STEM quiz

When an acid reacts with an alkali,

what is the process known as? State the products of the

reaction.

• Neutralisation; Oxygen gas and

  water

• Precipitation;

  Salt and water

• Neutralisation;

  Salt and water

• Precipitation; Insoluble salt and water

Answer explanation

Neutralisation is the process of forming a neutral substance (salt) by reacting an alkali and acid. Water (H2O) is formed through the reaction between hydroxide ion (OH-) and hydrogen ion (H+).

What is the observation made when red litmus paper

is added to solid/anhydrous sodium hydroxide? (Sodium hydroxide

is an alkali.)

• No change occurs

  (Red litmus paper

  remains red)

• Red litmus paper turns blue

• Red litmus paper decolourises

• Red litmus paper turns green

Answer explanation

Sodium hydroxide can only show its alkaline properties when it dissolves in water. (Ionises to form hydroxide ions, which turns moist red litmus paper blue)

An acid is a chemical substance with a pH level that is _______ than 7.

It is given that acid sample A has a pH level of pH 5.2 while acid sample

B is pH 2.6. Which acid is the stronger acid?

• Acid sample A

• Acid sample B

What are the ways to differentiate between an acid and an alkali? (Choose two)

• Blue and red litmus papers

• Phenolphthalein indicator

• Methyl-blue indicator

• Drinking it

Answer explanation

Why would you drink acid..

What are examples of alkali in our daily lives? (Choose two)

• Baking soda

• Vinegar

• Citrus fruits

• Ammonia

Answer explanation

Baking soda is a base that reacts with acids from butter (made of fatty acids) to release carbon dioxide. Carbon dioxide acts to make baked foods fluffy and leavened.

What are the two main types of electrical circuit?

• Congruent circuit

• Parallel circuit

• Perpendicular circuit

• Series circuit

When the switch is turned on, why does the bulb light up?

• Presence of potential difference

• Resistance in circuit

• Flow of electric current through the circuit

• The bulb absorbs photons from the Sun

Answer explanation

Potential difference is also known as voltage. Voltage is often known as the force that pushes electrons to flow out through the electric circuit from the negative terminal to the positive terminal.

A given series circuit has 4 light bulbs connected within the circuit. What happens when

one of the light bulb burns out?

• The circuit explodes

• The other light bulbs remain still light up

• The other light bulbs also burn out

• The light bulb that burnt out explodes

How is electrical current produced?

• Flow of electrons from the positive terminal to the negative terminal of the circuit

• Flow of photons through the electrical circuit

• Presence of potential difference that pushes electrons through the circuit

• Magic