# How to Read a Thermometer

### Guiding Questions

1. How can we tell what the temperature is?
2. What is a thermometer?
3. How do you read a thermometer?

## Objectives

#### Concepts:

Temperature is measured using an instrument called a thermometer.

#### Principles:

• Thermometers are commonly made from a glass bulb connected to a tube of glass with a numbered scale written on the outside.
• Inside the glass tube is a liquid like mercury or colored alcohol that rises and falls in the tube as the temperature around it warms or cools.
• When the temperature rises, the liquid in the glass tube warms up and molecules expand, which in turn takes up more space in the tube.

#### Facts:

• Most thermometers have two temperature scales: Fahrenheit and Celsius. Both scales are divided in two-degree increments.
• When you read the temperature on a thermometer, it should be vertical and your eyes should be level with the top of the liquid in the glass tube.
• Avoid handling the thermometer when you take your readings. The heat from your hands will transfer to the glass causing its temperature to rise.

#### Skills

• Making Observations
• Making Measurements
• Using Numbers

### Materials

1. Each student needs a thermometer, or pairs may share one.
2. Handout
3. Pencil

Room Preparation: No special needs. Need to be able to take temperature readings in different locations and outside.

Safety Precautions: Danger of broken glass! Handle thermometers with care.

## Procedures and Activity

### Introduction

1. How can we tell what the temperature is?
Share ideas, such as: we can feel the temperature or see our bodies react to temperature, as when we sweat or shiver. Or we can see evidence of the temperature by observing: a pond or pool of water freezing and thawing, wilting plant leaves on really hot days, seeing heat rise in a shimmer from pavement. Lead discussion to the point of realizing that we cannot tell the temperature accurately just by feeling it or observing our surroundings. We depend upon an instrument called a thermometer for accurate readings.
2. What is a thermometer?
Have students look at their thermometers. Help them define what this instrument is made of: a glass bulb connected to a long and thin glass tube; glass tube has numbers written on it; inside bulb and in tube is a liquid (either mercury or a colored alcohol). Share the two commonly used scales on thermometers—Fahrenheit and Celsius.
3. How do you read a thermometer?
Lead discussion and ideas to the following points:
• Your eyes should be level with the top of the liquid in the tube to read it accurately. (You can have them test this—seeing that the reading is not the same when you look down or up onto the degree lines on the tube.)
• Handling the thermometer can affect its reading, as heat transfers from your hands (if warmer) or to the (if cooler)

### Activity

1. Give each student or pair of students a thermometer.
2. Review safety precautions and fact that if thermometers are dropped or banged on a table they will break.
3. Have students read their thermometers in the room. Record their findings on the handout.
4. Go into another room or hallway. Have students read their thermometers and write down their findings.
5. Go outside. Have students read their thermometers and write down their findings.
6. Have students hold thermometer in their hands for a few minutes. Read thermometer and write down their findings.

## Closing - Original Questions

1. How can we tell what the temperature is?
2. What is a thermometer?
3. How do you read a thermometer?

## Evaluation

During discussion, note if students understand basic concepts of temperature and thermometer, The parts of a thermometer and how it works, and how to read a thermometer accurately. Students can also show others how to use and read a thermometer to share and to demonstrate what they know!

## Extension Ideas

Ask students to share ideas about why it is so important to determine temperature accurately. Who cares and why? Ideas may include the following:

• Farmers—so they know when to expect frost and can cover up plants or trees.
• Farmers—so they can take care of their animals in severe cold or hot weather.
• Pilots—so they know when there is danger of icing of wings and flaps.
• Chefs & Cooks—so they properly store, cook, and serve food.
• Mechanics—so they can tell if an engine overheats or cools properly.
• Parents—so they make sure children dress properly for the weather and outside activities.
• Nurse or doctor—to determine if a patient has a fever.
• Anyone—so they dress for the weather to avoid heat stroke or frostbite or to simply enjoy being outdoors during different temperatures and seasons.

Explore different kinds of thermometers and when or how they are used. Talk about where you see and find thermometers—refrigerators, clothes dryers, ovens and stoves, cars and tractors, signs and billboards, inside or outside a house or building ...

Some examples are medical thermometers, including the ear probe model, forehead detection strip, regular oral thermometer.

Variety of liquid thermometers. Variety of non-liquid, digital thermometers.

Look over other activities from CAPS: Does the Sun Influence the Temperature of the Earth?, Convection in Our Atmosphere, Keeping a Daily Weather Log, What Is Heat Transfer?, and What is Temperature?

## Prerequisite Vocabulary

Temperature
Measure of the average kinetic energy of the molecules of a substance

Thermometer
An instrument used to determine the temperature of our atmosphere

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Updated 23 Mar 10