Chemistry

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4

Mr. Davis performs a chemical reaction for the class. Which of these does NOT show evidence that a chemical reaction has occurred ?

Change in color

Change in shape

Formation of gas

Formation of a precipitate

Slide 36

Which is the correct symbol for the element sodium?

S

Se

Cl

Na

Slide 37

Which statement is usually true about the electrical properties of metals?

Metals have high electrical resistance.

Lightweight metals are the best conductors.

Metals and plastics are both good insulators.

Metals are good electrical conductors.

Slide 38

Students poured different liquids to see how the liquids became layered. The denser liquids at the bottom, the lighter liquids at the top. What tool was used in this experiment?

a balance scale

a thermometer

a magnet

a graduated cylinder

Slide 39

Tom places four objects in a tank of water. He makes the following observations. Which statement is correct based on Tom's observations?

The rock and the chalk have a density greater than water.

The rock and the chalk have a density less than water.

The cork and the can of soda have a density equal to water.

The cork and the can of soda have a density greater than water

Slide 40

The chemical symbol Al represents which metal on the periodic table?

arsenic

antimony

aurum

aluminum

Slide 41

Covalent bond

P+1

when two atoms share a pair of electrons.

P+1

Slide 42

Covalent bond

when two atoms share a pair of electrons.

P+1

P+1

It’s like both atoms have a filled orbital.

Slide 43

Covalent Bond

The sharing of a pair of electrons between 2 atoms.

(or even 2 or 3 pairs of electrons).

H2

Slide 44

Covalent Bond

The sharing of a pair of electrons between 2 atoms.

Li2

Slide 45

When one oxygen and two hydrogen atoms combine, what forms?

a different atom

a different element

a molecule

a neutron

Slide 46