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Matter & Change

Matter & Change. Matter classification. Try to Answer the Following Questions. 1. A compound is formed by… A single element Two or more atoms Two or more nuclei Electrons and neutrons Which statement best describes atoms and molecules in a liquid? They vibrate rapidly

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Matter & Change

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  1. Matter & Change

  2. Matter classification

  3. Try to Answer the Following Questions 1. A compound is formed by… • A single element • Two or more atoms • Two or more nuclei • Electrons and neutrons • Which statement best describes atoms and molecules in a liquid? • They vibrate rapidly • They form a definite structure • They slide past each other • They cannot be rearranged • What is the process of a liquid changing to a gas called? • Ice melting into water is a physical or chemical change? • Which state of matter has neither a definite shape nor definite volume?

  4. How did you do? • “B”: two or more atoms • “C”: atoms and molecules in a liquid slide past each other • Evaporation • Physical • Gas

  5. Introduction • What is chemistry? • The study of the composition of substances and the changes (both physical and chemical) they undergo • What lead to the development of chemistry? • Alchemy • What other sciences does chemistry contribute to? • Biology • Geology • Physics

  6. Hypothesis vs. Theory vs. Scientific Law • A HYPOTHESIS is a proposed reason for what is observed and it needs to be tested by means of an experiment • A THEORY is a thoroughly tested explanation of why experiments give certain results. • A theory tends to explain WHY things happen. You cannot prove a theory. • Scientific Law is a concise statement that summarizes the results of a broad spectrum of observations and experiments. • Scientific Law tends to explain WHAT things happen. You can prove a scientific law.

  7. Why does it “matter”? • What is matter? • “Everything that takes up space and has mass” • “Stuff” • What is mass? Amount of matter an object contains “How much stuff an object has” **This is NOT the same as weight

  8. Substances vs Mixtures • Matter is broken into categories. Matter can be either a substance or a mixture. • A substance has a uniform (constant) composition. This means that no matter the sample it will always have the same physical properties (looks the same).

  9. Two Types of Substances Elements • Made up of only one type of atom. • Look at the periodic table! • Ex: Ca, K, Cl Compounds • Made up of two or more types of atoms. • A given compound always contains the same, fixed ratio of elements. • Elements can combine in different ratios to form different compounds. • Ex: Table Salt, NaCl Glucose, C6H12O6

  10. Pure Substances • Element • composed of identical atoms • EX: copper wire, aluminum foil

  11. Pure Substances • Compound • composed of 2 or more elements in a fixed ratio • properties differ from those of individual elements • EX: table salt (NaCl)

  12. Pure Substances • For example… Two different compounds, each has a definite composition.

  13. Mixtures • A mixture is a physical blend of two or more substances. It has a variable composition, so each sample taken will have different amounts of each substance. • Mixtures are ALWAYS physical changes

  14. Types of mixtures • Heterogeneous mixtures -not uniform in composition -more than one phase (a phase is a part of a system that is uniform in composition and physical state) -Can be physically separated -Can visibly see differences -examples: tossed salad, gravel mix, rock, river water

  15. Types of Mixtures • Homogeneous mixtures -uniform in composition -one phase -also called a solution -easily confused with substances -examples: salt water, kool-aid

  16. Solutions • Another name for a homogenous mixture • Can be either a liquid or gas • Phase is used to describe any part of a sample with uniform composition and properties Single phase 3 phases

  17. A good question to ask yourself when trying to decide if something is a substance or a homogeneous mixture is to ask yourself if there is more than one kind of this material. • What is gasoline? • What is milk? • Are there different concentrations of salt? if so then it is a mixture!

  18. Examples: element hetero. mixture compound hetero. mixture solution • graphite • pepper • sugar (sucrose) • paint • soda

  19. Separating a Mixture • There are several ways to separate a mixture. A good way to figure out if matter is a substance or a solution is to see if you can separate it into parts by doing one of the following: • Physical separation • Filter (particle size, uses gravity) • Magnet (magnetism) • Decanting-pouring off a liquid (density) • Distillation (boiling point) • Centrifuging (density) • Chromatography (separates based on solubility) • Crystallization

  20. Properties of Matter • Matter contains both physical and chemical properties. • A physical property is a quality of a substance that is observed without changing the substance’s original composition. • Examples: Color, mass, density, hardness, odor, boiling point, solubility

  21. Chemical Properties • Chemical properties are a little more difficult to determine. A chemical property is the ability of a substance to undergo chemical reactions. • Examples: Rot, rust, decompose, decay, grow ferment

  22. Chemical vs. Physical Changes • Chemical Change • A change in the composition of a substance OR • Changing a substance to form a new substance • Examples: fermenting, rotting, burning, color change, gas given off, heat • Physical Change • A change in a substance without a change in its composition • Examples: mixing, cutting, changing from a solid to a liquid, dissolving, boiling

  23. Figure it out- Chemical or Physical? • Metals are shiny • Milk gets sour when left out • Metals can be made into wires • Bread rises when cooked • Nonmetals are not able to conduct electricity P, C, P, C, P

  24. States of Matter • There are four states of matter: solid, liquid, gas • Solid • Liquid • Gas • Plasma –gas like What is compressibility? Ability to squash something into a smaller volume

  25. Solid, Liquid, Gas (a) Particles in solid (b) Particles in liquid (c) Particles in gas

  26. Solids • Has a definite shape and volume • The particles are packed close together • Are almost incompressible, difficult to squeeze to a smaller volume • Very low kinetic energy

  27. Liquids • Indefinite shape—takes on the shape of the container its in • Definite volume • Flows, particles are arranged randomly and are close, but not as close as solids • Almost incompressible • Low to moderate kinetic energy

  28. Gas • Indefinite shape • Indefinite volume • The particles are usually much farther apart • Gases are easily compressed into a smaller volume • High kinetic energy

  29. Fourth State of Matter • Plasma • very high KE - particles collide with enough energy to break into charged particles (+/-) • gas-like, variableshape & volume • stars

  30. Kinetic Molecular Theory • KMT • Particles of matter are always in motion.

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