Differential Scanning Calorimetry(DSC)
The thermoanalytical technique which gives the difference in the amount of heat required to increase the temperature of the sample and the reference is called Differential scanning calorimetry. The difference in amount of heat is measured as function of temperature. Throughout the testing, both the reference and the sample are maintained in same temperature. The sample holder temperature is increased linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned.
There are two types of DSC:
• Power compensated DSC
• Heat Flux DSC
The power compensated DSC keeps the power supply constant. The heat flux DSC keeps the heat flux constant.
PRINCIPLE:
When the sample undergoes a physical transformation such as phase transitions, more or less heat will need to flow to it than the
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The temperature is measured with a repeatability of ±0.1°C.
Applications of Differential Scanning Calorimetry
• Metal alloy melting temperatures and heat of fusion.
• Metal magnetic or structure transition temperatures and heat of transformation.
• Intermetallic phase formation temperatures and exothermal energies.
• Oxidation temperature and oxidation energy.
• Exothermal energy of polymer cure (as in epoxy adhesives), allows determination of the degree and rate of cure.
• Determine the melting behavior of complex organic materials, both temperatures and enthalpies of melting can be used to determine purity of a material.
• Measurement of plastic or glassy material glass transition temperatures or softening temperatures, which change dependent upon the temperature history of the polymer or the amount and type of fill material, among other effects.
• Determines crystalline to amorphous transition temperatures in polymers and plastics and the energy associated with the
Thermodynamics is essentially how heat energy transfers from one substance to another. In “Joe Science vs. the Water Heater,” the temperature of water in a water heater must be found without measuring the water directly from the water heater. This problem was translated to the lab by providing heated water, fish bowl thermometers, styrofoam cups, and all other instruments found in the lab. The thermometer only reaches 45 degrees celsius; therefore, thermodynamic equations need to be applied in order to find the original temperature of the hot water. We also had access to deionized water that was approximately room temperature.
A characteristic property can help identify a substance. A characteristic property will never change even when the volume of a substance is varied. A characteristic property also does not change when a substance changes state in matter. A physical property cannot identify a substance. A physical property will change when the volume of a substance is varied. It can also change when the substance changes state in matter. For example, if the volume and mass of a substance changes then the physical appearance will also change. However, the density, which is a characteristic property, will not change at all. The boiling point of a substance is the temperature that a substance changes from a liquid to a gas. The boiling point of a substance is a characteristic property because the boiling point of a substance will never change even when the volume and mass changes. The only thing that will change is the time that it takes to reach that temperature. If the mass and volume of the substance is small, then it will take a small amount of time for the substance to reach the temperature. However if the mass and volume of the substance is larger, then it will take a longer time to reach the temperature. The purpose of this lab was to see if when the volume of a substance changes so does the boiling point.
Thermal methods of analysis have been in use for quite a long time. Their application in the analysis of pharmaceutical materials has made it possible for pharmacists and researchers to understand their contents and characteristics. However, thermal methods have several disadvantages that have led researchers to opt for nano-thermal methods of analysis. Nano-thermal analysis methods use special resolution imaging potential that is enhanced by the availability of atomic force microscopy and thermal analysis methods.
Studies have shown that big changes in temperature do not affect the capability of insulation. In one experiment, materials were set to a high heat of 300 degrees Celsius. After six months in this environment, the substances were cooled to room temperature. The dielectric constant showing the level of insulation had not changed ("Teflon PTFE fluoropolymer resin" 28).
Lastly, a calorimeter is a device for measuring the amount of heat given out or taken in during a chemical reaction. CHEMICAL EQUATIONS Hess’s Law: H_N+ H_S= H_R Change in Temperature: t=t_final-t_inital Mass of a Solution: 2.05g(1 mole)/40.00g=0.05125 mol NaOH Percent Error: % error= ((Sum of H_(N ) and H_S )-H_g)/
- Temperature was measured after and exact time i.e. 1 minute, 2 minutes, 3 minutes.
Most solid materials expand upon heating and contract when cooled because it undergoes a change in the energy state of its molecules or atoms. According to the atomic perspective, the average vibrational amplitude of an atom increases as the temperature rises. Each material has a property called ¡§coefficient of linear expansion¡¨ that is indicative of the extent to which a material expands upon heating or contracts when cooling. The coefficient of expansion is re very important to all structures and foundation of buildings to avoid the possibility of collapsing.
Melt flow rate is very commonly used for polyolefins, polyethylene being measured at 190 °C and polypropylene at 230 °C. The plastics engineer should choose a material with a melt index high enough that the molten polymer can be easily formed into the article intended, but low enough that the mechanical strength of the final article will be sufficient for its use.
Polymer-Polyethylene is partially crystalline as well as amorphous because it has crystalline and amorphous regions. Also it has linear chains so this is the simplest structure compared to a branched or network chain. This can be of an advantage to it over other types of materials as its good toughness and elongation makes it very significant in the engineering industry as it can be moulded or extruded into shape...
We heated up a brass weight by immersing it into boiling water for a while in order to assure that the metal’s temperature was the same as of the water.
A good example is a cup of hot tea with a slide of lemon inside. Having the slide of lemon as the first object and using that as a reference it can be compared to the temperature of other bodies. The water itself as the second object applying a process where having a thermometer that is calibrate by being brought into contact with the water.
Temperature is thermodynamic property of objects. It is an “indirect measure of the kinetic energy of the particles that make up matter” (Lerner 2008). Temperature determines the direction of the flow of energy between two objects. When they are put in contact with each other, the faster-moving molecules of higher temperature object will collide and increase moving speed of slower-moving molecules of the lower temperature object. This process stops when both objects have the same average molecular kinetic energies, or in other words, they are in thermal equilibrium with each other. Temperature is one of the most commonly measured parameters. Thermometer is a device that has an established temperature scale, based on its expansion property at different temperatures. When the thermometer is in thermal equilibrium with other objects, it indicates the degrees of objects’ temperatures. Temperature is measured against four temperature scales: Fahrenheit (F), Celsius (C), Kelvin (K), and Rankine (R) temperature scales, which names are based on the names of scientists who originated the temperature scales.
Given below is a table having initial and final temperature mention for different types of material, initial temperature is the maximum operating temperature of the cable and the final temperature is the limiting temperature of the cable.
The area under the curve represents the energy required to compensate for the thermal events of the sample. Some instruments represent endothermic processes (melting) as downward curves and exothermic processes (crystallisation) as upwards peaks, while other instruments show it in the opposite way. (18) DSC can be used to evaluate different thermal events including melting, solid-state transitions, crystallization, glass transitions … (19) DSC may therefore be used to differentiate between polymorphs according to their melting point or to examine the transformation of metastable systems. It is essential though to confirm the results of DSC with other characterization techniques such as Raman spectroscopy, IR spectroscopy and X-ray diffraction.
A. Comprehend the P-V-T behaviour of pure fluids and solve related problems. B. understand heat effects in chemical reactions and solve related problems.