Using Our Senses to Observe - Second Grade Science
Every scientific discovery begins with observation, and your primary tools for exploring the universe are your five senses: sight, hearing, touch, smell, and taste. Your senses collect information from your surroundings and send electrical signals through nerves to your brain, which interprets the signals into meaningful experiences. By sharpening your senses and recording what they detect, you can explore the properties of objects and living creatures with amazing clarity.
The Five Senses and Their Organs
Each of your five senses relies on a specialized organ designed to capture specific kinds of sensory information from the environment.
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| THE FIVE SENSES AND SENSORY ORGANS |
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| 1. SIGHT ----> Eyes (Detects light, color, shape, size) |
| 2. HEARING ----> Ears (Detects sound waves, pitch, volume) |
| 3. TOUCH ----> Skin (Detects texture, pressure, temperature) |
| 4. SMELL ----> Nose (Detects airborne scent molecules) |
| 5. TASTE ----> Tongue (Detects sweet, sour, salty, bitter) |
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Sight: Observing Appearance
Your eyes detect light reflecting off surfaces. Through sight, you determine an object's color, size, shape, pattern, and movement. When observing an apple, sight tells you it is round, shiny red with yellow speckles, and about eight centimeters wide.
Hearing: Detecting Sound and Vibrations
Your ears detect sound vibrations traveling through air, liquids, or solids. Hearing tells you how loud or quiet a sound is (volume) and how high or low the pitch sounds. When studying birds, hearing allows you to identify songbirds hidden high in the tree branches by their distinct chirps.
Touch: Feeling Textures and Temperatures
Your skin contains millions of tiny nerve receptors that sense texture, temperature, hardness, and pressure. Touch informs you whether a rock is rough, smooth, jagged, warm, cold, squishy, or rigid.
Smell: Sensing Aromas and Vapors
Your nose catches airborne chemical molecules. Smell alerts you to blooming pine needles, damp soil after rain, or smoke from a distant fire. In science, smell provides important clues about chemical reactions and living decay.
Taste: Analyzing Flavors Safely
Your tongue possesses thousands of taste buds that detect five primary flavors: sweet, salty, sour, bitter, and savory. While taste is a vital sense, scientists follow a strict rule: NEVER taste anything in a science investigation unless an adult specifically prepares a safe food activity.
Qualitative Versus Quantitative Observations
Scientists divide observations into two primary categories: qualitative and quantitative. Both types are essential for creating a complete scientific record.
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| QUALITATIVE VS. QUANTITATIVE OBSERVATIONS |
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| QUALITATIVE (Words and Descriptions) |
| - "The feather is fluffy, light gray, and very soft." |
| - "The liquid turned cloudy white and smells fruity." |
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| QUANTITATIVE (Numbers, Measurements, and Counts) |
| - "The feather has a length of 14 centimeters." |
| - "There are 6 distinct veins branching from the main stem." |
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Qualitative Observations
Qualitative observations describe the qualities, appearances, and characteristics of an object using words. They focus on colors, textures, odors, and sounds without using numerical measurements.
Quantitative Observations
Quantitative observations involve quantities, numbers, and precise measurements. Whenever you count the petals on a daisy, weigh a sample on a scale, or time how long a toy car rolls, you are making quantitative observations.
Science Observation Safety: The Wafting Technique
Some chemicals or natural substances produce strong vapors that could irritate your nose, throat, or lungs if inhaled directly. Scientists use a safe method called wafting rather than putting their face close to an open container.
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| THE WAFTING TECHNIQUE |
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| Container Gentle Wave of Hand |
| | | ( ( ( ( |
| |~~~~~| .--------. |
| |_____| | HAND | |
| '--------' |
| Gently wave your hand across the top to push a small breeze |
| of air toward your nose. Never sniff directly! |
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How to Waft
Hold the container about six to eight inches away from your face. Use your free hand to gently fan the air above the container toward your nose while taking a shallow breath. This carries just enough scent molecules for your nose to identify the odor safely without inhaling harsh fumes.
Chapter Review Exercises
Question 1: Name the five human senses and the specific sensory organ associated with each sense.
Question 2: What is the main difference between a qualitative observation and a quantitative observation? Provide an example of each for a fallen pinecone.
Question 3: Why is taste the only sense that scientists generally do not use during an unfamiliar lab investigation?
Question 4: Describe how to safely smell an unknown substance in a science setting using the wafting technique.
Solutions and Explanations
Solution 1: The five senses and their sensory organs are sight (eyes), hearing (ears), touch (skin), smell (nose), and taste (tongue).
Solution 2: Qualitative observations describe characteristics using descriptive words, while quantitative observations use numbers and measurements. For a pinecone, a qualitative observation is "the pinecone is dark brown, wooden, and prickly to touch." A quantitative observation is "the pinecone is 9 centimeters long and has 42 scales."
Solution 3: Scientists do not taste unknown lab substances because many chemicals, wild plants, minerals, and mold specimens contain toxic or poisonous compounds that could cause serious sickness or harm if swallowed.
Solution 4: To waft safely, hold the container several inches away from your face, hold your head upright, and use your hand to fan a gentle wave of air across the top of the container toward your nose. This allows you to detect the scent without inhaling concentrated or harmful fumes.