Chemistry Mid Term

Question 0

Heterogeneous mixture

Answer 0

Usually, it’s possible to physically separate components of a heterogeneous mixture

Question 1

Homogeneous mixture

Answer 1

You can’t use a simple mechanical means to separate them

Question 2

Scientific method

Answer 2

search for cause and effect relationships in nature.

Question 3

Chemical properties v.s. Physical change

Answer 3

A chemical property may only be observed by changing the chemical identity of a substance.

A physical property is an aspect of matter that can be observed or measured without changing it

Question 4

Indicators of Chemical Change

Answer 4

Change in Temperature.
Change in Color.
Noticeable Odor (after reaction has begun)
Formation of a Precipitate.
Formation of Bubbles.

Question 5

Chemistry prefixes

Answer 5

The prefix Kilo (k) - means 1000 times. The prefix Hecto (h) - means 100 times The prefix Deka (dk) - means 10 times. The prefix Deci (d) - means 0.1 times. The prefix Centi (c) - means 0.01 times. The prefix Milli (m) - means 0.001 times.

Question 6

Thomson’s Model

Answer 6

Plum pudding model

Question 7

Rutherford Model

Answer 7

Nuclear Model

Question 8

Dalton’s model

Answer 8

Billiard ball model - atoms are solid and invisible

Question 9

Thompson’s model

Answer 9

Raisin bun - negative electrons in a positive framework

Question 10

Rutherford’s model

Answer 10

The Rutherford model - Atoms are mostly empty space.

Negative electrons orbit a positive nucleus.

Question 11

The three laws

Answer 11

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1st Law, Law of Mass Conservation Matter is neither created nor destroyed in ordinary chemical reactions

2nd Law, Law of Definite Proportions Different samples of a pure compound always contains the same proportions of elements by mass

3rd Law, Law of Multiple Proportions Elements can combine in different ways to form different chemical compounds, with mass ratios that are small whole-number multipules of each other

Question 12

Thompson’s experiment

Answer 12

Used the cathoray tube. When a cathode ray was seen on the tube, it
(a) Bent toward the + plate and
(b) Bent away from the negative plate
Bent toward one pole of a magnet and away from the other

Question 13

Rutherford’s experiment

Answer 13

Rutherford shot alpha (α) particles at gold foil. Most particles passed through. So, atoms are mostly empty.
Some positive α-particles deflected or bounced back!
Thus, a “nucleus” is positive & holds most of an atom’s mass.

Question 14

Dobereiner

Answer 14

classified some elements into groups of three, which he called triads

Question 15

Newlands

Answer 15

he suggested that elements be arranged in “octaves” because he noticed that certain properties repeated every 8th element.

Question 16

Mendeleev

Answer 16

he published a table of the elements organized by increasing atomic mass

Question 17

Mosley

Answer 17

he determined the actual nuclear charge (atomic number) of the elements

Question 18

Seaborg

Answer 18

After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below