# Teacher Demo: Air Pressure

This demo illustrates the presence of atmospheric air pressure and shows how the force that it exerts is greater than the force of gravity in some situations.

## Procedure

Wear appropriate PPE: safety goggles.

1. Fill the glass with water right up to the brim.
2. Place the index card on top of glass and hold it firmly in place.
3. Predict

Students engage in Think, Pair, Share (see Teaching Suggestions/Hints):

• Think: What will happen when the glass is held upside down and the index card is no longer held in place?
• Pair: Discuss the question with a partner.
• Share: Hold a brief class discussion on the prediction.
1. Explain

Ask students to justify their predictions using their existing knowledge.

1. Observe

Lift the water-filled glass over the tray with one hand, holding the index card to the mouth of the glass with the other hand. Carefully turn the glass upside down. Release the card.

1. Explain

Ask students to explain their observations.

# Significant Figures in Measurements

Mr. Key outlines how we use numbers in science, with specific regards to precision and significance.

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# Teacher Demo: Marshmallow DNA Model

This demonstration will provide students with a visual representation of the structure of DNA.  Students will learn the different components that make a nucleotide, the correct base-pair connection between nitrogenous bases, and visually see the double helix structure of DNA.

## What happens?

In this demonstration, students will visually see what a DNA molecule looks like.  They will be able to determine the different components that makes up a nucleotide (phosphate, deoxyribose sugar, and nitrogenous base), will learn the correct base-pairing of bases in DNA (adenine always bonds with thymine and cytosine always bonds with guanine), will learn how many hydrogen bonds occur between each base pair, and will learn that phosphodiester linkages are formed between phosphate groups and deoxyribose sugars.  Students will also be able to identify the major groove and the minor groove in the double helix once the molecule is twisted.