“Gold melts at a high temperature” is a ___________ property. Explain your reasoning.
Physical because melting is a change in state and doesn’t create a new substance.
The density of zinc is 7.14 g/mL” is a ____________ property. Explain your reasoning.
Physical. Density is determined by comparing mass and volume. This does not change the substance.
Digesting a sandwich is a _______________ change. Explain your reasoning.
chemical because a new substance is formed.
Boiling alcohol is a _______________ change. Explain your reasoning.
Physical. It doesn’t change substances only states when boiled.
Is a cup of tea a pure substance, a mixture, an element or a compound? Explain your reasoning.
It’s a mixture of water, tea leaves and often milk and sugar. Even though they may be dissolved the are still distinct substances and have not bonded.
Is mineral water a homogeneous or heterogeneous mixture?
Is hydrochloric acid, HCl, an element or a compound?
What do we study when we study chemistry?
In a Physical change
No new substance is formed
In a Chemical change
New substances formed
What is an atom
Smallest particle of element.
An element is a substance consisting of atoms which all have the same number of protons - i.e. the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical methods.
What is a molecule?
Two or more atoms bonded together?
What is molecule of an element?
Two or more molecules of same element bonded together.
Define molecule of the compound
Two or more different atoms bonded together.
Define Pure substance
Contains only 1 type of particle.
Two or more substances that are mixed but not bonded.
Define Homogenous mixture (solution)
No individual substances identifiable. Equal distribution of particles ex coffee
Define heterogeneous mixture
Unequal distribution of particles
More than one phase.
Ex salad, oil and water
Element, compound or mixture? Why?
Sugar dissolved in water (H2O)
Homogenous mixture. Because it is equal distribution of particles and 2 or more elements mixed together but not bonded.
Element, compound or mixture? Why?
Element since it is found on the Periodic Table and only has one type of atom.
Element, compound or mixture? Why?
Compound because 2 or more different atoms are bonded together.
What is the location, mass and charge of
Proton in nucleus 1u mass. Positive charge
Neutron in nucleus 1u mass. Neutral charge.
Electron little to no mass, negative charge
What are isotopes?
Atoms of the same element which has the same atomic number but different mass number(different number of neutrons)
What is the modern atomic theory?
Matter is made up of atoms
Atoms are made of subatomic particles called protons neutrons and electrons.
Atoms of one kind of element cannot be change by chemical reaction into another atom.
Atoms of different elements combine to form compounds.
What is a radioisotope?
Isotope that emits radiation. Radioisotopes have important uses in medical diagnosis, treatment, and research.
RADIOISOTOPES are unstable by nature due to several things going on in the nucleus. They are isotopes by definition, but they have unusually high levels of unstable energy in the nucleus and thus emit this energy in the form of radiation.
They may undergo various types of radioactive decay (alpha, beta or gamma) or they may emit ionizing radiation, all in an effort to expel energy and become more stable.
By definition, “radioisotopes” are inherently unstable, whereas “isotopes” may be either stable or unstable… but usually refer to stable isotopes.
What is half life?
The time taken for 1/2 of the atoms in a sample to decay.
Compare a nuclear reaction with a chemical reaction.
Nuclear reaction - nuclei changes, new atom formed,lots of energy involved, # of protons change
Chemical - nuclei stays the same, no new atoms created or destroyed,less energy, # of electrons changed.
What are the three uses of medical isotopes
Treat, diagnose, sterilise
Factors to consider when using medical radioisotopes
Size of dose. Tissue type Rate of decay External internal Penetration power
Characteristics of the periodic table
118 elements 18 groups Metalloids 7 periods Non metals and metals Transition elements 3-12 Halogen group 17 Group 18 noble gasses Main group is 1-2, 13-18 Group number tells us valence electrons Elements arranged according to increasing atomic number.
Properties of metals
Conduct electricity Flexible High melting point Lustre Reaction with HCl Density
What is the quick way of knowing how many valence electrons an atom has
If the atom is in group 1-2 it’s group number is the number of valence
In groups 13-18 you can subtract 10 from group number to determine valence electrons
What is the quick way of knowing the # of energy levels
It corresponds to period number
Why do the members of group have the same chemical properties?
Same number of valence electrons.
Why do Li or Na react in a similar way.
Same group and have 1 valence electron
Name the subatomic particle that has the same mass as a neutron.
How many protons, electrons and neutrons in an atom of carbon-14?
How many protons and neutrons in the nucleus of the isotope Strontium- 88
How do alpha, beta and gamma radioactive decay differ in their penetration power?
Alpha and beta cannot penetrate skin, gamma can.
How many valence electrons does oxygen have?
Oxygen is in group 16 so it has 6 valence electrons.
Why do the members of a group have the same chemical properties?
They have the same number of valence electrons, which determine bonding.
Which has the larger atomic radius, magnesium or phosphorus? Why?
Mg because they both have 3 energy levels, but P has a more protons in its nucleus, so the P atom is smaller.
Which atom will lose electrons more easily, lithium or sodium? Explain.
Na because it has 3 energy levels and Li has only 2, so Na’s valenc electrons are held less tightly.
Which atom will gain electrons more easily, chlorine or bromine? Explain.
Cl because it’s smaller and has a greater pull on electrons
Use the electronegativity difference to determine whether the Mg – Cl bond is ionic or covalent.
3.16 - 1.31 = 1.85 > 1.7 so it’s ionic
What is the atomic number of bromine? What does it mean?
Atomic number is 35. It means that it has 35 protons.
Define mass number. If bromine’s mass number is 80, what does this mean?
Total number of protons and neutrons.Br has a total of 80 protons and neutrons in its nucleus.
How is an anion formed?
An atom gains electrons to form a negative ion.
How is a cation formed?
An atom loses electrons to form a positive ion
What are the transition elements?
What are Metalloids?
Elements that have properties of both metals and non metals.
As you move down the periodic table the atomic size _____
Why does the atomic size decrease as you cross to the right of the periodic table?
The greater the number of protons, the greater the pull on the electrons in the electron cloud reducing the size of the atom
Why do Cs and Fr react in a similar way? Which is the most reactive? Why?
They are both in group 1 and have 1 valence electron.
Fr is more reactive because it can easily lose its one electron. (Fr has 7 energy levels, while Cs has 6. This means Fr valence, electron is further away from the nucleus and gets less pull. This makes Fr lose its valence easier than Cs.)
Why do Cl and Br react in a similar way? Which is most reactive and why?
Cl and Br are both in group 17 and have 7 valence electrons.
Cl is more reactive because Cl has fewer energy levels. Fewer energy levels = greater pull.