A. It has mass.
Air is matter, and can't be seen thus not all matter can be seen.
Any liquid or gaseous is matter (water, air, etc.)
Since it can be liquid or gaseous it doesn't have to maintain it's shape and size to be matter.
Answer:
1677
Explanation:
Robert Plot discovered the first dinosaur bone, they thought It was just a human bone but later they found out it was a dinosaur bone.
Answer:
Malignant tumors are cancerous. They develop when cells grow uncontrollably. If the cells continue to grow and spread, the disease can become life threatening. Malignant tumors can grow quickly and spread to other parts of the body in a process called metastasis.
Answer: Van der Waals forces
Explanation:
Van der Waals forces are weak intermolecular forces that depend on the distance between two particles. They are caused by correlations in the change in polarization between two nearby particles. To put it in other words, when a particle changes its polarization (becomes more positive on one end and more negative on the other), so does the adjacent particle, and the next one, and so on. This causes these particles to stick together weakly.
The tiny "hairs" increase the surface area of the gecko's feet in contact with the wall, which makes the bond stronger and allows it to support all of its weight.
Because experiments have shown that geckos stick well to both hydrophobic and hydrophilic surfaces, we can assume there aren't any hydrogen bonds present.
Ionic bonds can't be present either because geckos wouldn't stick to electrically neutral surfaces, as these bonds require charged molecules.
