: Comprehending states of matter and its change Describe role of heat in changes states of matter and temperature’s substance also its application in daily life 3 5 • Before the 9th century, many scientist believed that heat was a fluid. • Heat as fluid firstly stated by Antoine Laurent Lavoisier, He said that when a hotter object was in contact with the colder object, then the fluid would flow • Some scientist disagreed with the concept of Heat as fluid. Those scientist proved that Heat was not a fluid, but a form of Energy Antoine Lavoiser 6 Heat energy is the total energy of particles composing a matter. Heat is one form of energy which is flowing from an object with higher temperature to another object with lower temperature The unit of Heat is Joule (J) Heat is also expressed in units of calories. One calorie defined as the amount of heat needed to heat 1 gram of water until its temperature increasing 1 C °. 1 calorie = 4.2 joules 1 joule = 0.24 calories Heat Transfer • Heat always moves from a warmer place to a cooler place. • Hot objects in a cooler room will cool to room temperature.e.g: tea, coffee • Cold objects in a warmer room will heat up to room temperature.e.g: butter, ice What do you think? Heat Transfer Conduction Convection Radiation Radiation How does heat energy get from the Sun to the Earth? ? There are no particles between the Sun and the Earth so it MUST travel by radiation RADIATION Radiation • The transfer of heat in rays, from a hot object, without needing a medium to pass through • It travels in all directions from a hot object • The hotter an object is, the more heat it will radiate out • Does the surface affect the way heat is radiated? What colour should we paint radiators? Which colour is better to wear on a sunny day? black or white? • A dull black surface will radiate and absorb heat better than a bright shiny surface. Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Dull metal Shiny metal Shiny black Dull black shiny metal The __________ container would be the warmest after ten radiation back minutes because its shiny surface reflects heat _______ dull black into the container so less is lost. The ________ container would emitting be the coolest because it is the best at _______ heat radiation. Radiation – Think Pair-Share Radiation travels in straight lines True/False Radiation can travel through a vacuum True/False Radiation requires particles to travel True/False Radiation travels at the speed of light True/False Radiation questions Why are houses painted white in hot countries? White reflects heat radiation and keeps the house cooler. Why are shiny foil blankets wrapped around marathon runners at the end of a race? The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold. Conduction • Transfer of heat is through a SOLID by being passed from one particle to the next • Particles at the warm end move faster and this then causes the next particles to move faster and so on. e.g: poker in fire spoon in tea • In this way heat in an object travels from: the HOT end the cold end Conduction • When you heat a metal strip at one end, the heat travels to the other end. • As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction Conductors/Insulators • If a substance easily allows heat to move through it, we can say it is a good conductor of heat. e.g: most metals • If a substance does not allow heat to pass through it easily we can say it is an Insulator. E.g: wood, plastic, glass • Why do many sauce pans have plastic handles? Conduction V Insulation Conductor or Insulator? • • • • • • • • Wood? Aluminium? Plastic? Glass? Iron? Polystyrene? Copper? Cardboard? Convection What happens to the particles in a liquid or a gas when you heat them? The particles spread out and become less dense. A liquid or gas. Convection • It is the way in which particles in a GAS or LIQUID move upwards, carrying heat with them • Think about when you boil water, the bubbles move upwards • Or think of a gas heater in the room, the heat rises around the room Convection Cools at the surface Cooler water sinks Convection current Hot water rises Convection Where is the cooling compartment put in a fridge? It is put at the top, because cool air sinks, so it cools the food on the way down. It is warmer at the bottom, so this warmer air rises and a convection current is set up. Should a radiator be called a radiator? Convection questions Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Why are boilers placed beneath hot water tanks in people’s homes? Hot water rises. So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water. of temperature 7 Not all substances have the same ability in absorbing heat. The ability to absorb heat determined by the nature of a substance called specific het capacity. Specific Heat Capacity (c) The specific heat capacity of a substance is defined as the heat required to raising the temperature of 1 kg of the substance by 1°C. The unit of specific heat capacity is joule per kilogram per Celsius degree (J/kg C°) 8 This proved that heat needed to raise the temperature of 1C ° alcohol is smaller than the heat needed to raise water temperature at 1C°. That is, alcohol heat faster than water. 9 The amount of heat (Q) required by an object is proportional to the mass of the object (m), depending on the specific heat capacity (c), and comparable to the increase in temperature(∆T). The change of heat (received heat or released heat) of a substance cannot be measured directly, but it can be calculated using the following equation. Q = m x c x ΔT Notes: Q = heat received or released (Joules) m = mass (kg) c = specific heat capacity (J/kg C°) ΔT = changes of temperature (C°) 10 Calculate heat needed to increasing temperature of 500 g water from 20 ° C to 100 ° C,if the specific heat of water is 4200 J/ kg C°? Given: m= 500 g =0.5kg c = 4200 J/kg C° ∆T = 100°C - 20°C = 80 C° Question: Q = …? Answer: Q = m x c x ∆T = 0.5 kg x 4200 J/kgC° x 80 C° = 168,000 J So the heat received by the water is 168,000 J The heat capacity of a substance is defined as the amount of heat required to raise its temperature by 1 C° Unit of Heat capacity is Joules per Celsius degree (J/C °) Heat capacity can be calculated using the following equations. C = m×c Q C= ∆T Notes: C = Heat capacity (J/C°) m = mass (kg) Q = heat received or released (Joules) c = specific heat capacity (J/kg C°) ∆T = changes of temperature (C°) 12 Answer these following questions! 1. Two containers of the same size are filled with water and sand respectively. If they are exposed to the sun heat, which one gets hotter more quickly? Why? 2. You’re heating a 3.0 kg glass block, specific heat capacity of 840 J/(kg.C °), raising its temperature by 60C°. What heat do you have to apply? 3. 2 kg of iron is heated from 15 °C to 30°C. If the heat required is 13,500 J, what is specific heat capacity of iron? 4. 42 kilojoules of heat released from the 2 kg of ice at temperatures 15 ° C. What is the temperature finally, if the specific heat of ice is 2100 J/kg. C° 5. To raise the temperature of an object from 10°C to 40°C, it required heat 60,000 J. Calculate the heat capacity of its object! • When a matter change its state, the temperature does not increase although the heat is continuously given. • The heat is used to changing the state of matter. • The heat used for changing the state of matter is calledLatent heat. 13 STATES OF MATTER SOLIDS •Particles of solids are tightly packed, vibrating about a fixed position. •Solids have a definite shape and a definite volume. Heat STATES OF MATTER LIQUID Particles of liquids are tightly packed, but are far enough apart to slide over one another. Liquids have an indefinite shape and a definite volume. Heat STATES OF MATTER GAS Particles of gases are very far apart and move freely. Gases have an indefinite shape and an indefinite volume. Heat PHASE CHANGES Description of Phase Change Solid to liquid Term for Phase Change Melting Liquid to Freezing solid Heat Movement During Phase Change Heat goes into the solid as it melts. Heat leaves the liquid as it freezes. PHASE CHANGES Description of Phase Change Liquid to gas Gas to liquid Solid to gas Term for Phase Change Heat Movement During Phase Change Vaporization, which includes boiling and evaporation Heat goes into the liquid as it vaporizes. Condensation Heat leaves the gas as it condenses. Sublimation Heat goes into the solid as it sublimates. • Melting point is the temperature 14 when a matter is starting to melt. Example: melting point of ice is 0°C • Freezing point is the temperature when a matter is starting to freeze. Example: freezing point of water is 0°C Melting point = Freezing point Melting point 15 The amount of heat absorbed by every 1 kg of matter for melting at its melting point is called Melting heat (L). The amount of heat released by 1 kg of matter for freezing at its freezing point is called Freezing heat (L). SI Unit of Melting Heat and Freezing Heat: J/kg 16 AMOUNT OF HEAT (Q) RECEIVED OR RELEASED BY A MATTER WHEN IT MELTS OR FREEZES Where: Q = amount of Heat received or released (J) m = mass of matter (kg) L = Melting heat or Freezing Heat (J/kg) Boiling point is the temperature when a matter is starting to boils. Example: boiling point of water is 100ºC Condensation point is the temperature when a matter is starting to condenses. Boling point = Condensation point Boiling point of a liquid is affected by air pressure • The greater the air pressure the greater the boiling point of liquid • On the sea level, at air pressure of 1 atm, the Boiling point boiling point of water is 100 º C. • At higher place, the air pressure is decrease and boiling point of water is also decrease. 17 18 The amount of heat absorbed by every 1 kg of matter for vaporize at its boiling point is called vapouring heat (U). The amount of heat released by 1 kg of matter for condense at its condensation point is called condensation heat (U). SI Unit of Vapouring Heat of Condensation Heat: J/kg 19 AMOUNT OF HEAT (Q) RECEIVED OR RELEASED BY A MATTER WHEN IT EVAPORATES OR CONDENSES Where: Q = amount of Heat received or released (J) m = mass of matter (kg) L = Vaporing Heat or Condensation Heat (J/kg) Substance Melting point(ºC) Helium -269,65 Nitrogen -209,97 Oxygen -218,79 Ethylalcohol -114 Water 0 Sulfur 119 Lead Aluminum 327,3 660 Silver 960,8 Gold 1063 Copper 1083 Melting Boilingpoint VapouringHeat Heat(J/kg) (ºC) (J/kg) 3 5,23x10 4 2,25x10 4 1,38x10 5 1,04x10 5 3,33x10 4 3,81x10 4 2,45x10 5 3,97x10 4 8,82x10 5 1,34x10 3 5,23x10 -268,93 -195,81 -182,97 78 100 444,6 1750 2450 2193 2660 1187 4 2,09x10 5 2,01x10 5 2,13x10 5 8,54x10 6 2,26x10 5 3,26x10 5 8,70x10 7 1,14x10 6 2,33x10 6 1,58x10 6 5,06x10 20 21 No Evaporation Boiling 1. Occursatanytemperature belowboilingpoint Occursatafixedtemperature (boilingpoint) 2. Occursontheliquid’ssurface Occursthroughouttheliquid 3 Nobubblesareformed Bubblesareformedinthe liquid 4 SlowProcess Quickprocess 22 • Heating – When we heated liquid, the molecules near the surface vibrate faster, which enable them to release from liquid’s surface • Blowing air through the liquid’s surface – If we blow air through the surface of a hot water, the air near the water surface would carry the water’s molecules at the surface. • Extending the surface – To make hot tea in a cup cold faster, you should pour on a saucer, because the surface area of the saucer is larger than on the cup, so the molecules have more chances to leave the water surface • Decreasing the pressure on the surface – If the pressure decreasing, the space between air molecules near the surface become looser and it make easier for the molecules of water to fill the empty space among the molecules of air. 23 1. If ice melting, the state change from …. to … 2. For melting, ice …. heat energy 3. During ice melted, temperature is….. and it is called … 4. Amount of heat energy used to melt you can calculate with the formula 5. During the water boil, the temperature is … and it is called … 6. During the water boil, the state change from … become … and is called … 7. During evaporation the water ……heat energy. 8. Quantity heat energy used to evaporation can calculate by the formula … 24 1. Calculate the quantity of heat required to melt 3 kg of ice on 0ºC ! (L = 3.36 x 105 J/kg) Known: m= 3 kg L = 3.36 x 105 J/kg = 336,000 J/kg Question: Q ? Answer: Q=mxL Q = 3 kg x 336,000 J/kg Q = 1,008,000 J = 1,008 kJ 25 2. Calculate the quantity of heat required to change 500 grams of water at a temperature of 100ºC into water vapor at a temperature of 100ºC! (U = 2270 kJ/kg) Known: m= 500 grams = 0.5 kg U = 2270 kJ/kg Question: Q Answer: ? Q=mxU Q = 0.5 kg x 2,270 kJ/kg Q = 1,135 kJ Q = 1,135,000 J 3. Calculate the heat required to change 1 kg of water at 26 temperature of 80ºC into 1 kg of water vapor at a temperature of 100ºC (specific heat of water is 4200 J/kgºC and vapouring heat of water is 2270 kJ/kg) Temperature Known: m= 1 kg ∆T = (100-80) Cº = 20 Cº c = 4200 J/kg Cº U = 2270 kJ/kg = 2,270,000 J/kg Question: Q total Answer: Q1 = m x c x ∆T Q2 100ºC Q1 80ºC Q2 = m x U Q total = Q 1 + Q 2 =(m x c x ∆T) + (m x U) =(1 kg x 4200 J/kg Cº x 20 Cº)+(1 kg x 2,270,000J/kg) = 84,000 J + 2,270,000 J = 2,354,000 J Heat(J) Example 27 4. Ice cube has mass 100 gram at 0ºC. If it heated until 20ºC the all ice become water. How much heat energy absorb? (melting heat of ice = 80 cal/g ; specific heat of water 1 cal/g cº) Known: m= 100 g ∆T = (20-0) Cº = 20 Cº L = 80 cal/g c = 1 cal/gCº Question: Q total Answer: Q1 = m x L Q2 = m x c x ∆T Q total = Q 1 + Q 2 = (m x L) + (m x c x ∆T) =(100 g x 80 cal/g ) + (100 g x 1 cal/g C ºx 20 Cº ) = 8,000 cal + 2000 cal = 10,000 cal 28 1. Calculate heat needed to change 100 gram of ice at – 30°C into water vapor at 120°C. cice = 2100 J/kg°C cwater = 4200 J/kg°C cwater vapor = 2010 J/kg°C Lice = 336,000 J/kg Uwater= 2,270,000 J/kg 29 • Joseph Black (16 April 1728 – 6 December 1799) was a Scottish physician, known for his discoveries of latent heat, specific heat, and carbon dioxide. 30 • When two substances or more are mixed, the amount of heat released by the substance with higher temperature is equal to the amount of heat absorbed by the substance with lower temperature. • Q released = Q received 31 100 grams of hot water at 40°C is mixed with 200 grams of water at 10°C . What is the final temperature of this mixture? T1 Given: m1= 100 grams T1= 40°C T2 = 10°C m2 = 200 grams ∆T1 = T1 - Tf Question: Tf (Final Temperature) Tf Solution Qreleased= Q received m1. cwater . ∆T1 = m2. cwater . ∆T2 m1. cwater . (T1 – Tf) = m2. cwater . (Tf – T2) T2 m1. (T1 – Tf) = m2. (Tf – T2) 100 g(40 – Tf) = 200 g. (Tf – 10) 4000 – 100Tf = 200 Tf – 2000 4000+2000 = 200 Tf+ 100 Tf 6000 = 300 Tf Tf = 6000/300 = 20°C ∆T2 = Tf – T2 32 1. The volume of water in glass B is half of the volume of water in glass A. The water is then mixed in glass C. The final temperature of the water in glass C is… 2. ½ kg of hot water at 80°C is mixed with 2 kg of cold water. What is the temperature of cold water if the final temperature of mixture is 24°C? THANKS!