Chemical reactions Flashcards
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What is a physical change?
Physical change:
-No new substances formed
-Usually involves appearance change
-Reversible
What is a chemical change?
Chemical change:
-One or more new substance/s formed
-Usually involves appearance change
-Detectable energy change (warms up, cools down, makes a sound, produces light)
How can you test to find out if the gas produced is hydrogen?
Place a burning splint next to the mouth of test tube.
A ‘squeaky pop’ as the gas ignites shows that hydrogen is the gas produced in this reaction.
What are exothermic reactions?
Exothermic reactions are chemical reactions which release energy from the chemicals into the surroundings. This energy is usually released as heat, so the surroundings get hotter.
What are endothermic reactions?
An endothermic reaction is a chemical reaction that absorbs energy from its surroundings, typically in the form of heat. This absorption of energy causes the reaction mixture and its surroundings to become cooler.
What is combustion?
Combustion is the scientific word for burning and is a type of chemical reaction. Combustion is the reaction when a substance burns and reacts with oxygen to produce heat and light energy.
What is a fuel?
A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work.
What are examples of being safe when doing chemical reactions?
Wear goggles and gloves
Take caution around spitting chemicals, open flame etc
What is produced when a fuel burns?
Water and Carbon Dioxide
H20 and C02
How do you test for carbon dioxide gas?
By bubbling the gas through limewater. If carbon dioxide is present, the limewater will turn from clear to cloudy/milky white
What is a decomposition reaction?
Decomposition is when one substance breaks down into two or more substances. An example would be thermal decomposition. This requires energy from its surroundings in the form of heat.
Chemical reactions can ____ or ____ __ energy as ___
Chemical reactions can release or take in energy as heat
What is an example of a decomposition reaction?
calcium carbonate –> calcium oxide + carbon dioxide
hydrogen peroxide –> water + oxygen
silver nitrate –> silver + nitrogen dioxide + oxygen
copper carbonate –> copper oxide + carbon dioxide
Always one substance into two or more
Why are decomposition reactions endothermic?
Decomposition reactions require energy from their surroundings. Thermal decomposition is an example where a substance needs to be heated for it to be decomposed.
What colour is copper carbonate and copper oxide?
Copper carbonate= green
Copper oxide= black
What is conservation of mass?
Conservation of mass: mass of reactants= mass of products
copper carbonate
2g
—>
copper oxide
1.2g
+
carbon dioxide
0.8g
Loss of mass in reactions
When one of the products is a gas it can escape into surroundings. This lowers the mass of a reaction.
What is the fire triangle?
The three requirements for a fire to occur. If any of these components are removed the fire will be stopped.
What are the different types of fire extinguishers?
Note- foam spray contains water, wet chemical comes out as a fine mist. Carbon dioxide is dense, prevents oxygen from entering
How can a metal react with an acid?
Acids react with most metals.
When an acid reacts with a metal, the products are a salt and hydrogen.
This is the general word equation for the reaction:metal + acid → salt + hydrogen
How can you make observations and conclusions during an experiment?
To make observations and conclusions in an experiment:
Observe what you see, hear, or measure (e.g. colour change, temperature rise, bubbles).
Record these changes carefully during the experiment.
Conclude by using your observations to explain what happened using scientific knowledge.
