Explanation:
Friction occurs because no surface is perfectly smooth. Rougher surfaces have more friction between them. Heavier objects also have more friction because they press together with greater force. Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.
It is b. sodium because it is in group 1
<h3><u>Answer;</u></h3>
<em>too small to be seen with an optical microscope </em>
<h3><u>Explanation;</u></h3>
- <em><u>An electron microscope is a type of microscope that is used to observe very tiny specimens whose features can not be observed by other types of microscopes.</u></em> It uses a beam of electrons to generate an image of a given specimen whose features can be clearly observed and studied.
- <em><u>Electron microscope has very high resolution and magnification as compared to other optical microscope </u></em>hence can be observed in the study of micro-organisms such as viruses which would be difficult to study their features using optical microscopes.
1 liter = 1000 cm^3
20cm * 20cm * 20cm = 8000 cm^3
8000/1000 = 8 liters
Since 1ml of water = 1 cm^3 = 1 grams
8 liters = 8000 grams = 8 kilograms