📚 Quick-reference Handbook of Formulas and Theorems for SQA Year 7 Science | SQA 七年级科学公式定理速查手册
This handbook brings together the most important formulas and theorems you will meet in Year 7 science, following the Scottish Curriculum for Excellence. Keep it handy for quick revision before tests and when solving problems in physics, chemistry and biology.
本手册汇总了你在七年级科学学习中会遇到的最重要的公式与定理，完全遵循苏格兰卓越课程体系。准备好随时翻阅，帮助你在物理、化学和生物测验中快速回忆并解决问题。
1. Speed, Distance and Time | 速度、距离与时间
Speed tells you how quickly an object moves. It is calculated by dividing the total distance travelled by the time taken. The symbol v is commonly used for speed, d for distance and t for time.
速度告诉你物体运动的快慢。它等于移动的总距离除以所用时间。通常用 v 表示速度，d 表示距离，t 表示时间。
v = d / t
2. Density, Mass and Volume | 密度、质量与体积
Density describes how tightly matter is packed together. It is the mass of a substance per unit volume. The Greek letter ρ (rho) represents density, m stands for mass, and V for volume.
密度描述了物质排列的紧密程度，即单位体积所含的质量。希腊字母 ρ 表示密度，m 为质量，V 为体积。
ρ = m / V
3. Pressure, Force and Area | 压力、力与面积
Pressure measures how much force is applied over a certain area. A large force over a small area results in high pressure. P stands for pressure, F for force and A for area.
压力衡量单位面积上所受的力。在相同力的情况下，面积越小压力越大。P 代表压力，F 代表力，A 代表面积。
P = F / A
4. Ohm's Law | 欧姆定律
Ohm’s Law links voltage, current and resistance in an electric circuit. It states that the current through a conductor is directly proportional to the voltage across it, as long as the temperature stays constant. V is voltage in volts, I is current in amperes, and R is resistance in ohms.
欧姆定律描述了电路中电压、电流与电阻的关系。它指出，在温度不变时，通过导体的电流与导体两端的电压成正比。V 为电压（伏特），I 为电流（安培），R 为电阻（欧姆）。
V = I × R
5. Work and Energy | 功与能量
Work is done whenever a force moves an object in the direction of the force. It is calculated as force multiplied by distance moved. In addition, kinetic energy (Ek) is the energy of motion, and gravitational potential energy (Ep) is the energy stored due to an object’s height.
当一个力使物体沿力的方向移动时，这个力做了功。功等于力乘以物体沿力的方向移动的距离。此外，动能 (Ek) 是物体由于运动而具有的能量，重力势能 (Ep) 是物体由于被举高而储存的能量。
W = F × d
Ek = ½ m v²
Ep = m g h
m is mass, v is speed, g is the gravitational field strength (about 9.8 N/kg on Earth) and h is height.
m 为质量，v 为速度，g 为重力场强度（地球表面约为 9.8 N/kg），h 为高度。
6. Power | 功率
Power is the rate at which work is done or energy is transferred. A powerful device transfers a large amount of energy in a short time. P represents power, E stands for energy, W for work and t for time.
功率是做功或能量转移的速率。大功率设备能在短时间内转移大量能量。P 表示功率，E 表示能量，W 表示功，t 表示时间。
P = E / t or P = W / t
7. Force and Newton's Laws | 力与牛顿定律
Newton’s Second Law explains how force, mass and acceleration are related. The net force on an object equals its mass multiplied by its acceleration. Weight is a specific force – the pull of gravity on an object’s mass.
牛顿第二定律阐明了力、质量和加速度之间的关系。物体受到的净外力等于其质量乘以加速度。重量是一种特殊的力——地球对物体质量的引力。
F = m × a
W = m × g
Newton’s First Law (Law of Inertia): An object stays at rest or moves at constant speed in a straight line unless acted upon by an unbalanced force. Newton’s Third Law: For every action there is an equal and opposite reaction.
牛顿第一定律（惯性定律）：任何物体都保持静止或匀速直线运动状态，除非有不平衡的外力迫使它改变。牛顿第三定律：每一个作用力都有一个大小相等、方向相反的反作用力。
8. Photosynthesis | 光合作用
Photosynthesis is the process by which green plants use light energy to combine carbon dioxide and water, producing glucose and oxygen. This reaction takes place in the chloroplasts, which contain chlorophyll.
光合作用是绿色植物利用光能，将二氧化碳和水转化为葡萄糖和氧气的过程。该反应在含有叶绿素的叶绿体中进行。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Light energy and chlorophyll are required for the reaction.
光能和叶绿素是反应的必要条件。
9. Respiration | 呼吸作用
Aerobic respiration releases energy from glucose using oxygen. It is the process that supplies energy for cell activities. Carbon dioxide, water and energy (in the form of ATP) are produced.
有氧呼吸利用氧气将葡萄糖分解，释放出能量，为细胞活动供能。产物是二氧化碳、水和能量（以 ATP 形式）。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
10. Conservation of Mass | 质量守恒定律
In any chemical reaction, the total mass of the reactants equals the total mass of the products. Atoms are rearranged, but none are created or destroyed.
在任何化学反应中，反应物的总质量等于生成物的总质量。原子只是重新组合，既没有被创造也没有被消灭。
mass(reactants) = mass(products)
11. Law of Reflection | 反射定律
When light strikes a smooth surface like a mirror, it bounces off in a predictable way. The angle of incidence is measured between the incoming ray and the normal (an imaginary line perpendicular to the surface). This angle always equals the angle of reflection.
当光射向镜面等光滑表面时，会以可预测的方式反射。入射角是入射光线与法线（垂直于表面的假想线）之间的夹角，它始终等于反射角。
∠i = ∠r
12. Principle of Moments | 力矩原理
A lever or seesaw is balanced when the clockwise moment equals the anticlockwise moment. Moment is the turning effect of a force and is calculated by multiplying the force by its perpendicular distance from the pivot.
当杠杆或跷跷板平衡时，顺时针力矩等于逆时针力矩。力矩是力的转动效果，等于力乘以从支点到力作用线的垂直距离。
F₁ × d₁ = F₂ × d₂
A larger force or a longer distance from the pivot produces a greater turning effect.
力越大或离支点的垂直距离越远，产生的转动效果越大。
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