Question
schile the following question. 2. Define Fick's second law of diffusion Compare and contrast paste and ointments __ 3. Photolysis __ 4.What is the use of narticle __ 5. Write the principle of microscopy determination of particle size __
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Kinslee
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Answer
2. **Fick's Second Law of Diffusion:** Fick's second law describes how the concentration of a substance changes over time due to diffusion. It states that the rate of change of concentration at a particular point in space is proportional to the second derivative of concentration with respect to position. Mathematically, it can be represented as:∂C/∂t = D * ∂²C/∂x²Where:* C is the concentration* t is time* D is the diffusion coefficient* x is the position**Comparison of Pastes and Ointments:**| Feature | Paste | Ointment ||---|---|---|| **Composition** | Higher proportion of solid materials dispersed in a smaller amount of liquid or oily base | Semi-solid preparations with a smooth, greasy texture. Can be oleaginous (hydrocarbon base), absorption bases, water-removable bases, or water-soluble bases. || **Consistency** | Thick, stiff, less greasy | Softer, more spreadable, greasy || **Occlusiveness** | More occlusive (forms a barrier on the skin) | Less occlusive than pastes || **Use** | Protective, absorbent. Good for weeping or oozing lesions. | Emollient, protective. Good for dry or scaly skin. || **Example** | Zinc oxide paste | Petroleum jelly |3. **Photolysis:** Photolysis is the decomposition or breakdown of a molecule by light. It occurs when a molecule absorbs a photon of light, causing it to transition to a higher energy state. This excited state can lead to the breaking of chemical bonds and the formation of new products. Photolysis is important in various natural processes, such as photosynthesis and the breakdown of pollutants in the atmosphere.4. **Uses of Nanoparticles:** Nanoparticles have a wide range of applications due to their unique properties arising from their small size. Some key uses include:* **Medicine:** Drug delivery, diagnostics, imaging* **Electronics:** Improved displays, more efficient solar cells, smaller and faster computer chips* **Cosmetics:** Sunscreens, anti-aging products* **Environmental remediation:** Water purification, air filtration* **Catalysis:** Increasing the rate of chemical reactions* **Materials science:** Creating stronger and lighter materials5. **Principle of Microscopy Determination of Particle Size:** Microscopy is a direct method for determining particle size. The principle involves visualizing particles under a microscope and measuring their dimensions. This can be done using a calibrated graticule (eyepiece micrometer) or image analysis software.The process typically involves:1. **Sample preparation:** Dispersing the particles on a slide in a suitable medium to avoid agglomeration.2. **Microscopic observation:** Viewing the particles under a microscope with appropriate magnification.3. **Measurement:** Measuring the dimensions (diameter, length, etc.) of a representative number of particles using the graticule or image analysis software.4. **Data analysis:** Calculating the average particle size and size distribution from the measured data.Different types of microscopy, such as optical microscopy, electron microscopy (SEM, TEM), and atomic force microscopy (AFM), can be used depending on the size range of the particles.