Year 5 Science Reversible and irreversible changes: check-up and practice test questions

Method. Read the reversible list.

1. Read the list. Melting and freezing are reversible changes of state.
   reversible changes of state
2. Decide. So the answer is yes.
   yes
3. Write the answer.
   yes

Check. Water freezes back into ice. ✓

Method. Read section 7.3.

1. Read the description. Burning makes new materials, which cannot easily be changed back.
   new materials
2. Decide. So the answer is no.
   no
3. Write the answer.
   no

Check. Burning is irreversible. ✓

Method. Read section 7.4.

1. Read the description. The reaction makes carbon dioxide gas.
   carbon dioxide
2. Name the gas. So the gas is carbon dioxide.
   carbon dioxide
3. Write the answer.
   carbon dioxide

Check. The bubbles are the gas escaping. ✓

Method. Read section 7.2.

1. Read the description. When a solid melts, it becomes a liquid.
   becomes a liquid
2. Fill the gap. So the missing word is liquid.
   liquid
3. Write the answer.
   liquid

Check. Melting is a change of state. ✓

Method. Read section 7.1.

1. Read the description. Dissolving is reversible, because the solid can be recovered by evaporating the water.
   recovered
2. Decide. So the answer is yes.
   yes
3. Write the answer.
   yes

Check. Evaporation gives back the sugar. ✓

Method. Add the three trials, then divide by three.

1. Add the trials. The three counts add to 45.
   14 + 16 + 15 = 45
2. Divide by three. Divide 45 by 3 to get 15.
   45 divided by 3 is 15
3. Write the answer.
   15

Check. Check: 15 + 15 + 15 = 45. ✓

Method. Read the arrows in the picture.

1. Read the arrows. There is only one arrow, from raw to cooked.
   one arrow
2. Decide. So the picture does not show a change back to raw, and the answer is no.
   no
3. Write the answer.
   no

Check. The cooked egg cannot be undone. ✓

Method. Read the story in section 7.3.

1. Read the story. Black soot is left on the glass.
   black soot
2. Name it. The new material is soot.
   soot
3. Write the answer.
   soot

Check. Soot is a new material made by burning. ✓

Method. Read section 7.2.

1. Read the description. Mixing is reversible, because the parts can be separated again.
   separated again
2. Decide. So the statement is false.
   false
3. Write the answer.
   false

Check. Sieving separates the mixture. ✓

Method. Think about the new materials.

1. Think about the wood. Burning changes the wood into new materials.
   new materials
2. Write the reason. So the wood cannot easily be changed back.
   changed back
3. Write the answer.
   Accept any sentence that says burning makes new materials, which cannot easily be changed back.

Check. New materials are not usually reversible. ✓

Method. Think about ice.

1. Think about ice. Ice turns into water, a liquid, when it melts.
   turns into water
2. Name it. The word is melting.
   melting
3. Write the answer.
   melting

Check. Melting is a reversible change of state. ✓

Method. Think about how the salt can be recovered.

1. Think about the salt. Evaporating the water leaves the salt behind.
   left behind
2. Decide. So the change is reversible.
   yes
3. Write the answer.
   yes

Check. The salt can be recovered. ✓

Method. Read section 7.3.

1. Read the description. Cooking changes the egg, so it cannot become raw again.
   cannot become raw
2. Decide. So the answer is no.
   no
3. Write the answer.
   no

Check. Cooking makes new materials. ✓

Method. Read section 7.4.

1. Read the description. The reaction makes a gas called carbon dioxide.
   carbon dioxide
2. Name the gas. So the gas is carbon dioxide.
   carbon dioxide
3. Write the answer.
   carbon dioxide

Check. The fizzing is the gas escaping. ✓

Method. Add the three trials, then divide by three.

1. Add the trials. The three counts add to 45.
   14 + 16 + 15 = 45
2. Divide by three. Divide 45 by 3 to get 15.
   45 divided by 3 is 15
3. Write the answer.
   15

Check. Check: 15 + 15 + 15 = 45. ✓

Method. Add the three trials, then divide by three.

1. Add the trials. The three trials add to 39 minutes.
   12 + 14 + 13 = 39
2. Divide by three. Divide 39 by 3 to get 13.
   39 divided by 3 is 13
3. Write the answer.
   13

Check. Check: 13 + 13 + 13 = 39. ✓

Method. Read section 7.3.

1. Read the list. Burning makes new materials, which cannot easily be changed back.
   new materials
2. Name it. So the answer is burning.
   burning
3. Write the answer.
   burning

Check. Dissolving, melting and freezing are reversible. ✓

Method. Think about the evidence.

1. Think about the candle. Burning makes new materials, such as soot and gases.
   soot and gases
2. Give the reason. The wax cannot easily be recovered, so the change is not reversible.
   not reversible
3. Write the answer.
   Accept any sentence that says burning makes new materials, such as soot or gases, which cannot easily be changed back.

Check. Soot is evidence of a new material. ✓

Method. Think about the reaction and its evidence.

1. Think about the reaction. The reaction makes new materials, including carbon dioxide gas.
   new materials
2. Give the evidence. The bubbles and fizzing are the evidence of the gas, so the change is irreversible.
   bubbles
3. Write the answer.
   Accept any two sentences that say new materials and a gas are made, so the original materials cannot easily be recovered; the evidence is the fizzing or bubbles.

Check. New materials cannot easily be changed back. ✓

Method. Think about the material.

1. Think about the water. The melted water is still the same material as the ice.
   same material
2. Give the reason. So no new material is made, and the change is reversible.
   reversible
3. Write the answer.
   no. Accept any sentence that says the water is still the same material, so the change is reversible and no new material is made.

Check. Melting and freezing are reversible changes of state. ✓