Standard VI Science
Second Mid Term Test 2024 - Solved Paper
Solutions
I. Choose the correct answer: (5 x 1 = 5)
1. The unit of heat is
(a) newton (b) joule (c) volt (d) celsius
Answer: (b) joule
2. Drying of wet clothes in air is an example of
(a) Chemical change (b) Undesirable change (c) irreversible change (d) physical change
Answer: (d) physical change
3. Formation of curd from milk is
(a) a reversible change (b) a fast change (c) an irreversible change (d) an undesirable change
Answer: (c) an irreversible change
4. The unit of measurement used for expressing dimension (size) of cell is _______.
(a) centimeter (b) millimeter (c) micrometer (d) meter
Answer: (c) micrometer
5. The 'control centre' of the eukaryotic cell is
(a) Cell wall (b) Nucleus (c) Vacuoles (d) Chloroplast
Answer: (b) Nucleus
II. Fill in the Blanks. (5 x 1 = 5)
6. Heat flows from a _______ body to a _______ body.
Answer: Heat flows from a hotter body to a colder body.
7. Magnet attracts iron needle. This is _______ change. (a reversible / an irreversible)
Answer: a reversible
8. Bursting of fire crackers is a _______ change whereas germination of seeds is a _______ change. (slow / fast)
Answer: Bursting of fire crackers is a fast change whereas germination of seeds is a slow change.
9. I take part in food production of a cell. Who am I? _______
Answer: Chloroplast
10. The instrument used to observe the cell is _______.
Answer: Microscope
III. Match the following. (5 x 1 = 5)
| Question | Correct Match |
|---|---|
| 11. Heat | Joule |
| 12. Temperature | Kelvin |
| 13. Thermal Equilibrium | No heat flow |
| 14. Ice cube | 0°C |
| 15. Boiling water | 100°C |
IV. True or False. If False, give the correct statement (5 x 1 = 5)
16. The unit of heat and temperature are the same.
Answer: False.
Correct Statement: The unit of heat is Joule and the unit of temperature is Kelvin (or Celsius).
Correct Statement: The unit of heat is Joule and the unit of temperature is Kelvin (or Celsius).
17. Steam is formed when heat is released from water.
Answer: False.
Correct Statement: Steam is formed when heat is absorbed by water.
Correct Statement: Steam is formed when heat is absorbed by water.
18. Burning of match stick is a reversible change.
Answer: False.
Correct Statement: Burning of a match stick is an irreversible change.
Correct Statement: Burning of a match stick is an irreversible change.
19. A cell is the smallest unit of life.
Answer: True.
20. New cells are produced from the existing cells.
Answer: True.
V. Give short answer. Write any 7 questions only. (7 x 2 = 14)
21. Make a list of electrical equipments at home which we get heat from.
Some electrical equipments at home that produce heat are:
- Electric iron (Iron box)
- Electric heater
- Water heater (Geyser)
- Electric stove (Induction stove)
- Microwave oven
22. From where do we get sources of heat?
We get heat from various sources:
- The Sun: The primary source of heat energy for Earth.
- Combustion: Burning of fuels like wood, coal, petrol, and gas.
- Electricity: Electrical energy can be converted into heat energy.
- Friction: Rubbing two surfaces together generates heat.
23. What is a solution?
A solution is a homogeneous mixture of two or more substances. In a solution, the substance that is dissolved is called the solute, and the substance in which the solute dissolves is called the solvent. For example, in saltwater, salt is the solute and water is the solvent.
24. Analogy
i) Ice cube : 0°C :: Boiling water : _______
ii) Curdling of milk : irreversible change :: Formation of clouds : _______ change
i) Ice cube : 0°C :: Boiling water : 100°C
ii) Curdling of milk : irreversible change :: Formation of clouds : reversible change
25. You are given some candle wax. Can you make a candle doll from it? What kind of change is this?
Yes, we can make a candle doll from candle wax by melting the wax and pouring it into a doll-shaped mould. This is a physical change because only the state and shape of the wax change, not its chemical composition. It is also a reversible change because the doll can be melted back into liquid wax.
26. Circle the odd one out. Give reason for your choice.
Glowing of a bulb, lighting of a Candle, breaking of a coffee mug, Curdling of milk
Odd one out: Glowing of a bulb.
Reason: Glowing of a bulb is a reversible physical change. All the other options (lighting of a candle, breaking of a coffee mug, curdling of milk) are irreversible changes.
Reason: Glowing of a bulb is a reversible physical change. All the other options (lighting of a candle, breaking of a coffee mug, curdling of milk) are irreversible changes.
27. Who discovered the cell in 1665?
Robert Hooke discovered the cell in 1665 while observing a thin slice of cork under his microscope.
28. What are the essential components of a cell?
The three essential components of a cell are:
- Cell membrane (Plasma membrane): The outer boundary of the cell.
- Cytoplasm: The jelly-like substance that fills the cell.
- Nucleus (in eukaryotes) or Nucleoid (in prokaryotes): The control center containing the genetic material.
29. Arrange in a correct sequence
Elephant, Cow, Bacteria, Mango, Rose plant.
Correct sequence (from simplest to most complex organism):
Bacteria → Rose plant → Mango → Cow → Elephant
30. One calorie heat energy is needed to raise the temperature of the water from 30°C to 31°C. How much heat energy is needed to raise the temperature of the water from 30°C to 35°C.
Given: To raise temperature by 1°C (from 30°C to 31°C), 1 calorie of heat is needed.
To find: Heat needed to raise temperature from 30°C to 35°C.
Temperature difference = 35°C - 30°C = 5°C.
Heat energy needed = (Temperature difference) × (Heat needed per °C) = 5°C × 1 calorie/°C = 5 calories.
VI. Answer in detail. Write any 4 questions only. (4 x 4 = 16)
31. Explain thermal expansion with suitable examples.
Thermal Expansion: Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature. When a substance is heated, its particles gain energy and move more vigorously, causing them to move farther apart and the substance to expand.
Examples:
Examples:
- Railway Tracks: Small gaps, called expansion joints, are left between sections of railway tracks. In the summer, the tracks heat up and expand. These gaps allow space for expansion, preventing the tracks from buckling or bending.
- Thermometers: A clinical thermometer works on the principle of thermal expansion. The mercury or alcohol inside the glass tube expands when it gets hot and rises up the tube to indicate the temperature.
- Bridges: Large bridges are often built with expansion joints to allow the structure to expand and contract with temperature changes without causing damage.
32. Distinguish between heat and temperature.
| Feature | Heat | Temperature |
|---|---|---|
| Definition | It is a form of energy that flows from a hotter body to a colder body. It represents the total kinetic energy of the particles in a substance. | It is the measure of the degree of hotness or coldness of a body. It represents the average kinetic energy of the particles. |
| Nature | It is a cause. Heat transfer can cause a change in temperature. | It is an effect. Temperature determines the direction of heat flow. |
| Unit | The SI unit is Joule (J). Another common unit is calorie (cal). | The SI unit is Kelvin (K). Other common units are Degree Celsius (°C) and Degree Fahrenheit (°F). |
| Measurement | It is measured using a calorimeter. | It is measured using a thermometer. |
33. Give one example for each case that happens around you.
a) Slow and fast change
- Slow change: Rusting of an iron gate.
- Fast change: Bursting of a balloon.
b) Reversible and irreversible change
- Reversible change: Melting of ice into water.
- Irreversible change: Cooking of rice.
c) Physical and chemical change
- Physical change: Tearing a piece of paper.
- Chemical change: Burning a piece of paper.
d) Natural and man-made change
- Natural change: Growth of a plant.
- Man-made change: Construction of a building.
34. Tabulate any five cell organelles and their function.
| Cell Organelle | Function |
|---|---|
| Nucleus | Controls all the activities of the cell; contains the genetic material (DNA). Often called the "brain" of the cell. |
| Mitochondria | Generates most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. Known as the "powerhouse" of the cell. |
| Ribosomes | Responsible for protein synthesis. They link amino acids together in the order specified by messenger RNA. |
| Chloroplast | (In plant cells) Site of photosynthesis, where light energy is converted into chemical energy (food). |
| Vacuole | Stores water, nutrients, and waste products. In plant cells, a large central vacuole helps maintain turgor pressure. |
35. Draw a neat labelled diagram of a prokaryotic cell.
A diagram of a prokaryotic cell (like a bacterium) includes the following parts:
Labels:
- Capsule: Outermost protective layer.
- Cell Wall: Provides structural support.
- Plasma Membrane: Regulates the passage of substances.
- Cytoplasm: Jelly-like substance filling the cell.
- Ribosomes: Sites of protein synthesis.
- Nucleoid: Region containing the single circular DNA.
- Flagellum: A tail-like structure used for movement.
- Pili: Hair-like structures used for attachment.