1. Department of Chemistry CHEM1010 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel: 931-6325 Email: hzhang@tntech.edu

2. CHEM1010/General Chemistry _________________________________________ Chapter 1. (L4)-Introduction Today’s Outline..Review: How to measure matter in a scientific way (the value of a property depends on unit)?..Energy and heat -Concept of energy -Concept of heat..Temperature -Concept of temperature -How to measure temperature (different units)

3. Chapter 1. (L4)-Introduction How to measure matter in a scientific way? Last time, we discussed on how to measure matter in a scientific way, i.e., doing measurements accurately -Any measurement of a property has two components: Value and unit; lack of either will make the measurement result meaningless. -The International System of Units or SI system, and commonly used units in the system Scientific expression of numbers, powers of 10 and prefixes -Measurement of some commonly used important physical properties (mass, length, area, volume, time)

4. Chapter 1. (L4)-Introduction Concept of energy Energy: Intuitive meaning..The ability to do something. It has something to do with changes, because doing something means causing certain changes. Examples: Cut a tree, carry a bag uphill, paddle a canoe, jump, throw a baseball, kick a soccer ball, engine moves a car, sunlight melts snow, electricity powers a fan to move air, charcoal burning heats/boils water, an apple falls from a tree to the ground

5. Chapter 1. (L4)-Introduction Concept of energy Energy: Scientific meaning..The ability to cause changes of matter, either physical changes or chemical changes..In other words, any physical or chemical changes require energy or release energy

6. Chapter 1. (L4)-Introduction Concept of energy Energy: Scientific meaning..Any matter has a certain level of energy..After matter changes, its energy level either goes up or down..If the energy level goes up, then the change needs energy..If the energy level goes down, then the change releases energy

7. Chapter 1. (L4)-Introduction Concept of energy Energy: Scientific meaning..Conservation of energy: Energy cannot be created nor destroyed...In other words, energy moves around in different matter, from this matter to another...Some matter gaining energy means some other matter loosing or releasing energy.

8. Chapter 1. (L4)-Introduction Concept of energy Energy: Scientific meaning Energy has various forms: Physical energy -mechanic energy -thermal energy -electrical energy -photo energy -magnetic energy Chemical energy Biological energy

9. Chapter 1. (L4)-Introduction Concept of energy Energy: Scientific meaning Energy transformation among different forms: -mechanic energy to thermal energy Example: friction to heat -mechanic energy to electrical energy Example: friction to electricity -chemical energy to electrical energy Example: battery -chemical energy to mechanical energy Example: gas burning to run car

10. Chapter 1. (L4)-Introduction Concept of energy The unit for energy:..Energy is a property of matter. To measure this property, we obviously need a unit just like measuring any other property...Commonly used energy units: The SI unit: joule, or J the common unit: calorie or cal (1 cal = the amount of heat needed to raise of temperature of 1 g water by 1 ºC) 1 kcal = 1000 cal = 10 3 cal Conversion: 1 cal = 4.184 J 1 kcal = 4184 J = 4.184×10 3 J

11. Chapter 1. (L4)-Introduction Concept of heat..Heat is a form of energy, called thermal energy...If matter gets heat, it becomes warm or hot; if matter looses heat, it becomes cool or cold...In other words, heat is moving around from one matter to another; if something gets heat, something else must loose it, and vise versa (energy conservation).

12. Chapter 1. (L4)-Introduction Concept of heat..Like water moves from a high position to a low position, heat moves from warm or hot matter to cool or cold matter until two things have the same hotness or coldness...Hot or cold, it is relative between two things. Example: B is hotter than A, but colder than C.

13. Chapter 1. (L4)-Introduction Concept of temperature..Temperature is a physical property of matter to measure how hot or cold the matter is; in other words, how much thermal energy it has... Just like water moves from a high position to a low position, heat moves from a high temperature to a low temperature until two things have the same temperature...With the introduction of temperature into science, we can tell exactly how hot or cold matter is by giving an exact value of temperature, not simply saying hot or cold.

14. Chapter 1. (L4)-Introduction Measurement of temperature..As discussed before, the value of any property depends on the unit used. The same is true for temperature...Units for temperature -The SI unit or scale: Kelvin, K It is based on scientific theory. It is an absolute scale, because at 0 K, matter would have the coldest temperature possible. So there is no negative value of temperature on Kelvin scale.

15. Chapter 1. (L4)-Introduction Measurement of temperature..Units for temperature (T) -The Celsius unit or scale: ºC, also called centigrade (Anders Celsius: a Swedish astronomer) It is based on physical property of water. It is a relative scale: 0 ºC is the freezing point of water, while 100 ºC is the boiling point of water. So there are negative values of T on the Celsius scale. The Celsius unit is still commonly used in routine laboratory work in science. -Conversion between Kelvin and Celsius units: K = ºC + 273

16. Chapter 1. (L4)-Introduction Measurement of temperature..Units for temperature (T) -The Fahrenheit unit or scale: ºF (Gabriel Fahrenheit: a Polish-born scientist) It is widely used in the USA. It is a relative scale: 32 ºF is the freezing point of water, while 212 ºF is the boiling point of water. So there are negative values of T on the Fahrenheit scale. -Conversion between Fahrenheit and Celsius units: ºC = (ºF – 32)/1.8 ºF = (ºC×1.8) + 32

17. Chapter 1. (L4)-Introduction Measurement of temperature..Some useful temperatures ºC ºFWhat Happens 260500a steak broils 180350bread and cake bake 100212water boils normally 40104human body has a high fever 38100summer day is hot 37 99normal human body temperature 0 32water freezes -5 21winter day is cold -10 14ice cream freezes -15 5home freezer is at proper T

18. Chapter 1. (L4)-Introduction Measurement of temperature..How to measure temperatures Principles of thermometers..Liquid expands with temperature Commonly used liquids: -Mercury (liquid metal at room temperature) -alcohol..Solid metal expands with temperature thermal couple

19. Chapter 1. (L4)-Introduction Energy, heat, and temperature Quiz Time 1. Heat is a form of (a) force; (b) electricity; (c) energy; (d) light 2. The SI unit for temperature is (a) ºC; (b) K; (c) ºF; (d) calorie 3. Which of the following is a unit for energy: (a) meter; (b) calorie; (c) kelvin; (d) liter

20. Chapter 1. (L4)-Introduction Energy, heat, and temperature Quiz Time 1. The normal human body temperature is 99 ºF, which is equivalent to (a) 73.2 ºC and 373.2 K; (b) 37.2 ºC and 237.2 K; (c) 37.2 º C and 310.2 K; (d) 73.2 ºC and 732.2 K. 2. 2092 J is equivalent to (a) 0.5 cal; (b) 500 kcal; (c) 5 kcal; (d) 0.5 kcal

21. Chapter 1. (L4)-Introduction Energy, heat, and temperature Quiz Time 1. The temperature of the Earth surface would be around 290 ºC without life (biosphere), which is equivalent to (a) 920 ºF and 653 K; (b) 554 ºF and 563 K; (c) 290 ºF and 563 K; (d) 554 ºF and 732 K. 2. Which unit scale for temperature is based on a scientific theory and does not have negative values: Is that (a) ºC; (b) K; (c) ºF; (d) nano