Diffusion of liquid

Diffusion of gases

Melting•Melting is when a solid changes into a liquid•Requires heat energy which transforms into kinetic energy, allowing the particles to move•Occurs at a specific temperature known as the melting point (m.p.) which is unique to each pure solid

Boiling•Boiling is when a liquid changes into a gasRequires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid.

•Occurs at a specific temperature known as the boiling point (b.p.) which is unique to each pure liquid

Freezing•Freezing is when a liquid changes into a solidThis is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same.

• Water for example freezes and melts at 0ºCRequires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance

Evaporation

•When a liquid changes into a gas. Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the b.p. of the liquid•The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate•No heat is required and evaporation occurs over a range of temperatures

Condensation

•When a gas changes into a liquid, usually on cooling. •When a gas is cooled its particles lose energy and when they bump into each other they lack the energy to bounce away again, instead they group together to form a liquid

No energy is required for condensation to occur and it takes place over a range of temperatures

Sublimation

•When a solid changes directly into a gas

•This happens to only a few solids such as iodine or solid carbon dioxide

•The reverse reaction also happens and is also called sublimation (sometimes called deposition or desublimation)

•Sublimation occurs at a specific temperature which is unique for a pure substance

Q-1.Draw diagrams to show the arrangement of particles in a solid, liquid and gas. Add note to each diagram.

2.Using the idea of particles, explain why a. You cannot pourb. You can pour liquids

3. Draw a diagram to show what happens to the particles, when a liquid cools to a solid

4. See if you can explain what happens to the particles when,a. A solid sublimes b. Wet clothes dry in sunshine

5. Oxygen is the gas we breathe in. It can be separated from the air. It freezes at -219C and boils at -183C.

a. In which state is oxygen at 0C and -200Cb. How would you turn oxygen gas into solid oxygen