valve a is closed during the course of the experiment and should not be touched, why?

Should the discharge valve be open or closed when starting the pump?

>If you start the pump discharge valve closed, it means no discharge head minimum resistance to the pump and minimum current drawn. Even though current taken during startup is more than normal, by closing discharge valve you can avoid extra load on the pump >If you have a check valve, then the discharge valve can be opened.

Why do valves need play to close?

When the valve is closed, a little play (also called valve clearance or valve lash) has to be there. When the engine gets hot, the play gets reduced due to expansion of the material. A little play is still needed though, without any play, the valve wouldn’t close fully, and things would wear out a lot faster.

Why can't you measure valve clearance when the valve is open?

Because when the valve is opened there is no clearance to measure. Clearance occurs when the valve is closed, and the lifter (rocker) is not in contact with the valve stem. This tiny gap is essential to ensure that the valve spring fully closes the valve and makes it gas-tight.

Why is it important to observe safety precautions in a lab?

Nonetheless, observing safety precautions in a microbiology lab is important to reduce the risk of exposure and to prevent microbes from leaving the laboratory. View the accompanying video, which shows a student arriving and setting up to begin lab. What's wrong?

Why should the teacher instruct students never to seal a test tube when it is being heated?

because if just the bottom is heated, vapor can be produced at he pint which will cause the entire contents to spurt out.

What does do not point the open end of a test tube being heated toward or anyone?

Do not point the open end of a test tube being heated at yourself or anyone else. - Heated metals and glass remain very hot for a long time. They should be set aside to cool and picked up with cau- tion. Use tongs or heat-protective gloves if necessary.

Which part of the body should a student avoid touching during a lab?

Always wash your hands after the lab. Keep your hands away from your face and mouth. Wear lab aprons in the classroom.

When initially lighting a Bunsen burner Why must the gas control supply valve and the barrel collar be completely closed?

8. A lit Bunsen burner with closed or partially closed air vents gives a yellow safety flame. Closing the air vents makes it easier to light the Bunsen burner and to observe the flame. The soft yellow flame should never be used to heat any- thing.

Why is it important for the test tube to be sealed?

Stoppers prevent the spillage of chemicals and create an airtight seal to the test tube. Before the fun of reusing such test tubes and corks, sterilizing them is equally very necessary as they come from a lab environment.

What happens to the temperature of the flame when the air hole is opened?

Increasing the amount of fuel gas flow through the tube by opening the needle valve will increase the size of the flame. However, unless the airflow is adjusted as well, the flame temperature will decrease because an increased amount of gas is now mixed with the same amount of air, starving the flame of oxygen.

What are the precautionary measures to taken before handling of laboratory animal?

When handling laboratory animals, gloves should be worn, adequate washing facilities should be provided and prophylactic immunisation against tetanus is strongly recommended. During dissections and post-mortem examinations, gloves, aprons (preferably disposable) and safety glasses or goggles should be worn.

What are the safety precautions inside the laboratory when you doing your experiment?

Safe Lab PracticesNo Food or Drink.Wear Your PPE and Proper Lab Attire.Good Hygiene.Use Proper Storage Containers.Label Your Work Space.Don't Work Alone.Stay Focused and Aware of Your Surroundings.Participate in Safety Exercises.More items...•

Which of the following is not a valid reason to avoid wearing contact lenses in the lab?

It is strongly recommended that students do NOT wear contacts lenses in the laboratory. Chemical vapors may penetrate the contact lens material and cause the lens to adhere to one's eye, which could be detrimental to the eye.

What does the valve in the Bunsen burner do?

The needle, or gas flow valve, is also located at the bottom of the barrel and screws into the base of the Bunsen burner. Like the collar, the needle valve can be turned counterclockwise or clockwise to control the flow of gas. Adjusting the needle valve allows the size of the flame to be controlled.

When lighting the Bunsen burner A Should the air hole be open or closed?

As soon as the gas tap is open place your lighted match about five centimetres directly above it. The Bunsen will light to give a yellow safety flame. A lighted Bunsen Burner with its air holes closed giving a yellow safety flame. You must never use the yellow safety flame to heat something.

Why do you light a Bunsen burner with the air hole closed?

If the air hole is open the flame burns in plenty of oxygen. Combustion is complete and a blue flame is seen. This means there is more energy released.

Why should you never point the test tube towards anyone while heating it?

Accidents happen even heating the test tube gently at an angle can result in heating liquid being shot out of the test tube. This is why the test tube must be pointed away from any other person and why the experimenter must always wear safety glasses.

Where should you point a test tube that is being heated?

0:211:28Heating substances in a test tube - YouTubeYouTubeStart of suggested clipEnd of suggested clipFull using a test tube holder the test tube should be held at an angle and moved in and out of theMoreFull using a test tube holder the test tube should be held at an angle and moved in and out of the Bunsen flame. It's important to make sure the test tube isn't pointing towards anybody when heating

When heating substances in a test tube are sure the open end points?

Always point the top ends of test tubes that are being heated away from people. 6. When heating a test tube, move it around slowly over the flame to distribute the heat evenly. 7.

Which safety precaution is recommended when a liquid is being heated in a test tube?

Always wear safety glasses. Always point the test tube away from any other person in the lab. Heat the test tube being held at an angle so there is a way for the gases produced to escape safely. Heat the test tube at the top of the solution not the bottom where a gas bubble can cause an explosion.