4th grade · Science · Unit 2 of 17
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.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 4.6(B) · comparing mixtures and solutions of solids and liquids in liquids
How we explain it
Children can open this short lesson before they practice.
- A pure substance is one kind of matter, like gold or table salt. A mixture has two or more, like salt water or air.
- In a solution, one thing dissolves into another, like sugar in water.
- Separate mixtures by sifting, filtering, magnets or letting water evaporate.
- Sugar dissolves faster in warmer water.
Example: How could you get iron filings out of sand? Magnets pull iron, but not sand. Move a magnet through the mixture. Answer: use a magnet
Mixtures & Solutions in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 2 of 17 in 4th grade Science, after Particles & Mass and before Thermal Energy.
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: Texas Education Agency (TEA)
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
Pure substance or mixture? Tap an item, then tap its basket.
Sort into: 🔹 pure substance · 🔀 mixture
- 💎diamond (pure carbon)
- 🌊salt water
- 🌬️air
- 🪴soil
- 💧distilled water
- 🧂table salt
🔹 pure substance: diamond (pure carbon), distilled water, table salt · 🔀 mixture: salt water, air, soil
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 2
Which method separates small pebbles from fine sand?
- boiling
- using a magnet
- sifting through a sieve
- evaporation
sifting through a sieve
Hint: A sieve (screen) has holes that let small grains fall through and keep the bigger pieces.
Question 3
In air (mostly nitrogen, with some oxygen), which is the solvent?
🧪- oxygen
- nitrogen
- air
nitrogen
Hint: The solute is what dissolves (usually the smaller amount). The solvent does the dissolving (usually the larger amount). Together they make the solution.
Question 4
A solution that can't dissolve any more solute is called…
- diluted
- evaporated
- saturated
- pure
saturated
Hint: Keep adding sugar to water and eventually it piles up on the bottom. The solution is full, or saturated.
Question 5
Which change makes sugar dissolve faster?
🥄- using bigger sugar lumps
- putting a lid on the cup
- stirring the water
- using colder water
stirring the water
Hint: Stirring, warmer water and smaller pieces all help a solute dissolve faster.
Question 6
What can Priya conclude from her experiment?
Seconds for a sugar cube to dissolve - Sugar dissolves faster in warmer water
- Water temperature makes no difference
- Sugar dissolves faster in colder water
- Sugar can't dissolve in hot water
Sugar dissolves faster in warmer water
Hint: Look at how the bars change as the water gets warmer. A shorter bar means less time to dissolve.