Diet and Growth
What are the six types of nutrient that the body needs?
Carbohydrate, protein, fat, vitamins, minerals, and water.
What is the equation for aerobic respiration and where exactly does respiration in the cell take place?
Answer: Glucose+Oxygen= CO2+Water(+Energy); in the mitochondria.
What is the equation for speed, and what is its standard unit?
speed = distance ÷ time. Standard unit:m/s or km/h.
What is an exothermic reaction?
A reaction where energy is given out.
In a solution, what do we call (a) the substance that dissolves and (b) the substance it dissolves into?
(a) The solute. (b) The solvent.
Which nutrient is needed for growth and repair, and which two are the main energy sources?
Protein for growth/repair; carbohydrates and fats for energy.
In what sequence does air travel through the respiratory system when you inhale?
1:nose, mouth
2:voicebox(larynx)
3:windpipe (trachea)
4:lung
5:bronchus (plural: bronchi)
6:bronchiole
7:air sacs
What happens to an object's movement when the forces on it are (a) balanced and (b) unbalanced?
(a) Balanced → no change in movement. (b) Unbalanced → a change in movement (speeding up, slowing down, or changing direction).
Burning combines a substance with which gas, and what type of reaction is this called?
Oxygen; it is an oxidation reaction.
What is a a)saturated solution and b)dilute solution?
a) solution that has more solute than solvent.
b) solution that has more solvent than solute.
Vitamin D is unusual compared with other vitamins. Explain why, and state which mineral it helps the body use and what that mineral is needed for.
Most vitamin D is not from food — it is made in the skin when sunlight falls on it. It helps the body absorb calcium, which is needed for strong bones and teeth.
What are 2 adaptations of air sacs?
1: large total surface area
2: thin walls
A car travels a distance of 1925m at a speed of 35 m/s. Calculate the time taken.
time = distance ÷ speed = 1925 ÷ 35 = 55 s.
Write the word equation for magnesium reacting with hydrochloric acid, and name the salt produced.
magnesium + hydrochloric acid → magnesium chloride + hydrogen. The salt is magnesium chloride.
How does increasing the temperature affect the solubility of most solutes, and why?
As temperature increases, solubility increases — most solutes dissolve more in hot water. This is because the particles gain more energy and more quickly, so more solute can dissolve.
Why does a person with anaemia feel tired? Link iron to the reason.
Iron is needed to make haemoglobin. Without enough iron, the body makes too little haemoglobin, so less oxygen is carried to the cells, which then cannot respire properly — leaving the person with lack of energy and feeling tired.
Gas exchange happens in the air sacs. Name the process by which gases move, and explain which way oxygen travels and why.
The process is diffusion. Oxygen moves from the air in the air sac (high concentration) into the blood (low concentration), because diffusion is particles moving from high concentration to low concentration.
Marcus weighs 600 N and sits 2 m from the pivot of a seesaw. Arun weighs 800 N. How far from the pivot must Arun sit to balance the seesaw?
Marcus's moment = force × distance = 600 × 2 = 1200 Nm. For balance, Arun's moment must also be 1200 Nm. distance = moment ÷ force = 1200 ÷ 800 = 1.5 m.
Reaction A — start: 8 °C → end: 25 °C
Reaction B — start: 40 °C → end: 30 °C
Which reaction is exothermic and which is endothermic? Explain your answer using the data.
Reaction A is exothermic: its temperature rose from 8 °C to 25 °C (a change of +17 °C), so thermal energy was given out to the surroundings.
Reaction B is endothermic: its temperature fell from 40 °C to 30 °C (a change of −10 °C), so thermal energy was taken in from the surroundings.
You must look at the temperature change (the rise or fall), not the final temperature. Even though B ended higher (30 °C vs 25 °C), it actually cooled down — so B took in heat, while A released it.
A chromatogram of a food dye shows three coloured spots at different heights. (a) Which colour is most soluble, and how can you tell? (b) Why would this method fail for permanent marker ink, and what should you change?
(a) The colour that travelled furthest up the paper is most soluble, because the solvent carries it further. (b) Permanent marker ink is insoluble in water, so it won't move — you'd need to use a different solvent.
Describe how the biceps and triceps move the arm at the elbow, and explain why two muscles are needed instead of one.
To bend the arm, the biceps contracts and the triceps relaxes. To straighten it, the triceps contracts and the biceps relaxes. Two muscles are needed because muscles can only pull (contract), not push — so a second muscle is required to move the bone back. This is called an antagonistic pair.
Red blood cells have no nucleus and no mitochondria. Explain how EACH of these unusual features helps the cell do its job.
A red blood cell's job is to carry oxygen using haemoglobin. Having no nucleus makes more room inside the cell for haemoglobin, so it can carry more oxygen. Having no mitochondria means the cell doesn't carry out respiration itself, so it doesn't use up the oxygen it is carrying — leaving more to deliver to other body cells.
Explain why a sharp knife cuts more easily than a blunt one. Then calculate the pressure when a force of 50 000 N acts on an area of 0.4 m².
pressure = force ÷ area. A sharp knife has a smaller area in contact, and for the same force a smaller area gives a greater pressure, so it cuts more easily. Pressure = 50 000 ÷ 0.4 = 125 000 N/m².
Iron rusts (iron + oxygen → iron oxide). (a) Name the two conditions both needed for rusting. (b) Give two ways iron can be protected, and explain how each works.
(a) Both water and oxygen (air). (b) Painting — stops oxygen reaching the iron; galvanising — coating it with zinc, which prevents oxygen reaching the iron.
Design an investigation to find out how the temperature of water affects how much salt will dissolve in it. State the independent variable, the dependent variable, two control variables, one safety hazard, and a solution to prevent the safety hazard.
Independent variable: temperature of the water (e.g. 20 °C to 80 °C). Dependent variable: the mass of salt that dissolves. Control variable: the volume of water, and the type of salt (and stirring). Safety hazard:hot water can burn the skin. Protection: wearing gloves, lab coat (and goggles).