Year 5 Science: Dissolving solids in water
Part of the Year 5 Science solutions and separating mixtures chapter. Chapter overview · whole chapter on one page
Dissolving solids in water
Some solids dissolve in water. When a solid dissolves, its particles spread out evenly through the liquid, and you can no longer see them. Salt and sugar dissolve in water. Sand and pebbles do not dissolve.
A fair test for dissolving uses the same amount of each solid, the same amount of water, and the same stirring for the same time.
| Solid stirred into water | Does it dissolve? |
|---|---|
| salt | yes |
| sugar | yes |
| sand | no |
| pebbles | no |
Key ideas
- Some solids dissolve in water, and others do not.
- Salt and sugar dissolve in water.
- Sand and pebbles do not dissolve in water.
- A fair test keeps the solid, the water and the stirring the same.
Method. Read the second column.
- Read the rows. The sugar row says yes, and the sand row says no.yes and no
- Choose the solid that dissolves. So the solid that dissolves is sugar.sugar
- Write the answer. sugar
Check. Sugar dissolves in water. ✓
Method. Count the yes rows.
- Read the column. The yes rows are salt and sugar.two yes rows
- Count them. So two solids dissolve.2
- Write the answer. 2
Check. The other two, sand and pebbles, do not dissolve. ✓
Method. Read the sand row.
- Read the row. The sand row says no.no
- Decide. So sand does not dissolve.no
- Write the answer. no
Check. Sand stays as grains in the water. ✓
Watch out
Watch out: when a solid dissolves, it does not disappear. Its particles are still in the water, just too small to see.
Try it (with your teacher). With your teacher, stir one teaspoon of salt into a cup of room-temperature water for one minute. Repeat with one teaspoon of sand. Look at each cup. Which solid dissolved? Write yes or no for each. Do not taste anything.
Exam tip
Grown-up tip. Ask: “Where has the salt gone? Can you still see it?” Let your child stir for the same time each time.
Exercise 6A Dissolving solids in water
Method. Read the second column.
- Read the column. The yes rows are salt and sugar.salt and sugar
- Name them. So the two solids that dissolve are salt and sugar.salt and sugar
- Write the answer. salt and sugar
Check. Both are soluble in water. ✓
Method. Read the pebbles row.
- Read the row. The pebbles row says no.no
- Decide. So pebbles do not dissolve.no
- Write the answer. no
Check. Pebbles stay as they are in the water. ✓
Method. Read the key ideas in section 6.1.
- Read the key idea. When a solid dissolves, its particles spread out evenly through the liquid.spread out evenly
- Fill the gap. So the missing word is evenly.evenly
- Write the answer. evenly
Check. The particles are too small to see. ✓
Method. Read the watch-out box in section 6.1.
- Read the watch-out. The particles are still in the water, but too small to see.still in the water
- Decide. So the statement is false.false
- Write the answer. false
Check. The solid is still there, spread through the liquid. ✓
Method. Count the no rows.
- Read the column. The no rows are sand and pebbles.sand and pebbles
- Count them. So two solids do not dissolve.2
- Write the answer. 2
Check. Two do, and two do not. ✓
Method. Read the table.
- Read the table. The salt row says yes, so salt dissolves.yes
- Name the solid. The solid in a salt cellar is salt.salt
- Write the answer. salt
Check. Salt dissolves in water. ✓
Method. Think about the solids in the table.
- Think about the table. Sugar dissolves and sand does not, so sugar will dissolve and sand will not.sugar dissolves
- Decide. So Priya is right, and the answer is yes.yes
- Write the answer. yes
Check. Sugar dissolves, and sand does not dissolve at all. ✓
Method. Read the no rows.
- Read the no rows. The pebbles row says no.no
- Name the solid. So pebbles is a solid that does not dissolve.pebbles
- Write the answer. pebbles
Check. Accept pebbles. ✓
Method. Think about what makes a test fair.
- Think about the test. Only the solid should change between tests.only the solid
- Write the reason. If the amounts changed as well, we could not compare the results fairly.compare fairly
- Write the answer. Accept any sentence that says the same amounts make the test fair, so only the solid changes.
Check. A fair test changes one thing only. ✓
Method. Think about what stirring does.
- Think about the particles. Stirring moves the water around the solid.moves the water
- Write the reason. So the solid dissolves faster and spreads evenly.dissolves faster
- Write the answer. Accept any sentence that says stirring helps the solid to spread through the water and dissolve.
Check. Stirring helps the solid to dissolve. ✓