Elements, Compounds and Mixtures

1. Elements, Compounds and Mixtures

2. Elements Reminder • An element is a pure substance that cannot be separated or broken down into simpler substances by physical or chemical means. • A pure substance is a substance in which all of the “building-block” particles are identical. • For elements, the building-block particles are called atoms.

3. Elements Questions • 1. A property of an element that does not depend on the amount of the element is called: • A. electromagnetic property • B. Finite property • C. Unique property • D. Characteristic property • 2. How are metalloids NOT similar to metals? • A. they have some properties of nonmetals • B. Some are shiny, while others are dull • C. They are somewhat malleable and ductile • D. Some are good conductors of electrical current.

4. Compounds • A compound is a substance composed of two or more elements that are chemically combined. • Elements combine by reacting, or undergoing a chemical change, with one another. • A chemical reaction is the process by which substances change into new substances.

5. Read Page 138 • Look at the 4th sentence in paragraph 3, what does the pronoun ‘it’ refer to? • Look at the 2nd sentence in paragraph 4, what does the phrase ‘This process’ refer to?

6. Compound – elements combine • During a chemical reaction, the atoms of two or more elements react with each other to form molecules of compounds. • The properties of the new compound are different from the properties of the elements that formed the compound. • Copy Figure 2 on page 139.

7. Chemical Reaction Demonstration • Write down 2 observations about what you see. You are witnessing a reaction between Magnesium Wire and the Oxygen in the air. 2. What are the two elements in the compound? • Magnesium Oxide is different from the elements Magnesium and Oxygen

8. Properties of Compounds • Each compound has unique physical and chemical properties. • Elements always join in a specific ratio to form a specific compound. Salt is 39.34% sodium and 60.66% chlorine

9. Breaking Down Compounds • The only way to break down a compound is through a chemical change. • Some compounds can be broken down into their elements. H2O  H2 + O2 • Other compounds can be broken down to form simpler compounds instead of elements. H2O  OH + H

10. Breaking Down Compounds Match the compound with the elements that make it up: • Sodium Chloride • Carbon Dioxide • Calcium Carbonate • Ammonia • Magnesium Oxide • Nitrogen + Hydrogen • Carbon + Oxygen • Magnesium + Oxygen • Sodium + Chlorine • Calcium + Carbon + Oxygen

11. Compounds in Your World • Compounds are all around you. They make up the food you eat, your clothes, even you! • The compounds found in nature are not usually the raw materials needed by industry. Often, these compounds must be broken down to provide elements or other compounds that can be used as raw materials. (aluminum oxide) • Proteins and carbon dioxide are two compounds that play an important role in living things.

12. Compounds Questions • 1. When two or more elements join together chemically, • A. a compound is formed • B. a mixture is formed • C. a substance that is the same as elements is formed • D. the physical properties of the substance remains the same. • 2. The physical properties of compounds do NOT include • A. melting point. C. reaction to light • B. density D. color

13. More Compounds Questions 3. By what process can compounds be broken down? -a. physical changes -b. chemical changes -c. compound changes -d. either physical or chemical changes 4. Which of the following is NOT true of compounds? • The unique set of properties of a compound differ from the properties of the elements that make the compound. • The particles are made of atoms of elements that are chemically combined • Different samples of any compounds have the same elements in the same proportion • They can be separated by physical means

14. Compounds Quick Lab Directions: Analysis: Make observations for Compound A Make observations for Compound B Make observations of compounds with vinegar Baking soda reacts with vinegar, flour does not. Which compound is flour? How do you know? • Place a small amount of compound A in the small clear cup • Place a small amount of compound B in the other clear cup • Observe the color and texture of each compound and record your observations • Add vinegar to each cup, Record your observations

15. Mixtures • A mixture is a combination of two or more substances that are not chemically combined. • Each substance in a mixture keeps its identity because no chemical change happens when a mixture is made. • The components of a mixture do not need to be mixed in a definite ratio. • Read page 142

16. Examples of Mixtures • Rocks (granite is made of felspar, mica and quartz) • Pizza • Salad Dressing • Lemonade

17. Types of Mixtures • Homogenous Mixtures: these mixtures are the same all the way through (salt water, lemonade) 2. Heterogeneous Mixtures: these mixtures are not the same all the way through (salad dressing, pizza)

18. Separating Mixtures • If you don’t like mushrooms you can just pick them off your pizza. That is separating the mixture. • Not all mixtures are easy to separate. • Ways to separate mixtures: Distillation, Magnet, Centrifuge, Dissolving- Filtering-Evaporating

20. Mixtures Vs. Compounds

21. Mixtures Questions • Pick from these words: ratio, nitrogen, concentration, distillation, dilute • A mixture of liquids can be separated by ______________? • Solutions can be described as being concentrated or _________. • The amount of a substances in a given quantity of a mixture, solution or ore is known as the ___________.