Graphing skills Flashcards
What is a graph?
A graph is a diagram that shows the relationship between 2 (or more) things.
How to draw a graph?
Remember to explain each of the details and definition.
Step 1:
Draw the x-axis (horizontal line) and the y-axis (vertical line). For experiments, the x-axis usually represents the INDEPENDENT variable while the y-axis usually represents the DEPENDENT variable. [The independent variable is what the scientist manipulate e.g. mass of fertilizer added. The dependent variable is what the scientist measure e.g. height of the plant.]
Step 2:
Label the axes. Include the units (if applicable).
Step 3:
Select a suitable scale for each axis. Select evenly spaced intervals that include all your data. Be sure that the smallest interval of your graph paper is a whole number - do not choose odd intervals e.g. 10 small squares represent interval of 3. The graph should occupy about half the graph paper.
Step 4:
Plot your data on the graph - use a small ‘x’ for each data point.
Step 5:
Either join the data points using straight lines or draw a line of best fit.
Note: a line of best fit is a straight line (but can also be a curve) drawn through the centre of a group of data points. It usually passes through a few data points but also have some data points above and below it. The number of data points above and below it should be about the same.
Note: at this level in Chemistry, most graphs would pass through the origin (point 0.0).
NOTE: When comparing gradient (or slope), use the terms __________ or ____. It is not advisable to say ________ or _________, since gradient can have a _____ value.
NOTE: When comparing gradient (or slope), use the terms “steeper” or “less steep”. It is not advisable to say “greater” or “smaller”, since gradient can have a negative value.
For both the x-axis and y-axis, _______ and ________ must be written.
For both the x-axis and y-axis, labels and units must be written.
The graph should take up at least _________ of the graph grid or paper.
The graph should take up at least half the size of the graph grid or paper.
What is the chemical equation of the decomposition of hydrogen peroxide?
The balanced chemical equation for the decomposition of hydrogen peroxide
2H2O2 –> 2H2O + O2
Group the following substances into these groups.
Substances:
air, petrol, silicon, salt water, hydrogen, bronze, calcium, diamond, gold
Groups:
(a) Pure substances–> Elements–> metals
(b) Pure substances–> Elements–> Non-metals
(c) Mixtures–> Element + Element
(d) Mixtures–> Elements + compounds
(e) Mixtures–> A mixture of compounds.
(a) Calcium, gold
(b) Hydrogen, diamond, silicon
(c) Bronze
(d) Air
(e) Petrol, saltwater
Magnesium oxide and carbon dioxide cannot be put into any of the five groups because they are compounds. Suggest 2 categories of compounds so that the magnesium oxide and carbon dioxide can be included in the scheme.
Either of these answers are accepted
The first category is a compound formed by chemically combining a metallic element with a non-metallic element and the second category is a compound formed by chemically combining 2 or more non-metallic element.
or
The 2 categories of compounds are ionic compounds (e.g. magnesium oxide) and covalent compounds (e.g. CO2)
What is the approximate percentage composition of dry air (by volume)?
78% Nitrogen
21% Oxygen
0.9% Argon
0.04% Carbon dioxide
Why is the majority of the composition of air nitrogen while oxygen is only 21%?
The majority of the composition of air is nitrogen (78%) because nitrogen molecules (N₂) are chemically inert and do not readily react with other gases or substances in the atmosphere. Nitrogen’s stable diatomic molecular form allows it to remain abundant in the air over time. In contrast, oxygen (O₂) makes up about 21% of the atmosphere because oxygen is highly reactive and is involved in processes such as combustion and respiration, leading to its lower concentration compared to nitrogen. Additionally, oxygen’s higher reactivity means it is consumed more quickly than nitrogen, maintaining its percentage in the atmosphere at a stable but lower level. The balance between nitrogen’s stability and oxygen’s reactivity results in nitrogen being the dominant component of air.
What is an element?
Elements comprises particles that contain only one type of atom.
What is a compound?
There is only one type of particle, and each particle is made up of different atoms that are chemically bonded in a fixed ratio.
What is a mixture?
The particles may be made up of one type of atom or different types of atoms, and the particles are distinct from each other.
