Pressure Bottle Barometer

Step 1:                Obtain the following materials from your teacher or parent:

§         A juice bottle

§         A clear plastic straw

§         A fist full of clay

§         A cup of warm water

§         A bottle of food coloring

§         A roll of masking tape

§         A permanent marker

§         A piece of gum

Step 2:                Start to chew a piece of gum as you begin to prepare your barometer.

Step 3:                Pour the warm water into your juice bottle, filling it up about halfway.  (See Figure 1 – Fill Line.)

Step 4:                Add five (5) drops of food coloring to the water.

Step 5:                Mix the water and food coloring with the straw.

Step 6:                Suck on the straw until the water level 2 in the straw is above the water level 1 in the juice bottle.                                                                                                                                                                       

Step 7:                Place the gum that you have been chewing at the end of the straw so that when you let go of the straw, the water level stays above the water level 1 in the juice bottle. 

Step 8:                Place some clay around the mouth of the bottle and around the straw in order to form an airtight seal.

Step 9:                Tear off a small piece of tape and place it on the outside of the bottle so that the bottom of the tape is at the same level as the water inside the straw.  (See Figure 1 - Labeled Tape.)

Step 10:      Write the time and date on the piece of tape with the permanent marker. 


Crushing With Air

Objective: To demonstrate air pressure and its potential crushing ability.

Materials Needed:

Instructions:

Step 1:         Stand the bottle upright in a bowl.

Step 2:         Pour the hot water into the bottle and leave it for a short time. 

Step 3:         Screw the top onto the bottle. 

Step 4:         Lay the bottle in the bowl and pour ice-cold water over it.

Step 5:         Stand the bottle up.

Questions:

·        What happened?

·        Which is stronger – the pressure of the air outside or the pressure of the air inside the bottle?

·        What made the bottle crush?

* The bottle retains its shape in a normal atmospheric condition because the air pressure inside the bottle is the same as the air pressure outside.  The bottle collapses as the warm air inside the bottle cools since it exerts less pressure.  The pressure of the air outside is stronger and crushes the bottle. 


Paper Plunge

Objective: To demonstrate the pressure, or pushing power, of air.

Materials Needed:

Instructions:

Step 6:         Fill the bowl with water.

Step 7:         Crumple up a piece of paper and place it into the bottom of the glass.

Step 8:         Plunge the glass straight down into the bowl of water.

Questions:

·        What happens to the paper?

·        Where is the water level in the glass?

* Water can only get into the glass by displacing the air inside it.  Air likes to rise, since it is less dense (lighter, essentially) than water.  Since the cup blocks the only way up, the air is trapped, and therefore will not let water move into the cup and touch the water.

Seal with Air

Objective: To demonstrate the pressure, or pushing power, of air.

Materials Needed:

Instructions:

Step 9:         Hold the glass over a bowl.

Step 10:     Pour some water into the glass. 

Step 11:     Place the plate or card on the glass. 

Step 12:     Hold down the card (or plate) so that it touches the rim all the way around. (If there are any gaps, this experiment won’t work!)

Step 13:     Still holding the card, turn the glass upside down. 

Step 14:     Let go of the card (or plate).

Questions:

·        What happened?

·        What made the water stay inside the glass?

* The water stays inside the glass because water and air inside the cup cause a suction force, holding the plate against the cup.  The sudden shifting of the water and air inside the cup acts in a similar fashion as a plunger.