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Topic 1

Topic 1. Mrs. Kuhn Chemistry Center for Creative Arts. Scientific Method. State the problem and observe. Observations may be either qualitative (describing physically observed phenomena) or quantitative (involving numerical measurements). Propose an explanation (aka hypothesis).

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Topic 1

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  1. Topic 1 Mrs. Kuhn Chemistry Center for Creative Arts

  2. Scientific Method • State the problem and observe. Observations may be either qualitative (describing physically observed phenomena) or quantitative (involving numerical measurements). • Propose an explanation (aka hypothesis). • Perform experiments to test hypothesis. Results and conclusions may lead to further experimentation.

  3. States of Matter • All matter has two distinct characteristics: mass and volume. • Solids: definite shape and volume. Particles are closely packed and only vibrate in fixed positions. • Liquids: indefinite shape and definite volume. Particles in liquid are free to move. • Gases: No definite shape or volume. Particles are free to move and expand to fill container.

  4. Solid Liquid Gas

  5. Properties of Matter

  6. Physical Changes • Involve altering shape, size, or state without changing chemical composition. • SOLIDLIQUID _______________ • GASLIQUID _______________ • SOLIDGAS _______________ • LIQUIDSOLID _______________ • GASSOLID _______________ • LIQUIDGAS _______________

  7. Chemical Changes • In chemical changes or reactions, the atoms of a substance are rearranged. The chemical composition of the new substance differ from the original. • Examples?

  8. Heat Transfer • When physical or chemical changes produce or absorb heat, the amount of heat involved is calculated using the specific heat capacity of the substance. ∆H = m x c x ∆T ∆H = amount of heat change m = mass of substance c = specific heat capacity ∆T = change in temperature in Celsius (determined by subtracting the final temp from the initial temp)

  9. Common Heat Capacities

  10. Specific Heat Capacity Sample Problems 1. What quantity of energy is required to raise the temperature of 10 grams of water from 15°C to 50°C? 2. A 5.0 gram sample of an iron nail requires 37.75J of energy to change its temperature from 25°C to 32.5°C. Is the nail made of pure iron? Explain.

  11. Density • Density is another attribute of matter. Density describes the relationship between a substance’s mass and its volume. • Density = mass/volume • d = m/v d = g/cm3 d = g/ml

  12. Density practice • What is the density of an object if its mass is 124 grams and its volume is 130 mls? • What is the density of a cube if its dimensions are 3cm x 4 cm x 2 cm and its mass is 10.0 g? (Remember: v= l x w x h)

  13. Common Densities

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