Atoms, elements and mixtures
Separating the colours in a felt-tip pen
Is a black felt-tip ink a pure substance or a mixture?
Watch first
Clear up the difference between an element, a compound and a mixture.
What you need
Tick each one as you find it — 0 of 5 ready.
Plan the fair test
- Change: Which pen ink you test
- Measure: Number of separate colours that appear
- Keep the same: Same paper, same water depth, same starting line height
Objectives this evidences
- Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography
Do it, one step at a time
Step 1 of 4
- Step 1. Cut a strip of filter paper. Draw a pencil line 2 cm from the bottom and put an ink spot on it.
- Step 2. Hang the strip so the bottom edge sits in water but the ink spot stays above the water line.
- Step 3. Watch the water climb for about ten minutes, then take the strip out and let it dry.
- Step 4. Repeat with two other pens and compare how many colours each one separates into.
What should happen
Black ink splits into several colours, so it is a mixture. A single-colour spot suggests a pure dye.
Think about: Why draw the starting line in pencil rather than pen?
Write up your result
A sentence or two is enough to save it.
The lessons behind this practical
Each one opens with the same short film, and the film has a written transcript underneath if reading is easier than watching.
Now the quiz for this topic
Questions come from the lessons behind this practical, so nothing is asked that has not been taught.
Quiz
Atoms, elements and mixtures quiz
4 questions from the lessons in this stage. No timer, and you can try again as many times as you like.