The Material world

Question 2

What is concentration?

Answer 2

The amount of solute dissolved in a given quantity of solution.

Question 3

What are the main units used for concentration?

Answer 3

• g/L
• % (m/V)
• % (m/m)
• ppm

Question 4

What does g/L mean?

Answer 4

Grams of solute per liter of solution.

Question 5

What does % (m/V) mean?

Answer 5

Grams of solute per 100 mL of solution.

Question 6

What does ppm mean?

Answer 6

Milligrams of solute per 1 liter of solution.

Question 7

Convert: 3.5 g/L to ppm.

Answer 7

3.5 g/L × 1000 = 3500 ppm

Question 8

Convert: 0.025% (m/V) to ppm.

Answer 8

0.025 × 10,000 = 250 ppm

Question 9

If 6 g of salt is dissolved in 200 mL of solution, what is the concentration in % (m/V)?

Answer 9

(6 ÷ 200) × 100 = 3%

Question 10

What does the pH scale measure?

Answer 10

The acidity or basicity of a substance.

Question 11

What pH values are acidic?

Answer 11

Below 7

Question 12

What pH values are basic?

Answer 12

Above 7

Question 13

What is the pH of a neutral substance?

Answer 13

7

Question 14

How much more acidic is a solution with pH 3 compared to pH 5?

Answer 14

100x (10 × 10)

Question 15

What are common acidic substances?

Answer 15

• Lemon juice (pH 2)
• Vinegar (pH 2.2)

Question 16

What are common basic substances?

Answer 16

• Soapy water (pH 10)
• Baking soda (pH 8.3)

Question 17

What is an ion?

Answer 17

An atom or molecule that has gained or lost electrons and has a charge.

Question 18

How do metal atoms become ions?

Answer 18

By losing electrons (positive ions).

Question 19

How do non-metal atoms become ions?

Answer 19

By gaining electrons (negative ions).

Question 20

What allows a solution to conduct electricity?

Answer 20

Mobile ions in solution (electrolytic dissolution).

Question 21

What happens when HBr dissolves in water?

Answer 21

It dissociates into H⁺ and Br⁻ ions, making the solution conductive.

Question 22

What are the 3 components of the fire triangle for combustion?

Answer 22

• Fuel
• Oxidizing agent
• Ignition temperature

Question 23

What is combustion?

Answer 23

A chemical reaction with oxygen that releases heat and light.

Question 24

Give the balanced equation for photosynthesis.

Answer 24

6 CO₂ + 6 H₂O + energy → C₆H₁₂O₆ + 6 O₂

Question 25

Give the balanced equation for cellular respiration.

Answer 25

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy

Question 26

What is an acid-base neutralization reaction?

Answer 26

A reaction between an acid and a base to produce salt and water.

Question 27

What is the general form of a neutralization reaction?

Answer 27

Acid + Base → Salt + Water

Question 28

Example: What are the products of HCl + NaOH?

Answer 28

NaCl + H₂O

Question 29

What is the law of conservation of mass?

Answer 29

Mass is not created or destroyed during a chemical reaction.

Question 30

If 10g of Na reacts with 15g of Cl to form NaCl, what is the mass of the product?

Answer 30

25g

Question 31

Balance: H₂ + O₂ → H₂O

Answer 31

2 H₂ + O₂ → 2 H₂O

Question 32

Balance: C₂H₆ + O₂ → CO₂ + H₂O

Answer 32

2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O

Question 33

What is the Rutherford-Bohr model?

Answer 33

An atomic model where electrons orbit a dense, positively charged nucleus.

Question 34

What is the charge and location of a proton?

Answer 34

Positive, in the nucleus

Question 35

What is the charge and location of an electron?

Answer 35

Negative, in orbitals

Question 36

What does the group number on the periodic table tell you?

Answer 36

Number of valence electrons

Question 37

What does the period number tell you?

Answer 37

Number of electron shells

Question 38

What do elements in the same group have in common?

Answer 38

Similar chemical properties and same number of valence electrons

Question 39

What is an electrical charge?

Answer 39

A physical property of particles like electrons and protons.

Question 40

What is static electricity?

Answer 40

An imbalance of charges typically caused by friction.

Question 41

How do objects with the same charge interact?

Answer 41

They repel.

Question 42

How do objects with opposite charges interact?

Answer 42

They attract.

Question 43

What is Ohm’s Law?

Answer 43

V = IR

Question 44

Calculate: What is the voltage across a 4Ω resistor with 3A current?

Answer 44

V = 4 × 3 = 12V

Question 45

Calculate: A resistor has 6Ω and voltage is 18V. What is the current?

Answer 45

I = V/R = 18/6 = 3A

Question 46

What is the role of a battery in a circuit?

Answer 46

Provides energy and a potential difference.

Question 47

What does a resistor do in a circuit?

Answer 47

Slows down current and converts energy to another form.

Question 48

What is a series circuit?

Answer 48

A circuit where components are connected end to end.

Question 49

What is a parallel circuit?

Answer 49

A circuit where components are on separate branches.

Question 50

What is the difference between AC and DC?

Answer 50

AC reverses direction; DC flows in one direction.

Question 51

What is the formula for electrical power?

Answer 51

P = VI

Question 52

What is the formula for electrical energy?

Answer 52

E = PΔt

Question 53

Calculate: What is the power if V = 12V and I = 2A?

Answer 53

P = 12 × 2 = 24W

Question 54

Calculate: How much energy is used by a 1000W device in 2 hours?

Answer 54

E = PΔt = 1000W × 2h = 2000 Wh or 2 kWh

Question 55

Convert 2000 J to kJ.

Answer 55

2000 ÷ 1000 = 2 kJ

Question 56

Convert 3600 s to hours.

Answer 56

3600 ÷ 3600 = 1 h

Question 57

What happens when two magnets with the same poles are near each other?

Answer 57

They repel.

Question 58

What is the direction of magnetic field lines?

Answer 58

From North to South

Question 59

What is the Right-Hand Rule?

Answer 59

Point your thumb in direction of current; curled fingers show magnetic field direction.

Question 60

How can you increase the magnetic field strength of a wire?

Answer 60

Increase current or use better conductor.