Tides, melting points and kinds of matter
Tides and the tidal range, the Earth’s tilt, melting and boiling points, and organic matter. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
Tides
| Word | Meaning |
|---|---|
| Tidal range | The difference between high and low water |
| Spring tide | Big range; at new and full moon |
| Neap tide | Small range |
Tides matter to fishermen: they affect safety and where the fish are. The Moon is a satellite: a body that orbits another, in an orbit.
Melting and boiling points
- Melting point: where a solid becomes liquid. Boiling point: where a liquid becomes a gas.
- Every pure substance has its own melting point: this helps to identify substances.
Organic and inorganic
| Organic | Inorganic |
|---|---|
| Comes from living things | Does not come from living things |
| Leaves, wood, bones | Stone, sand, water |
Dead organic matter breaks down in the soil and makes it rich. Plants use sunlight to make food and give off oxygen. Coal is the fossil fuel South Africa uses most for electricity.
Remember this and test yourself
- A tide is the regular rise and fall of the sea, caused by the Moon’s gravity. Most places get two high tides a day.
- Spring tide: very high and very low tides, at new and full moon. Neap tide: a small tidal range.
- The Earth’s axis is tilted about 23.5°.
- Ice melts at 0 °C; iron has a very high melting point. Each pure substance has its own melting point.
- Organic matter comes from living things; decomposers break down dead organic matter and enrich the soil.
Write these points in your book. Read them again the night before the test.
Spring tide = the sea springs high (Sun and Moon in line). Neap tide = the sea takes a nap (small range).
Important words
First say what the word means, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: Tides, melting points and kinds of matter- Read one part together and ask your child to tell it back in their own words.
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Follows CAPS for Grade 7 Natural Sciences. Always check your teacher’s notes and textbook too.