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1. first of all, what is stomata?
=> stomata are tiny pores present in leaves and are surrounded by guard cells.
functions of stomata are as follows :-
⏺stomata help in transpiration. transpiration is the process of losing extra water in plants.
⏺these pores also help in gas exchange. like carbondioxide and oxygen. they take in carbondioxide for the process of photosynthesis and release oxygen.
2. difference between speed and velocity :-
SPEED :-
(i) speed is the rate of distance per unit time.
(ii) speed is a scalar quantity.
VELOCITY :-
(i) velocity is the displacement per unit time.
(ii) velocity is a vector quantity.
3. desirable characters of bee varieties for honey production :-
⏹it must be high yielding. means bees must yield high quantity of honey.
⏹bees mustn't sting much.
⏹they should stay in the beehive for long durations.
⏹bees must breed well.
4. the temperature remain constant during the change of state because all the heat gets used up to change the state by overcoming the forces of attraction between the particles.
this heat is known as latent heat.
5. (a)water is essential for our life because :-
• water is used by all living organisms on this Earth. all cellular processes take place in water (as a medium).
• all reactions in our body occurs between the substances which are dissolved in water.
• water also maintains body temperature.
• water makes up to 70% in the body of all living organisms.
(b) greenhouse effect is the effect in the rise of the temperature. greenhouse gases like carbondioxide, methane, water vapour etc trap heat and radiations of Earth that falls on the Earth's surface and then don't allow them to escape back to space. because of this, the temperature of our environment rises and this is called greenhouse effect.
6. (a) given the frequency of the sound = 100hz
time given = 1min = 60 seconds
therefore no. of vibrations in one minute = 100 × 60
= 6000 vibrations
(b) reverberation is the repeated reflection of a sound. to reduce it, the roof or walls of any room or auditorium are covered with sound-absorbent materials.
7. manure is an organic material whereas fertilizers are made from pesticides. excessive use of fertilizers can damage the soil and can reduce soil fertility. whereas manure helps in maintaining the fertility of soil. manure improve soil's water holding capacity and also the amount of trapped air in the soil. manure don't have any negative effects in soil.
8. we are advised to take nourishing food when we are sick because they have many protiens and nurtients which are necessary for our body. when we are sick, we are very week and those nutritive values will help us to recover fast.
(b) two conditions essential for being free of disease are :-
◻ healthy and clean environment
◻ mental stability.
9. we know that as the potential energy increases, the kinetic energy decreases. in a moving pendulum, when the bob goes to the center, the potential energy decreases, and the kinetic energy increases. and when it move from center to the other side, the kinetic energy goes down and potential energy goes up.
this way, a swinging pendulum is an example of energy conversation.
10. a. squamous epithelium tissue is present in the inner lining of our mouth.
b. tendon connects muscle to bone in our body.
c. phloem transports food in plants.
d. apidose stores fat in our body.
e. blood has a fluid matrix.
f. nervous tissue is present in our brain.
11. (a) napthalene balls disappear with time without leaving any solid because of the process of sublimation. sublimation is a process where solid directly changes to it's gaseous state without getting converted to liquid state. similarly, napthalene balls get converted to gaseous state directly.
(b) we can get smell of perfume several meters away because the particles of gas are very loosely packed. they are very far way from each other. that's why the particles of perfume get mixed with particles of gas easily. and hence, we can smell perfume several meters away.
(c) water kept in earthen pot become cool during summer because as we know that evaporation causes cooling effect. earthen pot has many minute holes. from that holes, the water starts to evaporate and absorb all heat from left over water and surroundings and leave the water cool behind.