Air in the form of a gas

1. Air in the form of a gas What is air made of?

2. It is a gas! What is air made of? What is the difference between air and oxygen? Air has weight, pressure. It expands, contracts and compresses. The study of what matter is made of – atoms and molecules and how they react with each –other – is known as chemistry. Early chemistry scientists, or chemists, discovered that air is actually a kind of gassy soup – a mixture of many different gasses. Each kind of gas contains a different combination of atoms and molecules.

3. Lights out Materials • A small candle • An empty glass jar • A shallow pan • Water • Food colouring • A black marker • A Stopwatch

4. Lights out Procedure • Begin by lighting the candle and letting a few drops of wax fall into the middle of the pan. Blow out the candle and secure it onto the wax. This will keep the candle from falling over. • Add enough water to the pan so that it is 2 to 3 centimeters deep. Add a few drops of food colouring to the water. • Turn the jar upside down over the candle and into the water. Observe the water level inside the jar. Mark the level with your black marker pen, then remove the jar. • Make a prediction about what will happen when you light the candle and put the jar over it again. • Light the candle, and place the jar back over the burning candle. Carefully observe what happens. • Do the experiment three or four times, using the other jars of different shapes and sizes. Record what happens.

5. Lights out! The candle needs oxygen to burn. One fifth of the air, or just over 20 percent, is made up of oxygen. Oxygen is the key ingredient needed for anything to burn. So, as burning happens, oxygen is used up. In this experiment, when the candle used up all of the oxygen in the jar, the flame went out. But what caused the water to rise?

6. Lights Out! Think back to the last lesson about what happens to air when it is heated or cooled. When you first covered the flame, the air heated up and then expanded. You may have seen some air being pushed out of the jar in the form of bubbles as you dropped the jar into the water. When the flame burned up all of the oxygen in the air, it went out. This caused the air to cool slightly, and then to contract. The combination of the air contracting and the oxygen being consumed meant that the air took up less space. The water rose to fill the space.