write down the formula for any substance entering into reaction.place the (+) sign
between the formulas as needed and put the yield after the last one.
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Chemical bonds are made and broken by chemical reactions. After chemical bonds have been broken, then energy is released, and if a chemical bond is made, then energy is absorbed.
It is considered a physical change. A chemical change involves chemical reactions that change the substance into another substance. A physical change typically only modifies the form or phase.
Chemical changes occur when a substance combines with another to form a new substance, called synthesis or, alternatively, decomposes into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. Some reactions produce heat and are called exothermicreactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. Understanding chemical changes is a major part of the science ofchemistry. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an energy change as new products are generated. An example of a chemical change is the reaction between sodium and water to produce sodium hydroxide and hydrogen. So much energy is released that the hydrogen gas released spontaneously burns in the air.
If you mean changing one element into another, like uranium 238 into plutonium 239, which happens in nuclear reactors, the word is 'transmutation'. Otherwise many chemical reactions form new substances, without the elements involved changing, and these would be called 'chemical reactions'.
when there is an injury an open wound is formed after a series of chemical reactions inituiated by thrombokinase the inactive fibrinogen is cinverted into active fibrin threads that form a gauze over the wound and stops the bleeding