Chemistry - concrete, copper + alloys

Question 1

What is the symbol expression for calcium carbonate?

Answer 1

CaCO3

Question 2

Give the symbol equation for calcium carbonate being heated to break down and form calcium oxide and carbon dioxide

Answer 2

CaCO3 -> CaO + CO2

Question 3

symbol euation for calcium oxide + water -> calcium hydroxide

Answer 3

CaO + H2O -> Ca(OH)2

Question 4

what does cement + sand + water give?

Answer 4

Mortar

Question 5

what does cement + sand + agrregate + water give?

Answer 5

Concrete

Question 6

copper metal is extracted by heating crushed ore with carbon. Why does this work?

Answer 6

Because carbon is more reactive than copper

Question 7

Malachite is a green mineral containing copper carbonate. It breaks down (decomposes) to form copper oxide and carbon dioxide when heated. Give the symbol equation

Answer 7

CuCO3 -> CuO + CO2

Question 8

copper oxide is heated wth carbon to form copper and carbon dioxide. This is a reduction reaction because oxygen is removed. Give the symbol equation

Answer 8

2CuO + C -> 2Cu + CO2

Question 9

Copper (II) sulfate solution is an electrolyte. What does this term mean?

Answer 9

A liquid that conducts electricity

Question 10

Negatively charged cathode is pure copper. During electrolysis, copper is deposited and the cathode gains mass. Give the symbol equation

Answer 10

Cu2+ + 2e- -> Cu (reduction)

Question 11

Positively charged anode is impure copper. During electrolysis, copper dissolves and it loses mass. Give the symbol equation

Answer 11

Cu - 2e- -> Cu2+ (oxidation) which is oxidation because electrons are lost

Question 12

What is an alloy?

Answer 12

a mixture of two or more elements, at least one of which is a metal

Question 13

What is amalgam used for?

Answer 13

tooth fillings

Question 14

What does amalgam mainly contain?

Answer 14

mercury

Question 15

What is brass used for?

Answer 15

musical instruments and coins

Question 16

What does brass mainly contain?

Answer 16

copper and zinc

Question 17

What is solder used for?

Answer 17

joining electrical wires

Question 18

What does solder mainly contain?

Answer 18

lead and zinc

Question 19

What are smart alloys? GIve an example too

Answer 19

otherwise known as ‘shape-memory alloys’ - when bent out of shape, they return to their original shape when heated. For example, nitinol is used for spectacle frames. The composition of the alloy is adjusted during manufacture to ensure the frame returns to its original shape below room temperature. If someone sits on theuir glasses, the frame returns to its original shape when they stand up again.