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Transcript of Chemical Change
and heat energy How can you tell whether a change is a chemical change? Colour Changes The rusting of iron is a chemical change. The strong ductile iron metal is slowly transformed into a brittle, easily crumbled, red powder. This red powder is a new substance, and is quite different from the original metal. The new red material is non-magnetic, its density is less, and it is no longer a good conductor of electricity. As in the case of autumn leaves, a change in colour is a clue to indicate a chemical change.
Perhaps you have found a half eaten apple that turns brown. The reason is that a chemical change occurs when food spoils.
The process of combustion in which coal, wood or oil is consumed is another chemical change. The products of combustion of wood no longer resemble the original wood, these being largely a gas (carbon dioxide), water and ash.
The conversion of the food we eat to living tissues is also an example of chemical change. what is a chemical change?
A chemical change is when two or more substances chemically combine to form an entirely new substance Bonds are broken and formed between different atoms in a chemical change. When particles
of the original materials collide with one another the breaking and forming of bonds take place. change of odor change of colour change in temparature change of form light heat or sound is given off formation of gasses the decomposition of organic material All Chemical reactions have two parts
The reactants- the substances you have started with
The Product- the substance formed from the reactants In a chemical reaction The way atoms are joined is changed Atoms aren't created or destroyed when copper reacts with chlorine
copper chlorine is formed
The word equation for this is:
Copper+Chlorine Copper (11) Chloride
The chemical reaction for copper and chlorine is the change in temperature In order for a reactant to occur the particles must collide and they must collide with enough energy Examples of a chemical change Off-Gassing
A smell or fumes climbing up from the test solution is noticed if a gas is produced in the course of a chemical reaction. An example is mentos and coke (hydrochloric acid and calcium carbonate) Heat
Energy is released when chemicals react. Heat energy is produced which makes for what is known as an exothermic reaction. When two things are mixed together in the kitchen heat is produced due to the act of mixing the substances together, and then a chemical change occurs. Heat decrease
Not every reaction can be illustrated by the expression of the increase of heat. Sometimes, when a reaction occurs, the test solution actually decreases in heat which is known as an endothermic reaction. An example of an endothermic reaction is the reaction of baking soda with calcium citrate. Precipitate
Sometimes chemists observe a chemical change in a test solution by watching for the formation of a precipitate, or a solid resulting when two liquids are added to each other. This occurs because one of the products of the chemical reaction is not soluble in the test solution. Colour Change
Sometimes, the solution changes colour when two chemicals react. One of the most popular applications of this chemical behaviour is in law enforcement, as investigators and chemists use colour changes in chemical spot tests to determine the identity of potential illegal substances.