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Chapter 3 Matter and Energy.

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Presentation on theme: "Chapter 3 Matter and Energy."— Presentation transcript:

1 Chapter 3 Matter and Energy

2 Homework Assigned Problems (odd numbers only)
“Questions and Problems” to 3.41 (begins on page 61) “Additional Questions and Problems” to 3.69 (page 87-88) “Challenge Questions” and 3.75, (page 88)

3 Matter Matter is any material that has mass and occupies space
Matter is made up of small particles Atoms Molecules Includes all things (living and nonliving) such as plants, soil, and rocks Any material we use such as water, wood, clothing, etc. The materials we use

4 Matter and Energy Chemistry is the study of matter
The properties of different types of matter The way matter behaves when influenced by other matter and/or energy Nearly all changes that matter undergoes involves the release or absorption of energy Energy is the part of the universe that has the ability to do work Energy can do work or transfer heat

5 Classification of Matter

6 Pure Substance Matter that has a definite and constant composition
Always contains the same substance, never varies Either elements or compounds, all of one type A pure sample of water only contains water molecules Pure table salt contains only salt

7 Pure Substances Elements
Substances which can not be broken down into simpler substances by chemical reactions Fundamental substances Compounds Two or more elements combined chemically in a definite and constant ratio Can be broken down into simpler substances Most of matter is in the compound form Two types of pure substances

8 Compounds Compounds Results from a chemical combination of two or more elements Can be broken down into elements by chemical processes Properties of the compound not related to the properties of the elements that compose it Water is composed of hydrogen and oxygen gases (combined in a 2:1 ratio)

9 Mixtures Something of variable composition
Result from the physical combination of two or more substances (elements or compounds) Made up of two or more types of substances physically mixed Not mixed in a fixed ratio, no chemical combination between the two substances You can dissolve a small amount of sugar in water and then increase the amount of sugar

10 Compounds vs. Mixtures Compounds are not mixtures
Cannot be separated by a physical process Can be subdivided by a chemical process into two or more simpler substances Mixtures Unlike compounds, mixtures can be separated by a physical process Retain the properties of their individual components

11 Types of Mixtures Two types of mixtures: Homogeneous mixture:
Same uniform composition throughout Not possible to see the two substances present Heterogeneous mixture: Composition is not uniform throughout the sample. It contains visibly different parts or phases

12 Types of mixtures Homogenous mixtures A sugar solution
14 karat gold, a mixture of copper and gold Air, a mixture of gases (oxygen, nitrogen) Heterogeneous mixture Oil and vinegar Raisin cookies Sand Pure substance i.e. copper (all elements are pure substances)

13 Classification of Matter
Physical Methods Chemical Methods

14 Properties of Matter Many properties used to identify chemical substances Two types Physical Properties Chemical Properties Properties can be: Directly observable The interaction of the matter with other substances

15 States of Matter Solid Has a rigid, definite shape and definite volume
Liquid Has an indefinite shape and a definite volume. It will take the shape of the container it fills Gas Has an indefinite shape and an indefinite volume. It will take the shape and completely fill the volume of the container it fills


17 Physical Properties Physical Properties Physical Changes
Characteristics of matter that can be observed or measured without changing its identity or composition Characteristics that are directly observable Color, odor, physical state, density, melting point, boiling point Physical Changes Cutting a piece of metal, melting ice

18 Physical Change A process that alters the appearance of a substance but does not change its identity or composition No new substance is formed Most common are changes of state

19 Chemical Properties Chemical Properties
Describes the ability of a substance to react and change into a new substance Properties that matter exhibits as it undergoes changes in chemical composition During a chemical change, the original substance is converted into one or more new substances with different chemical and physical properties

20 Chemical Change A change in the fundamental components of the substance: A substance undergoes a change in chemical composition Also called a chemical reaction Conversion of material(s) into one or more new substances Wood burning, iron rusting, alka seltzer tablet into water

21 Classifying Properties
The boiling point of ethyl alcohol is 78 °C Physical property – describes an inherent characteristic of alcohol, its boiling point Diamond is very hard Physical property – describes inherent characteristic of diamond – hardness Sugar ferments to form ethyl alcohol Chemical property – describes behavior of sugar, ability to form a new substance (ethyl alcohol)

22 Classifying Changes Melting of snow Burning of gasoline
Physical change – a change of state but not a change in composition Burning of gasoline Chemical change – combines with oxygen to form new compounds Rusting of iron Chemical change – combines with oxygen to form a new reddish-colored substance (ferric oxide)

23 Classifying Changes Iron metal is melted
Physical change – describes a state change, but the material is still iron Iron combines with oxygen to form rust Chemical change – describes how iron and oxygen combine to make a new substance, rust (ferric oxide) Sugar ferments to form ethyl alcohol Chemical change – describes how sugar forms a new substance (ethyl alcohol)

24 Temperature A measure of how hot or cold a substance is compared to another substance Fahrenheit Scale, °F Used in USA Water’s freezing point = 32°F, boiling point = 212°F Celsius Scale, °C Used in science (USA) and everyday use in most of the world Temperature unit larger than the Fahrenheit Water’s freezing point = 0°C, boiling point = 100°C

25 Temperature Kelvin Scale, K SI Unit Used in science
Temperature unit same size as Celsius Water’s freezing point = 273 K, boiling point = 373 K Absolute zero is the lowest temperature theoretically possible No negative temperatures Differs from the Celcius scale only in numerical values assigned to their reference points

26 Converting °C to °F Units are different sizes
Fahrenheit scale: 180 degree intervals between freezing and boiling Celsius scale: 100 degree intervals between freezing and boiling


28 Converting °C to °F To convert from °C to °F
Different values for the freezing points Different size of the degree intervals in each scale 32 °F 0 °C add 32 to the °F value

29 Example A cake is baked at 350 °F. What is this in Centigrade/Celsius? In Kelvin?

30 Converting °C to K Temperature units are the same size
Differ only in the value assigned to their reference points K = °C + 273 25°C is room temperature, what is the equivalent temperature on the Kelvin scale? K = °C + 273 25 ºC = 298 K 25 ºC = 298 K 25 ºC = 298 K

31 Energy Capacity to do work or supply heat
Electrical, radiant, mechanical, thermal, chemical, nuclear Two forms of Energy Potential: Stored energy Kinetic: Motion energy All physical changes and chemical changes involve energy changes

32 Forms of Energy Potential energy: Determined by an objects position
Chemical energy is potential energy stored in the bonds contained within a molecule. It is released in a chemical reaction Kinetic energy Energy that matter acquires due to motion Converted from the potential energy All physical changes and chemical changes involve energy changes These changes convert energy from one form to another

33 Units of Energy The joule (J) is the SI unit of heat energy
The calorie (cal) is an older unit used for measuring heat energy (not an SI unit) The amount of energy needed to raise the temperature of one gram of water by 1°C The Cal is the unit of heat energy in nutrition 4.184 J = 1 cal 1 kcal = 1000 cal 1 Cal = 1000 cal = 1 kcal

34 Specific Heat Heat energy is the form of energy most often released or required for chemical and physical changes Every substance must absorb a different amount of heat to reach a certain temperature Different substances respond differently when heat is applied

35 Specific Heat If 4.184 J of heat is applied to:
1 g of water, its temperature is raised by 1 °C 1 g of gold, its temperature is raised by 32 °C Some substances requires large amounts of heat to change their temperatures, and others require a small amount The precise amount of heat that is required to cause a substance to have a rise in temperature is called a substance’s “specific heat”

36 Specific Heat The amount of heat energy (q) needed to raise 1 gram of a substance by 1 °C Specific to the substance The higher the specific heat value, the less its temperature will change when it absorbs heat SH values given in table 3.7, page 76 Only for heating/cooling not for changes in state

37 Specific Heat Expression with Calories and Joules
1 cal is the energy needed to heat 1 g of water 1 °C 1 cal is J Make a conversion factor from the statements

38 Specific Heat Equation
The rearrangement of the SH equation gives the expression called the “heat equation” SH q = heat SH = specific heat (different for each substance) m = mass (g) ∆T = change in temperature (°C)

39 Specific Heat Equation
Energy (heat) required to change the temperature of a substance depends on: The amount of substance being heated (g) The temperature change (initial T and final T in °C) The identity of the substance Identiy of a substance will determine the specific heat value and how much heat it will absorb

40 Energy and T The amount the temperature of an object increases depends on the amount of heat added (q) If you double the added heat energy (q), the temperature will increase twice as much. When a substance absorbs energy, q is positive, temperature increases When a substance loses energy, q is negative, temperature decreases

41 Converting Energy Units
Use same problem solving steps as before (Chapter 2) State the given and needed units Write the unit plan to convert the given unit to the final unit State the equalities and the conversion factors Set up the problem to cancel the units Pepsi One™ contains 1 Calorie per can. How many joules is this? State the given and needed units 1 Cal = 1000 cal 4.184 J = 1 cal

42 Calculating Mass Using Specific Heat
The 4184 J from the Pepsi One™ will heat how many grams of water from 0°C to boiling?

43 Calculating Mass Using Specific Heat
How many grams of water would reach boiling if the water started out at room temperature (25°C)?

44 Calculating The Temperature Change Using Specific Heat Values
If 50.0 J of heat is applied to 10.0 g of iron, by how much will the temperature of the iron increase?

45 end

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