Physical and Chemical Changes

Stainless steel is resistant to rusting, though it is made from iron. Why?

1. Because it is steel
2. Because it is resistant to stains
3. Because it is made from iron, chromium, nickel and manganese
4. Because it is galvanised

Why are the water pipes in our homes galvanised?

1. To prevent rusting of iron
2. To coat them with a layer of zinc
3. To prevent their leakage and breakage
4. All of them

For rusting, which of the following is essential?

1. Presence of water is essential
2. Presence of oxygen is essential
3. Presence of both water and oxygen is essential
4. Presence of air is essential

Fraction of ship's iron has to be replaced every year because

1. It prevents rusting of iron
2. Its color fades away
3. Ship can move properly in water only after replacement
4. All the above

Select the following chemical changes: (i) Copper metal drawn into wires (ii) Burning of paper (iii) Digestion of food (iv) Breaking of glass

1. (i), (ii) & (iii)
2. (ii) & (iii)
3. (i) & (iv)
4. (i), (iii) & (iv)

While preparing copper sulphate crystals from copper sulphate solution, dilute sulphuric acid is used instead of concentrated sulphuric acid, because

1. Concentrated sulphuric acid is corrosive in nature
2. Dilute sulphuric acid makes large crystals
3. Concentrated acid is ineffective
4. Both (a) & (b)

The process of obtaining pure crystals of copper sulphate from copper sulphate solution is known as

1. Galvanization
2. Evaporation
3. Crystallization
4. Rusting

Complete the reaction: Carbon dioxide + Lime water → ___ + ___

1. Calcium carbonate, water
2. Calcium hydroxide, oxygen
3. Calcium oxide, water
4. Calcium carbonate

When magnesium ribbon burns in air, it leaves an ash which is

1. Mg(OH)2
2. MgO
3. MgS
4. MgSO4

When magnesium oxide (MgO) reacts with water to form magnesium hydroxide [Mg(OH)2], a base, it turns ___ litmus to ___

1. Blue, red
2. Blue, colourless
3. Red, blue
4. Colourless, blue

Baking soda is common name for

1. Sodium carbonate
2. Sodium hydrogen carbonate
3. Calcium carbonate
4. Sodium hydroxide

Ozone layer is present in

1. Atmosphere
2. Clouds
3. Soil
4. Water

Explosion of a firework produces

1. Heat & light
2. Heat only
3. Gases only
4. Heat, light, sound & unpleasant gases

Burning is a chemical change and is always accompanied by production of

1. Sound
2. Heat
3. Gas only
4. Sound & heat

The process of depositing layer of zinc on iron is known as

1. Galvanization
2. Crystallization
3. Rusting
4. Layering

When copper sulphate reacts with iron, green coloured ___ solution and brown coloured ___ deposition is formed

1. Iron oxide, copper sulphide
2. Iron sulphate, copper
3. Iron sulphate, copper oxide
4. Iron sulphide, copper oxide

Lime water turns milky when ___ gas is passed through it

1. Carbon dioxide
2. Hydrogen
3. Oxygen
4. Nitrogen dioxide

Chemical change is always accompanied by: (i) Production of sound (ii) Heat and light (iii) Change in mass (iv) Change in color

1. (i), (ii) & (iii)
2. (ii) & (iv)
3. (i) only
4. (i), (ii) & (iv)

Stainless steel is made by mixing iron with carbon and metals like ___ to iron

1. Magnesium, sodium, calcium
2. Chromium, Nickel, Manganese
3. Cobalt, Potassium, Iron
4. Potassium, Sodium, Chromium

During rusting the layer which is deposited on the surface of iron is

1. Fe2O
2. Fe2O2
3. Fe2O3.xH2O
4. Fe(OH)3

To prevent iron from rusting a coating of this metal is deposited

1. Calcium
2. Chromium
3. Sodium
4. Potassium

The elements required for rusting of iron

1. Oxygen and moisture
2. Only oxygen
3. Hydrogen and oxygen
4. Only water vapours

The gas in the atmosphere which acts as a natural shield against ultra violet radiations

1. Oxygen
2. Sulphur dioxide
3. Hydrogen
4. Ozone

When vinegar reacts with baking soda the gas evolved is

1. Hydrogen
2. Oxygen
3. Carbon dioxide
4. Nitrogen dioxide

Blue vitriol is the common name of

1. Copper sulphate
2. Copper oxide
3. Copper hydroxide
4. Magnesium sulphate

Pick out physical changes from the following: (i) Rusting of iron (ii) Dissolving salt in water (iii) Change of water to ice (iv) Cooking of food

1. (i) & (ii)
2. (ii) & (iii)
3. (i), (ii) & (iii)
4. (iii) & (iv)

When magnesium ribbon is burnt, a brilliant ___ flame is observed

1. Yellow
2. Blue
3. White
4. Green

Select the correct alternative(s): (i) Melting of ice is a physical change (ii) A physical change is due to change in physical properties of a substance (iii) A physical change is always irreversible in nature (iv) Burning of candle is an example of physical change

1. (i) & (ii)
2. (i) & (iv)
3. (i), (ii) & (iv)
4. (ii) & (iii)