7th grade · Science · Unit 9 of 10
Mixtures & Solutions
Mix it, dissolve it, separate it
What your child practices
Telling pure substances from mixtures, mechanical mixtures from solutions, solutes and solvents, comparing concentration, and choosing separation methods like filtering, evaporation, magnets and distillation.
Maine Learning Results learning standard: MS-PS1-2 · properties such as solubility that tell pure substances and mixtures apart
How we explain it
Children can open this short lesson before they practice.
- A pure substance has one kind of particle. A mixture has more than one.
- In a mechanical mixture you can see the parts. In a solution, the solute dissolves in the solvent.
- Separate by filtering, evaporating, using a magnet or distilling.
Example: Cup A has 10 g of sugar in 100 mL of water. Cup B has 20 g in 100 mL. Which is more concentrated? Both have the same amount of water. Cup B has more sugar in it. Answer: Cup B
Mixtures & Solutions in Maine
In the Maine Learning Results, this is unit 9 of 10 in 7th grade Science, after Earth's Moving Surface and before Particles and Heat.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Maine Department of Education
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
Black marker ink spreads up wet paper and splits into blue, red and yellow bands. What separation method is this?
🖊️- magnetism
- filtration
- distillation
- chromatography
chromatography
Hint: Chroma means color. Different dyes travel up the paper at different speeds.
Question 2
Salt stirred into water seems to disappear. What happened?
🧂- It melted into a liquid
- It was destroyed
- It turned into water
- It dissolved, forming a solution
It dissolved, forming a solution
Hint: The salt is still there (taste it!). Its particles spread out evenly among the water particles. That's dissolving, not melting.
Question 3
What is a pure substance?
- two substances stirred together
- anything found in nature
- any liquid you can see through
- matter made of only one kind of particle
matter made of only one kind of particle
Hint: Distilled water, table salt and gold are pure substances. Each is made of just one kind of particle.
Question 4
Pure substance or mixture? Tap an item, then tap its basket.
Sort into: 🔹 pure substance · 🔀 mixture
- 💨oxygen gas
- 🪴soil
- 💎diamond (pure carbon)
- 🌬️air
- 🪙pure gold
- 🧱concrete
🔹 pure substance: oxygen gas, diamond (pure carbon), pure gold · 🔀 mixture: soil, air, concrete
Hint: A pure substance is made of only one kind of particle. A mixture has two or more substances combined, even if it looks like one thing.
Question 5
Which cup of sugar water is the least concentrated?
Sugar water cups Cup Sugar Water A 5 g 100 mL B 3 g 100 mL C 4 g 200 mL D 24 g 200 mL - Cup B
- Cup C
- Cup A
- Cup D
Cup C
Hint: Concentration is how much solute is dissolved in an amount of solvent. Work out the grams of sugar in each 100 mL of water, then compare.
Question 6
Which change makes sugar dissolve faster?
🥄- putting a lid on the cup
- using colder water
- stirring the water
- using bigger sugar lumps
stirring the water
Hint: Stirring, warmer water and smaller pieces all help a solute dissolve faster.