (NaCl) Made form 2 dangerous elements. Na reacts violently with water. Cl is a poisonous gas. When combined they form a harmless compound.

Compounds Some compounds can be broken down into their elements by chemical changes. Other compounds break down to form simpler compounds instead of elements. Example: Carbon dioxide can be broken down into individual elements

Compounds The only way to break down a compound is through a chemical change. Sometimes, energy is needed for a chemical change to happen. 2 ways to apply energy to a chemical change: Heat Electric current Example: Heating the compound mercury oxide breaks it down into mercury and oxygen.

Compounds Examples of compounds: Proteins (amino acids) Carbon dioxide (C and O) Ammonia: (N and H) Aluiminum oxide (Al and O)

Ch. 4 Sec. 2 Review 1) How do elements combine with one another? 2) What is a molecule? 3) How are molecules formed? 4) List 3 physical properties. 5) How are compounds identified? 6)What are 2 ways to apply energy to make a chemical change occur?

Section 3: Objectives Describe 3 properties of mixtures. Describe 4 methods of separating the parts of a mixture. Analyze a solution in terms of its solvent and solute. Explain how concentration affects a solution. Explain how a colloid and a suspension differ.

Mixtures All mixtures share certain properties. A mixture is a combination of 2 or more substances that are not chemically combined. When 2 or more materials are put together and do not react, they form a mixture. For a compound to be created, a chemical reaction must take place.

Mixtures No chemical change happens when a mixture is made. Each substance in a mixture has the same chemical properties it had before the mixture formed. Each substance in a mixture keeps its identity. Depending on the mixture, you may or may not be able to see all of the components. Example: Salt water

Mixtures No chemical change occurs when a mixture is created. Physical changes can occur to mixtures without changing the properties of the mixture. There are many ways to separate the components of a mixture.

Mixtures These are 3 ways to separate mixtures: Distillation: Heat is used to separate different parts Magnetism: Forces separate different metals/non-metals Centrifuge: Separates mixtures by density

Mixtures A solution is a mixture that appears to be a single substance. The reason for this is, a solution is composed of 2 or more substances that are distributed evenly among each other. The process in which particles separate and spread evenly throughout a mixture is known as dissolving.

Mixtures In solutions, the solute is the substance that gets dissolved. The solvent is the substance in which the solute is dissolved. In other words, the solute gets dissolved and the solvent does the dissolving. The solvent dissolves the solute.

Mixtures A measure of the amount of solute dissolved in a solvent is concentration. Concentration can be expressed in grams of solute per mL of solvent. (g/mL) Dilute and concentrated are terms used to describe solutions. Dilute solutions contain less solute than concentrated solutions.

Mixtures Examples of mixtures include: Salt water (NaCl and H2O) Antifreeze (Alcohol and water) Brass (Zinc in copper) Soft drinks (CO2 in H20) These appear to be compounds but are actually solutions.

Ch. 4 Sec. 3 Review 1) How is a mixture formed? 2) What is the only type of change that can occur to a mixture? Why? 3) List 3 ways to separate mixtures. 4) What does “dissolving” mean? 5) What is the difference between a solute and solvent? 6) What is the difference between diluted and concentrated solutions? 7) List 3 of the 4 examples of mixtures.