Secrets of Water and Air
FoundationWater and air have no colour, smell or taste and no fixed shape; air takes up space — try the experiment and see.
- Water and air have no colour, smell or taste, and no fixed shape.
- Water flows, always from high to low.
- Air cannot be seen, but it takes up space — bubbles are the proof.
文體小知識：探究記敘帶我們動手做實驗：先觀察現象，再想一想，最後找出結論。
§Text Passage
1Water and air are the two things we know best; we meet them every day, yet they hide many secrets. They share a common feature: no colour, no smell and no taste. Clear water looks transparent, and air cannot be seen or touched, but both truly exist.
2Neither water nor air has a fixed shape. Pour water into a cup and it takes the shape of the cup; pour it into a bowl and it takes the shape of the bowl. Water flows from high places to low places. A balloon puffs up when blown and shrinks when the air runs out — air has no fixed shape either.
3How can we prove air exists? Try a small experiment: push a tissue into the bottom of a cup, turn the cup upside down and push it straight down into water. Take the cup out and touch the tissue — it is still dry! The air inside the cup takes up space and keeps the water out, so the tissue stays dry.
4Try again with the cup tilted, and you will see strings of bubbles rising — that is the air escaping from the cup. When the air leaves, water rushes in to fill the space, and the tissue gets wet. This experiment tells us: air cannot be seen, but it truly takes up space.
5Water and air are necessary for all living things. So we should save water and never pour away unused drinking water; we should also keep the air clean by taking public transport more and burning less rubbish. Knowing the secrets of water and air, let us treasure them all the more.
1Summary 重點摘要
Water and air have no colour, smell or taste and no fixed shape; air takes up space — try the experiment and see.
2Vocabulary cards Vocabulary
What things look like; water and air have no colour.
What the nose senses; water and air have no smell.
What the tongue senses; clear water has no taste.
The outer form of a thing; water and air have no fixed shape.
Water moving from high places to low places.
Air truly exists and fills a place.
A small test to check our ideas.
Little round balls of air rising in water.
Able to see through, like clear water.
3Step by step Steps
- Step 1: Observe the features of waterTake a cup of clear water. Look first: things behind the cup can be seen clearly, so water has no colour and is transparent. Smell: no smell. Taste a little: no taste. Follow the safety rule when observing: never smell or taste unknown liquids without asking a teacher or an adult. Remember the three no's of water: no colour, no smell, no taste — these are the features of water.
- Step 2: Water has no fixed shape and flowsPour water into a round cup and it becomes round; pour it into a square box and it turns square; spill it on the table and it runs in all directions. Water has no fixed shape and always flows to lower places. Water dripping between the fingers when we wash hands and rain sliding down the window both show water flowing. That is why we need containers to hold water, or it soon runs away.
- Step 3: Observe the features of airAir also has no colour, smell or taste, and no fixed shape; it cannot be seen or touched. How do we know it exists? Watch leaves and flags fluttering outside — air is pushing them. Blow through a straw into water and strings of bubbles rise. Blow up a balloon, let go, and the air shoots out, flying the balloon around the room. All these show that air truly exists though invisible, and it is quite powerful too.
- Step 4: Small experiment — the dry tissuePrepare a clear cup, a tissue and a basin of water. Push the tissue firmly into the bottom of the cup so it will not fall out when the cup is upside down. Turn the cup upside down and push it straight down into the water, hold for five seconds, then lift it straight out. Touch the tissue — it is dry! Think: if the cup held nothing at all, water would rush in at once and the tissue would be soaked. Why is it dry?
- Step 5: The science behind the experimentThe tissue stayed dry because the cup was full of air. Though invisible, air takes up space and keeps the water outside. Tilt the cup into the water and bubbles appear — the air is escaping. When the air leaves, water fills the space and the tissue gets wet at once. The contrast of dry and wet proves the conclusion: air takes up space. That is the scientific result of our little experiment.
- Step 6: Treasure water and airWater and air are treasures all living things need: people are in danger after days without water, and cannot live minutes without air. So save water: turn off the tap while brushing teeth, do not play with water in the shower, and pour only as much as you can drink. Keep the air clean: walk or take public transport more, and tell an adult if someone burns rubbish. Knowing the secrets of water and air, learn to love them too.
5Worked example Example
Example: Ming pushed a cup with a tissue inside straight down into the water — the tissue stayed dry. His sister tilted her cup into the water — the tissue got wet. Why were the results different?
- In the first try the cup went in upside down and straight, so the air inside could not escape.
- The air took up space and kept the water out, so the water never touched the tissue and it stayed dry.
- In the second try the tilted cup left an opening, and the air escaped as bubbles.
- With the air gone, water rushed in to fill the space and soaked the tissue.
- Answer: The difference is caused by air. When the cup went in straight, air stayed inside taking up space, so water could not enter and the tissue stayed dry. When the cup tilted, air escaped as bubbles, water rushed in, and the tissue got wet. The experiment proves air takes up space.
6Common mistakes Mistakes
7Quick check Quick check
Q1What features do water and air share?
Q2What happens to water in different containers?
Q3Why did the tissue stay dry in the experiment?
Q4What are the bubbles when the cup tilts?
Q5Name one way to save water.
8Recap Recap
- Water and air have no colour, smell or taste, and no fixed shape.
- Water flows, always from high to low.
- Air cannot be seen, but it takes up space — bubbles are the proof.
- Dry tissue experiment: air blocks the water so the tissue stays dry.
- Water and air keep us alive — save water and keep the air clean.