What you will learn
- Name the solute and the solvent in a salt or sugar solution.
- Explain why evaporation works and a cloth does not.
- Read a thermometer in degrees Celsius and name the parts you use.
When salt or sugar disappears into water, it has not been destroyed. It has dissolved. The mixture is a solution. The solid that dissolved is the solute. The liquid that did the dissolving is the solvent. In this lesson the solvent is water.
You can get the solid back by letting the water evaporate, which means the water turns to vapour and leaves. Warmth and a wide surface speed that up. You will also learn how to read a thermometer safely, with an adult.
Solute, solvent and solution
Stir a spoon of salt into a cup of water. If the salt disappears and the water looks clear, you have a solution. The salt is still there. You can taste that only as part of a plan an adult approves, using kitchen salt, never using an unknown powder.
Sugar and water make a solution too. Sand and water do not, if the sand settles at the bottom. Dissolving is different from sinking.
Words to keep straight: solute is the solid, solvent is the water, solution is the mixture.
Worked example 1
In a cup of sugar water, which is the solute and which is the solvent?
Show me how
The sugar dissolved, so sugar is the solute.
The water did the dissolving, so water is the solvent.
The whole mixture is the solution.
How to separate, and why a cloth fails
If you pour salty water through a cloth, the salt goes through with the water. The salt pieces in a solution are too small to be caught that way. A sieve or a cloth separates bits that have not dissolved, such as sand.
To separate the dissolved salt, let the water evaporate. Pour a shallow layer onto a plate and leave it in a warm place. The water leaves. The salt stays as solid crystals. A warmer temperature makes evaporation faster. A wider surface, a plate instead of a deep narrow cup, also makes it faster.
You have separated the solute from the solvent. You have not destroyed either one. The water has gone into the air as vapour.
Worked example 2
Malik pours salt water through a clean cloth and expects salt to be left on the cloth. What will he see, and what should he do instead?
Show me how
The salt water passes through. Little or no salt is left on the cloth.
He should put a shallow layer in a warm place and wait for the water to evaporate.
The salt crystals remain after the water has left.
Watch out! A common mistake
Hotter does not mean a child should boil water alone. Faster evaporation is a science idea. The safe investigation uses warm water an adult prepares, or sunshine on a plate.
The thermometer
A laboratory thermometer measures temperature. On the picture, use the Celsius scale. The other scale is for older students. You do not need it.
The bulb is the tip that goes in the liquid. The column is the liquid that rises inside the tube. The scale is the numbered line. Read across at eye level. If you look from above or below, the number can look wrong. Give the unit: degrees Celsius.
Your fingers warm the bulb, so do not hold the bulb while you read it. An adult places the thermometer. Do not use it as a toy sword. Do not put a laboratory thermometer in your mouth.
Investigate, with an adult
Materials. Kitchen salt, water, a clear cup, a spoon, a shallow plate, a laboratory thermometer, paper and a pencil. An adult is part of the materials list.
Steps. With the adult, stir salt into water until it dissolves. Pour a little onto the plate. Put the plate in a warm sunny place. The next day, look for crystals. The adult measures the warm water and you read the Celsius scale at eye level. Write the temperature and what you observed.
Safety. Do not taste unknown mixtures. Do not boil water yourself. Do not hold the thermometer by the bulb. If the thermometer breaks, step back and call an adult. Wear shoes. Tie long hair back.
Try it
TRY ITSolution lab
Let’s practise
Work each one in your copybook. Open Hint if you are stuck, then open Show answer to check.
1. In salt water, name the solute and the solvent.
Hint
The solid dissolved. The liquid did the dissolving.
Show answer
Salt is the solute. Water is the solvent.
2. Why does salty water pass through a cloth?
Hint
Think about the size of what is dissolved.
Show answer
The dissolved salt is too small for the cloth to catch, so it stays in the water.
3. What does evaporate mean in this lesson?
Hint
It is what the water does, not what the salt does.
Show answer
The water turns to vapour and leaves. The salt can remain as a solid.
4. Name two things that make evaporation faster.
Hint
One is about heat and one is about the shape of the container.
Show answer
A higher temperature and a wider surface.
5. Name the bulb, the column and the scale, and say what each is for.
Hint
Start at the tip.
Show answer
The bulb is the tip that goes in the liquid. The column is the liquid that moves inside. The scale is the numbered line we read.
6. Why do you read a thermometer at eye level?
Hint
Think about a wrong view from above.
Show answer
Looking from above or below can make the number look wrong.
7. Write one safety rule for this investigation.
Hint
An adult is involved.
Show answer
An adult handles hot or warm water, and a child does not boil water alone or hold the bulb of the thermometer.
8. Sand sits at the bottom of a cup of water. Is the sand the solute? Say why.
Hint
Did it disappear into the water?
Show answer
No. A solute dissolves. Sand that settles has not dissolved.
Quiz
Lesson quiz: 10 questions
Answer every question, then press Check my answers. Score 8 or more to earn the Solution Sorter badge.
Separating Dissolved Solids and Using a Thermometer: worksheet
Name: ____________________ Date: ______________
Part A: Let’s practise
1. In salt water, name the solute and the solvent.
2. Why does salty water pass through a cloth?
3. What does evaporate mean in this lesson?
4. Name two things that make evaporation faster.
5. Name the bulb, the column and the scale, and say what each is for.
6. Why do you read a thermometer at eye level?
7. Write one safety rule for this investigation.
8. Sand sits at the bottom of a cup of water. Is the sand the solute? Say why.
Part B: Quiz
1. In sugar water, the solute is
(a) the water
(b) the sugar
(c) the cup
(d) the thermometer
2. The solvent in these investigations is
(a) salt
(b) water
(c) sand
(d) cloth
3. Which method gets dissolved salt back from water?
(a) Pouring it through a cloth
(b) Letting the water evaporate from a shallow dish
(c) Stirring faster and then stopping
(d) Adding pebbles
4. Dissolved salt is trapped by an ordinary cloth.
True or False? Circle one: True / False
5. Evaporation is faster when
(a) the surface is wider and the place is warmer
(b) the cup is covered tightly and kept cold
(c) the salt is replaced with pebbles
(d) the thermometer is shaken
6. The bulb of a thermometer is
(a) the numbered line
(b) the tip that goes in the liquid
(c) the salt crystal
(d) the solvent
7. You should read the scale
(a) with your eyes level with the column
(b) from near the ceiling
(c) while holding the bulb in your fist
(d) by tasting the water
8. A laboratory thermometer belongs in your mouth.
True or False? Circle one: True / False
9. The unit for the temperature in this lesson is
(a) degrees Celsius
(b) metres
(c) grams of salt only
(d) kilometres
10. Sand at the bottom of a cup is
(a) a solute that has dissolved
(b) not a solution of sand
(c) the solvent
(d) a pupa
Answers (for the adult)
Part A
1. Salt is the solute. Water is the solvent.
2. The dissolved salt is too small for the cloth to catch, so it stays in the water.
3. The water turns to vapour and leaves. The salt can remain as a solid.
4. A higher temperature and a wider surface.
5. The bulb is the tip that goes in the liquid. The column is the liquid that moves inside. The scale is the numbered line we read.
6. Looking from above or below can make the number look wrong.
7. An adult handles hot or warm water, and a child does not boil water alone or hold the bulb of the thermometer.
8. No. A solute dissolves. Sand that settles has not dissolved.
Part B
1. (b) the sugar
2. (b) water
3. (b) Letting the water evaporate from a shallow dish
4. False
5. (a) the surface is wider and the place is warmer
6. (b) the tip that goes in the liquid
7. (a) with your eyes level with the column
8. False
9. (a) degrees Celsius
10. (b) not a solution of sand
Recap
- A solution is a solute dissolved in a solvent. Salt or sugar is the solute. Water is the solvent.
- A cloth does not recover dissolved salt. Evaporation does.
- Warmer temperature and a wider surface speed evaporation.
- Read a thermometer at eye level, in degrees Celsius, without holding the bulb.
- An adult leads any investigation with warm water or glass.
Words to know
- solute
- The solid that dissolves.
Example: Salt is the solute in salt water. - solvent
- The liquid that does the dissolving.
Example: Water is the solvent in this lesson. - solution
- A mixture formed when a solute dissolves in a solvent.
Example: Clear salt water is a solution. - evaporate
- Turn from liquid into vapour and leave.
Example: Water evaporates from a warm plate. - scale
- The numbered line on a thermometer.
Example: We read the Celsius scale.
Try it at home
- With an adult, dissolve a spoon of kitchen salt in a little water, pour it on a plate, and leave the plate somewhere warm. The next day, describe what is left. Do not taste it.
- Ask an adult to show you a thermometer. Point to the bulb and the scale without touching the bulb.
Test tips
Tips for class tests
- Say solute and solvent. Do not swap them.
- If the question says dissolved, do not choose the sieve or the cloth.
- Write the unit: degrees Celsius.
For parents and teachers
After this lesson, your child should be able to:
- Identify solute, solvent and solution for salt water and sugar water.
- Explain evaporation, surface area and temperature, and why filtering fails.
- Name thermometer parts and read Celsius at eye level, with the safety rules.
Please lead the practical. Use kitchen salt only, never an unknown chemical. Warm water is enough. Do not let a child boil water or pick up broken glass. The photograph shows Celsius and a second scale. Standard 3 only needs degrees Celsius.
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Previous: Adaptations: How Animals and Plants Fit Their Homes
Next: Parts of a Flower
Course: Standard 3 Science
Updates
2026/11/07
– Published this lesson and linked the previous and next lessons.
– First draft of this Science lesson, with two hands-on activities, practice, a quiz badge, a worksheet and credited pictures.
Attributions to media used in this post:
Thermometer photo by Martinvl, CC BY-SA 3.0, via Wikimedia Commons. https://commons.wikimedia.org/wiki/File:CelsiusKelvinThermometer.jpg
© 2026 Vedesh Kungebeharry. All rights reserved.
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