Ice takes up more space
Fill a plastic cup with water up to a mark and put it in the freezer. By morning the ice will have risen above the line: water expands as it freezes. Don't use a closed glass bottle for this — it can crack.
Lessons
Lessons and materials
Each lesson in this section is one small observation that fits on a kitchen table. We briefly describe what you'll see and give an explanation that makes sense without formulas. Lessons are grouped by topic, so it's easy to take one topic a week and work through it from start to finish.
An explanation sticks better when you've seen the thing happen with your own eyes first and only then read why it happens.
How this section works: each card says what we observe and what causes it. We don't retell textbook chapters or follow any particular curriculum: the lessons suit pupils of different ages, and the adult chooses how deep the explanation goes.
Water and ice
Three observations about how water behaves as it cools and what makes some objects sink while others float.
Sink or float
Drop a few safe objects into a bowl of water: a spoon, a cork, an apple, an ice cube. Write down your guesses first, then check. This makes it easier to notice that it isn't only about the size of the object.
Melting on a plate
Put identical ice cubes in different spots around the home: on the windowsill, in the shade, on a plate with salt and one without. Note when each cube disappears and look for what speeds up melting.
Air and pressure
Air is invisible, but you can trap it in a cup and put it to work.
A dry tissue under water
Fix a crumpled tissue to the bottom of a cup, turn the cup upside down and lower it straight into a bowl of water. Check whether the tissue stays dry and think about what stopped the water rising inside.
Balloon and baking soda
The adult pours a little ordinary vinegar into a plastic bottle, and baking soda goes into a balloon. Stretch the balloon over the bottle neck and lift it: the carbon dioxide released blows it up without any help from your breath.
Light and colour
For these lessons you need a sunny day or a bright desk lamp switched on by an adult.
A rainbow in a glass
Stand a glass of water on the windowsill so a sunbeam passes through it, and lay a sheet of white paper on the floor. The water acts like a prism and splits white light into rainbow colours. Never look straight at the sun.
Shadows change shape
Trace the shadow of a toy in the morning, at midday and in the evening on the same sheet. Compare the length and direction and think about how they relate to the position of the sun.
Simple mechanics
You can build a lever and a ramp from a ruler, a pencil and a pile of books.
A ruler lever
Lay a ruler across a pencil, put an eraser on one end and press the other end with your finger, closer to and further from the pivot. Note where the load is easiest to lift.
A ramp of books
Make a ramp from a board and some books and roll a toy car down from different heights. Measure with a ruler how far it travels and write the numbers in a table.
Plants
Living things change slowly, but they give you the most material for your diary.
A shoot looks for light
Put sprouted seeds in a box with a hole in one side. After a few days the stems will bend towards the hole: plants grow towards light, and this is called phototropism.
A seed on a paper towel
Spread bean or pea seeds on a damp paper towel in a clear container and draw what has appeared every day: a root, a shoot, the first leaves.
Related sections
- Tasks
Week-long observation tasks: a plant by the window, water in the freezer and testing your own hypothesis.
- Methods
The scientific method in simple words, an observation diary and presenting your result in class.
- Glossary
Clear definitions of words you meet in experiments, from hypothesis to phototropism.
Sources
- School science textbooks (in general terms)
- Safety rules for experiments (in general terms)
The experiments are described in general terms, based on school science textbooks, guides for young researchers and safety rules. Results at home may differ from what you expect, so repeat each experiment together with an adult and write down honestly what you actually saw.