C20 Unit 1 3 Energy And Changes
- 1. Changes in Matter Physical Changes: - There are three major types of energy changes: - phase, chemical and nuclear . Phase Change: - There is no change in chemical composition , only the change in phase is noted. As a substance changes from one phase to another, it either absorbs energy ( endothermic change ) or releases energy ( exothermic change ). - Example: H 2 O (s) H 2 O (l)
- 2. Solid Liquid Gas Plasma Melting Fusion Vapourization Ionization Sublimation De-ionization Condensation Freezing Solidification Deposition
- 3. Chemical Change: - The reactant(s) have different chemical composition than the product(s). - Evidence of a chemical change occurring: - colour change - formation of a solid ( precipitate ) in a solution - production of a gas ( bubbling ) - energy change ( heat being lost or absorbed ) Example: 2 H 2 O (l) O 2(g) + 2 H 2(g)
- 4. Nuclear Change or Transmutation: - One kind of element is changed to form another kind of element . Fission : splitting of atoms Examples: Alpha Decay Beta Decay Fusion : atoms coming together Example: atomic mass protons alpha emission - 留: alpha particles or helium nuclei ( ) electron emission
- 5. Energy and Matter Kinetic Energy : - energy of motion - the mass of an object and how fast it is moving determines the total energy it has Potential Energy : - stored energy - may be due to: - an objects vertical position relative to another object - energy used to push atoms apart - used to hold subatomic particles together Example : A car travelling at has less energy than when it is moving at .
- 6. Examples : - a ball held 1 m above the ground has more potential energy than being held 0.5 m above the ground - gasoline has potential energy stored in chemical bonds - splitting atoms releases stored nuclear energy that holds the subatomic particles together
- 7. Law of Conservation of Energy Energy cannot be created nor destroyed but can only be transformed from one form to another . Energy Kinetic Potential Heat Mechanical Sound Electrical Light Chemical Nuclear Gravitational