#### • Class 11 Physics Demo

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#### • examples of exothermic reactions in everyday life

Question:

Answers:Cooking something. Like cooking eggs, meat, or baking. Once it is cooked then it is a physical change that can not be reversed.

Question:So, we were doing experiments in class and the teacher told us to bring close toe shoes the day before...well, i forgot and now i have to find 5 physical changes and 4 chemical changes at my house, describe the materials before and after, and record why it is a physical change...I am so confused right now =/ Can someone please help me? You could give examples of what i could do (i have to preform the experiment-stupid i know) and tell me why they are physical or chemical changes, it would really be helpful, cuz it's due tomorrow (Monday August 30th, 2010)

Answers:chemical changes: 1- cooking of the raw food : in this process the raw food will chang to the cooked food and after cooking, the food doesn't have the same quality before cooking. 2- digestion of food: your body can't use the foods before digestion. digestion makes the to very small parts and molecules in order that your body can use the food. 3- burning of wood in fireplace: when the wood is burning, it will transform to ash and its not wood anymore, so its a chemical change. 4- Rusting of iron:When it is raining a lot or there is water in somewhere in you home, for example your bathroom, the irons in the house structure become rusted and they won't have the qualities that iron has, because it had an reaction with oxygen. Physical changes: 1- Cutting the paper: When you cut a piece of paper, there will be smaller pieces of paper while the quality of the paper didn't change and it's the same paper before cutting and that is why it is physical change. 2- Boiling of water : When you heat the water until it boils, it changes to vapor but its chemical structure doesn't change and it is the same H2O before boiling. 3- melting of ice: when you put ice in a warm water, it starts to melt, but its chemical structure is H2O and it is the same chemical structure before melting. 4- breaking a glass: When you break a glass, it will break to smaller parts but its qualities won't change and it is the same glass before breaking. 5- dissolving of sugar in water: when you dissolve some sugar in water, it is a physical change. Because if you bil that water the you can see that sugar again. so dissolving sugar in water doesn't change the chemical qualities of sugar and only change its physical structure.

Question:I need examples of longitiudinal, transverse and surface waves in everyday life (i.e you do this task that encounters or uses that type of wave). thank you! I need about 3 for each type of wave.

Answers:Transverse wave: light waves are all transverse electromagnetic waves Sound waves travelling ON the surface of a medium are transverse eg: sound wave travelling along the surface of a table..... Longitudinal wave: A sound wave that travels IN or along the medium: eg: a wave travelling IN air or In water........ Examples of transverse waves include seismic S (secondary) waves, and the motion of the electric (E) and magnetic (M) fields in an electromagnetic plane wave, which both oscillate perpendicularly to each other as well as to the direction of energy transfer. Therefore an electromagnetic wave consists of two transverse waves, visible light being an example of an electromagnetic wave. Examples of longitudinal waves are sound, ultrasound, and earthquake P-waves. a surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities Examples are the waves at the surface of water and air (ocean surface waves), or ripples in the sand at the interface with water or air. Another example is internal waves, which can be transmitted along the interface of two water masses of different densities.

Question:I need it ASAP!!