hard 12th grade science questions

All metals are hard except sodium and potassium, which are soft and can be cut with a knif..

: It is a device used by the people who are hard of hearing. Here the sound waves, which are received by the hearing aid are reflected into a narrower area leading to the ea..

Question: Explain whether the following are physical or chemical changes. Give one reason for your answer. 1) Formation of curd 2) Ripening of fruit 3) Bending a glass tube by heating 4) Melting of wax 5) Formation of wine Answer: 1) Chemical change New substance (curd) with a ..

Most of the alpha particles passed straight through the gold foil without any deflection from their original path A few alpha particles were deflected through small angles and few were deflected through large angles Very few alpha particles rebounded completely on hitting the gold foil and turn..

Since most of the alpha particles pass straight through the gold foil without any deflection it shows there is a lot of empty space in an atom Some of the alpha particles are deflected through small and large angles, which shows that there is a 'centre of positive charge' in an atom, which rep..

Coal is formed in nature by the 'carbonisation' of wood. Conversion of wood to coal under the influence of high temperature, high pressure, and in the absence of air is termed carbonisation. Amongst coal varieties, anthracite is the purest form. It contains about 94 - 95% of carbon. The common..

Our natural resources are our assets whose prudent and sustainable use is necessary for the well being of humans and other living other organisms. Unfortunately, the continuous and ever increasing demand for basic items of survival and technological developments have caused us to explore and explo..

Water stored in a reservoir is capable of rotating turbines kept at a lower level. Water stored in a reservoir possesses energy by virtue of its position. A nail hit hard with a hammer gets fixed while if the hammer is just placed on the nail, the nail hardly moves. The ham..

Synthetic detergents have the same type of molecular structure as soaps i.e. a tadpole like molecule having two parts at each end i.e., one large non-polar hydrocarbon group that is water repelling (hydrophobic) and one short ionic group usually containing the or group that is water attracting ..