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Conditions for Chemical Change
The criterion for a chemical change is the production of one or more new substances. Therefore, certain conditions should be met in order to bring about a chemical change. The necessary conditions are:
· A minimum amount of energy needed to initiate a reaction (activation energy) should be supplied in the form of heat, light or electric current. In a chemical change, the reactants combine to form new products. For this process it is necessary to break the old bonds of the reactants and form fresh bonds, in order to give new products. This requires a certain amount of energy.
· For the occurrence of any reaction, the molecules or atoms of the reactants must collide with one another, in order to break old bonds and form new bonds.
· The speed with which the chemical reaction takes place is called the rate of the chemical reaction. This should be appreciable, to bring about the change.
· The rate of a reaction depends on following factors:
1) Temperature
2) Presence of light
3) Presence of catalyst
4) Electricity
5) Pressure
Temperature
Certain chemical reactions do not take place at room temperature but occur readily at a higher temperature. Thus heat is required to start the reaction e.g. fuels like coal and wood only start burning when heated to a certain temperature (ignition temperature).
Presence of Light
Some reactions take place only in light and do not take place in dark e.g. photosynthesis in green plants or reaction between H2 and Cl2 to form HCl.
Presence of a Catalyst
A catalyst is a substance that increases the rate of chemical reaction without itself undergoing any change.
Examples: Hydrogenation of oils to form fats takes place faster, in presence of nickel.
Decomposition of potassium chlorate (KClO3) is greatly accelerated in presence of MnO2 (Manganese dioxide).
Electricity
Certain reactions take place with the help of an electric current.
Example: Decomposition of water (acidulated) to give hydrogen and oxygen gas.
Pressure
Some chemical reactions need very high pressure to proceed. Example, in the manufacture of ammonia from nitrogen and hydrogen (Haber's process), a pressure of over 200 atmosphere is required, in presence of a catalyst iron and a temperature of 450oC to 500oC.
What else can I help you with?
A chemical formula written over the arrow in a chemical equation signifies?
A chemical formula written over the arrow in a chemical equation is that of the catalyst used in the reaction.
What occur in a chemical reaction and why are chemical reaction important?
This is the energy needed to get us from our starting point to the top of the hill would be the activation enery
Are enzymes used in a chemical reaction?
Yes. Enzymes lower the activation energy needed to start a chemical reaction so that they can occur at temperatures safe for the organism.
The amount of energy needed to cause a chemical reaction to occur is the?
The amount of energy necessary to cause a chemical reaction to occur is called activation energy.
What comes out of a reaction?
Chemical changes occur after a chemical reaction.
Which is the best description of activation energy?
The amount of energy needed to start a chemical reaction. Source: Biology class
What does an enzyme do to the activation energy needed to start a chemical reaction?
Enzymes are catalysts, they reduce the activation energy.
What is proteins that reduce the amount of energy needed to start a chemical reaction are called?
Proteins that reduce the amount of energy needed to start a chemical reaction are called enzymes. Enzymes act as catalysts by lowering the activation energy required for a reaction to occur, thus speeding up the reaction.
Why do you need a catalyst during a enzyme reaction?
A catalyst speeds up the rate of a chemical reaction by lowering the activation energy needed for the reaction to occur. In the case of an enzyme-catalyzed reaction, the enzyme serves as a biological catalyst, allowing the reaction to occur more efficiently and at lower energy levels than it would without the enzyme.
What changes the rate of a chemical reaction or allows a chemical reaction to occur?
Heat?
What is the substance of a chemical reaction that accelerates?
A substance that accelerates a chemical reaction is called a catalyst. Catalysts work by lowering the activation energy needed for a reaction to occur, which speeds up the reaction without being consumed in the process.
What must energy do to break achemical bonds for a reaction to occur?
Energy must be absorbed to break chemical bonds for a reaction to occur. This energy input is needed to overcome the bond's stability and allow new bonds to form in the reaction.
