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Understanding Physical and Chemical Properties for Science Students

Explore the nature of matter, learn to identify substances based on properties, and develop computation skills for scientific explanations. Dive into concepts like density, flammability, and changes in properties. Practice problems included.

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Understanding Physical and Chemical Properties for Science Students

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  1. Physical and Chemical Properties and Changes • GPS Standards: SC1. Students will analyze the nature of matter and its classifications. • Identify substances based on chemical and physical properties. • SCSh5. Students will demonstrate the computation and estimation skills necessary for analyzing data and developing reasonable scientific explanations. • e. Solve scientific problems by substituting quantitative values, using dimensional analysis and/or simple algebraic formulas as appropriate. 8/10/10

  2. physical property = characteristic of a substance that can be observed or measured WITHOUT changing the identity (chemical formula) of the substance. Most physical properties do NOT depend on the size or source of the sample. • chemical property: characteristic of a substance that can be observed or measured only by performing a chemical reaction with the substance (the reaction causes a CHANGE in the substance’s formula). Most chemicalproperties do NOT depend on the size or source of the sample. • physical change = a change in the physical form or properties of a substance that occurs WITHOUT changing the identity (formula) of the substance. • chemical change = a CHANGE in the chemical formula of a substance that occurs through a chemical reaction, forming one or more new substances.

  3. density flammability fruit ripening batteries “dying” boiling color boiling point breathing burning precipitates forming neutralization shape reactivity shape/texture change sublimating volume condensing decomposition rate density flammability color reactivity boiling point decomposition rate shape volume boiling fruitripening shape/texture change batteries “dying” sublimating breathing condensing burning precipitates forming neutralization

  4. deposition changing mass/volume melting point phase color change acid/base character colored paper fading melting photosynthesis dissolving electrical conductivity evaporating hardness magnetic character mass density flammability magnetic character color reactivity boiling point decomposition rate mass shape acid/base character volume melting point phase electrical conductivity hardness boiling fruitripening shape/texture change batteries “dying” sublimating breathing condensing burning deposition precipitates forming changing mass/volume neutralization melting color change dissolving colored paper fading evaporating photosynthesis

  5. Properties can also be classified another way: extensive properties: depend on amount of matter that is present in the sample. Can be physical or chemical. examples = mass, volume, some chemical reactivities, etc. intensive properties: do NOT depend on amount of matter that is present in the sample. Can be physical or chemical. examples = melting/boiling points, density, hardness, electrical conductivity, magnetism, color, shape, reactivity, combustibility, acid/base character, etc.

  6. Density density (D) = the relationship between the mass (m) and volume (V) of a substance. acceptable units for mass include grams (g), kilograms (kg), etc. acceptable units for volume include cubic centimeters (cm3), liters (L), milliliters (mL), etc. acceptable units for density include g/cm3, g/L, g/mL, kg/L, etc. the volume measurement of a density problem can calculated in two ways: water displacement = method for measuring the volume of an irregular object. an object is dropped into a measured amount of water in a graduated cylinder or beaker. D = m V

  7. water displacement = method for measuring the volume of an irregular object. an object is dropped into a measured amount of water in a graduated cylinder or beaker. the difference between the initial volume of the water and the new volume of the water is equivalent to the object’s volume. measured size = method for measuring the volume of a regular object (such as a rectangular prism, sphere, or cylinder) by measuring the length of the sides/radius. practice problems: Ex1: If 15.68 g of a liquid occupy a space of 44.5 mL, what is the density of the liquid in g/cm3?

  8. Ex1: If 15.68 g of a liquid occupy a space of 44.5 mL, what is the density of the liquid in g/cm3? D = _____________ m = _____________ V = _____________ Ex2: The density of silver is 10.49 g/cm3.  If small bar of pure silver measures 3.4 cm by 1.8 cm by 3.7 cm, what would the mass be for this sample? D = _____________ m = _____________ V = _____________ ? 15.68 g 44.5 mL 1 mL = 1 cm3 ...so 44.5 mL = 44.5 cm3 D = m V = 15.68 g = 44.5 cm3 .35 g/cm3 V = lwh = (3.4 cm)(1.8 cm)(3.7 cm) 10.49 g/cm3 ? 22.644 cm3 V = 22.644 cm3 VV D = m V m = VD = (22.644 cm3)(10.49 g/cm3) = 237.54 g

  9. Ex3: The density of a lead cylinder is 11.34 g/cm3.  What would be the length of a 364.5 g cylinder of this metal if its radius is 2.7 cm? D = _____________ m = _____________ V = _____________ m = VD V = m D __ ___ D D 11.34 g/cm3 364.5 g ? V = 364.5 g = 11.34 g/cm3 32.14 cm3 V = r2h __ _____ r2r2 32.14 cm3= (2.7 cm)2 h = V = r2 1.40 cm

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