Chemistry Unit

Question 1

What is a pure substance?

Answer 1

Made of only one type of particle.

Example: Water (H₂O), Aluminum (Al)

Question 2

What is a mixture?

Answer 2

Made of more than one kind of particle, not chemically combined.

Example: Salad, air

Question 3

What is cohesion?

Answer 3

When water sticks to itself.

Example: Water droplets

Question 4

What is adhesion?

Answer 4

When water sticks to other substances.

Example: Water on glass

Question 5

What is a chemical change?

Answer 5

A change that results in a new substance with different properties.

Example: Burning wood

Question 6

What is a physical change?

Answer 6

A change in form or appearance, but the substance stays the same.

Example: Melting ice

Question 7

What is density?

Answer 7

The amount of matter in a certain space (mass ÷ volume).

Unit: g/cm³ or g/mL

Question 8

What is mass?

Answer 8

The amount of matter in an object.

Unit: grams (g) or kilograms (kg)

Question 9

What are the charges and masses of the 3 subatomic particles?

Answer 9

Protons: 1+, heavy
Neutrons: 0, heavy
Electrons: 1−, light

Question 10

What are the two categories of pure substances?

Answer 10

Element: One kind of atom (e.g., Oxygen).
Compound: Two or more elements chemically combined (e.g., H₂O).

Question 11

What is a homogeneous mixture?

Answer 11

Looks the same throughout.

Example: Milk, ketchup

Question 12

What is a heterogeneous mixture?

Answer 12

You can see the different parts.

Example: Chocolate chip cookie, salad

Question 13

Name 3 properties to tell melted ice cream from milk.

Answer 13

Ice cream: Pink, sweet, sticky.
Milk: White, thin liquid, lighter density.

Question 14

Density formula?

Answer 14

D = m / V

Question 15

Volume formula?

Answer 15

V = m / D

Question 16

Mass formula?

Answer 16

m = D × V

Question 17

Calculate the density of 50g mass and 20mL volume.

Answer 17

D = 50g / 20mL = 2.5 g/mL

Question 18

Volume of a lead block with mass 5kg and density 55g/cm³?

Answer 18

V = 5000g / 55g/cm³ = 90.9 cm³

Question 19

Mass of gold bar with density 19.3g/cm³ and volume 50cm³?

Answer 19

m = 19.3 × 50 = 965g

Question 20

If a gold bar weighs twice as much, what changes?

Answer 20

Mass and volume increase. Density stays the same.

Question 21

If an object weighs 2000g, will it float in water?

Answer 21

Not enough info — need volume to calculate density.

Question 22

Who proposed the 4 atomic models?

Answer 22

Dalton: Solid sphere
Thomson: Plum pudding
Rutherford: Nucleus with electrons outside
Bohr: Electrons in energy levels

Question 23

Physical or Chemical Change?
Ripping paper → ?

Answer 23

Physical

Question 24

Physical or Chemical Change?
Burning paper → ?

Answer 24

Chemical

Question 25

Physical or Chemical Change? Boiling water → ?

Answer 25

Physical

Question 26

Physical or Chemical Change? Vinegar + baking soda → ?

Answer 26

Chemical

Question 27

Words that indicate chemical or physical change: Colour change → ?

Answer 27

Chemical

Question 28

Words that indicate chemical or physical change: Melting → ?

Answer 28

Physical

Question 29

Words that indicate chemical or physical change: Bubbles → ?

Answer 29

Chemical

Question 30

Words that indicate chemical or physical change: Boiling → ?

Answer 30

Physical

Question 31

Words that indicate chemical or physical change: Evaporating → ?

Answer 31

Physical

Question 32

Words that indicate chemical or physical change: Precipitate forms → ?

Answer 32

Chemical

Question 33

Which subatomic particle has almost no mass?

Answer 33

Electron

Question 34

What is found in the nucleus?

Answer 34

Protons and neutrons

Question 35

What determines the mass of an atom?

Answer 35

Protons + Neutrons

Question 36

Is a chocolate chip cookie an element, compound, or mixture?

Answer 36

Heterogeneous mixture

Question 37

Is lead an element, compound, or mixture?

Answer 37

Element

Question 38

What is matter?

Answer 38

Anything that has mass and takes up space.

Question 39

Neon is an example of what?

Answer 39

Element, Pure Substance, Noble Gas (All of the above)