Interactive thermometer

What the thermometer shows

A liquid thermometer shows temperature by the height of the liquid in a thin tube: warmer liquid expands and rises. This one has two scales on the same tube. The left side is Fahrenheit (°F), used for weather in the United States, and the right side is Celsius (°C), used in science and in most countries. Drag the liquid, use the Warmer and Cooler buttons, or use the arrow keys, in steps of 1 °F or 1 °C.

Landmarks marks water freezing (32 °F, 0 °C), room temperature (about 68 °F, 20 °C), body temperature (about 98.6 °F, 37 °C), water boiling at sea level (212 °F, 100 °C) and −40°, where both scales read the same. The readout gives the temperature in both units and describes how it would feel. Show the conversion adds the formula with the numbers filled in.

Why reading a scale is a skill

A thermometer is a vertical number line, and the marks between labeled numbers are not always worth 1. On this one, each small Fahrenheit mark is 2 degrees and each small Celsius mark is 1. Children have to work out what each mark is worth before they can read it, which is the same thinking they need for rulers, measuring jugs and graph axes. Temperatures below zero also give one of the most natural introductions to negative numbers.

Common mix-ups

• Assuming every mark is worth 1. Count how many spaces there are between two labeled numbers first.
• Reading the wrong scale. Check the °F or °C label at the top before reading.
• Thinking −10° is warmer than −5°. Below zero, the bigger the number after the minus sign, the colder it is.
• Thinking 0 °F is the freezing point. Water freezes at 32 °F, which is 0 °C.

A 10-minute thermometer session

• Turn on Landmarks. Ask the child to set each one and read it on both scales.
• Ask how much each small mark is worth on the Fahrenheit side and on the Celsius side.
• Press Challenge. The numbers hide, so the child reads the scale and presses Check.
• Set a temperature below freezing and talk about what happens to water there.
• Finish by finding −40°, the temperature where both scales agree.

Where it fits by grade

• Grades 1 to 3: reading scales and describing weather. NGSS asks kindergarten students to observe local weather (K-ESS2-1) and grade 3 students to record typical weather in tables and graphs (3-ESS2-1).
• Grade 6: positive and negative numbers describe opposite values, such as temperatures above and below zero (6.NS.C.5).
• England: Year 2 measures temperature in °C using thermometers, Year 5 interprets negative numbers in context, and Year 6 calculates intervals across zero.

Learning more

Negative numbers are on Eurekami's skill map, and Daily Practice brings them back when they start to fade. Lessons draw number lines live from the numbers in each question, and teachers can print worksheets with answer keys.