Complete Guide to Temperature Measurement - Exercise 21.1

Master temperature measurement: reading thermometers, comparing temperatures, adding/subtracting temperatures, word problems, and temperature conversion through these 5 detailed exercises.

Solution: Exercises 1 to 3
1 Reading Thermometer
Exercise 1
Look at the thermometer. It shows 72°F. What temperature does it read?
Thermometer showing 72°F
Definition:

Temperature: A measure of how hot or cold something is.

Fahrenheit (°F): A unit for measuring temperature where water freezes at 32°F and boils at 212°F.

Celsius (°C): Another unit for measuring temperature where water freezes at 0°C and boils at 100°C.

Reading Method:
  1. Look at the red line inside the thermometer
  2. Find the number where the red line stops
  3. Read the temperature from the scale
  4. Note the unit (°F or °C)
Thermometer Reading
72°F
Temperature
72°F
Step 1: Observe the thermometer

The red liquid rises up the glass tube as temperature increases

Step 2: Locate the red line

Find where the red liquid stops in the tube

Step 3: Read the temperature

The red line is at the 72 mark on the Fahrenheit scale

Step 4: State the temperature

The thermometer reads 72°F

The temperature is 72°F
Final answer:

The temperature is 72°F

Applied rules:

• Reading scale: Match the red line to the closest marked number

• Units: Always include the temperature unit (°F or °C)

• Accuracy: Read to the nearest whole degree for basic thermometers

2 Comparing Temperatures
Exercise 2
Which temperature is warmer: 65°F or 70°F?
Definition:

Comparing temperatures: Determining which temperature is higher or lower

Warmer/Colder: Higher temperature means warmer, lower temperature means colder

Temperature 1
65°F
Temperature 2
70°F
Comparison
70°F > 65°F
Step 1: Compare the numbers

We have 65°F and 70°F

Step 2: Determine which is greater

Since 70 > 65, then 70°F > 65°F

Step 3: Answer the question

70°F is warmer than 65°F

70°F is warmer than 65°F
Final answer:

70°F is warmer than 65°F

Applied rules:

• Number comparison: Compare the numerical values

• Higher = Warmer: Greater temperature value means warmer

• Same units: Only compare temperatures with the same unit

3 Adding Temperatures
Exercise 3
If the morning temperature was 50°F and it increased by 15°F, what is the new temperature?
Definition:

Temperature change: When temperature increases or decreases

Addition: Adding a positive change means temperature increases

Subtraction: Adding a negative change means temperature decreases

Starting Temp
50°F
Change
+15°F
New Temp
65°F
Step 1: Identify starting temperature

The morning temperature was 50°F

Step 2: Identify the change

It increased by 15°F (positive change)

Step 3: Add the temperatures

50°F + 15°F = 65°F

Step 4: State the final temperature

The new temperature is 65°F

50°F + 15°F = 65°F
Final answer:

The new temperature is 65°F

Applied rules:

• Addition: Add the change to the original temperature

• Same units: Keep the same temperature unit

• Positive change: Means temperature increases

Temperature Rules and Methods
\(T_{final} = T_{initial} + \Delta T\)
Temperature Change Formula
Water Freezes
32°F or 0°C
Freezing Point
Water Boils
212°F or 100°C
Boiling Point
Room Temp
~70°F or ~20°C
Comfortable Temperature
Key Temperature Terms:

Hot: High temperature (feels warm or burning)

Cold: Low temperature (feels cool or freezing)

Warm: Moderate temperature (comfortable, not too hot or cold)

Cool: Moderately low temperature (refreshing, not too cold)

Temperature Reading Steps:
  1. Look at the thermometer scale
  2. Find where the red liquid stops
  3. Read the number at that point
  4. Include the unit (°F or °C)
Hot weather: Above 80°F feels hot, above 90°F is very hot
Cold weather: Below 32°F means water freezes, below 20°F is very cold
Body temperature: Normal is 98.6°F (37°C)
Comfortable: Room temperature is usually 68-72°F
Common mistakes: Not including units, misreading the scale, confusing Celsius with Fahrenheit.
Learning tip: Remember water freezes at 32°F and boils at 212°F.
Temperature Facts to Remember:

• Water freezes at 32°F (0°C)

• Water boils at 212°F (100°C)

• Normal room temperature is about 70°F

• Normal body temperature is 98.6°F

• Higher number = warmer temperature

Solution: Exercises 4 to 5
4 Subtracting Temperatures
Exercise 4
The temperature at noon was 75°F. In the evening it dropped by 20°F. What was the evening temperature?
Definition:

Temperature decrease: When temperature goes down (negative change)

Subtraction: To find new temperature after a decrease

Starting Temp
75°F
Decrease
-20°F
Evening Temp
55°F
Step 1: Identify starting temperature

Noon temperature was 75°F

Step 2: Identify the change

Temperature dropped by 20°F (negative change)

Step 3: Subtract the change

75°F - 20°F = 55°F

Step 4: State the evening temperature

The evening temperature was 55°F

75°F - 20°F = 55°F
Final answer:

The evening temperature was 55°F

Applied rules:

• Subtraction: Subtract the decrease from the original temperature

• Same units: Keep the same temperature unit

• Negative change: Means temperature decreases

5 Word Problem
Exercise 5
On Monday, the temperature was 60°F. On Tuesday, it was 10 degrees warmer than Monday. On Wednesday, it was 5 degrees cooler than Tuesday. What was the temperature on Wednesday?
Definition:

Multi-step temperature problem: Requires multiple calculations over time periods

Warmer/Cooler: "Warmer" means add, "cooler" means subtract

Monday
60°F
Tuesday
70°F
Wednesday
65°F
Step 1: Find Tuesday's temperature

Tuesday was 10 degrees warmer than Monday

60°F + 10°F = 70°F

Step 2: Find Wednesday's temperature

Wednesday was 5 degrees cooler than Tuesday

70°F - 5°F = 65°F

Step 3: State the answer

The temperature on Wednesday was 65°F

Step 4: Verify the sequence

Monday: 60°F → Tuesday: 70°F → Wednesday: 65°F ✓

Wednesday: 65°F
Final answer:

The temperature on Wednesday was 65°F

Applied rules:

• Step-by-step: Solve one day at a time

• Warmer = Add: "Warmer" means to add degrees

• Cooler = Subtract: "Cooler" means to subtract degrees

Temperature Laws, Methods, Rules, Definitions
\(T_{new} = T_{old} + \Delta T\)
Temperature Change Formula
Key definitions:

Temperature: A measure of how hot or cold something is.

Thermometer: A tool used to measure temperature.

Fahrenheit (°F): Temperature scale where water freezes at 32°F and boils at 212°F.

Celsius (°C): Temperature scale where water freezes at 0°C and boils at 100°C.

Complete methodology:
  1. Reading thermometers: Look at the red liquid line and match to the scale
  2. Comparing temperatures: Compare numerical values (higher number = warmer)
  3. Adding/subtracting: Use addition for increases, subtraction for decreases
  4. Word problems: Break down into smaller steps
Tip 1: Remember water freezes at 32°F and boils at 212°F.
Tip 2: Normal room temperature is about 70°F.
Tip 3: Normal body temperature is 98.6°F.
Tip 4: When temperature drops, subtract; when it rises, add.
Common errors: Forgetting units, misreading thermometers, confusing addition/subtraction for temperature changes.
Exam preparation: Practice reading thermometers, comparing temperatures, and solving multi-step problems.
Important temperature facts:

• Water freezes at 32°F (0°C)

• Water boils at 212°F (100°C)

• Room temperature is about 70°F

• Body temperature is 98.6°F

• Higher number = warmer temperature

• Lower number = colder temperature

Temperature Visualization: Weekly Weather Patterns
Exercise 6: Daily Temperature Trends
Consider the daily temperatures for a week:
Monday: 60°F
Tuesday: 65°F
Wednesday: 70°F
Thursday: 75°F
Friday: 72°F
Saturday: 68°F
Sunday: 64°F

Analysis: The chart shows how temperatures changed throughout the week.

  • Warmest day: Thursday (75°F)
  • Coolest day: Monday (60°F)
  • Temperature range: 15°F (75°F - 60°F)

Questions & Answers

Question: I don't understand how to read a thermometer. The red line doesn't always stop exactly on a number. How do I know what temperature it is?

Answer: Great question! Reading a thermometer can be tricky at first. Here's how to handle readings that fall between numbers:

  • Look at the scale markings on the thermometer
  • If the red line is halfway between two numbers, round to the nearest whole number
  • Some thermometers have smaller marks between the larger numbers (like 61°F, 62°F, etc.)
  • For basic thermometers, just find the closest marked number

Example: If the red line is between 65°F and 66°F but closer to 65°F, you would say the temperature is 65°F.

Practice tip: Look at thermometers at home, in weather apps, or on TV weather reports to get comfortable with different temperature readings!

Question: Why do we sometimes use °F and sometimes °C? How do I know which one to use?

Answer: Good observation! Different countries use different temperature scales:

  • Fahrenheit (°F): Used mainly in the United States. Water freezes at 32°F and boils at 212°F.
  • Celsius (°C): Used in most other countries. Water freezes at 0°C and boils at 100°C.

In Grade 2, you'll mostly work with Fahrenheit because that's what's commonly used in the US. Your teacher will tell you which unit to use for each problem.

Memory tip: C comes before F in the alphabet, and Celsius numbers are generally smaller than Fahrenheit numbers!

Question: How do I remember if 50°F is hot or cold?

Answer: Here's a helpful way to think about temperature ranges:

  • Below 32°F: Very cold (water freezes!)
  • 32°F - 50°F: Cold, wear a jacket
  • 50°F - 65°F: Cool, might need a light sweater
  • 65°F - 75°F: Comfortable, nice weather
  • 75°F - 85°F: Warm, getting hot
  • Above 85°F: Hot, very warm

So 50°F is on the cool side - not freezing cold, but cool enough that you might want a light jacket!

Remember: 32°F is the freezing point of water, and normal body temperature is about 98°F.

Question: My child struggles with temperature word problems. Any strategies to make them easier?

Answer: Yes! Here are effective strategies for temperature word problems:

  • Draw a number line: Show temperatures on a line to visualize increases/decreases
  • Circle key words: "warmer" means add, "cooler" means subtract, "increased by" means add, "decreased by" means subtract
  • Solve step by step: Don't try to do everything at once
  • Check reasonableness: Does the answer make sense? If temperature increased, should the number be bigger?

Example: "Temperature was 60°F, then went up 10°, then down 5°" → 60 + 10 = 70, then 70 - 5 = 65°F

Practice with real-life examples: "If it's 70°F now and gets 5 degrees warmer, what will it be?"

Question: What happens if the temperature goes below zero? Can we have negative temperatures?

Answer: Yes, absolutely! Negative temperatures exist and are very important:

  • On the Fahrenheit scale, temperatures below 32°F can go negative
  • Temperatures below 0°F are very cold
  • For example, -10°F is 10 degrees below zero, which is extremely cold!

Think of it like this: if you're at 5°F and it gets 10 degrees colder, you go to -5°F.

In winter, many places experience negative temperatures. It's still cold, just measured differently!

Note: In Grade 2, you'll probably work mostly with positive temperatures, but it's good to know negative ones exist.