General
What is an indicator and what is its use?
Indicators are substances used to test the pH (acidity level) of another substance by changing colour according to the pH strength.
The melting of ice is a (physical/chemical) change.
The reactants are on the left of a chemical equation.
Which pH is neutral?
pH 7
Define half life of a radioisotope.
The time it takes for half of a radioisotope to decay.
What is heartburn and where does it occur?
Heartburn occurs in the stomach when the stomach acid is too acidic, and affects
List 2 examples of physical changes.
What does the arrow represent in chemical equations?
The arrow means 'chemically combine to form' or 'chemically reacts to produce' and shows the way that the reaction proceeds.
The reactants 'chemically combine to form' the products.
The reactants --> the products.
the pH scale goes from which number to which number?
1 to 14.
Beta Several m of concrete or lead
Gamma piece of paper
Alpha 3mm of aluminum
Alpha: piece of paper
Beta: 3mm of aluminumGamma: several m of concrete or lead
MgCl2
How many magnesium ions and chlorine ions are present in this formula?
Mg = 1
Cl = 2
List 2 examples of chemical changes.
Many correct answers: Eg. the body breaking down glucose, wood burning, acids and bases reacting to give salt and water
State the law of conservation of mass.
Matter cannot be created or destroyed, only converted from one form into another. The mass of the products must equal the mass of the reactants.
The antacid neutralises the stomach acid to salt and water, making the overall environment less acidic.
Explain the atomical difference between Carbon 12 and 14.
They are isotopes, meaning they have a different amount of neutrons. Carbon 12 has 6 and Carbon 14 has 8.
A reaction produces bubbles of gas and an increase in temperature. What type of reaction is this?
Chemical reaction - exothermic.
is photosynthesis an endothermic or exothermic reaction?
Endothermic - it required energy from the sun to raise the energy of the reactants enough to chemically combine.
Write a general chemical word equation for a neutralisation reaction.
Acid + base --> salt + water
List 2 common acids and 2 common bases.
Bases: bicarb (baking) soda, antacid tablets, soap, bleach
Cobalt-60 has a half life of 5 years. How many years would it take until a quarter of the sample of Cobalt-60 remains?
10 years
Working:
After 5 years we have half remaining, after 10 years we have a quarter remaining.
Fill in the missing blanks
Magnesium + --> magnesium oxide
23 g + --> 62 g
Magnesium + Oxygen --> magnesium oxide
23 g + 39 g --> 62 g
List 5 signs that a chemical reaction has taken place.
colour change, precipitation (production of a solid), fizzing (production of gas), temperature change (hotter or colder), production of light, explosion
Write a general word equation for a neutralisation reaction between an acid and a carbonate.
acid + carbonate --> salt + water + carbon dioxide
What would happen if water is added to dilute the substance?
The red colour tells us the substance is acidic. If it is diluted, it would become weaker and less acidic and potentially turn orange.
Four half lives = 15 atoms left
working:
1) 240/2 = 120
2) 120/2 = 60
3) 60/2 = 30
4) 30/2 = 15