A.1: Water Flashcards
State what water is the medium of: (1)
- Life (1)
State the type of bond between hydrogen and oxygen atoms in a water molecule: (1)
- Polar covalent bonds (1)
Define the term polar molecule: (2)
A molecule that contains an uneven distribution of charges . (1), causing one side of the molecule to be partially negative and the other side to be partially positive.
Explain why electrons are pulled closer to the oxygen in a water molecule: (4)
- It is more electronegative (1)
- Because oxygen has a partial negative charge (1)
- So the oxygen side become more negative
- So the hydrogen side has a less negative but more positive charge.
State the bond that forms between hydrogen and oxygen atoms between different molecules: (1)
- Weak hydrogen bond (1)
Define the term cohesion: (1)
The ability of water molecules to attract and stick to other water molecules.
Describe how water molecules are kept together: (2)
- Through the weak hydrogen bonds (1)
- Between hydrogen and oxygen atoms (1)
Define the term xylem: (1)
Special pathway that is used to transport water and nutrients up the plant.
Explain how cohesion allows water to be moved up the xylem: (4)
- Hydrogen bonds between water molecules hold each other together (1)
- So they are cohesive and help to pull each other up.
- Transpiration allows water to be lost.
- So another water molecule is pulled up to replace it.
Define the term transpiration: (1)
- The process of water movement through a plant (1)
- And its evaporation from aerial parts, like leaves, stems and flowers.
Explain why water striders can ‘walk’ on water
- There are cohesive forces between molecules which creates surface tension
- The cohesive force (weak hydrogen bonds) takes more energy to break than the strider exerts
- So the surface of the water is maintained.
Define the term surface tension: (1)
When cohesive forces between liquid molecules allow the liquid to resist an external force. (1)
Define the term adhesion: (1)
The ability of water molecules to stick to other surfaces and molecules
Explain how adhesion occurs in soil: (5)
- Some materials in soil have polar properties.
- This allows water to form hydrogen bonds and stick to the soil
- This allows capillary action to occur
- Where water moves through spaces of a porous material.
- Which allows water to be absorbed by plant roots
Define the term capillary action: (2)
- The movement of water within spaces of a porous material. (1)
- Due to the forces of adhesion, cohesion and surface tension.
Explain how adhesion allows water to move up the plant:
- The xylem walls are made of lignin and are polar.
- Allows the xylem wall and water molecules to attract
- Creates tension which supports upward movement vs gravity.
Define the term hydrophilic: (1)
Substances that have a tendency to be attracted to water.
Explain why sodium chloride (salt) dissolves in water:
- Ionic bonds between sodium and chlorine atoms break apart into 2 charged ions. (1)
- Positively charged sodium will be attracted to the partially negative oxygen (1)
- The negatively charged chloride will be attracted to the partially positively charged hydrogen (1)
- Water molecules wrap around and encloses the ions. (1)
State what water can be described as: (1)
- A universal solvent (1)
Define the term metabolism: (1)
The sum of chemical reactions in the body that change food into energy.
Explain why phospholipids can make up the cell membrane: (1)
- They contain structures which are hydrophobic (1)
- These structures are more attracted to each other than the surrounding water
- This creates a barrier because they cannot dissolve in water. (1)
Define the term specific heat: (1)
The amount of energy needed to rise the temperature of a substance by 1 degrees celcious. (1)
Explain why water has a high specific heat:
- Due to hydrogen bonds that hold water molecules together (1)
- It takes a lot of energy to break these bonds and get water molecules to move. (1)
Explain why the specific heat capacity of water is a benefit to aquatic organisms: (3)
- Water can withstand large fluctuations in temperature (1)
- Which keeps things constant, such as body temperature. (1)
- This is because chemical reactions occur in the body. (1)
Define the term thermal conductivity: (1)
The rate at which heat can move through a material
Define the term buoyancy: (1)
The ability to float on water.
Explain how viscosity in water works: (1)
When molecules move, they tend to stick together due to the friction between them. (1)
Explain how the physical properties of water allow the Pusa hispida (Ringed seal) to survive: (6)
- Buoyancy (2)
- Viscosity (1)
- Thermal Conductivity (3)
- The seal is buoyant enough to keep its snout over the water. (1)
- This allows an easy supply of air. (1)
- The seal has a streamlined shape and paddle-life feet to overcome the viscosity of water. (1)
- Water has a high thermal conductivity. (1)
- They minimize heat loss by having a thick blubber under their skin. (1)
- This reduces heat loss from the seals internal organs. (1)
Explain how the physical properties of water allow the Gavia artica (Black-Throated Loon) to survive: (5)
- Buoyancy (1)
- Viscocity (2)
- Thermal conductivity: (2)
- The buoyancy of water allow it to keep afloat. (1)
- Webbed feet and streamlined body shape allows the loon to dive for fish and other food sources in the water. (1)
- It also allows the bird to overcome the viscosity of water and move along the surface. (1)
- They have an oil gland near the tail and rubs this on their feathers. (1)
- This makes them waterproof. (1)
Describe the temperature of water in the early times of Earth: (2)
- Exceeded 100 degrees celcious. (1)
- So it would have been boiled into gas and lost into space. (1)
Explain a theory how water was obtained on Earth: (1)
- Water was delivered from large, colliding asteroids. (1)
- Due to its position from the sun, water could be housed on the planet and exist in a liquid state. (1)
- The gravitational pull holds the water on earth. (1)
Explain why there is no water on Mars: (2)
- Due to the chemistry of the sediment that reacts with water. (1)
- Through hydration reactions (1)
Explain what will happen if a planet is: (5)
- Too close to a star (2)
- Too far from a star (2)
- Just right from the star (1)
- The temperature will be too great for water to exist. (1)
- So it will vapourise into a gas. (1)
- Water will exist as a solid. (1)
- By freezing into ice. (1)
- The liquid state of water can exist. (1)
