CS Week 2. TLB

A student calibrates an unmarked liquid-in-glass thermometer by marking the column when the thermometer is in steam at 100°C and when it is in melting ice at 0°C. He then uses the thermometer to find the temperature of some melted wax. The diagram shows the marks and measurements made by the student.

What is the temperature of the melted wax?

• 15°C

• 20°C

• 75°C

• 130°C

Answer explanation

100°C ÷ 20 cm = 5°C per cm.

Mark for melted wax is at 15cm, therefore, 

15 cm X 5°C per cm = 75°C.

Which row correctly shows examples of transverse and longitudinal waves?

• A

• B

• C

• D

A ray of light travels from air into glass. The refractive index of the glass is 1.5. Which of the following pairs of angles are correct?

• A

• B

• C

• D

Answer explanation

Refractive index, n = sin i / sin r 

I is angle of incidence and r is angle of refraction

The heat from the hot water in a metal radiator passes through the metal and then spreads around the room.

What are the main processes by which the heat is transferred?

• A

• B

• C

• D

To protect a polished table, a cork mat may be put on the table underneath a mug containing hot liquid.

Why is this effective?

• Cork is a good conductor

• Cork is a good radiator

• Cork is a poor conductor

• Cork  is a poor radiator

Answer explanation

Cork is usually made up of  poor conducting materials .

The equation shows the reaction between sodium and water. 

xNa + yH2O → 2NaOH + H2 

What are the values of x and y for the equation to be balanced? 

• X = 1

  Y = 1

• X = 1

  Y = 2

• X = 2

  Y = 1

• X = 2

  Y = 2

Answer explanation

Count the atoms for each elements on the right and left side off the equation and match the number of atoms left and right side 

A spatula measure of compound Z is stirred into a beaker containing some dilute hydrochloric acid. Another spatula measure of Z is stirred into a beaker of aqueous sodium hydroxide. In both experiments, Z dissolves and a neutral solution is made. What is Z? 

• A basic Oxide

• A Carbonate

• An acidic Oxide

• An amphoteric Oxide

Steel objects are often galvanised to prevent rusting. Galvanising involves coating the object by dipping it in a molten metal. Which metal is used? 

• Chromium

• Lead

• Tin

• Zinc

Answer explanation

Zinc is more reactive than any kind of steel, so it protects steel.

Q, R, S and T are four metals. 

T reacts slowly with hydrochloric acid. 

Q does not react with acid. 

R reacts with steam but not with cold water. 

S reacts violently with cold water. 

What is the order of reactivity of the four metals, most reactive first? 

• Q -> T -> R -> S

• Q -> R -> T-> S

• S -> Q -> R -> T

• S -> R -> T -> Q

Answer explanation

S is the most reactive as it can react to cold water 

  

Q is the least reactive as it doesn’t react with acid 

R is more reactive than T because R can react with cold water whereas T reacts slowly with hydrochloric acid

A number of different reactions produce hydrogen gas. Which pair of reactions both produce hydrogen?

• A

• B

• C

• D

Answer explanation

Remember the general equations for these reactions 

  

Equations that produce hydrogen: 

  

1. Metal + Acid -> Salt + Hydrogen 

  

2. Metal + water -> Metal hydroxide + hydrogen 

  

Doesn’t produce hydrogen: 

  

1. Acid + alkali -> Salt + water 

2. Acid + Carbonate -> Salt + water + carbon dioxide