1. Elements, Compounds and Mixtures

2. Warm Up 9/25 1. Draw a Bohr Model for Boron 2. How many valence electrons does it have? have? 3. Do you think it is very reactive based on it’s number of valence electrons? it’s number of valence electrons?

3. Matter Anything that takes up space and has mass. Anything that takes up space and has mass. There are 3 groups of matter: There are 3 groups of matter: 1. Elements 2. Compounds 3. Mixtures

4. Elements An element is the basic building block of matter. You cannot break matter down into a more pure substance than its elements. An element is the basic building block of matter. You cannot break matter down into a more pure substance than its elements. **If you can find it on the periodic table then it is an element. **If you can find it on the periodic table then it is an element.

5. You can see the same sample throughout (element)

7. Compounds Two or more elements that have chemically combined to form a different substance. Two or more elements that have chemically combined to form a different substance. You CANNOT separate the particles You CANNOT separate the particles Ex. Table salt (Na + Cl = sodium chloride) Ex. Table salt (Na + Cl = sodium chloride)

8. Compounds The stars and circles chemically combined to form suns. This process cannot be undone.

10. Molecules Molecules are when two gases combine chemically (can either be two of the same or two different gases). Molecules are when two gases combine chemically (can either be two of the same or two different gases). Ex. H 2 O is one molecule of water Ex. H 2 O is one molecule of water

13. Pure Substance It’s properties are constant throughout the whole sample (every single part of it is the same). It’s properties are constant throughout the whole sample (every single part of it is the same). Elements and compounds are pure substances, but mixtures are not because the properties of mixtures change throughout! Elements and compounds are pure substances, but mixtures are not because the properties of mixtures change throughout! Ex. Orange juice=mixture Ex. Orange juice=mixture Water=pure substance Water=pure substance Orange juice can be separated and water cannot be separated in the same way.

14. Mixtures Two or more elements that are physically combined, not chemically Two or more elements that are physically combined, not chemically Can easily separate the parts Can easily separate the parts (Ex. a cheeseburger) (Ex. a cheeseburger) Ex. Dirt and sand (if you wanted, you could easily take out the hearts) Ex. Dirt and sand (if you wanted, you could easily take out the hearts)

17. Types of Mixtures There are two types of mixtures: There are two types of mixtures: 1. Homogeneous (homo means “same”) 2. Heterogeneous (hetero means “different”)

18. Homogeneous Mixtures Have the same appearance and composition throughout. Have the same appearance and composition throughout. Each region of a sample is identical to all other regions of the sample (one phase). Each region of a sample is identical to all other regions of the sample (one phase). Ex. Salt water, sugar water and air

20. Heterogeneous Mixtures Consist of visibly different substances or phases. Consist of visibly different substances or phases. Ex. Chocolate chip cookies, oil and vinegar, milk, pizza and a bowl of raisin bran cereal Ex. Chocolate chip cookies, oil and vinegar, milk, pizza and a bowl of raisin bran cereal

23. Solutions A solution is a mixture of two or more substances. A solution is a mixture of two or more substances. At least two substances must be mixed in order to have a solution. At least two substances must be mixed in order to have a solution.

24. Solutes vs. Solvents The substance in the smallest amount or the one that dissolves or disperses (gets mixed) is called the SOLUTE. The substance in the smallest amount or the one that dissolves or disperses (gets mixed) is called the SOLUTE. The substance in the larger amount is called the SOLVENT. The substance in the larger amount is called the SOLVENT.

25. Solutes vs. Solvents In most common instances water is the solvent. In most common instances water is the solvent. Water is considered to be the “universal solvent” because just about everything will dissolve in it. Water is considered to be the “universal solvent” because just about everything will dissolve in it. Oil is considered to be insoluble because it will not dissolve. Oil is considered to be insoluble because it will not dissolve.

26. Concentrated vs. Diluted Since solutions are mixtures, their compositions may vary over a very wide range. Since solutions are mixtures, their compositions may vary over a very wide range. A concentrated solution has a relatively large (but non-specific) amount of solute dissolved in a solvent. A concentrated solution has a relatively large (but non-specific) amount of solute dissolved in a solvent. A diluted solution has a smaller quantity of solute dissolved. A diluted solution has a smaller quantity of solute dissolved.

27. Alloys A homogeneous mixture of two or more metals. A homogeneous mixture of two or more metals. Metal mixtures can have greater strength, hardness or malleability than by themselves. Metal mixtures can have greater strength, hardness or malleability than by themselves.

28. Alloy Examples Brass (copper and zinc) Brass (copper and zinc) Stainless Steel (chromium, nickel, and iron) Stainless Steel (chromium, nickel, and iron) Sterling Silver (copper and silver) Sterling Silver (copper and silver)

29. Colloid Colloid- a heterogeneous solution with medium sized particles. Colloid- a heterogeneous solution with medium sized particles. Colloid particles may be seen in a beam of light. Colloid particles may be seen in a beam of light. Examples: Milk, dust, smoke mist, fog Examples: Milk, dust, smoke mist, fog