Give Reason For the following:

Q1) Mixing of sand with water is a reversible change.

Q2) Mixing of cement with water is an irreversible change.

Q3) Burning of sugar is a chemical change.

Reversible changes are the change  where the substances in the mixture don’t change.
while when one or more of the substances actually change then these are called Non-reversible and can’t return to what they were.
A chemical change is a change in which something new is formed (irreversible). The starting materials change into an entirely different substance or substances. This new substance has a different chemical composition than the starting materials.
Therefore we can account for the following changes:

a) Sand in water is reversible since it could be seived to separate.
b) cement  in water is a chemically irreversible change, they react with each other to form concrete.
c) similarly when sugar is burnt, it is changed to some other substances (CO2 and H2O.)
hence it is a chemical change.

  • 2

1) Mixing of sand with water is a reversible change because sand and water can be separated by filtration.

2) Mixing of cement with water is an irreversible change because once mixed they cannot be separated.

3) When sugar is burned it decomposes into carbon and water.Water becomes steam and carbon is left behind.So, a new substance is formed.Thus, burning of sugar is a chemical change.

  • 2

1) Mixing of sand with water is a reversible change because sand and water can be separated by filtration.

2) Mixing of cement with water is an irreversible change because once mixed they cannot be separated.

3) When sugar is burned it decomposes into carbon and water.Water becomes steam and carbon is left behind.So, a new substance is formed.Thus, burning of sugar is a chemical change.

  • 1

1) Mixing of sand with water is a reversible change because sand and water can be separated by filtration.

2) Mixing of cement with water is an irreversible change because once mixed they cannot be separated.

3) When sugar is burned it decomposes into carbon and water.Water becomes steam and carbon is left behind.So, a new substance is formed.Thus, burning of sugar is a chemical change.

  • 1
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