📚 Year 8 AQA Science: Formula & Theorem Quick Reference Handbook | Year 8 AQA 科学：公式定理速查手册
This quick-reference handbook gathers every essential formula and theorem from the Year 8 AQA Science course. Whether you are revising physics equations, biology magnification, or chemistry word equations, use this collection to test yourself, check units, and build confidence before assessments.
本速查手册汇集了 Year 8 AQA 科学课程中的每一个重要公式与定理。无论你是在复习物理方程、生物学放大公式还是化学文字方程式，都可以用这本手册自测、核对单位，在评估前建立信心。
1. Speed, Distance and Time | 速度、距离和时间
The speed of an object tells us how fast it is moving. It is the distance travelled in a certain amount of time.
物体的速度告诉我们它运动的快慢，是单位时间内通过的距离。
speed = distance ÷ time or v = d / t
Speed is measured in metres per second (m/s) when distance is in metres (m) and time is in seconds (s). For longer journeys, kilometres per hour (km/h) may be used.
当距离以米 (m) 为单位、时间以秒 (s) 为单位时，速度的单位是米/秒 (m/s)。在较长路程中，也可使用千米/小时 (km/h)。
The formula can be rearranged to find distance or time:
公式可变形来求距离或时间：
distance = speed × time and time = distance ÷ speed
A straight line on a distance–time graph means the object is travelling at constant speed; a steeper slope represents a higher speed.
在距离–时间图中，一条直线表示物体做匀速运动；斜率越陡表示速度越快。
2. Acceleration | 加速度
Acceleration is the rate at which an object's speed changes. It can be an increase in speed, a decrease (deceleration), or a change in direction.
加速度是物体速度变化的快慢。可以是速度增加、减慢（减速）或方向的改变。
= (final velocity − initial velocity) / time or a = (v − u) / t
The unit of acceleration is metres per second squared (m/s2). A positive value means the object is speeding up; a negative value means it is slowing down.
加速度的单位是米/秒² (m/s2)。正值表示物体在加速，负值表示物体在减速。
3. Forces and Newton's Second Law | 力与牛顿第二定律
When a resultant force acts on an object, the object accelerates in the direction of the force. The size of the acceleration depends on the mass of the object and the size of the force.
当物体受到合力作用时，它会沿力的方向加速。加速度的大小取决于物体的质量和力的大小。
force = mass × acceleration or F = m × a
Force is measured in newtons (N), mass in kilograms (kg) and acceleration in m/s2. This relationship is Newton's Second Law of Motion.
力的单位是牛顿 (N)，质量的单位是千克 (kg)，加速度的单位是 m/s2。这一关系就是牛顿第二运动定律。
4. Weight and Gravitational Field Strength | 重量与重力场强度
Weight is the force acting on an object due to gravity. It is different from mass: mass is the amount of matter in an object and does not change, while weight changes with the gravitational field strength.
重量是由于重力作用在物体上的力。它与质量不同：质量是物体所含物质的多少，不会变化；而重量会随重力场强度改变。
weight = mass × gravitational field strength or W = m × g
On Earth, g is approximately 9.8 N/kg, but you can use 10 N/kg for most calculations in Year 8. Weight is measured in newtons (N).
在地球上，重力场强度 g 约为 9.8 N/kg，但在 Year 8 的大多数计算中可以使用 10 N/kg。重量的单位是牛顿 (N)。
5. Pressure in Fluids and Solids | 流体和固体中的压力
Pressure tells us how concentrated a force is. A sharp knife cuts easily because the same force acts over a very small area, producing a large pressure.
压力表示力的集中程度。一把锋利的刀容易切割，是因为同样的力作用在很小的面积上，产生了很大的压力。
pressure = force ÷ area or p = F / A
Pressure is measured in pascals (Pa) or newtons per square metre (N/m2). Force is in newtons (N) and area in square metres (m2).
压力的单位是帕斯卡 (Pa) 或牛顿/平方米 (N/m2)。力的单位是牛顿 (N)，面积的单位是平方米 (m2)。
In liquids, pressure increases with depth. This is a theorem you can observe with holes at different heights in a bottle.
在液体中，压力随深度增加而增大。这是一个可以通过在不同高度扎孔的瓶子来观察的定理。
6. Density | 密度
Density describes how closely packed the particles in a material are. A dense material has a lot of mass in a small volume.
密度描述了材料中粒子排列的紧密程度。密度大的材料在很小的体积内拥有很大的质量。
density = mass ÷ volume or ρ = m / V
Mass is usually measured in grams (g) or kilograms (kg), and volume in cubic centimetres (cm3) or cubic metres (m3). The units of density are g/cm3 or kg/m3.
质量通常以克 (g) 或千克 (kg) 为单位，体积以立方厘米 (cm3) 或立方米 (m3) 为单位。密度的单位是 g/cm3 或 kg/m3。
7. Work Done and Energy Transfer | 做功与能量转移
In science, 'work done' is the amount of energy transferred when a force moves an object. If a force does work, energy is shifted from one store to another.
在科学中，“做功”是指力使物体移动时所转移的能量大小。如果一个力做了功，能量就会从一个储存转移到另一个储存。
work done = force × distance or W = F × d
Work done is measured in joules (J), force in newtons (N) and distance in metres (m). Lifting a book or pushing a trolley are everyday examples of work being done.
功的单位是焦耳 (J)，力的单位是牛顿 (N)，距离的单位是米 (m)。提起一本书或推动一辆手推车都是做功的常见例子。
8. Power and Efficiency | 功率与效率
Power is the rate at which work is done, or how quickly energy is transferred. A more powerful motor completes the same task in less time.
功率是做功的快慢，也就是能量转移的速率。一台功率更大的马达能在更短的时间内完成同样的任务。
power = work done ÷ time or P = W / t
Power is measured in watts (W), where one watt is one joule per second. The work done must be in joules (J) and time in seconds (s).
功率的单位是瓦特 (W)，1 瓦特等于 1 焦耳/秒。做功必须以焦耳 (J) 为单位，时间以秒 (s) 为单位。
No device is perfect: some input energy is always wasted, often as heat. Efficiency compares useful output to total input.
没有设备是完美的：一部分输入能量总是被浪费，通常转化为热量。效率比较了有用输出与总输入。
efficiency = useful output energy ÷ total input energy × 100%
Efficiency can be expressed as a decimal or a percentage. A higher percentage means less energy is wasted.
效率可以用小数或百分数表示。百分数越高表示浪费的能量越少。
9. Electrical Circuits – Ohm's Law | 电路——欧姆定律
In an electrical circuit, the current, voltage and resistance are linked by a simple rule known as Ohm's Law. This law holds true for many components, especially at constant temperature.
在电路中，电流、电压和电阻通过一个叫作欧姆定律的简单规则联系在一起。该定律对许多元件都成立，特别是在温度恒定的条件下。
voltage = current × resistance or V = I × R
Voltage is measured in volts (V), current in amperes or amps (A), and resistance in ohms (Ω).
电压的单位是伏特 (V)，电流的单位是安培 (A)，电阻的单位是欧姆 (Ω)。
Another useful relationship connects charge, current and time:
另一个有用的关系式将电荷、电流和时间联系在一起：
charge = current × time or Q = I × t
Charge is measured in coulombs (C), current in amps (A) and time in seconds (s).
电荷的单位是库仑 (C)，电流的单位是安培 (A)，时间的单位是秒 (s)。
10. Magnification in Biology | 生物学中的放大率
When using a light microscope, you can calculate how many times larger the image appears compared with the real specimen. This is the magnification formula.
使用光学显微镜时，可以计算出图像比真实标本大多少倍。这就是放大率公式。
magnification = image size ÷ actual size of specimen
Both sizes must be in the same unit, usually millimetres (mm) or micrometres (µm). Magnification has no unit because it is a ratio.
两个尺寸必须使用相同的单位，通常为毫米 (mm) 或微米 (µm)。放大率没有单位，因为它是一个比值。
The same formula can be rearranged to find the real size of a cell if you know the drawing size and the magnification used.
如果知道绘图尺寸和所用放大倍数，也可以用同一个公式变形求出细胞的实际大小。
11. Law of Conservation of Mass in Chemistry | 化学中的质量守恒定律
The law of conservation of mass states that in a chemical reaction no atoms are created or destroyed; they are only rearranged. Therefore the total mass of the reactants always equals the total mass of the products.
质量守恒定律指出，在化学反应中，原子不会被创造或毁灭，只会重新排列。因此，反应物的总质量总是等于生成物的总质量。
For example, when magnesium is burned in air, it gains mass because oxygen from the air combines with the magnesium. However, if you weigh the sealed system, the total mass stays the same.
例如，当镁在空气中燃烧时，因为空气中的氧与镁结合，质量会增加；但若称量一个密闭系统内的总质量，则会保持不变。
This theorem underpins all balanced symbol equations. A balanced equation has the same number of each type of atom on both sides.
这个定理是所有配平符号方程式的基础。配平后的方程式两边每种原子的数目都相等。
12. Chemical Word Equations – Key Reactions | 化学文字方程式——关键反应
Word equations show the names of reactants and products without using symbols. They help you recall important reactions taught in Year 8.
文字方程式用名称展示反应物和生成物，不使用化学符号。它们有助于回忆 Year 8 所学的几个重要反应。
Photosynthesis:
carbon dioxide + water → glucose + oxygen
The reaction takes place in chloroplasts, using light energy. The balanced symbol equation is 6CO2 + 6H2O → C6H12O6 + 6O2.
该反应在叶绿体中进行，需要光能。配平的符号方程式为 6CO2 + 6H2O → C6H12O6 + 6O2。
Aerobic respiration:
glucose + oxygen → carbon dioxide + water
Energy is released in this reaction, which occurs in the mitochondria of living cells.
该反应释放能量，发生在活细胞的线粒体中。
Neutralisation (acid + alkali):
acid + alkali → salt + water
For example, hydrochloric acid + sodium hydroxide → sodium chloride + water. This is an ionic reaction where H+ and OH- ions form water.
例如，盐酸 + 氢氧化钠 → 氯化钠 + 水。这是一个离子反应，H+ 与 OH- 离子生成水。
Factors affecting reaction rate – key theorems: Increasing temperature, concentration, or surface area speeds up most reactions. Adding a catalyst also increases the rate without being used up.
影响反应速率的因素——关键定理：升高温度、提高浓度或增大反应物的表面积都会加快大多数反应的速率。加入催化剂也能提高速率，而催化剂本身不会被消耗。
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