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2 Properties of Substances

3 A property is a characteristic of a substance. Each substance has a set of properties that are characteristic of that substance and give it a unique identity. Properties of a Substance

4 Physical Properties

5 The inherent characteristics of a substance that are determined without changing its composition. Examples: ttaste ccolor pphysical state mmelting point bboiling point

6 2.4 times heavier than air color is yellowish-green odor is disagreeable melting point –101 o C boiling point –34.6 o C Physical Properties of Chlorine

7 Chemical Properties

8 Describe the ability of a substance to form new substances, either by reaction with other substances or by decomposition.

9 It will not burn in oxygen. It will support the combustion of certain other substances. It can be used as a bleaching agent. It can be used as a water disinfectant. It can combine with sodium to form sodium chloride. Chemical Properties of Chlorine

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11 Physical Changes

12 Changes in physical properties (such as size shape and density) or changes in the state of matter without an accompanying change in composition. Examples: Physical Changes ttearing of paper cchange of ice into water cchange of water into steam hheating platinum wire

13 Chemical Changes

14 In a chemical change new substances are formed that have different properties and composition from the original material.

15 Formation of Copper(II) Oxide Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black material. The black material is a new substance called copper(II) oxide. Copper is 100% copper by mass. Copper (II) oxide is: 79.94% copper by mass 20.1% oxygen by mass. The formation of copper(II) oxide from copper and oxygen is a chemical change. The copper (II) oxide is a new substance with properties that are different from copper.

16 Formation of Copper(II) Oxide Copper(II) oxide is made up of Cu 2+ and O 2- Neither Cu nor O 2 contains Cu 2+ or O 2- A chemical change has occurred.

17 Water is decomposed into hydrogen and oxygen by passing electricity through it. Decomposition of Water The composition and physical appearance of hydrogen and oxygen are different from water. The hydrogen explodes with a pop upon the addition of a burning splint. The oxygen causes the flame of a burning splint to intensify. They are both colorless gases.But the burning splint is extinguished when placed into the water sample.

18 Chemical Equations

19 Water decomposes into hydrogen and oxygen when electrolyzed. reactant products yields

20 Chemical symbols can be used to express chemical reactions

21 Water decomposes into hydrogen and oxygen when electrolyzed. reactant yields 2H 2 O2H 2 O2O2 products

22 Copper plus oxygen yields copper(II) oxide. yield product reactants heat

23 Copper plus oxygen yields copper(II) oxide. yield product reactants heat 2CuO2O2 2Cu 2 O

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25 Conservation of Mass

26 No change is observed in the total mass of the substances involved in a chemical change.

27 sodium + sulfur  sodium sulfide 46.0 g32.1 g78.1 g 78.1 g product mass products 78.1 g reactant → mass reactants =

28 Heat: Quantitative Measurement

29 Heat A form of energy associated with small particles of matter. Temperature A measure of the intensity of heat, or of how hot or cold a system is.

30 Units of Heat Energy

31 The SI unit for heat energy is the joule (pronounced “jool” rhymes with fool). Another unit is the calorie J = 1 cal (exactly) Joules = 1 calorie This amount of heat energy will raise the temperature of 1 gram of water 1 o C.

32 Specific Heat

33 The specific heat of a substance is the quantity of heat required to change the temperature of 1 g of that substance by 1 o C.

34 Specific Heat of Substances Substance Specific heat (cal/g  C) Water1.00 Ethyl alcohol0.511 Ice0.492 Steam0.481 Iron0.113 Copper Gold Lead0.0305

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36 The units of specific heat in calories are:

37 The relation of mass, specific heat, temperature change ( Δ t), and quantity of heat lost or gained is expressed by the general equation: Heat (cal) = mass (g)  specific heat (cal/g  C)  Δt (  C)

38 Example

39 Calculate the specific heat of a solid in cal/g o C if cal raise the temperature of 125 g of the solid from 25.0 o C to 52.6 o C. heat = (mass)(specific heat)Δt heat = (g)(specific heat)Δt heat = cal mass = 125 g Δt = 52.6 o C – 25.0 o C = 27.6 o C cal cal g  C =

40 Energy in Chemical Changes

41 In all chemical changes, matter either absorbs or releases energy.

42 Energy Release From Chemical Sources Type of Energy Energy Source ElectricalStorage batteries LightA lightstick. Fuel combustion. Heat and LightCombustion of fuels. Body Chemical changes occurring within body cells.

43 Chemical Changes Caused by Absorption of Energy Type of Energy Chemical Change Electrical Electroplating of metals. Decomposition of water into hydrogen and oxygen LightPhotosynthesis in green plants.

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