In a fermentation tank, molasses solutio is mixed with yeast enzymes. After three days alcohol was observed. The speed of the reaction in this case is
Slow
Medium
Fast
Very fast
We keep food at low temperature in a refrigerator because it
Saves money
Makes food more tastier
Kills bacteria present in the food
In fashinable to keep the food in the refrigerator
When two substances interact in a change:
The rate and extent of change is always the same
The rate and extent of change depend on the conditions under which the change occurs
Only the rate depends on the conditions under which the change occurs, and the extent remains same
The extent of change may vary, but the rate of change is always the same
On heating, the colour of zinc oxide changes from white to yellow. This is a/an
Physical change
Chemical change
Photochemical change
Irreversible change
The chemical reactions which are initiated by electricity are called
Electromagnetic interaction
Electrochemical reactions
Electrification
Electrophysical changes
A substance which alters the rate of reaction:
Reactant
Product
Ingredient
Catalyst
When you burn petrol,flames are produced. This is a/an
Endothermic reaction
Exothermic reaction
Reversible reaction
The process of heating a liquid to a high temperature and rapidly cooling it to kill bacteria is called
Pasteurization
Chlorination
Bacterial infection
Sublimation
Which of the following statements is true ?
Chemical changes are reversible
Only very few chemical reactions are reversible
Growth of a tree is periodic change
Rusting of iron is a fast change
Pick out the chemical change from the following
Melting of ice
Burning of coal in air
Freezing of water
None
