Year 7 CCEA Science: Formula & Theorem Quick Reference Handbook | 7 年级 CCEA 科学：公式定理速查手册

📚 Year 7 CCEA Science: Formula & Theorem Quick Reference Handbook | 7 年级 CCEA 科学：公式定理速查手册

Welcome to your handy summary of all the key formulas, equations and theorems you will meet in Year 7 CCEA Science. Use this guide to quickly review how forces, energy, matter and living systems follow predictable rules. Each section gives you the formula first, then explains how to use it with the correct units. Keep it close for homework, class tests and end-of-topic assessments.

欢迎查看这份 7 年级 CCEA 科学核心公式、方程式和定理的实用速查手册。用这本手册快速复习力、能量、物质和生命系统如何遵循可预测的规律。每个小节先给出公式，再说明如何使用以及正确单位。请将它放在手边，用于家庭作业、课堂测验和单元结束评估。

1. Speed, Distance, Time | 速度、距离、时间

Speed tells us how quickly an object moves. When a car travels a certain distance in a certain time, its average speed can be found using a simple relation.

速度表示物体运动的快慢。当一辆汽车在一定时间内行驶了一定的距离，其平均速度可以用一个简单的关系求得。

Speed = Distance ÷ Time

This means average speed equals the total distance travelled divided by the total time taken. The standard units are metres per second (m/s) for science experiments and kilometres per hour (km/h) for vehicles. Always check that distance and time are in matching units before you calculate.

这意味着平均速度等于总行驶距离除以总所用时间。科学实验中的标准单位是米每秒（m/s），车辆常用公里每小时（km/h）。在计算之前，务必检查距离和时间是否使用了匹配的单位。

Distance = Speed × Time

If you know the average speed and the time, you can find the distance by multiplying them.

如果已知平均速度和时间，可以用乘法求出距离。

Time = Distance ÷ Speed

To work out how long a journey takes, divide the distance by the speed.

要计算一段行程需要多长时间，用距离除以速度即可。

2. Density, Mass, Volume | 密度、质量、体积

Density is a property of a material that describes how much mass is crowded into a given volume. It helps explain why some objects float and others sink.

密度是材料的一种性质，描述一定体积内容纳了多少质量。它有助于解释为什么有些物体浮起而有些下沉。

Density = Mass ÷ Volume

Density is calculated by dividing the mass of an object by its volume. In the laboratory, mass is measured in grams (g) or kilograms (kg), and volume in cubic centimetres (cm³) or cubic metres (m³). This gives density units of g/cm³ or kg/m³. Water has a density of about 1 g/cm³ – substances with a lower density than water float.

密度由物体的质量除以体积计算。实验室中，质量用克（g）或千克（kg）测量，体积用立方厘米（cm³）或立方米（m³）测量。得到的密度单位是 g/cm³ 或 kg/m³。水的密度约为 1 g/cm³——密度比水小的物体会浮起。

Mass = Density × Volume

If you know the density and the volume, you can find the mass by multiplication.

如果已知密度和体积，可以通过乘法求出质量。

Volume = Mass ÷ Density

Similarly, the volume can be found by dividing the mass by the density.

同样地，体积可以通过质量除以密度求得。

3. Force, Mass and Acceleration | 力、质量和加速度

When an unbalanced force acts on an object, it makes the object speed up, slow down or change direction. The link between the force, the object’s mass and its acceleration is one of the most powerful ideas in science.

当不平衡的力作用在物体上时，会使物体加速、减速或改变方向。力、物体的质量以及加速度之间的联系是科学中最强大的思想之一。

Force = Mass × Acceleration

This equation is known as Newton’s Second Law of Motion. Force is measured in newtons (N). To get a force in newtons, mass must be in kilograms (kg) and acceleration in metres per second squared (m/s²). For example, a 2 kg object that speeds up by 5 m/s² each second experiences a force of 10 N.

这个方程被称为牛顿第二运动定律。力的单位是牛顿（N）。为了得到以牛顿为单位的力，质量必须用千克（kg），加速度用米每二次方秒（m/s²）。例如，一个 2 kg 的物体以每秒 5 m/s² 加速，受到的力为 10 N。

Weight = Mass × Gravitational Field Strength

On Earth, the gravitational field strength is approximately 10 N/kg. Your weight is simply the force of gravity pulling on your mass: Weight (N) = mass (kg) × 10.

在地球上，重力场强约为 10 N/kg。你的重量就是重力对你的质量所产生的拉力：重量（N）= 质量（kg）× 10。

4. Pressure, Force, Area | 压强、力、面积

Pressure is a measure of how concentrated a force is on a surface. The same force will produce higher pressure if applied over a smaller area.

压强是衡量力在表面上集中程度的量。同样的力，如果作用在较小的面积上，就会产生较大的压强。

Pressure = Force ÷ Area

Pressure is measured in pascals (Pa) when force is in newtons (N) and area is in square metres (m²). One pascal means a force of one newton is spread over one square metre. Sharp knives cut easily because the small area of the blade creates a very high pressure.

当力的单位是牛顿（N）、面积单位是平方米（m²）时，压强的单位是帕斯卡（Pa）。1 帕意味着一牛顿的力分布在 1 平方米的面积上。锋利的刀容易切割，是因为刀刃面积小，产生了很高的压强。

Force = Pressure × Area

This can be used to find the total force pushing on a surface if the pressure and area are known.

如果已知压强和面积，可以用这个公式求出作用在表面上的总力。

5. Work, Force, Distance | 功、力、距离

In science, ‘work’ means energy transferred by a force causing an object to move. Work is only done when part of the force acts in the direction of movement.

在科学里，“功”表示由力引起的使物体移动的能量转移。只有力的一部分沿运动方向起作用时，才算做了功。

Work Done = Force × Distance

Work done is measured in joules (J), force in newtons (N) and distance in metres (m). Lifting a 10 N weight up by 2 m does 20 J of work. The energy used to do this work has been transferred to the object’s gravitational potential store.

做功的单位是焦耳（J），力用牛顿（N），距离用米（m）。将一个 10 N 的物体向上提起 2 m，做了 20 J 的功。用来做这个功的能量已经转移到物体的重力势能储存中。

6. Hooke’s Law: Force and Extension | 胡克定律：力与伸长量

When you stretch a spring by hanging weights on it, the extension (extra length) is directly proportional to the force applied – as long as you do not stretch it too far.

当你在弹簧上挂重物拉伸它时，只要没有拉得过长，伸长量（增加的长度）与施加的力成正比。

Force = Spring Constant × Extension

This is called Hooke’s Law. Force (N) equals the spring constant (N/m) multiplied by the extension (m). The spring constant tells you how stiff the spring is – a higher value means a stiffer spring. On a force–extension graph, the straight line through the origin shows that the spring obeys Hooke’s Law.

这被称为胡克定律。力（N）等于弹簧常数（N/m）乘以伸长量（m）。弹簧常数告诉你弹簧有多硬——数值越大，弹簧越硬。在力-伸长量图上，穿过原点的直线表明弹簧遵循胡克定律。

7. Electrical Circuits: Ohm’s Law | 电路：欧姆定律

In an electrical circuit, components like lamps and resistors limit the current flow. The relationship between voltage, current and resistance can be captured in a key equation.

在电路中，像灯泡和电阻器这样的元件会限制电流的流动。电压、电流和电阻之间的关系可以用一个关键方程式表达。

Voltage = Current × Resistance

This is Ohm’s Law. Voltage (V) is measured in volts, current (I) in amperes (amps), and resistance (R) in ohms (Ω). For a fixed resistor at constant temperature, the current flowing is directly proportional to the voltage across it. This means if you double the voltage, the current doubles too.

这就是欧姆定律。电压（V）单位是伏特，电流（I）单位是安培，电阻（R）单位是欧姆（Ω）。对于一个温度不变的固定电阻器，流过它的电流与其两端电压成正比。这意味着如果把电压加倍，电流也会加倍。

Resistance = Voltage ÷ Current

Resistance tells you how difficult it is for current to pass through a component. You can calculate it by dividing the voltage across the component by the current through it.

电阻告诉你电流通过一个元件的难易程度。你可以通过将元件两端的电压除以流过它的电流来计算。

8. Conservation of Mass in Chemical Reactions | 化学反应中的质量守恒

In every chemical reaction, atoms are rearranged but not created or destroyed. This fundamental principle is called the conservation of mass.

在每一个化学反应中，原子被重新排列，但没有被创造或毁灭。这一基本原则称为质量守恒。

Total Mass of Reactants = Total Mass of Products

If you could collect all the substances produced in a reaction and measure their mass, it would be exactly equal to the mass of the starting substances. In an open container, some gas may escape, so the measured mass may appear to drop – but the mass of the whole system including any gas remains unchanged.

如果你能收集到反应生成的所有物质并测量它们的质量，会发现它们恰好等于起始物质的质量。在敞口容器中，一些气体可能会逸出，因此测量质量似乎会下降——但包括任何气体在内的整个系统的质量保持不变。

9. Particle Theory and States of Matter | 粒子理论与物质状态

The particle model explains why solids, liquids and gases behave differently. Although there is no single formula, understanding these relationships helps you explain changes of state and density.

粒子模型解释了为什么固体、液体和气体的行为不同。虽然没有单一的公式，但理解这些关系有助于解释物态变化和密度。

Solid: Particles are held very close together in a regular pattern. They vibrate in fixed positions. Solids have a fixed shape and volume.
固体: 粒子紧密地排列成规则的图案，在固定位置上振动。固体有固定的形状和体积。

Liquid: Particles are still close together but can slide past each other. Liquids have a fixed volume but take the shape of their container.
液体: 粒子仍然靠得很近，但可以相互滑动。液体有固定的体积，但会随容器形状而改变形状。

Gas: Particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed.
气体: 粒子相距很远，并快速地朝各个方向运动。气体没有固定的形状或体积，可以被压缩。

Heating a substance gives particles more kinetic energy. In solids, this makes them vibrate faster; in liquids and gases, they move faster. Energy input during a change of state, such as melting, does not raise temperature; instead it is used to break particle bonds.

加热物质会给粒子更多的动能。在固体中，这使粒子振动更快；在液体和气体中，它们运动得更快。在熔解等物态变化过程中，输入的能量并不会升高温度，而是用于打破粒子间的键合。

10. Photosynthesis and Respiration | 光合作用和呼吸作用

Living organisms depend on two key biochemical processes to capture and release energy. Word equations summarise the reactants and products involved.

生物体依赖两个关键的生物化学过程来捕获和释放能量。文字方程式总结了所涉及的反应物和生成物。

Photosynthesis
Carbon dioxide + Water → Glucose + Oxygen

This reaction takes place in the chloroplasts of plant cells. Light energy is absorbed by chlorophyll and used to convert the reactants into glucose, which stores energy, and oxygen, which is released. Photosynthesis only happens during daylight.

这个反应发生在植物细胞的叶绿体中。光能被叶绿素吸收，并用来将反应物转化为储存能量的葡萄糖以及释放出的氧气。光合作用只在白天进行。

Aerobic Respiration
Glucose + Oxygen → Carbon dioxide + Water

All living cells carry out respiration to release energy from glucose. Aerobic respiration uses oxygen and produces carbon dioxide and water as waste. The energy released is used for movement, growth and keeping warm. Respiration happens continuously, day and night.

所有活细胞都进行呼吸作用，从葡萄糖中释放能量。有氧呼吸使用氧气，并产生二氧化碳和水作为废物。释放的能量用于运动、生长和保持体温。呼吸作用日夜不停地进行。

11. Key Constants and Measurement Conversions | 关键常量和测量转换

Some constants appear in many science questions. Knowing them by heart saves time and makes calculations easier.

一些常数出现在许多科学问题中。熟记它们可以节省时间，使计算更容易。

Speed of light in a vacuum	c ≈ 3.00 × 10⁸ m/s
Speed of sound in air (20 °C)	≈ 343 m/s (often rounded to 340 m/s)
Gravitational field strength on Earth	g ≈ 10 N/kg
Density of water	1 g/cm³ (or 1000 kg/m³)
1 litre to cm³	1 L = 1000 cm³ = 0.001 m³

These values help when you tackle problems on waves, forces, density and states of matter. Always use the correct unit conversions: 1 kilometre = 1000 metres, 1 hour = 3600 seconds, 1 tonne = 1000 kilograms. A quick check of your units often catches mistakes before they happen.

这些数值在处理波、力、密度和物质状态的问题时很有帮助。始终使用正确的单位转换：1 公里 = 1000 米，1 小时 = 3600 秒，1 吨 = 1000 千克。快速检查单位往往能在犯错之前发现错误。

Published by TutorHao | Science Revision Series | aleveler.com

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