4. 10. *Water is a good solvent in living organisms. 1 10 9. Hydrogen bonds are stronger then covalent bonds. 9 2 8. An atom that has gained or lost electron is called an ion. 1 10 7. If solution-A has a pH of 2 and solution-B has a pH of 5 then solution-B is a stronger base then solution-A 2 9 6. *Atoms in a water molecule are held together by the sharing of electrons. 2 9 5. *Ice floats because water molecules in ice are more tightly packed then in liquid water. 10 1 4. *If the atmos in a molecule share electrons equaly, the molecule is said to be non-polar. 1 10 3. A bathtub full of lukewarm water may hold more heat than a teakettle full of boilling water. 3 8 2. The smallest particle of an element is a molecule. 10 1 1. Table salt, water, and carbon are all compounds. 8 3 FALSE TRUE
18. LE 2-4a 2 2 2 Protons Neutrons Electrons Helium atom Mass number = 4 6 6 6 Protons Neutrons Electrons Carbon atom Mass number = 12 Electron cloud Nucleus 2e – 6e –
20. LE 2-6a Electron Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Hydrogen (H) Atomic number = 1 Carbon (C) Atomic number = 6
21. LE 2-6b Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8
22. LE 2-7 Transfer of electron Na Sodium atom Cl Chlorine atom Na Sodium ion Cl Chloride ion Sodium chloride (NaCl)
39. LE 2-15 Acidic solution OH H H H H OH H H H OH OH OH OH OH H H H H H H Increasingly ACIDIC (Higher concentration of H ) Neutral solution OH OH OH OH OH OH H H Basic solution NEUTRAL H pH scale Lemon juice, gastric juice Grapefruit juice, soft drink Tomato juice Human urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Oven cleaner Increasingly BASIC (Lower concentration of H )