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Unit 2: Matter and Change

Unit 2: Matter and Change. OBJECTIVES. Students will be able to: define matter describe the states of matter (solid, liquid, gas) identify the characteristics of of a substance, element and compound distinguish between physical and chemical change

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Unit 2: Matter and Change

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  1. Unit 2: Matter and Change

  2. OBJECTIVES Students will be able to: • define matter • describe the states of matter (solid, liquid, gas) • identify the characteristics of of a substance, element and compound • distinguish between physical and chemical change • identify properties of matter (chemical, physical, intensive, extensive) • identify changes in matter that occur (physical and chemical change) • explain the law of conservation of mass

  3. WHAT IS MATTER? • Matter is anything that takes up space and has mass • Matter or not? • gold • sound • sunlight • air • water • heat • thoughts

  4. MASS & WEIGHT • Mass is the measure of the amount of matter that makes up an object • Weight is a measure of the force of gravity on an object • weight = mass x gravity • weight varies depending on distance from the earth’s surface • Because the value never changes, scientists use mass, not weight to measure matter

  5. STATES OF MATTER

  6. GAS vs. VAPOR • Gases and vapors are similar, but terms should not be used interchangeably • Gas refers to a substance that is naturally in the gaseous state at room temperature: hydrogen gas • Vapor refers to the gaseous state of a substance that is a solid or a liquid at room temperature: water vapor

  7. THE PHASES OF WATER solid liquid gas

  8. MatterAnything that has mass and takes up space Pure SubstanceMatter with an unique and unchanging composition MixturesA combination of 2 or more pure substances physical change ElementPure substance that cannot be broken into more simpler substances CompoundAtoms of two or more elements that are chemically united in a fixed proportion HomogeneousMixture/SolutionMixture with a uniform composition HeterogeneousMixtureMixture does not appear to be the same throughout chemical change

  9. (PURE) SUBSTANCE • A substance is a form of matter with an unique and unchanging composition (composition doesn’t change from sample to sample) • Examples: Water, salt • What about salt water? • All pure substances are either elements or compounds

  10. ELEMENT • An element is a substance that cannot be broken into more simpler substances • Examples: gold (Au), oxygen (O2) • To date, there are 118 elements

  11. COMPOUNDS • Compounds are substances composed of atoms of two or more different elements that are chemically united in a fixed proportion • Water (H2O), sugar (sucrose, C12H22O11), ammonia (NH3) • Compounds can be separated back into its elements (by chemical means) • Electrolysis of water: • 2H2O  2H2 + O2

  12. PROPERTIES OF MATTER • Every pure substance has a unique set of properties • A property is a characteristic that allows us to recognize a certain type of matter

  13. PHYSICAL PROPERTIES • Physical properties are those properties that can be measured without changing the identity of the substance: • color, odor, melting point, boiling point, density, hardness, taste • Physical properties are either extensive or intensive

  14. CHEMICAL PROPERTIES • Chemical properties describe the way a substance may change or react to form other substances • Corrosion, flammability • The inability of a substance to change is also a chemical property • Argon gas is inert • To observe a chemical property a chemical change must occur

  15. PROPERTIES OF COPPER

  16. CHANGES IN MATTER • A physical change is a change that alters the appearance of the substance drastically but leaves its composition unchanged: • bend, grind, split, crush, boil, freeze, melt, vaporize

  17. Chemical Change (Chemical Reaction) • In a chemical change a substance is transformed into a chemically different substance • When hydrogen burns in air it reacts with oxygen to form water • The new substances formed have different compositions and different properties • Terms: Explode, rust, oxidize, corrode, tarnish, ferment, burn, rot etc.

  18. Formation of a gas or solid; color change; energy change; odor EVIDENCE OF CHEMICAL CHANGE

  19. PHYSICAL OR CHEMICAL CHANGE? • Plants use carbon dioxide and water to make sugar. • On a cold day, water vapor in the air forms frost.

  20. THE LAW OF CONSERVATION OF MASS • Mass (matter) is neither created nor destroyed during a reaction…mass is conserved: Massreactants = Massproducts

  21. PRACTICE PROBLEM • In a complete reaction of 22.99 g of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed? • A 12.2-g sample of X reacts with a sample of Y to form 78.9 g of XY. What is the mass of Y that reacted?

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