Topic 1 Part 4 - Testing scientific questions Flashcards
What is the difference between a dependent and an independent variable?
The independent variable is the thing you change (vary) during an experiment. The dependent variable is the change that you observe as a result during an experiment.
Which is the dependent and the independent variable in an experiment investigating how much sugar can be dissolved in water when the temperature of the water is raised?
The temperature of water is the independent variable and the amount of sugar dissolved is the dependent variable.
What is the name of the interaction between two adjacent water molecules?
This attraction between adjacent water molecules in liquid water is called hydrogen bonding.
What is meniscus
the curved upper surface of a liquid in a tube.
Why does surface tension happen with water?
When there is no water molecules above the water to pull it up (because the air above are not polar), the water molecules below and across are pulling the water creating a tight surface layer.
How does the pond skater manage to walk on the surface of the water?
The pond skater’s flexible legs enable its weight to be distributed over a large surface area, so that it can use surface tension to its advantage. The pond skater is managing to walk on the water’s surface without breaking the attraction between adjacent water molecules. So it is not breaking the surface skin on the water.
You may have already come across some gases found in the Earth’s atmosphere; can you recall what these are and what their chemical symbols are?
Air contains nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2) and very small amounts of other gases.
Can you think of two variables which could affect the amount of gases dissolved in water?
Both temperature and pressure will affect the amount of gases dissolved in water.
Does the amount of dissolved gases in water increase or decrease with higher temperature?
Decreases
Does the amount of dissolved gases in water increase of decrease with higher pressure?
Increases
Many people like carbonated drinks (or soda). How is it possible to increase the amount of carbon dioxide (CO2) dissolved within carbonated drinks?
Carbonated drinks are canned at low temperature and under pressure in order to increase the CO2 dissolved in solution.
Coal-burning power plants heat water to produce steam which turns turbines to make electricity. After using the water, it is cooled before being returned to rivers or lakes. Why is it important to cool the water before returning it to the rivers or lakes?
If the water is returned to the rivers and lakes while it is still heated, it would raise the temperature of the rivers and lakes and allow the dissolved gases essential for the aquatic life to escape
What is a whirlpool?
A whirlpool is a body of water in a circular motion that is produced when opposing currents meets.
What is the proper term for any whirlpool that has at its centre a downdraft (i.e. a small-scale current of sinking air)?
A Vortex
