Chapter 1 Flashcards
What is matter? What about when is there is no matter?
Matter is defined as any substance that has mass and volume (takes up space). It makes up the observable universe and together with energy (light, sounds, etc) forms the basis of all objective phenomena. A space devoid of all matter is called a vacuum.
What is matter composed of?
Matter is composed of elementary particles known as quarks and leptons (the class of elementary particles that includes electrons). Quarks combine into protons and neutrons and, along with electrons, form atoms of the elements of the periodic table.
What is a chemical? What is a compound?
A chemical is anything made of matter. A compound is a substance made of two or more atoms.
What is a model? Which do chemists use and what are their comparative benefits?
A way or a method of representing a structure or idea. Chemists use space-filling model (useful for seeing relative size of atoms) and ball-and-stick model (for seeing relative position of the centres of constituent atoms).
Is a water molecule straight or bent?
Water molecule is bent! The atoms are not connected in a straight line.
What is risk?
- a situation involving exposure to danger.
- the possibility that something unpleasant or unwelcome will happen.
- a person or thing regarded as a threat or likely source of danger.
What is hazard?
Hazards are components of risk: they are defined as the potential to cause harm and can be an object or a situation that poses a level of threat to life, health, property or environment.
What is control measure?
An action taken to reduce the risk associated with a hazard.
Colour codes for S, Cl, C, O, N, H?
Yellow green black red navy white
Most common elements in human body. How much is water? Third most abundant element in universe by mass.
O oxygen 65.0
C carbon 18.0
H hydrogen 10.0
N nitrogen 3.0
Ca calcium 1.5
P phosphorus 1.2
K potassium 0.4
S sulfur 0.25
Cl chlorine 0.20
Na sodium 0.20
water 70%
Oxygen!!
Size of raindrop in the cloud and as it falls to earth. How many times can you divide the average raindrop before it is not water anymore?
0.01mm (or 10 to the power of -5 metres) . Raindrops coalesce to 2mm as they fall to earth. You can divide an average raindrop 67 and it is still water. After that, you’re splitting the molecule into constituent parts.
Visualise atom v droplet.
One way of trying to visualise the size of an atom within a water droplet is to imagine the water droplet magnified to the size of the Earth; an atom would be roughly the size of a tennis ball.
How to keep a scientific notebook.
Use permanently bound notebooks and number the pages. Never remove pages from the notebook. Loose-leaf should be avoided and any attachments should be stapled.
The notebook should be hard-backed, since this offers more protection against spillages and also adds to its durability in hostile environments.
Do sign and date each entry.
Entries should be made in permanent ink and in chronological order. Avoid using pencils.
Record all the observations that you make during the course of the experiment. Remember to include the units of measurement. Don’t be embarrassed about writing down mistakes or accidents.
Include raw data and also interpreted results, making clear which is which.
Detecting electrons.
Does the strength of the running stream of water affect your results?
Does the size of the object used (comb or inflated balloon) have an effect on your observations?
Is the weather affecting your experiment?
State relative mass of electron versus neutron and proton.
The mass of a neutron is almost the same as the mass of a proton. Both the proton and the neutron have a relative mass of 1. The mass of a proton (or a neutron) is nearly 1840 times that of an electron.
static electricity
form of electricity resulting from the imbalance between positive and negative charges within a material that occurs when electrons (the negatively charged particles in an atom) move from one material to another. If the electron-receiving material is either isolated or not an electrical conductor, it tends to hold on to the electrons, resulting in a buildup of electric charge. Since this charge is not moving, it is referred to as static electricity. When conditions allow the built-up charge to flow, the surplus of static electricity is discharged, and it becomes current electricity.
covalent bonding
ionic bonding
Polarisation
The term polarisation is commonly used to describe this partial separation of charge and can be represented as δ− (delta minus) and δ+ (delta plus). The Greek letter delta δ is used to represent ‘a little bit’, since it amounts to less than one electron’s worth. In Figure 1.12, the oxygen atom has a partial negative charge δ− and the hydrogen atom has a partial positive charge δ+. This is known as a polar bond. Covalent bonds between two different elements will always present some polarisation.
Is the covalent bond between two atoms of the same element polar or non-polar?
The covalent bond between two atoms of the same element is non-polar because both atoms attract the shared electrons to the same extent.
In which situation can a molecule with polar bonds still be non-polar?
A molecule can have polar bonds and still be non-polar if these bonds are evenly distributed (e.g. in a symmetrical linear molecule).
What is a hydrogen bond?
Due to its bent geometry, water is a polar molecule and this causes the positive hydrogen of one water molecule to be attracted to the negative oxygen of another water molecule (Figure 1.13). This attraction is called a hydrogen bond.
Name participants in a chemical reaction, the action they take, and the need for the equation to be in harmony. What else beyond element name do you need to follow the elements in parenthesis?
Reactants GO TO product. Chemical equation must be balanced. Reactant state (l, g, s)
Reading graphs.
For reading graphs, locate a quantity on one axis (for example the x-axis) and draw a line vertically from the selected quantity until it meets the curve. You can then draw a line horizontally from the intersection to meet the vertical axis (y-axis) and read off the corresponding quantity.
The SI base unit of mass?
KILOgram!!
Creating tables.
A table is a set of data organised in rows and columns.
A table must have a meaningful title explaining the data contained.
Every column should have a meaningful heading explaining what data are in that column.
Units are generally given only in the column heading. When you are recording results in the table rows, you only have to write down the numbers.
The preferred OU notation for column headings is ‘Column heading/unit’, for example ‘Mass/g’. The ‘/g’ in the column heading indicates that every entry in that column has been divided by ‘g’. Thus, if you were to take one value out of the table, you would need to multiply it by ‘g’ in order to get the full value (e.g. the mass of water is 100 g). You may come across another convention in other text books where the units are given in brackets, for example ‘Mass (g)’. This simply indicates that all the values in that column should be assumed to have the units of g.
Traits differentiating ice, liquid water and water vapour.
Shape and volume (fixed and not)
Weight v mass.
In scientific use, the term weight means the downward pull on the mass of an object due to gravity, e.g. the downward pull that makes an apple fall to the ground.
? Variables: dependent, independent and controlled.
Lowest and highest recorded air temperature. Temp above which N goes from liquid to gas. Temp at which water boils at the top of Everest.
The lowest air temperature ever recorded on Earth is -89.2°C (-128.6°F). This temperature was recorded on July 21, 1983, at the Russian (formerly Soviet) Antarctic station Vostok.
The highest recorded air temperature on Earth occurred on July 10, 1913, at Furnace Creek Ranch in Death Valley, United States, where the temperature reached 56.7°C (134.1°F)
- 196 deg C
71 deg C
Atmospheric pressure. In what region are most atmospheric molecules located?
Atmospheric pressure is the pressure due to the weight of the air. At higher altitudes the number of molecules of gases decreases – approximately half of the molecules in the atmosphere are contained within the first 6 km above the Earth’s surface.
Reading a graph.
To find the atmospheric pressure corresponding to an altitude of 9 km you need to find the point on the vertical axis representing this altitude. You could draw a line horizontally from the selected altitude until it meets the curve. You could then draw a line vertically from that intersection to meet the horizontal axis and read off the corresponding atmospheric pressure. You should find that the atmospheric pressure corresponding to an altitude of 9 km is 29 kPa (i.e. 29 000 Pa).
Atm pressure at sea and 9km
Atmospheric pressure at sea level (corresponding to an altitude of 0 km) is approximately 100 kPa. In fact, as we said in the previous section, the atmospheric pressure at sea level is 101 325 Pa.
At 9km alt, it is 29 kPa.
Triple point of water.
The triple point is the temperature and pressure at which the three phases (gas, solid and liquid) of water coexist. For water, the triple point occurs at a temperature just above 0 °C and at a very low pressure. Watch Video 2.2 which shows liquid water and ice in a glass dish, surrounded by water vapour, existing simultaneously in a controlled chamber under triple point conditions.
How to boil water at sea level at under 100 deg C?
Syringe experiment!
Can you make a hole in water? Describe movement of molecules depending on phase of water.
Looking in detail at the molecular structure of ice you can see large hexagonal channels which could be deemed as empty spaces or ‘microscopic holes’. This orderly structure with water molecules locked into place by hydrogen bonds will collapse only when ice melts. In liquid water the molecules retain some structural order but are closer than in ice and have some limited movement.
In water vapour the water molecules are free to move in all directions.
Water density variation depending on phase. Other liquid density depending on phase. Explanation for this.
The explanation as to why water behaves differently is because, on freezing, the space between the water molecules increases (as we observed in Practical 3), making ice less dense than water. Most other solids (such as olive oil cubes) have less space between molecules than do their corresponding liquids; unlike water, most liquids tend to shrink after freezing and this makes them more dense in their solid form than in their liquid form.
Why is water denser than ice? What is density of water, ice, Dead Sea?
The water molecules in ice are more ordered and spaced further apart than the molecules in liquid water. This means there is more empty space between the molecules in ice and so a smaller number of water molecules will fit into the same volume.
1,000 - 917 - 1,200 kg/m3
What is the ion called when chlorine gains an electron?
By analogy with the sodium ion, the chloride ion is written as Cl−. Note the different term – a chlorine atom becomes a chloride ion in this case
How are sodium and chloride ions arranged in a salt molecule?
regular, internal structure of NaCl in which its ions arrange themselves in a cubic array.
What is a solution and what are its component parts?
In chemistry, a solution is a homogeneous (uniform) mixture in which a substance (known as the solute) dissolves in another substance (known as the solvent). A solvent is usually a liquid, but it could also be a gas. Water is an excellent solvent and it is also called the universal solvent.
Is water a polar or non-polar solvent? And oil? What solute dissolves in what type of solvent?
Water is polar. Oil is non-polar, it does not have a separation of charge. “Like prefers like to dissolve.”
What do you call substances that don’t mix?
Immiscible
What is the formula of sucrose? Is it polar?
Sucrose is a polar molecule where the oxygen atoms have a slight negative charge and the hydrogen atoms have a slight positive charge. As we discussed in Section 1.8, different atoms will attract electrons to different extents. Oxygen and hydrogen atoms don’t share electrons equally and the bonding between them is known as a polar bond. To create a polar molecule, the polar bonds should collectively produce a separation of charge, or polarisation. The sucrose molecule is not symmetric so the polar bonds are not balanced across the molecule, and hence there is some separation of charge.
Why does sugar and salt dissolve in water?
The polar water molecules attract the negative and positive areas on the sucrose molecule making the sucrose molecules separate from each other and dissolve in water. Same with salt where the (neg) oxygen molecules in the water “shepherd away” the (pos) sodium ions.
What is the physical explanation for salts dissolving in water?
In order for salts to dissolve in water, the strong attractive forces between ions have to be replaced by other equally strong forces. Hydrogen bonds are weaker than the attraction between two ions in a crystal structure, but many hydrogen bonds together exert a considerable force which can exceed the strength of the ionic attraction.
What is solubility and what varies it, e.g.?
The amount of substance that can be dissolved in water. Temperature (except for NaCl).
What are molecular ions?
Not all ions are formed from a single charged atom. Molecular ions are larger charge particles consisting of a group of atoms that has lost or gained some electrons. For example, potassium nitrate (KNO3) is an ionic compound formed by ionic bonding between a positively charged potassium ion (K+) and a negatively charged molecular ion (nitrate ion, NO3-).
Water density anomaly. Remember experiment with red and blue water.
For most pure liquids density decreases with increasing temperature. However, for water, density increases with increasing temperature up to 4 °C. After 4 °C water behaves like other liquids. Liquid water, therefore, has a maximum value for its density.
Heating liquid water above 4 °C causes molecules to speed up and spread slightly apart, occupying a larger volume. This will result in a decrease of its density.
Temp variation in a pond in summer and winter.
The temperature changes at different depths in the pond. The warm air warms the surface layer of water in a pond. Deeper layers of water are colder.
The cold air cools the surface layer of pond water. This cooler water sinks lower in the pond because it has a higher density than the water below it.
When the air cools the surface water to about 4 °C, this water has its maximum value of density and drops to the bottom of the pond and forms a layer there. As the water at 4 °C drops to the bottom of the pond, it displaces the water there which rises nearer the surface and is cooled.
As the air cools to below 0 °C, the surface layer of water freezes at 0 °C and becomes ice as shown in Figure 3.8. The ice formed floats on the surface because ice is less dense than water and it forms an insulating layer on the surface of the pond. The layer of ice at 0 °C cools the layer of water below it to just above 0 °C. The layer of water at 4 °C stays at the bottom of the pond because it is the densest layer.
The importance of floating ice and of the water density anomaly.
If water behaved in the same way as olive oil (as we observed in Video 3.1), then in winter ice forming on the surface of water bodies such as ponds and lakes would immediately sink to the bottom rather than floating on the surface, and the ponds and lakes would freeze from the bottom up.
Floating ice forms a thermally insulating layer that slows down the rate at which more ice can form. The ice on the top of a water body absorbs and reflects sunlight and allows for rapid thawing.
If ice sank to the bottom, many ponds and lakes would freeze completely in the winter, killing all the fish. In spring, the uppermost part of the ice in contact with the warmer spring air would melt first. This layer of water on top of the ice would stop the warmer air reaching the ice below and it would thus inhibit melting at the bottom of the pond or lake.
As well as the fact that ice floats, the discovery that water has a maximum value for its density at about 4 °C also has important implications for aquatic life. We have already noticed that ponds do not freeze solid at 0 °C. This is due to the two properties of water acting in harmony.
Dependent v independent variable.
The independent variable is the thing you change (vary) during an experiment. The dependent variable is the change that you observe as a result during an experiment.
Hypothesis. Null Hypothesis.
My hypothesis (for uploading)
is that by dissolving progressively larger amounts of salt into tap water, the density of the solution will increase and therefore a raw egg will go from being fully submerged in plain water to being able to at least partially float in saturated saline solution. The independent variable is mass of sodium chloride dissolved in water and the dependent variable is volume of egg submerged in saline solution.
NB Drop of Surgical spirit on plate with thin layer of water experiment.
What’s the attraction between two water molecules?
Hydrogen bonding.
What is surface tension? Are air molecules polar?
However, the water molecules right at the water–air surface have no water molecules above them pulling them upwards. The air molecules above the surface are not polar. So the overall effect on these surface water molecules is that they are both pulled downwards towards the deeper liquid and sideways, which results in a tight surface layer. This effect is called surface tension and it gives the water the appearance of a skin on the surface of the water.
Why are dew drops spherical?
when water droplets are formed on a leaf, they are nearly spherical in shape. This is because the water molecules are strongly attracted to each other and only very weakly attracted to the leaf and the air.
What is the meniscus? How many types are there?
You may have observed that the upper surface of the liquid is curved; this curved surface is called the meniscus. In the case of water in a glass container, you can observe a concave (curved in) meniscus. This is due to the water molecules being more strongly attracted to the glass than to each other, causing the liquid to climb the walls of the container. However, you can also observe a convex (curved out) meniscus for other liquids and surfaces (e.g. mercury in a glass tube).
Why does my pond skater float?
An object is made to stay on the surface if it is placed on the surface of the water so gently that it does not break the attraction of adjacent water molecules, thus preserving the tense ‘skin’ on the surface of the water. The water acts like an elastic material and stretches as objects rest on its surface.
Why do objects sink?
The objects sink because their density is higher than the density of water.
What gases is air comprised of?
Air contains nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2) and very small amounts of other gases.
Coal-burning power plants heat water to produce steam which turns turbines to make electricity. After using the water, it is cooled before being returned to rivers or lakes. Why is it important to cool the water before returning it to the rivers or lakes?
If the water is returned to the rivers and lakes while it is still heated, it would raise the temperature of the rivers and lakes and allow the dissolved gases essential for the aquatic life to escape.
What is a whirlpool?
A whirlpool is a body of water in circular motion that is produced when opposing currents meet. A whirlpool in an ocean can be caused by the tides. Most whirlpools are not very powerful.
What is a vortex?
The proper term for any whirlpool that has at its centre a downdraft (i.e. a small-scale current of sinking air) is a vortex.
What are eddies?
On a larger scale, we can use satellites to see whirlpools (or ‘eddies’) in the oceans. These oceanic eddies are responsible for the transport of large amounts of water, heat and debris between different areas of the planet and may have implications for climate change.
What is water stress and how many people will it affect by 2050?
It has been estimated that water stress will affect around 50% of the world’s population by 2050. A state of water stress is when there is less than 1700 m3 of water per person per year. Water stress is controlled by a number of factors, including supply and demand, water sources and water quality. It is therefore possible for an area to be in a state of water stress even if there is plenty of available water; for example, if the water quality is poor.
What are the steps involved in the scientific method?
The scientific method is a process by which scientists ask and answer scientific questions.
A hypothesis is an educated guess about how something works.
‘Water is already full of ‘holes’, but they are so tiny that you can’t see them.’
‘I would just freeze the water first and then chip or melt a hole in the ice.’
‘Any object you drop in water will make a hole in it, even if the object floats and only makes a small hole.’
‘What do you mean by a hole in water?’
‘I would blow bubbles of air through the water.’
‘I would create a whirlpool.’
A simple model used to picture atoms consists of a central atomic nucleus where protons and neutrons can be found with electrons moving around this nucleus in shells. These shells are at different distances from the nucleus and have empty space between them.
When water freezes the water molecules are locked in place by hydrogen bonds in an orderly structure with hexagonal channels. Making a hole in a solid looks like an easy solution.
In liquid water, hydrogen bonds are constantly forming and breaking. Objects are able to push aside water molecules to create space for themselves. The density of the object determines whether the object floats or sinks in water.
This is a good answer. Before scientists start any experiment, a clear question should be asked. The experiment can be then designed properly to test the question.
Molecules of gases can dissolve in water. In fact dissolved oxygen in water is essential for aquatic life. When heating water, small bubbles of dissolved gases will start forming at temperatures below 100 °C and when water gets hotter water vapour bubbles moving through the liquid will appear.
There are examples in nature of huge holes in oceans that are caused by the tides.
