Understanding the Composition of Matter: Elements, Compounds, and States

1. Objectives • To learn about the composition of matter • To learn the difference between elements and compounds • To define the three states of matter

2. A. The Particulate Nature of Matter • Matter has mass and occupies space. • It is composed of tiny particles called atoms.

3. B. Elements and Compounds Elements • Elements contain only one type of atom – elemental copper contains only copper atoms and elemental gold contains only gold atoms.

4. B. Elements and Compounds Compounds • Compounds are substances that contain two or more different types of atoms.

5. C. The States of Matter • Matter exists in three states: • Solid: a rigid substance with a definite shape • Liquid: has a definite volume but takes the shape of its container • Gas: takes the shape and volume of its container

6. Structure of a Solid • Molecules are held close to each other by their attractions of charge. • They will bend and/or vibrate, but will stay in close proximity. • Video Clip

7. Structure of a Solid

8. Structure of a Liquid • Molecules will flow or glide over one another, but stay toward the bottom of the container. • Motion is a bit more random than that of a solid. p • Video Clip

9. Structure of a Liquid

10. Structure of a Gas • Molecules are in continual straightline motion. • The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other. • When the molecules collide with each other, or with the walls of a container, there is no loss of energy. • Video Clip

11. Structure of a Gas

12. The Kinetic Molecular Theory explains the forces between molecules and the energy that they possess. This theory has 3 basic assumptions. • Matter is composed of small particles (molecules). • The measure of space that the molecules occupy (volume) is derived from the space inbetween the molecules and not the space the molecules contain themselves. • The molecules are in constant motion. This motion is different for the 3 states of matter. • Solid = low KE & strong attractive forces • Liquids = KE & attractive forces are higher than solids and lower than gases • Gases = High KE & weak attractive forces

13. The amount of matter and total mass remains the same Law of Constant Composition (Law of Conservation of Mass) = All samples of a given compound have the same proportions of their constituent elements. All Physical and Chemical Changes involve some transfer of energy. Energy can be as heat or light (Can cause physical/chemical changes) Law of Conservation of Energy: Energy is not created of destroyed, only changed. Laws Regarding Matter

14. Laws Regarding Matter • Law of definite proportion • A given compound always contains exactly the same proportion of elements by mass • Law of multiple proportions • When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers.

15. Objectives • To learn to distinguish between physical and chemical properties. • To learn to distinguish between physical and chemical changes.

16. A. Physical and Chemical Properties and Changes • Properties are used to identify and separate the substance. • Ex: Substance = metals Properties = conduct electricity • Matter has both physical and chemical properties. • Chemical properties describe a substance’s ability to change to a different substance. • Physical properties are the characteristics of a substance that do not involve changing to another substance. • Examples are: shape, size and color, melting point, boiling point

17. A. Physical and Chemical Properties and Changes • Matter undergoes physical and chemical changes. • A physical change involves a change in one or more physical properties but no change in composition. • Ex: cutting, melting, boiling, freezing

18. A. Physical and Chemical Properties and Changes • Matter undergoes physical and chemical changes. • A chemical change transforms a substance into one or more new substances. • Ex: electrolysis, precipitates, formation of light/heat

19. Objectives • To learn to distinguish between mixtures and pure substances • To learn methods of separating mixtures

20. A. Mixtures and Pure Substances • Matter can be classified as a mixture or a pure substance.

21. Classification of Matter: • Mixtures = a blend of two or more kinds of matter, each of which retains its own identity and properties. • - Parts can mixed together physically and usually can be separated. • - Contain various amounts of different substances, so the composition needs to be specified. (% Mass = EX: 5 % NaCl and 95 % water) • Homogeneous (solutions): Uniform in composition (Saltwater, air, milk, alloys) • Heterogeneous: not uniform throughout (can be separated) (pizza, concrete, salad)

22. Water is a compound. All the components are the same—H2O molecules. A. Mixtures and Pure Substances • A pure substance always has the same composition. • Pure substances are of two types: • Elements which cannot be broken down chemically into simpler substances • Compounds which can be chemically broken down into elements

23. Homogeneous Mixtures

24. Mixture vs. Solution

25. Mixture vs. Compound

26. Summary: The Organization of Matter

27. Separation techniques of mixtures: • Filtration = to filter a solid from a liquid • Filtrate • Residue • Decant = used when the mixture consists of substances of different densities. • The less dense substances is carefully poured off of the more dense one. • Centrifugation - used when the substances have very similar densities, or when one of the substances consists of very fine particles suspended in a liquid. • Electrolysis – electric current to separate water into hydrogen gas and oxygen gas

28. B. Separation of Mixtures Mixtures can be separated into pure substances by various means. • filtration

29. Chromatography This technique separates substances (dyes and pigments) on the basis of differences in solubility in a solvent. • Paper Chromatography = A solvent travels through paper by capillary action and carries the pigments with it. Different pigments are deposited at different places on the paper depending on how much they like the solvent compared to how much they like to stick to the paper. • Solvent • Solute

30. Separation Techniques • Distillation = to remove dissolved substances from a liquid or to separate a mixture of liquids that have different boiling points. • The original liquid is heated. • The temperature is measured. • The vapor is collected and condensed back into a liquid. • The new liquid is collected.

31. B. Separation of Mixtures Mixtures can be separated into pure substances by various means. • distillation