Answer:
1) The statements describing solids are:
b) The particles vibrate on the spot.
e) The particles stay in contact and slide past one another as they move.
The particles are in fixed positions, close to one another.
The statements describing liquids are:
c) The particles are close to one another but can move around.
The statements describing gases are:
a) Particles are far apart and rarely collide with each other.
d) The particles move freely in all directions.
2) When substances diffuse into and out of cells, they must move through the cell membrane. The cell membrane acts as a barrier that separates the inside of the cell from its surroundings. It is selectively permeable, allowing certain substances to pass through while blocking others.
3) The energy for diffusion comes from the random motion of particles. In a substance, the particles are constantly moving due to their kinetic energy. This random motion leads to collisions between particles and causes them to spread out from an area of high concentration to an area of low concentration, which is the process of diffusion.
4) Three examples of diffusion in organisms are:
- The exchange of oxygen and carbon dioxide in the lungs:
In the respiratory system, oxygen from the air diffuses into the bloodstream, while carbon dioxide, a waste product, diffuses out of the bloodstream and into the air in the lungs. Oxygen is a gas, and carbon dioxide is also a gas.
- The absorption of nutrients in the small intestine:
In the digestive system, nutrients from the digested food diffuse across the walls of the small intestine and into the bloodstream. These nutrients include molecules such as glucose and amino acids, which are solutes.
- The movement of substances across cell membranes:
In cells, various substances such as ions, water, and small molecules diffuse across the cell membrane. For example, ions like sodium and potassium diffuse through ion channels, water molecules diffuse through specialized channels called aquaporins, and small molecules like oxygen and carbon dioxide diffuse directly through the lipid bilayer of the membrane. The substances being diffused can be gases or solutes, depending on the specific case.