6th grade · Science · Unit 1 of 17
Particles & Mixtures
Pure substances and mixtures
What your child practices
The particle theory of matter, the states of matter, pure substances versus mixtures, and homogeneous versus heterogeneous mixtures.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 6.6(A); 6.6(B) · the structure and particle motion of solids, liquids and gases, and mixtures
How we explain it
Children can open this short lesson before they practice.
- A pure substance has only one kind of particle, like copper or table salt. A mixture has more than one.
- A homogeneous mixture looks the same throughout (salt water). A heterogeneous one has visible parts (salad).
- Solids have the strongest attraction between particles. Gas particles have large spaces, so gases squeeze easily.
- In ice, water and vapor, the particles are the same. Only their arrangement and motion change.
Example: Is muddy water homogeneous or heterogeneous? You can see bits of mud floating in it. Visible parts mean heterogeneous. Answer: heterogeneous
Particles & Mixtures in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 1 of 17 in 6th grade Science, before The Periodic Table.
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? Sort each one.
Sort into: 💎 pure substance · 🥣 mixture
- 🍲vegetable soup
- 🟠a copper wire
- 🧂pure table salt
- 💧distilled water
- 🌊salt water
- 🌬️air
- 💨oxygen gas
- 🥜trail mix
💎 pure substance: a copper wire, pure table salt, distilled water, oxygen gas · 🥣 mixture: vegetable soup, salt water, air, trail mix
Hint: A pure substance is one kind of matter (an element like gold, or a compound like water). A mixture is two or more substances physically combined.
Question 2
Brass is copper and zinc mixed evenly throughout a solid. It is a…
- pure substance because it is a solid metal
- heterogeneous mixture
- gas
- homogeneous mixture
homogeneous mixture
Hint: Brass is an alloy: a mixture that looks the same throughout.
Question 3
What is a pure substance?
- Any clear liquid
- A mixture of two clean liquids
- Matter made of only one kind of particle
- Any substance that is safe to drink
Matter made of only one kind of particle
Hint: Gold and water are pure substances because each has one kind of particle.
Question 4
Water as ice, as liquid water and as water vapor has the same kind of particle. What differs in each state?
- How the particles are arranged and how they move
- The kind of particle
- The number of different substances
- Whether the water is pure
How the particles are arranged and how they move
Hint: Changing state changes the arrangement and motion, not the kind of particle.
Question 5
Which would be a homogeneous mixture?
- gravel
- sugar dissolved in water
- a salad
- sand and water
sugar dissolved in water
Hint: Dissolved sugar is evenly mixed and cannot be seen as separate parts.
Question 6
Homogeneous or heterogeneous? Sort each mixture.
Sort into: 🥛 homogeneous (looks the same throughout) · 🍕 heterogeneous (different parts show)
- 🌬️air in a clean room
- 🧂salt dissolved in water
- 🥗a salad
- 🍎clear apple juice
- 🏖️iron filings mixed with sand
- 🥣cereal in milk
🥛 homogeneous (looks the same throughout): air in a clean room, salt dissolved in water, clear apple juice · 🍕 heterogeneous (different parts show): a salad, iron filings mixed with sand, cereal in milk
Hint: In a homogeneous mixture the parts are evenly mixed and look like one substance. In a heterogeneous mixture you can see different parts.