Physical and chemical changes Flashcards
Physical change
A change where no new chemical compounds are formed. During a physical change the state of the substance changes but not its identity
Chemical change
A change that entails the transformation of one or more substances to either one or more substance. Its a result of a chemical reaction
Characteristics of physical change
Arrangement of particles changes doesnt form new products Is reversible No change in mass No energy is used to break bonds between atoms only intermolecular forces
Characteristic of chemical change
Forms a new substance
Particles change and regroup. Decomposition occurs and bonds are broken
Usually permanent
Quantity of specific substance changes but the total amount of materials stays the same
Energy is either absorbed or released
May change color produce an odor
Decomposition reaction
A single substance breaks down to form 2 or more simple substances
Synthesis reaction
Substances bond with each other to form a new substance. The substances bonded can either be elements or compounds
Energy changes in chemical reactions
Reactants need energy to break the bonds between the reactant molecules to release atoms
For bonds to break, energy must be absorbed
When new bonds are formed energy will be released again
Exothermic reaction
A reaction in which energy is emitted into the environment. The product has less energy than the reactants. The total energy released to form bonds is smaller than total energy to break bonds
Law of conservation of mass
In a chemical reaction the sum of the mass of the reactants is equal to the sum of the mass of the products
Law of constant composition
Different samples of a compound has the same composition
Chemical reactions in terms of energy transfer
Old bonds are broken and new bonds form
Reactants need energy to break bonds and release atoms
Energy is absorbed for bonds to break and released again when new bonds form
Endothermic reaction properties
Weak bonds form Low energy input Positive empalthy Energy is added to reactants Empalthy is bigger than 0
Exothermic reaction properties
Strong bonds form High energy output Energy is added to the products Change in empalthy is bigger than 0 Negative empalthy Energy is given off
Potential energy
The energy that an object has as a result of its position above a certain level
Gravitational potential energy
The energy that an object has as a result of its positions in a gravitational field relative to certain reference point
