MATTER IN OUR SURROUNDINGS
ACTIVITY-
Q. Why do we observe that the level of water does not change even after dissolving salt in it??
ANS- When we dissolve salt in water , the particles of salt get into spaces between particles of water so this shows that the level of water does not change.
HOMEWORK
PROPERTIES OF PARTICLE
1. The particles of the matter are very small in size.
2. The particles of matter are continuously in motion , means they have kinetic energy.
3. The particles of matter have space between them.
Why solids are hard??
ANS- Solids are usually hard because they are tightly packed together and solids can maintain their shape own.
GIVE REASONS
Q.1. Why is table hard?
ANS- The table is hard because its rigidity is very high and
compressibility is not shown.
Q.2. Diver is able to cut water?
Ans- Water is fluid , i.e changes its shape when applied force.The diver is able to cut the water by applying force and changing its shape.
Q.3. The smell of hot sizzling food reaches our nose?
ANS- The smell of hot sizzling food reaches our nose as due to high speed of particles and large space between gases show the property of diffusing very fast into other gases.
Homework
Latent heat of fusion
The heat required to change 1 kg of solid into liquid completely is known as latent heat of fusion. It is absorbed by a body during a constant temperature process that is specified in some way.
Latent heat of vapourisation
The heat required to change 1 kg of liquid into vapours at atmospheric pressure is known as the latent heat of vapourisation.
Evaporation
The process of conversion of liquid into vapours is known as evaporation.
Factors affecting the rate of evaporation
1. Temperature- The rate of evaporation is directly proportional to the rise in temperature . more the temperature more will be the evaporation.
2. Humidity- The rate of evaporation is inversely proportional to the humidity. It means that the more the humidity is the less is the rate of evaporation.
3. Wind speed- The rate of evaporation is directly proportional to the wind speed. It means that more is the wind speed more will be the rate of evaporation.
4. Surface area- The rate of evaporation increases when the surface area increases as when the surface area will be increase the evaporation will also be increased.
EXERCISE
Q1. Convert the following into celsius scale-
(a) 293 K = 293-273 = 20*C
(b) 470 K = 470-273 = 197*C
Q2. Convert the following into kelvin-
(a) 25*C = 25 + 273 = 298 K
(b) 373*C = 373+273 = 646 K
Q3. Give reason for the following-
(a) Naphthalene balls disappear with time without leaving any solid.
Ans- It happen because naphthalene balls sublime and directly changes into vapour state without leaving any solid.
(b) We can get the smell of perfume sitting several meters away.
Ans- It happens because perfume contain volatile solvent and
diffuse faster and can reach people sitting several meters away.
Q4. Arrange the following substances in increasing order of forces of attraction between the particles - water, sugar, oxygen.
Ans- Oxygen-water-sugar
Q5. What is physical state of water at-
(a) 25*C= liquid
(b) 0*C= solid or liquid
(c) 100*C= liquid and gas
Q6. Give reason-
(a) Water at room temperature is a liquid.
Ans- Water at room temperature is a liquid because its freezing point is 0*C and boiling point is 100*C.
(b) An iron almirah is a solid at room temperature.
Ans- It is because the melting point of iron is higher than room temperature.
Q7. Why is ice a 273 K more effective in cooling than water a same temperature?
Ans-Ice at 273 K will absorb heat energy or latent heat from medium to overcome the fusion to become water. Cooling effect of ice is more than water at same temperature because water does not absorb extra heat from medium.
Q8. What produces more severe burns , boiling water or steam?
Ans- Steam at 100*C will produce more severe burns as extra heat is hidden in it called latent heat whereas the boiling water does not have this hidden heat.
FUNDAMENTAL UNIT OF LIFE
CELL
Cell is the structural and functional unit of life.
Homework
Q. Why does the water come out from the cucumber when we add salt in it?
Ans- The salt cause water to be drawn out of the cucumber. Water is drawn to it because it goes from a higher concentration to the lower concentration. When there is random motion that will always happen and is called diffusion. In the cells of cucumber allows the water through but not the salt.
EXERCISE
Q.1. Make a comparison and write down ways in which plant cells are also different from animal cells?
Ans - Plant Cell -1. Plant cells have cell wall.
2. Vacuole is large and present in centre of the cell.
3. They have plastids.
Animal cell- 1. Animal cells do not have cell wall.
2. Vacuole is small.
3. They do not contain plastids.
Q.2. How is prokaryotic cell different from a eukaryotic cell?
Ans- Prokaryotic cell is generally smaller in size , nuclear region is poorly defined , the cell organelles are not membrane bounded and has a single chromosome.
Eukaryotic cell is generally larger in size , nuclear region is well defined with nuclear membrane. Membrane bounded cell organelles are present and has more then one chromosome.
Q.3. What would happen if the plasma membrane ruptures or breaks down?
Ans- If plasma membrane ruptures or break down then the molecules of some substances will freely move in and out.
Q.4. What would happen to the life of a cell if there was no golgi apparatus?
Ans- Golgi apparatus has the function of storage , modification and packaging of the products in vesicles. If there were no golgi bodies , packaging and dispatching of materials synthesised by the cell will be stocked.
Q.5. Which organelle is known as the powerhouse of the cell? why?
Ans- Mitochondria is known as powerhouse of the cell because it releases the energy required for the different activities of life.
Q.6. Where do the lipids and the proteins consisting the cell membrane get synthesised ?
Ans- Lipids and proteins are synthesised in ER( Endoplasmic Reticulum).
Q.7. How does amoeba obtain it's food?
Ans- Amoeba take it's food by the cell membrane which forms the food vacuole.
Q.8. What is osmosis?
Ans- Osmosis is the process of movement of water molecule from a region of higher water concentration through a semi permeable membrane to a region of lower water concentration.
MOTION
What is motion?
The change in position of an object with respect to the point is known as motion.
DISTANCE
It is the total path covered by the object. It is denoted by 's' and its SI unit is 'm' ( metre).
The distance is not specified in measuring the distance. Only magnitude is measured so, distance is a scalar quantity.
SPEED
Speed is the distance covered by the object per unit time. It is denoted by 'v'.
Speed is scalar quantity. The SI unit of speed is m/s square.
SCALAR QUANTITY
The physical quantities in which only magnitude is measured and direction is not specified is called scalar quantity.
HOMEWORK
Q. Define the scalar quantity and name 5 physical quantities which are scalar and give reason why these physical quantities are scalar.
Ans- We can define scalar quantity as-
A scalar quantity is specified by a single value with an appropriate unit and has no direction.
5 Physical quantities are Mass , Distance , Speed , Volume , pressure etc. These physical quantities are scalar because in all the above quantities direction is not specified and the magnitude is measured.
DATE- 6th July
Graph of the above table:-
It is a non-uniform motion.
EXAMPLES
(Both theoretical and numerical questions)
1. An object travels 16 m in 4 s and then another 16 m in 2 s. What is the average speed of the object?
ANS- Total distance covered by the object = 16+16 = 32m
Total time taken = 4+2 = 6s
Therefore, average speed of the object = 32 = 5.33 m s-1
6
2 . The odometer of a car reads 2000 km at the start of a trip and 2400 km at the end of the trip. If the trip took 8 h, calculate the average speed of the car in km h–1 and m s–1.
ANS- Total distance covered by the object = 2400-2000 = 400km
Total time taken = 8h
Therefore, average speed of the object = 400 = 50 km h-1
8
In m s–1 = 13.9 m s–1.
3 . Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. Find the average speed and average velocity of Usha.
ANS- Total distance covered by Usha in 1 min is 180 m.
Displacement of Usha in 1 min = 0 m
Average speed of the object = 180 = 3 m s-1
60
Average velocity = Displacement = 0m = 0 m s-1
Total Time 60
4.Starting from a stationary position, Rahul paddles his bicycle to attain a velocity of 6 m s–1 in 30 s. Then he applies brakes such that the velocity of the bicycle comes down to 4 m s-1 in the next 5 s. Calculate the acceleration of the bicycle in both the cases.
ANS- In the first case
U=0 , V=6 m s-1 , t = 30sec , a = ?
a = V-U = 6-0 = 1 m s-2 = 0.2 m s–2
t 30 5
In the second case
U=6 m s-1 , V=4 m s-1 , t = 5sec , a = ?
a = V-U = 4-6 = -2 m s-2 = -0.4 m s–2
t 5 5
5. A train starting from rest attains a velocity of 72 km h–1 in 5 minutes. Assuming that the acceleration is uniform, find (i) the acceleration and (ii) the distance travelled by the train for attaining this velocity.
ANS- U=0, V= 72 km h-1 = 20 m s-1, t = 5min = 300sec
(i) a = V-U = 20-0 = 1 m s-2
t 300 15
(ii) by IInd equation of motion
S= ut + 1/2 at*2
S= 0X300 + 1/2 X 1/15 X 90000
S= 3000m = 3km
6. A car accelerates uniformly from 18 km h–1 to 36 km h–1 in 5 s. Calculate
(i) the acceleration and
(ii) the distance covered by the car in that time.
ANS- U= 18 km h-1 = 5 m s-1 , V= 36 km h-1 = 10 m s-1 , t = 5 s
(i) a = V-U = 10-5 = 1 m s-2
t 5
(ii) by II nd equation of motion
S= ut + 1/2 at*2
S= 5X5 + 1/2 X 1 X 25
S= 25 + 12.5 = 37.5 m
7. The brakes applied to a car produce an acceleration of 6 m s-2 in the opposite direction to the motion. If the car takes 2 s to stop after the application of brakes, calculate the distance it travels during this time.
ANS- a = -6 m s-2 , t = 2 sec , V= 0 m s-2
by I st equation of motion
V=U+at
0= U+(-12)
0=U-12
U= 12 m s-1
by II nd equation of motion
S= ut + 1/2 at*2
S= 12X2 + 1/2 X -6 X 4
S= 24 - 12 = 12 m
1. Soil
2. Water
3. Air
The total number of nutrients present in plants are 16 ,
these nutrients can be classified into two types of nutrients-
1. Micronutrients- These nutrients are supplied in small
amount. The major nutrients supplied by micronutrients
Nitrogen , Potassium and Phosphorus. These nutrients
supply 7 nutrients.
2. Macronutrients- These nutrients are required in large
amounts therefore called macronutrients. These nutrients
supply 6 nutrients.
Table-
The total number of nutrients present in plants are 16 ,
these nutrients can be classified into two types of nutrients-
1. Micronutrients- These nutrients are supplied in small
amount. The major nutrients supplied by micronutrients
Nitrogen , Potassium and Phosphorus. These nutrients
supply 7 nutrients.
2. Macronutrients- These nutrients are required in large
amounts therefore called macronutrients. These nutrients
supply 6 nutrients.
Table-
SOURCE
|
NUTRIENTS
|
Air
|
carbon, oxygen
|
Water
|
hydrogen, oxygen
|
Soil
|
(i) Macronutrients:
nitrogen, phosphorus,
potassium, calcium,
magnesium, sulphur
(ii) Micronutrients:
iron, manganese, boron,
zinc, copper,
molybdenum, chlorine
|
No comments:
Post a Comment
Note: only a member of this blog may post a comment.