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: H2O(s) → H2O(l)

Solid

Liquid

Gas

Plasma

MeltingFusion

Vapourization

Ionization

Sublimation

De-ionization

Condensation

FreezingSolidification

Deposition

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 H2O(l) → O2(g) + 2 H2(g)

Nuclear Change or Transmutation:

- One kind of element is changed to form another kind of element.

Fission: splitting of atoms

Examples:

Alpha Decay α42Ra223

88Th22790 +→

atomic mass

protons

alpha emission

- α: alpha particles or helium nuclei ( )

He42

Beta Decay β01N14

7C146 −+→ electron emission

Fusion: atoms coming together

Example: nHeHH 10

42

31

21

+→+

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

Example: A car travelling at has less energy than when it is

moving at .

hkm10

hkm100

Potential Energy:

- stored energy

- may be due to:

- an object’s vertical position relative to another object

- energy used to push atoms apart

- used to hold subatomic particles together

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

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