In the same way that a large solid holds its shape, the atoms inside of a solid are not allowed to move around too much. and molecules in liquids and are bouncing and floating around, free to move where they want. The molecules in a solid are stuck in a specific or arrangement of atoms. The atoms still vibrate and the fly around in their orbitals, but the entire atom will not change its position.​

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?