Science 1 Marks Question

For rusting the presence of both oxygen and water or water vapour is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting.

Two methods by which rusting of iron can be prevented are galvanization and painting.

1. Colour of the solution in the beaker changes from blue to green.
2. A brown coloured deposit is found on the surface of the iron nail.

True.

physical change.

Stainless steel is an alloy of iron. When iron is mixed (or alloyed) with carbon, chromium and nickel, then stainless steel is obtained. Stainless steel does not rust at all.

Chemical change.

Digestion of food → Chemical change

1. Iron + air + water → iron oxide
2. Copper sulphate + iron → iron sulphate + copper

Properties such as shape, size, colour and state of a substance are called its physical properties.

True.

When iron nails are dipped in copper sulphate solution, then the colour of the solution changes to green.

In burning always heat is produced, the old bonds of the reactants are break down and fresh bonds are formed, resulting in formation of new product with different properties of that of earlier products.

Changes in which new substances are formed are called chemical changes.

Beating aluminium to make aluminium foil → Physical change

The speed with which the chemical reaction takes place is called the rate of the chemical reaction.

Melting is the process of turning a solid to a liquid.

Metals like chromium and nickel are mixed (alloyed) with iron to make stainless steel.

The process of obtaining crystals from its hot saturated solution is called crystallisation.

Stainless steel is an alloy of Iron with carbon and other metals like chromium, nickel and manganese.

True.

Chemical process.

Magnesium oxide is basic in nature because it turns red litmus solution to blue.

Chromium, nickel and manganese.

Since Mumbai is a coastal region, the moisture content in the air is more as compared to that in Delhi. Therefore, iron articles rust faster.

For rusting the presence of both oxygen and water or water vapour is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting.

Melting of ice is also a change where solid changes into liquid state.

When magnesium is burnt in air then a brilliant white flame is obtained.

Burning of coal → Chemical change

During photosynthesis, the plants intake carbon dioxide and water in the presence of chlorophyll and sunlight to form two new substances, i.e. glucose (food) and oxygen gas. So, photosynthesis is a chemical change.

Melting of wax → Physical change

We should eat freshly cut apple because if we leave the apple after cutting, it starts turn to brownish due to the oxidation of the essential nutrients present in it and its food value decreases.

Chemical change.

Ethanoic acid reacts with sodium hydrogen carbonate to evolve brisk effervescence of carbon dioxide.

When we burn a cracker, it explode Explosion produces heat, light, sound and unpleasant gases that pollute the atmosphere. Many new products are formed. So, it is a chemical change.

Ripening of a fruit is a chemical change because after ripening, a new product with different properties is formed.

Souring of milk is a chemical change because original substances present in milk lose their nature and identity and form new chemical substances.

Presence of water and presence of oxygen.

The following changes accompany the formation of new substances: change in state, colour, temperature, odour, sound may be produced or gas may evolve.

These are chemical changes.

Carbon dioxide cuts the contact of fire with oxygen which is needed for combustion and fire extinguishes from lack of oxygen.

The chemical name of baking soda is Sodium hydrogen carbonate.

Evaporation.