What is this skill?
Everything you can touch is matter, and in daily life matter comes in three forms. A solid, like a rock, a book or a spoon, keeps its own shape. A liquid, like milk, juice or water, flows and takes the shape of its container. A gas, like the air in a balloon or steam, spreads out to fill all the space it is in. Second graders learn to sort things into these three groups and to describe what happens when matter changes from one state to another.
In this practice a child answers "Which one is a solid?" (ice, not water or steam) and "Which one is a liquid?" (milk). Sorting games use solid, liquid or gas with a rock, a book, juice, water, air in a balloon and steam, and solid or liquid with a spoon, a coin, honey, oil and soda. Questions about change ask what happens to ice when it gets warm (it melts into water), what water turning into ice is called (freezing) and which word means a liquid changing into a gas (evaporating). A puddle that disappears on a sunny day shows that most of the water went into the air as a gas. A true-or-false question says air is a gas even though you cannot see it, and another says water that freezes is still water, just in a different state.
Why it matters
This is the child's first look at chemistry and physics. The same stuff can look and act completely different, and the practice makes that idea concrete with the one substance every child knows: water.
Understanding melting, freezing and evaporating explains daily life, such as why ice cream gets runny, why a puddle goes away and why a cold glass gets wet on the outside.
It also builds the base for the water cycle in 4th grade and for atoms and molecules in later grades, where states of matter are explained by how tiny parts move.
Common mistakes
- Thinking a gas must be something you can see. Air is all around us and is invisible. A balloon shows that air takes up space.
- Calling a powder or sand a liquid because it pours. Each grain is a small solid that keeps its shape, which is why sand holds a pile and water does not.
- Believing the water in a puddle just stops existing. It moves into the air as a gas, which is called evaporating.
- Mixing up melting and freezing. Melting is solid to liquid when something gets warm, and freezing is liquid to solid when it gets cold.
How to help at home
- Put an ice cube in a bowl in the sun and a second one in the shade. Ask your child which melts faster and where the water went when it dried up.
- Fill a zip-top bag with air and squeeze it. Ask where the air went when it was let out, and show that you can feel but not see it.
- Make a solid, liquid and gas hunt in the kitchen. Look for juice, a spoon, a steaming kettle with a grown-up and the air in a bag of chips.
- Freeze a small cup of juice and let it melt. Ask whether it is still juice and what changed.
Worked examples
These are real questions from the Tutorsaurus solids, liquids and gases practice, with the answers worked out.
Example 1
A solid keeps its own shape.
Answer: True. True! Solids like blocks and rocks keep their shape unless you break or bend them.
Example 2
You can pour it and it has no shape of its own. What is it?
Choices: Rock, Liquid, Solid
Answer: Liquid. A liquid pours and takes the shape of whatever holds it.
Example 3
Which word means a liquid changing into a gas?
Choices: Melting, Freezing, Evaporating
Answer: Evaporating. Evaporating is a liquid turning into a gas. Freezing makes a solid and melting makes a liquid.
Printable worksheet (PDF) — one page of questions from this practice that work on paper, easier ones first, with an answer key on page 2. Free to print, no sign-up.