Particle Theory of Matter - Convection

Observing Convection 1

Aim: To observe convection in a liquid 

Equipment: 200 mL beaker, water, tweezers, a crystal of potassium, permanganate, a drinking straw, Bunsen burner, heat mat, tripod and gauze mat.

Method:

1. Set up a Bunsen burner on a heat proof mat. Put the gauze mat on the tripod but leave it just to one side of the Bunsen burner.
2. Fill a 200 mL beaker with 150 mL cold water.
3. Place the beaker on top of the tripod and gauze and allow it to settle for a few minutes.
4. carefully insert a drinking straw down one side of the beaker, ensuring the straw is touching the bottom of the beaker. Be careful as you do not want to disturb the water too much.
5. Using tweezers, drop a crystal of potassium permangante down the inside of the straw. Wait for the crystal to settle on the bottom of the beaker.
6. Very gentle, so to not disturb the water, remove the straw.
7. Light the Bunsen and Slide it under the tripod so that you are only heating the outside of the beaker where the crystal is. Observe.

Observation: The particle colour from the permanganate rises vertically, then travels horizontally across the surface of the water. Small circular currents can be seen transferring the purple colour through the beaker.

Explanation: When the water nearest the Bunsen flame is heated, the space between the water particles increases. This means this region of water becomes less dense and rises. Denser colder water flows into replace the rising water. This set ups a convection current. 

This is the Hot water:

 

This is the Cold water: