WorksheetsChemical reactions and human eye
Total questions: 24
Worksheet time: 56mins
At noon, the Sun appears white as
blue colour is scattered the most
red colour is scattered the most
light is least scattered
all the colours of the white light are scattered away
It is necessary to balance a chemical equation in order to satisfy the law of:
Conservation of motion
Conservation of momentum
Conservation of mass
Conservation of energy
All the methods mentioned below can be used to prevent the food from getting rancid except:
i. Storing the food in the air-tight containers
ii. Storing the food in refrigerator
iii. Keeping the food in clean containers
iv. Always touching the food with clean hands
(i) and (ii)
(i) and (iii)
(i), (iii) and (iv)
(iii) and (iv)
The splitting of white light into different colours on passing through a prism is called
Reflection
Refraction
Dispersion
Spectrum
When white light enters a glass prism from air, the angle of deviation is least for
Blue light
Yellow light
Violet light
Red light
Which of the following gases is used in the storage of fat and oil containing foods for a long time?
Argon
Oxygen
Nitrogen
Neon
The neutralization reaction between an acid and a base is a type of:
Double displacement reaction
Addition reaction
Decomposition reaction
Displacement reaction
Which of the following is a natural phenomenon which is caused by the dispersion of sunlight in the sky?
Twinkling of stars
Advanced sunrise and delayed sunset
Stars seem higher than they actually are
Rainbow
Before burning in air, the magnesium ribbon is cleaned by rubbing with a sand paper to:
Make the ribbon surface shinier
Remove the layer of magnesium oxide from the ribbon surface
Remove the layer of magnesium carbonate from the ribbon surface
Remove the moisture from the ribbon surface
A chemical reaction does not involve:
Formation of new substances having entirely different properties than that of the reactants
Breaking of old chemical bonds and formation of new chemical bonds
Rearrangement of the atoms of reactants to form new products
Changing of the atoms of on element into those of another element to form new products
One of the following processes does not involve a chemical reaction. That is:
Melting of candle wax when heated
Burning of candle wax when heated
Digestion of food in our stomach
Ripening of banana
The layer of air in atmosphere whose temperature is less than the hot layer behave optically as :
Denser medium
Rarer medium
Inactive layer
Either (a) or (b)
Three beakers labelled as A, B and C each containing 25 ml of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solution contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct?
(i) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has occurred.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(i) only
(i) and (iv)
(ii) and (iii)
All the given statements are true.
Give the ratio in which hydrogen and oxygen are present in water by volume.
1:2
2:1
1:8
8:1
A substance added to food containing fats and oils is called:
Oxidant
Rancid
Coolant
Antioxidant
Why is red colour selected for danger signal lights? (2 marks)
What is meant by spectrum of white light? How can we recombine the components of white light after a prism has separated them? (2 marks)
Write the chemical equation of the reaction in which the following changes have taken place with an example of each:
(i) Change in colour
(ii) Change in temperature
(iii) Formation of precipitate
(Note: either write down the reaction in words or you can use notation like oxygen = O2) (3 marks)
Why does the colour of copper sulphate solution change when an iron nail is dipped in it? (2 marks)
Explain why do the planets not twinkle but the stars twinkle. (2 marks)
Name the part of our eyes that helps us to focus the lens on nearby and distant objects in quick succession.
(a)
The sky appears dark instead of blue to an astronaut. State its reason. (2 marks)
What is redox reaction? Identify the substance oxidised and the substance reduced in the following reactions.
(i)2PbO + C —–> 2Pb + CO2
(ii)MnO2 + 4HCl —–> MnCl2 + 2H20 + Cl2
(4 marks)
Define combination reaction. Give one example of a combination reaction which is also exothermic. (2 marks)
