Inside the Human Body
Which organ pumps blood around the body?
The heart
What is the unit of force?
Newton
What is the smallest unit of an element that retains its chemical properties?
Atom
What is the term for an organism that makes its own food?
Producer
What is the bouncing back of light from a surface called?
Reflection.
Name the blood vessel that carries blood from the heart to the lungs.
A car travels 60 metres in 10 seconds. Calculate its speed.
Speed = distance ÷ time = 60 ÷ 10 = 6 m/s.
Is pure distilled water an element or a compound?
A compound.
What is the main source of energy for most ecosystems?
Sun
What is the name of the line drawn at 90° to a surface where a light ray hits?
The normal.
Explain why breathing rate increases during exercise.
Muscles need more oxygen for respiration and produce more carbon dioxide, which must be removed.
A student exerts a force of 100 N over an area of 0.5 m². Calculate the pressure.
Pressure = force ÷ area = 100 ÷ 0.5 = 200 Pa.
A gold ring has a mass of 20 g and contains 15 g of gold. Calculate its percentage of gold.
(15 ÷ 20) × 100 = 75%.
Explain why mangrove trees can survive in muddy coastal environments.
They have adaptations such as specialised roots that help them obtain oxygen in waterlogged soil and remain stable in soft mud.
The angle of incidence is 35°. What is the angle of reflection?
35°
A student breathes faster after running. Explain how this helps the body.
It increases oxygen intake and removes carbon dioxide more quickly.
Why does a sharp knife cut more easily than a blunt knife when the same force is applied?
The sharp knife has a smaller contact area, so it produces greater pressure.
Explain the difference between an element and a compound.
An element contains one type of atom. A compound contains two or more different elements chemically combined.
What may happen to a food chain if the number of primary consumers decreases?
Predators may have less food and their populations may decrease. Producers may increase because fewer are eaten.
Why does a pencil appear bent when partly placed in water?
Light changes direction when it passes between water and air because its speed changes. This is refraction.
A person has a diet containing too little iron. Explain how this may affect their energy levels.
Iron is needed to make haemoglobin. Less haemoglobin means less oxygen can be transported to cells, reducing aerobic respiration and energy release.
A student walks 100 m in 50 s. Another student walks 150 m in 60 s. Calculate both speeds and identify the faster student.
First student: 100 ÷ 50 = 2 m/s. Second student: 150 ÷ 60 = 2.5 m/s. The second student is faster.
A 30 g jewellery sample contains 18 g of gold and 12 g of silver. Calculate the percentage by mass of gold and silver.
Gold: (18 ÷ 30) × 100 = 60%. Silver: (12 ÷ 30) × 100 = 40%.
A forest is cleared and replaced by buildings. Explain two possible effects on the ecosystem and one effect on the local climate.
Possible effects: habitat loss and reduced biodiversity; disruption of food chains. Local climate may become hotter because there is less shade and less cooling through transpiration.
A light ray strikes a plane mirror at an angle of incidence of 40°. Calculate the angle between the incident ray and the reflected ray.
Angle of reflection = 40°. Angle between the rays = 40° + 40° = 80°.