BIOLOGY
A plant is kept in a dark cupboard for several days. Its leaves remain green at first, but its growth slows. Which important process is being limited?
Photosynthesis
An unknown element is shiny, can be bent into shape and conducts electricity. Is it most likely a metal or non-metal? Give two pieces of evidence.
A metal, because it is malleable and conducts electricity. Its shiny appearance is another clue.
Two students push a box in opposite directions. One pushes with 15 N and the other with 9 N. Calculate the resultant force.
6 N in the direction of the 15 N push.
You are measuring 25 mL of water using a measuring cylinder. Why should your eyes be level with the bottom of the meniscus when reading it?
To avoid parallax error and obtain a more accurate volume measurement.
I study living organisms and their interactions with the environment. What type of scientist am I?
A biologist.
A root hair cell has a long, thin extension, while a leaf cell contains many chloroplasts. Explain how these differences help each cell perform its function.
The root hair extension increases surface area for absorbing water and mineral ions. Chloroplasts absorb light for photosynthesis in leaf cells.
An unknown solution turns universal indicator orange. Is it acidic or alkaline? What approximate pH range would you expect?
Acidic, approximately pH 3–4, depending on the indicator chart.
A ball is thrown vertically upward. Describe what happens to its kinetic energy and gravitational potential energy as it rises.
Kinetic energy decreases while gravitational potential energy increases.
A student accidentally spills a small amount of an unknown chemical onto their hand. What should they do immediately?
Tell the teacher immediately and rinse the affected skin thoroughly with running water, following laboratory safety procedures.
I investigate crime scenes by analysing fingerprints, fibres, blood and other evidence. What is my career?
A forensic scientist.
In the food chain grass → grasshopper → frog → snake, a disease kills many frogs. Predict two possible changes to other populations.
Grasshoppers may increase because fewer frogs eat them. Grass may decrease because more grasshoppers feed on it. Snakes may also decline due to reduced food.
A student mixes vinegar with baking soda. Bubbles form and the container feels cooler. Give two observations that suggest a chemical reaction has occurred.
Gas bubbles are produced and the temperature decreases, indicating a chemical reaction involving an energy change.
A cyclist stops pedalling on a level road but continues moving for a short time before stopping. Explain which forces cause the bicycle to slow down.
Air resistance and friction or rolling resistance act against its motion and gradually slow the bicycle.
You must investigate whether sugar dissolves faster in hot or cold water. Name two variables that should be kept constant.
For example, the mass and particle size of sugar, volume of water and stirring method. Any two suitable controlled variables.
I study earthquakes and the movement of tectonic plates. What type of scientist am I?
A forensic scientist.
A geologist, particularly a seismologist for earthquake research.
Describe how viruses replicates itself
A virus infects a host cell and creates more parts of itself and makes new viruses
-Men Yuan
A student adds an alkali slowly to an acid. Universal indicator changes from red to green, then purple. Explain what happened at each stage.
Red indicates acidic conditions; green indicates approximately neutral conditions; purple indicates that excess alkali has made the mixture alkaline.
Two identical bulbs are connected in series to a battery. One bulb burns out. Explain what happens to the second bulb and why.
The second bulb also goes out because the circuit becomes incomplete, so current cannot flow.
You are given a mixture of sand, salt and water. Describe how to obtain dry sand and then recover the dissolved salt.
Filter the mixture to separate the sand, then dry the sand. Evaporate water from the filtrate to recover the salt as crystals.
A town's river suddenly contains dead fish and an unusual chemical smell. Name two types of scientists who could investigate the problem and explain what each would study.
An environmental chemist could test the water for pollutants. An ecologist or aquatic biologist could investigate effects on fish and other organisms.
All the fungi and bacteria that decompose dead organisms disappear from a forest. After several years, plants begin growing poorly even though sunlight and rainfall remain normal. Suggest the connection.
Dead matter is no longer broken down efficiently, reducing the recycling of mineral nutrients into the soil. Plants cannot obtain enough nutrients for healthy growth.
A student heats 12 g of magnesium in air. The magnesium oxide produced has a mass of 20 g. Explain where the extra 8 g came from and why mass is still conserved.
The magnesium combined with 8 g of oxygen from the air. The combined mass of magnesium and oxygen equals the mass of magnesium oxide.
Why are high tides and low tides experienced at many coastal locations approximately twice each lunar day, rather than just once?
The Moon's gravitational influence produces two tidal bulges on opposite sides of Earth. As Earth rotates, many coastal locations pass through both bulges, giving two high tides and two low tides in approximately 24 hours 50 minutes.
Two students investigate how temperature affects dissolving time. Student A tests hot water once and cold water once. Student B repeats each test three times. Explain why Student B's results are more reliable and identify one possible source of unfairness that both students must control.
Repeated trials help identify anomalous results and allow a mean to be calculated. They should control factors such as sugar mass, particle size, water volume and stirring.
Which career is medicine for animals?
veterinarian