Praxis: Thermometer theory

By Medicine Hat News on October 6, 2018.

I have to be honest, I am not sure I would want to be a forecaster this week — snow in October! In all honesty though, I do not think that weather forecasters have an easy job. Have you ever taken a moment to think about how complex the science of weather is? How can you predict what is going to happen in a couple of hours or even days? Well, the simplest instrument in telling the weather is a thermometer and this week, I thought we could investigate how they work. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– water

– red food colouring

– empty plastic 500 mL bottle

– plasticine

– permanent marker

– straw

– scissors

– ice

– bucket

– hot water

– stick thermometer

– ruler

– glycerine (you can purchase this in the pharmacy section)

– kettle/hot water

Procedure

Fill the empty plastic bottle about 2/3 full of tap water.

Add a few drops of food colouring to the water. Put the lid on and shake it well. You want it to be nice and dark. Keep adding colouring until you reach the desired colour.

Add one teaspoon of glycerine to the water. This step is important as by adding the glycerine, the water will evaporate at a much slower rate and you can use your thermometer longer.

Remove the lid from the bottle and discard.

Take a small piece of plasticine and work with it between your fingers so you can soften it up. Once it is nice and pliable set it aside for a minute.

Using a ruler, measure six centimetres from one end on the straw. Mark this with a straight line and the permanent marker.

Take the soft plasticine and wrap it around the straw at the mark you just made.

The plasticine should be quite thickly wrapped around the straw. If you need to, you can add some more.

Place the straw with the plasticine around it in the mouth of the bottle.

Make sure the end of the straw is a few centimetres off of the bottom. If it is too long, remove and trim the straw with the scissors.

Seal the straw in the bottle with the plasticine. Push all around to ensure a tight seal.

Observe the water in the bottle.

Allow the bottle to sit undisturbed for a short period of time. This will give you the room temperature reading. Mark this on the outside of the plastic bottle with a straight line or mark and label it “room temperature.” Look at a real thermometer for an official temperature. You can also add this measurement to the bottle if you wish.

Fill a bowl with ice water. Place the homemade thermometer in the bowl.

Observe what happens to the water. The water in the straw should have moved. Using the permanent marker, place this mark on your bottle.

If you want an official reading, place the real thermometer in the bowl for a temperature reading. Have an adult help you using hot water.

Record this on the bottle.

As an extension, why not go outside and try to predict the temperature just like a weather forecaster!

Explanation

When the water was hot, it should have risen7 up in the straw. When the water is hotter, the molecules move much faster. The faster they move, the more they spread out and up the straw. When you go outside, if it is hot out, the water level should have gone up.

The exact opposite should have happened when the water is cold. This is why the water level on the straw should have been quite low. This is why individuals sometimes say the mercury is falling when the temperatures outside are getting colder.

The 27th annual Praxis Family Science Olympics will be held at Medicine Hat College Oct. 13 from 10 a.m.-3 p.m.. Please bring your entire family for this great free hands on science day. There will be something for everyone.

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.

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