Physical And Chemical Change Flashcards
What a physical change?
A change in which the chemical compositions of a substance does not change
The change is only temporary
What kind of changes are physical changes?
Temperature Expand Colour (sometimes) Conductivity Phase
What is a temperature physical change?
When heat energy is added to a substance, the average kinetic energy of the particles increases
What is a physical change in which a substance expands?
When the temperature of a substance rises, the speed of the particles increases
They then occupy more volume
How does a substance change colour in a physical change?
Electrons become energised and jump to higher energy levels
When they return to their ordinary energy levels they emit energy
This is perceived in the form of light i.e colour
How does the conductivity of a substance change during a physical change?
If heat energy is added
Particles move more energetically
It is harder for an electrical current to flow
How does a physical change induce a phase change?
If particles are given enough heat energy
They will have enough kinetic energy to overcome the force of attraction that hold them in their lattice
What is the main factor that contributes to a physical change?
Heat energy
What is a chemical change?
When the chemical composition of a substance changes
New substances are formed due to this change
What are the “new substances” formed after a chemical reaction?
The products
What are the original substances in a chemical reaction called?
Reactants
What is a chemical reaction in which new bonds are created called?
Synthesis
What is an example of a synthesis reaction?
The formation of water molecules
How is a chemical reaction shown?
The atomic symbols for each reactant are shown on the left
An arrow indicates a chemical reaction has taken place
The product are represented in the same way in the right
What is the name of a chemical reaction in which bonds are broken?
Decomposition
What is a method that can be used in a decomposition reaction?
Electrolysis
What is electrolysis?
A electric current which is run through a substance to decompose the compound
What are three laws of chemical reactions?
Conservation of atoms
Conservation of mass
Constant composition
What is the law of Conservation of Atoms?
The number of atoms in the reactants is the same as the number of atoms in the products
No atoms can disappear, they are simply rearranged
What is the law of Conservation of Mass?
The relative mass of the sum of the reactants is equal to the relative mass of the sum of the products
What is the Law of Constant Composition?
The ratio of elements in a compound is fixed
i.e. If identical reactants are used in two identical chemical reactions, they will form exactly the same compound
