Science for Grade 7
1 Introduction to Science
1-1 Definition of Science
1-2 Importance of Science in Daily Life
1-3 Scientific Method
1-3 1 Observation
1-3 2 Hypothesis
1-3 3 Experimentation
1-3 4 Analysis
1-3 5 Conclusion
2 Matter and Its Properties
2-1 States of Matter
2-1 1 Solid
2-1 2 Liquid
2-1 3 Gas
2-2 Properties of Matter
2-2 1 Mass
2-2 2 Volume
2-2 3 Density
2-2 4 Solubility
2-3 Changes in Matter
2-3 1 Physical Changes
2-3 2 Chemical Changes
2-4 Mixtures and Solutions
2-4 1 Types of Mixtures
2-4 2 Separation Techniques
3 Force and Motion
3-1 Types of Forces
3-1 1 Gravitational Force
3-1 2 Frictional Force
3-1 3 Magnetic Force
3-1 4 Electrostatic Force
3-2 Motion
3-2 1 Speed and Velocity
3-2 2 Acceleration
3-2 3 Newton's Laws of Motion
3-2 3-1 First Law (Inertia)
3-2 3-2 Second Law (Force and Acceleration)
3-2 3-3 Third Law (Action and Reaction)
4 Energy
4-1 Forms of Energy
4-1 1 Kinetic Energy
4-1 2 Potential Energy
4-1 3 Thermal Energy
4-1 4 Electrical Energy
4-1 5 Light Energy
4-1 6 Sound Energy
4-2 Energy Conversion
4-2 1 Mechanical to Electrical
4-2 2 Chemical to Thermal
4-2 3 Light to Electrical
4-3 Conservation of Energy
5 Heat and Temperature
5-1 Temperature
5-1 1 Measurement of Temperature
5-1 2 Temperature Scales
5-2 Heat Transfer
5-2 1 Conduction
5-2 2 Convection
5-2 3 Radiation
5-3 Effects of Heat
5-3 1 Expansion
5-3 2 Change of State
6 Light and Sound
6-1 Light
6-1 1 Sources of Light
6-1 2 Reflection
6-1 3 Refraction
6-1 4 Lenses and Mirrors
6-2 Sound
6-2 1 Production of Sound
6-2 2 Properties of Sound
6-2 3 Reflection of Sound
6-2 4 Applications of Sound
7 Earth and Space
7-1 Earth's Structure
7-1 1 Crust
7-1 2 Mantle
7-1 3 Core
7-2 Earth's Atmosphere
7-2 1 Layers of the Atmosphere
7-2 2 Weather and Climate
7-3 Solar System
7-3 1 Planets
7-3 2 Sun
7-3 3 Moon
7-4 Space Exploration
7-4 1 Rockets
7-4 2 Satellites
7-4 3 Space Stations
8 Living Organisms and Ecosystems
8-1 Classification of Living Organisms
8-1 1 Kingdoms
8-1 2 Species
8-2 Ecosystems
8-2 1 Components of an Ecosystem
8-2 2 Food Chains and Webs
8-3 Adaptations
8-3 1 Physical Adaptations
8-3 2 Behavioral Adaptations
8-4 Human Impact on Ecosystems
8-4 1 Pollution
8-4 2 Conservation Efforts
9 Health and Nutrition
9-1 Human Body Systems
9-1 1 Circulatory System
9-1 2 Respiratory System
9-1 3 Digestive System
9-1 4 Nervous System
9-2 Nutrition
9-2 1 Essential Nutrients
9-2 2 Balanced Diet
9-3 Diseases and Prevention
9-3 1 Infectious Diseases
9-3 2 Non-infectious Diseases
9-3 3 Hygiene and Prevention
10 Environmental Science
10-1 Natural Resources
10-1 1 Renewable Resources
10-1 2 Non-renewable Resources
10-2 Pollution
10-2 1 Air Pollution
10-2 2 Water Pollution
10-2 3 Soil Pollution
10-3 Sustainable Development
10-3 1 Importance of Sustainability
10-3 2 Sustainable Practices
10-4 Climate Change
10-4 1 Causes of Climate Change
10-4 2 Effects of Climate Change
10-4 3 Mitigation Strategies
7.4.1 Rockets Explained

Understanding Rockets

Key Concepts

1. Basic Principles of Rocket Propulsion

Rockets operate on the principle of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. Rockets expel mass (usually hot gases) in one direction to propel themselves in the opposite direction.

2. Rocket Engines

Rocket engines generate thrust by burning fuel and expelling the resulting gases at high velocities. The most common types of rocket engines include liquid-fueled engines, solid-fueled engines, and hybrid engines.

3. Stages of a Rocket

Rockets are often designed in stages to optimize performance. Each stage contains its own engines and fuel, and they are jettisoned as they are used up to reduce the weight of the rocket.

4. Thrust and Velocity

Thrust is the force that propels a rocket forward, while velocity is the speed at which the rocket moves. Both are critical for achieving orbit or reaching other destinations in space.

5. Payload

The payload is the cargo or equipment that a rocket carries, such as satellites, spacecraft, or scientific instruments. The design of the rocket must accommodate the weight and size of the payload.

6. Launch and Orbit

The launch process involves lifting the rocket vertically and then tilting it to follow a trajectory that will place the payload into the desired orbit. Achieving orbit requires precise control of velocity and direction.

7. Applications of Rockets

Rockets are used for various purposes, including launching satellites, conducting scientific research, transporting astronauts to the International Space Station, and exploring other planets.

Explanation of Each Concept

1. Basic Principles of Rocket Propulsion

Rockets work by expelling mass in one direction to create a force in the opposite direction. This is known as thrust. The expelled mass is typically hot gases produced by burning fuel. The force generated by the expelled gases pushes the rocket forward.

2. Rocket Engines

Liquid-fueled engines use separate tanks for fuel and oxidizer, which are mixed and burned in the combustion chamber. Solid-fueled engines use a single solid propellant that burns from the inside out. Hybrid engines combine elements of both liquid and solid fuels.

3. Stages of a Rocket

A multi-stage rocket has multiple sections, each with its own engines and fuel. As each stage's fuel is consumed, the stage is detached, reducing the rocket's weight and allowing the remaining stages to accelerate more efficiently. This process continues until the payload reaches its destination.

4. Thrust and Velocity

Thrust is the force that propels the rocket forward, measured in newtons. Velocity is the speed and direction of the rocket, measured in meters per second. Both must be precisely controlled to achieve the desired trajectory and orbit.

5. Payload

The payload is the cargo that the rocket carries. It can include satellites for communication and weather monitoring, scientific instruments for research, or spacecraft for human exploration. The rocket's design must account for the weight and size of the payload to ensure successful delivery.

6. Launch and Orbit

During launch, the rocket ascends vertically to clear the atmosphere and then tilts to follow a specific trajectory. To achieve orbit, the rocket must reach a velocity of about 28,000 kilometers per hour. This process requires precise control of thrust and direction.

7. Applications of Rockets

Rockets are essential for space exploration and scientific research. They launch satellites for communication, navigation, and weather forecasting. They also transport astronauts to the International Space Station and enable missions to explore other planets, such as Mars.

Examples and Analogies

Example 1: Rocket Propulsion

Think of a rocket like a balloon. When you let go of a balloon after inflating it, the air rushes out, and the balloon flies in the opposite direction. Similarly, a rocket expels gases to propel itself forward.

Example 2: Multi-Stage Rocket

Imagine a multi-stage rocket as a relay race. Each runner (stage) carries the baton (payload) and passes it to the next runner as they tire. This allows the baton to reach the finish line faster and with less effort.

Analogy: Thrust and Velocity

Think of thrust as the power of a car's engine, and velocity as the speed at which the car is moving. Both are necessary for the car to reach its destination efficiently.