What’s the Matter?

1. What’s the Matter?

2. The Basics • What is Chemistry? • What is matter? • How do we measure matter? • Mass = qty of matter in an object

3. The Nitty Gritty • What’s the smallest unit of matter? • Atom: as in, one oxygen atom • One or more atoms of the SAME type only is called an…? • Element. For example, the element oxygen (usually found as O2 which is what we use for cellular respiration, or O3, ozone)

4. The Nitty Gritty, continued • What do you get when you chemically combine two or more atoms? • A molecule • For example, a water molecule has two hydrogen and one oxygen atoms.

5. The Nitty Gritty, continued • If we combine (many of the same) molecules that contain at least two different elements we will get a…? • Compound;as in a glass of purified water (H20), table salt (NaCl), or dry ice (CO2)

6. Check for Understanding • Compare and contrast element and compound • Both made up of atoms • Both contain only one type of something • Element has only one type of atom, while compound has only one type of molecule, but must have more than one type of atom. • BUT! an element may contain molecules, as the element oxygen in the air contains O2molecules • All compounds are molecules, but not all molecules are compounds!

7. Energy and States of Matter • The state of matter with the lowest energy is…? • Solid – molecules are in a fixed position with respect to one another; they’re not moving around. • Think: Party, no music, everyone just standing around, or sitting

8. Energy and States of Matter • Add energy (heat) to a solid, and what happens?... • It Melts to a liquid – molecules rolling around each other, but not in a fixed state. Fixed volume, but has a variable shape. • Think: party is warming up, soft music playing. Crowded dance floor of people slow-dancing. As more people get up to dance, floor fills up and eventually spills into seating area and eventually the whole room is full of slow dancing couples.

9. Energy and States of Matter • Add energy (heat) to a liquid substance, and what happens? • Evaporates to become a gas. The molecules move around so much, they can’t stay close together. They need more space to “get their energy out” • Can you extend the analogy? • The temperature at which this boiling happens is called…? • The Boiling Point

10. Energy and States of Matter • Take away energy (reduce heat) and you get the whole process in reverse • Gas condenses to liquid • Liquid freezes to solid • Pair up the following temperature points: Boiling point, freezing point, condensing point, melting point • Boiling point pairs with condensing point; freezing and melting are same points, also.

11. Check for Understanding • Create your own analogy for solid/liquid/gas states of matter, and a substance going back and forth between them.

12. Skipping liquids • Sublimation – solid goes straight to gas • i.e. dry ice • Deposition/ resublimation – solid to gas

13. Put it all together • Fill in the boxes and arrows liquid

14. Extend your brain • So what’s the difference between evaporation and boiling??? • What’s the difference between vapor and gas??? • What’s the difference between fluid and liquid???

15. Physical vs. Chemical PropertiesCh 2.2 • Physical property: characteristic of a substance that can be observed and measured without changing the composition of the substance • List as many examples as you can of physical properties of substances • Density, color, odor, volume, melting point, boiling point, physical state, etc. • Chemical properties: describes the ability (or inability) of a substance to combine with or change into one or more other substances (i.e. its reactivity)

16. Physical Properties:Intensive vs. Extensive Intensive Don’t vary with quantity Color, odor, density, … If you take away some of the salt from a salt block, you still have salty taste, just less of it. The salt keeps its intensive properties Extensive Varies with quantity If you take away some salt from a salt block, its mass will change.

17. Physical vs. Chemical Changes • Physical changes • state changes (solid – liquid – gas) don’t change the chemical properties or composition of a substance. • The molecules are the same, just at different distance from each other. • Can you think of other examples? • Chemical changes • Change the chemical properties • Actual molecules in new substance(s) are different from what you started with • i.e., splitting 2H2O 2H2 + O2 • Can you think of more examples?

18. Mix it up Ch 2.3 • Mixture – has variable composition, different types of parts • i.e., air, water from the tap, hot chocolate, paint, 14k gold, stainless steel (metal mixtures are called alloys) • Heterogenous “hetero” means different • Homogenous “homo” means same • Solution = homogenous mixture Non-homogenized milk

19. Mix it Up • The solvent is the substance that the solute dissolves in • Any questions? • So, if I stir sugar into my coffee, which is which? • Once the solute is dissolved, as long as there’s none left at the bottom, what do you call the new coffee? • A homogenous mixture, or solution • What if there’s sugar left at the bottom? That would be called…? • A Heterogeneous mixture

20. Classifying Matter • A “pure substance”, refers to…? • Any pure element or compound, in any phase of matter. • Try these examples: are they pure substances, homogenous mixtures or heterogeneous mixtures? • Maple syrup • The oxygen and helium in a scuba tank • Oil and vinegar salad dressing • Table salt

21. Separating Mixtures How do we separate a liquid from a solid? (Think - spaghetti from its boiling water) Filtration How do we separate two mixed liquids? Distillation – a separation process that depends on the different boiling points of the substances.