The Material world

Question 1

What is a solution?

Answer 1

A homogeneous mixture where a solute is dissolved in a solvent.

Question 2

What is the solute?

Answer 2

The substance being dissolved (usually smaller amount).

Question 3

What is the solvent?

Answer 3

The substance doing the dissolving (usually larger amount, like water).

Question 4

What are the 3 units of concentration?

Answer 4

1. g/L (grams per liter)
2. % (grams per 100 mL)
3. ppm (parts per million = grams per 1,000,000 mL)

Question 5

Practice Q: Convert 36g/100mL to g/L.

Answer 5

(36 ÷ 100) × 1000 = 360 g/L

Question 6

Practice Q: A 4% solution has how many grams of solute in 200 mL?

Answer 6

(4g/100mL) × 200mL = 8g

Question 7

Practice Q: 2g of salt in 500mL → concentration in g/L?

Answer 7

(2 ÷ 500) × 1000 = 4 g/L

Question 8

What is the pH scale?

Answer 8

A scale from 0 to 14 that measures the concentration of H⁺ ions in a solution.

Question 9

pH < 7 means…?

Answer 9

Acid

Question 10

pH > 7 means…?

Answer 10

Base

Question 11

pH = 7 means…?

Answer 11

Neutral (pure water)

Question 12

What are ions?

Answer 12

Charged atoms formed when electrons are gained or lost.

Question 13

R we gonna pass our exam

Answer 13

FUCK YES

Question 14

Practice Q: What type of substance is an electrolyte?

Answer 14

A substance that forms ions in water and conducts electricity (like NaCl).

Question 15

Practice Q: Which has higher conductivity — tap water or distilled water?

Answer 15

Tap water (it contains minerals/ions)

Question 16

Practice Q: Which will increase conductivity? A) Adding sugar B) Adding salt

Answer 16

B. Adding salt

Question 17

What is a chemical change?

Answer 17

A change that produces a new substance with different properties.

Question 18

What are 5 clues of a chemical reaction?

Answer 18

1. Colour change
2. Temperature change
3. Gas production
4. Precipitate formed
5. Light/sound emitted

Question 19

What is the law of conservation of mass?

Answer 19

In a chemical reaction, the total mass of reactants = total mass of products.

Question 20

Practice Q: 23g of Na reacts with 35g of Cl₂. How much NaCl is formed?

Answer 20

23 + 35 = 58g

Question 21

What is a balanced equation?

Answer 21

An equation where the number of atoms of each element is the same on both sides.

Question 22

BALANCE: H₂ + O₂ → H₂O

Answer 22

2H₂ + O₂ → 2H₂O

Question 23

BALANCE: C₃H₈ + O₂ → CO₂ + H₂O

Answer 23

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

Question 24

What is combustion?

Answer 24

A reaction where a substance reacts with O₂ to produce CO₂, H₂O, and energy.

Question 25

What are the 3 requirements for combustion?

Answer 25

1. Fuel 2. Oxygen 3. Ignition temp

Question 26

What are the types of combustion?

Answer 26

- Complete (blue flame, CO₂ + H₂O) - Incomplete (orange flame, CO + soot)

Question 27

What is acid-base neutralization?

Answer 27

Acid + Base → Salt + Water

Question 28

Example: HCl + NaOH → ?

Answer 28

NaCl + H₂O

Question 29

What is photosynthesis?

Answer 29

6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂

Question 30

What is cellular respiration?

Answer 30

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy

Question 31

Which organelle does photosynthesis?

Answer 31

Chloroplast (plants only)

Question 32

Which organelle does respiration?

Answer 32

Mitochondria (in plants & animals)

Question 33

Practice Q: Which is a combustion reaction? A) 2Na + Cl₂ → 2NaCl B) CH₄ + O₂ → CO₂ + H₂O

Answer 33

B

Question 34

What is the Rutherford-Bohr model?

Answer 34

A model of the atom with protons/neutrons in the nucleus and electrons in orbits.

Question 35

What does the atomic number represent?

Answer 35

Number of protons (and electrons in a neutral atom).

Question 36

How do you calculate neutrons?

Answer 36

Mass number - atomic number = neutrons

Question 37

What are valence electrons?

Answer 37

Electrons in the outermost shell of an atom.

Question 38

Why are valence electrons important?

Answer 38

They determine chemical reactivity and bonding.

Question 39

What do groups (columns) in the periodic table indicate?

Answer 39

Same number of valence electrons.

Question 40

What do periods (rows) in the periodic table indicate?

Answer 40

Same number of electron shells.

Question 41

What types of elements are on the left of the periodic table?

Answer 41

Metals — good conductors, malleable, solid

Question 42

What types of elements are on the right?

Answer 42

Non-metals — poor conductors, brittle

Question 43

Practice Q: How many valence electrons in oxygen (Group 16)?

Answer 43

6

Question 44

Practice Q: Which atom is more reactive, Na (Group 1) or Ne (Group 18)?

Answer 44

Na — wants to lose 1 e⁻, Ne is stable

Question 45

What is electric current?

Answer 45

The flow of electric charge through a conductor.

Question 46

Formula for current?

Answer 46

I = q / Δt

Question 47

Units for current?

Answer 47

Amperes (A)

Question 48

What is voltage?

Answer 48

The difference in electric potential between two points.

Question 49

Formula for voltage?

Answer 49

V = E / q

Question 50

What is resistance?

Answer 50

The opposition to current flow in a material.

Question 51

Ohm’s Law?

Answer 51

V = I × R

Question 52

Practice Q: A current of 2 A flows through a 6Ω resistor. What is the voltage?

Answer 52

V = 2 × 6 = 12V

Question 53

Practice Q: Resistance = 10Ω, Voltage = 5V → Current?

Answer 53

I = V/R = 5 ÷ 10 = 0.5 A

Question 54

What is electrical power?

Answer 54

P = V × I

Question 55

Units for power?

Answer 55

Watts (W)

Question 56

Formula for electrical energy?

Answer 56

E = P × Δt

Question 57

Practice Q: A 60W bulb runs for 2 hours. Energy used?

Answer 57

60 × 7200 = **432,000 J**

Question 58

Conversion: 1 kWh = ?

Answer 58

3.6 million joules (3.6 × 10⁶ J)

Question 59

What causes a magnetic field?

Answer 59

Moving electric charges.

Question 60

What is an electromagnet?

Answer 60

A coil of wire (solenoid) wrapped around a metal core that becomes magnetic when current flows.

Question 61

What increases electromagnet strength?

Answer 61

- More coils - More current - Iron core

Question 62

What is the direction of magnetic field lines?

Answer 62

From north to south outside the magnet.

Question 63

What happens if you break a magnet in half?

Answer 63

You get two magnets, each with its own N & S pole.

Question 64

What is the rule for charged particles?

Answer 64

Like charges repel, opposite charges attract.

Question 65

What is the law of conservation of energy?

Answer 65

Energy cannot be created or destroyed — only transformed.

Question 66

What is energy efficiency?

Answer 66

The percentage of energy converted into useful energy.

Question 67

What is the formula for energy efficiency?

Answer 67

Formula: Efficiency (%) = (Useful energy / Total energy) × 100

Question 68

Practice Q: A device uses 1200J and outputs 900J of useful energy. What’s the efficiency?

Answer 68

(900 / 1200) × 100 = 75%

Question 69

Practice Q: A fan is 80% efficient and uses 400J. How much useful energy?

Answer 69

400 × 0.8 = 320J

Question 70

What are some examples of energy transformations?

Answer 70

1. Battery: chemical → electrical 2. Bulb: electrical → light + heat 3. Motor: electrical → mechanical

Question 71

What is electrical charge?

Answer 71

A physical property of matter that causes it to experience a force when near other charged matter; measured in coulombs (C)

Question 72

What is static electricity?

Answer 72

A build-up of electric charge on the surface of an object, usually caused by friction

Question 73

What are the three methods of charging?

Answer 73

Friction, conduction, and induction

Question 74

What is charging by friction?

Answer 74

Transferring electrons between objects by rubbing them together

Question 75

What is charging by conduction?

Answer 75

A charged object touches a neutral one, sharing its charge

Question 76

What is charging by induction?

Answer 76

A charged object is brought near a neutral one, causing a temporary separation of charges

Question 77

What happens when two objects with the same charge interact?

Answer 77

They repel each other

Question 78

What happens when two objects with opposite charges interact?

Answer 78

They attract each other

Question 79

What is the magnetic field of a live wire?

Answer 79

A circular magnetic field around a current-carrying wire

Question 80

How do you determine the direction of a magnetic field around a wire?

Answer 80

Use the Right-Hand Rule: Thumb = current, curled fingers = magnetic field direction

Question 81

What are forces of attraction and repulsion?

Answer 81

Like charges repel; opposite charges attract

Question 82

What is Coulomb’s Law (in simple terms)?

Answer 82

The electric force increases with more charge and decreases with more distance