because convection currents are caused by the liquid being heated, becoming less dense due to increased kinetic energy and rising. if you are heating the top of the test tube, there is nowhere for them to 'rise' to, so no current is formed, as they do not reach a place where they cool and sink to the bottom. thus convection currents are only formed when heating the bottom of a test tube.
This is due to the type of heat transfer which takes place. In a liquid (or a fluid in general), heat is transferred by convection, in which the BOTTOM part of the liquid gets heated, becomes less dense, moves upwards and is replaced by cold and denser liquid from the top. This is why a liquid is heated from below. By the way, water is a poor conductor of heat, which means that if heated at the top, no convection would take place and little conduction would take place meaning that the whole of the liquid would not become hot. Cold denser water would remain at the bottom and hot less dense water at the top.
- the test tube may break- the liquid can be spread outside
Yes, it is correct.
I donโt understand IM ON A TEST LOL (jk itโs convection losers)
Wear goggles and a laboratory apron Hold the test tube with a test tube clamp not in your bare hand. If the liquid is nonflammable it may be heated in the flame of a Bunsen burner, otherwise a hot water bath over a hot plate may be more advisable. If heating in the flame of a Bunsen burner hold the test tube at an angle and move the tube in and out of the cool area of the flame. Alway point the opening of the test tube AWAY from yourself and others.
Science test tubes; generally made of pyrex to reduce breakage, are tubual containers often used in experiments. They can be heated, and cooled, and can you can use liquid or powder substances in them.
The distillate
Drink it the liquid.
Liquid Penetration test stands for a such test that can be done from the victim's end using petrol, kerosene, greaseetc.
the two ratios that measure liquidity is acid test and current ratio. the acid test ratio is current assets- stock/ current liabilities the current ratio is current assets/ current liabilities
You should never point the open end of the test tube when heating liquids toward yourself or others for your own safety. Liquids inside the test tube when heating may release some gases and might affect someone when you point the open end of the test tube to them. when heating the test tubes, position it diagonally and move it slowly sidewards so we can prevent cracking or breaking of the test tubes if directly positioned on fire.
The alcohol is not heated in starch test because it's flameable,so will cause fire or disrupt the experiment.so results would be incorrect or not accurate.