Grade 6 | Science | Unit 2 - Concept 2 - Lesson 4 - Heat transfer in the different Materials скачать в хорошем качестве

Grade 6 | Science | Unit 2 - Concept 2 - Lesson 4 - Heat transfer in the different Materials

Welcome dear students! When observing cooking pots, you will notice that: • Cooking pots are made of thermal conductor materials such as metal. • The handles of cooking pots are made of thermal insulator materials such as wood or plastic. Note The thermal insulator material that we use to make the handles of cooking pots is safe to touch during cooking as it isn't a good conductor of heat. There are two factors that affect the thermal insulation of the handles of cooking pots, which are: 1. Type of material. 2. Length of handle. 1. Type of material: The type of material from which the handles of cooking pots is made of affects the thermal insulation of these handles. Example: • If you place 2 pans with 18 cm handle on stove, where: • The handle of one of them is made of plastic. • The handle of the other pan is made of wood. • Then measure the temperature at three places on the handles during heating. • The following table shows the results of this activity: Matter of handle: Plastic Length of handle (cm): 18 Time heated (min): 10 Temperature near to the pan (°C): 54 Temperature at the middle of the handle (°C): 24 Temperature at the end of the handle (°C): 23 Matter of handle: Wood Length of handle (cm): 18 Time heated (min): 10 Temperature near to the pan (°C): 60 Temperature at the middle of the handle (°C): 26 Temperature at the end of the handle (°C): 25 Figures (for illustration) Pan with plastic handle: 54°, 24°, 23° Pan with wooden handle: 60°, 26°, 25° 2 Length of handle: The length of handle is an important factor which affects the thermal insulation of the handle of a cooking pot. Example: • If you place 2 pans with plastic handles on stove, where: • The handle of one of them with 18 cm. • The handle of the other pan with 36 cm. • Then measure the temperature at three places on the handles during heating. • Matter of handle: Plastic (Column 1) | Plastic (Column 2) • Length of handle (cm): 18 | 36 • Time heated (min): 10 | 10 • Temperature near to the pan (°C): 54 | 54 • Temperature at the middle of the handle (°C): 24 | 23 • Temperature at the end of the handle (°C): 23 | 22 Figures (for illustration): • Pan with plastic handle (18 cm length): Temperatures are 54°, 24°, and 23°. • Pan with plastic handle (36 cm length): Temperatures are 54°, 23°, and 22°. From the previous examples, we can conclude that: • The measurements of temperature differ from one place to another along the handle of the pan. • The handle is warmer closer to the pan, and it is cooler as we go far away from the pan because the heat travels very slowly along the handle, that is made of a thermal insulating material. • The plastic handle is better than the wooden handle in thermal insulation when their lengths are equal as shown in the first example. • The thermal insulation of the handle increases as the length of the handle increases, where the temperature of the long handle was always lower than that of the short handle as shown in the second example. When any matter changes from one state into another by gaining or losing of thermal energy, its mass does not change and this is called the law of conservation of mass. Law of conservation of mass : The mass of a substance does not change when this substance changes from one state into another. So, no matter is destroyed or created, but it just changes from one state into another. Examples : • When you put a bowl of ice cubes on the flame, the ice cubes changes into liquid water. • The mass of the ice cubes before heating equals the mass of water after heating. 1. If you put a plastic cup of a juice in a freezer, it freezes but its mass does not change before and after freezing. There are some cases that the mass of a substance before the change does not equal the mass of the same substance after the change. That is because the substance is mixed with other substance. #Science_Grade6 #mrraoufashraf #Science_Grade6 #HeatTransfer #ThermalInsulation #Conduction #EverydayScience #STEMLearning #ScienceInLife #YoungScientists #LearningByObservation Mr. Raouf Ashraf