Grade 4 (age 9-10)

Separating Mixtures

A mixture is two or more substances mixed together, and we can pull them apart by how their parts differ in size or property. Sand is caught by filter paper, iron bits are lifted out with a magnet, and salt water is evaporated to leave the salt. Tap each button to watch the three methods in action.

How do we separate mixtures?

🔬 Filtering

①Separates by size

②Example: sand + water → filter paper

③Use the difference in properties

④If one method fails, combine several

Why can we separate them?

💡 Difference in Properties

①Different size → filter (sieve, filter paper)

②Different boiling points → evaporate, boil

③Magnetic vs not → magnet

④Different weight → settle

⑤Each substance has its own unique property

Summary

Separation Principle

Property difference → choose the method

Use differences in size, melting/boiling, magnetism, etc.

3 Common Methods

Filter (size) / Evaporate (boiling) / Magnet (magnetism)

First identify which property differs

🎯 Key Points

①Mixture: two or more substances mixed together

②Filter: by size (sand+water)

③Evaporate: by boiling point (salt water)

④Magnet: by magnetism (iron+sand)

⑤We use these methods often in daily life

Examples and Unit Test

Example 1

How can you pick out the sand from a mixture of sand and water?

Sand grains are large and water is made of tiny particles, so their sizes differ.

Filtering with filter paper lets the water pass while the sand is caught on the paper.

▸ Filter it with filter paper (using the size difference)

When particle sizes differ, separate by filtering.

Example 2

Iron filings and salt are mixed together. What tool would you use to pick out only the iron filings?

Iron filings stick to a magnet, but salt does not (difference in magnetism).

Holding a magnet near it makes only the iron filings stick and separate out.

▸ A magnet (using the difference in magnetism)

The difference in being attracted to a magnet separates the iron filings.

Unit-test style

Which statement about separating mixtures is correct?

①Filtering uses the difference in boiling point

②A magnet separates materials like iron that stick to it

③Salt in salt water is caught by filter paper

④A mixture can be separated by only one method

⑤Evaporation uses the difference in particle size

▸ ② A magnet separates materials like iron that stick to it

Iron is attracted to a magnet, so a magnet can separate materials like iron.

Filtering uses size (①), evaporation uses boiling point (⑤), salt dissolves in water and is not caught by filter paper (③), and a mixture can be separated using several methods together (④).

← Previous

Earth's Appearance

Shadows & Mirrors