1) Analyse the following equation:
2Na + 2H2O…..2NaOH + H2
Choose the correct alternative:
a) The law of constant composition/law of conservation of mass tells us that when we write equstions like this we should never change the formulae of reactants or products to balance the equation.
b) The law of constant composition /law of conservation of…[Read more]
L. Chitsa started the topic BALANCING CHEMICAL EQUATION(PHSC GRADE 10: 20/07/2020) in the forum PHYSICAL SCIENCE Grade 10 9 months, 3 weeks ago
THE REACTION BETWEEN HYDROGEN AND NITROGEN
Hydrogen + Nitrogen…ammonia
H2 + N2 …….. NH3
The 2s and the 3 are subscripts( written in front but below the H, the N and the NH)
There are 2 N atoms on the left hand side and only one N atom on the right side of the equation arrow.
The number of N atoms can be balanced by multiplying the…[Read more]
L. Chitsa started the topic SURFACE AREA AS A FACTOR AFFECTING REACTION RATE(PHSC GRADE 12: 18/07/2020) in the forum PHYSICAL SCIENCES Grade 12 9 months, 3 weeks ago
-The rate of reaction increases when the surface area of a SOLID reactant is increased.
-The surface area is increased by crushing the solid lumps into a fine powder so that a large surface area is exposed for the reaction.
-If powdered calcium carbonate is reacted with hydtochloric acid, the production of carbon dioxide…[Read more]
L. Chitsa started the topic RELATIONSHIP BETWEEN VOLUME AND TEMPERATURE(PHSC GRADE 11: 17/07/2020) in the forum PHYSICAL SCIENCE Grade 11 9 months, 3 weeks ago
The volume of a fixed mass or amount of gas, at constant pressure, is directly proportional to the absolute temperature of the gas.
Temperature should be in kelvin
V is directly proportional to T
Then V = kT
Then V/T = k
V1/T1 = V2/T2
A group of learners conducted an…[Read more]
L. Chitsa started the topic REPRESENTING CHEMICAL CHANGE(PHSC GRADE 10:17/07/2020) in the forum PHYSICAL SCIENCE Grade 10 9 months, 3 weeks ago
-We use BALANCED chemical equations to represent chemical change.
-To write these equations we use the law of conservation of matter.
-Balanced chemical equations form the basis of the quantitative study of chemistry.
-we always start with a balanced chemical equation before we can carry out any calculations regarding the…[Read more]
L. Chitsa started the topic FACTORS AFFECTING RATE OF REACTION(PHSC GRADE 12: 17/07/2020) in the forum PHYSICAL SCIENCES Grade 12 9 months, 3 weeks ago
A) NATURE OF REACTANTS
-During a chemical reaction, the bonds in the reactant molecules must be broken or weakened first to form free atoms. These free atoms can then rearrange to form new bonds in product molecules.
-The individual properties of the reactants vary a lot, including:
i) state of matter (ii)molecular size (iii)bond type (iv)bond…[Read more]
L. Chitsa started the topic COMPARING GASES, SOLIDS AND LIQUIDS(PHSC GRADE 11: 15/07/2020) 16/07/2020) in the forum PHYSICAL SCIENCE Grade 11 9 months, 3 weeks ago
Refer to the work that i posted on the 19th of june and two or so lessons before that to go through the following activity:
DRAW A TABLE WITH FOUR COLUMNS WITH THE FOLLOWING COLUMN HEADINGS: KINETIC THEORY OF MATTER; SOLIDS; LIQUIDS; GASES.
Fill in the following, in the form of rows now, and under the columb kinetic theory of matter:
L. Chitsa started the topic FURTHER ELABORATION ON LAW OF CONSTANT COMPOSITION(PHSC GRADE 10:16/07/2020) in the forum PHYSICAL SCIENCE Grade 10 9 months, 3 weeks ago
The law of constant composition or CONSTANT PROPORTIONS states that all samples of a given chemical compound have the same elemantal composition. The elements of a pure compound are always present in definite proportion by mass.
For example, any sample of pure water always contains 88.81% oxygen and 11.19% hydrogen.
-we can use the law of…[Read more]
THE LAW OF CONSTANT COMPOSITION
All samples of a given chemical compound have the same elemental composition.
-when elements combine to form compounds they do so in ratios or fixed proportions that are specific to each compound. Water in its natural state, for example, always has hydrogen and oxygen combined in the ratio 2:1 (H2O).…[Read more]
L. Chitsa started the topic CONSERVATION OF MATTER CONTINUED( PHSC GRADE 10: 08/07/2020) in the forum PHYSICAL SCIENCE Grade 10 10 months ago
THE HABER PROCESS
The synthesis(production/formation) of ammonia gas in the Haber process is an important industrial process. Hydrogen gas and nitrogen gas are reacted to form ammonia.
Write the chemical formulae of the following compounds:
a) hydrogen molecule, not hydrogen atom.
b) nitrogen molecule, not atom.
Here is…[Read more]
L. Chitsa started the topic LAW OF CONSERVATION OF MATTER(PHSC GRADE 10: 06/07/2020) in the forum PHYSICAL SCIENCE Grade 10 10 months ago
CONSERVATION OF MATTER
When elements or compounds combine to form new products in chemical reactions, the number of atoms of each element in the reactants is always the same as the number of atoms of that same element in the products. In other words, no matter nor mass is lost when elements or compounds undergo chemical change. This principle is…[Read more]
100% correct Hisack.
The synthesis reaction (a reaction where products are formed, as opposed to decomposition reactions where reactants are chemically broken down) between hydrogen and oxygen to form water, is a chemical change.
Hydrogen gas is first prepared in the laboratory by reacting zinc with hydrochloric acid. The liberated hydrogen gas is then reacted with…[Read more]
L. Chitsa started the topic DECOMPOSITION OF HYDROGEN PEROXIDE(PHSC GRADE 10: 29/06/2020) in the forum PHYSICAL SCIENCE Grade 10 10 months, 1 week ago
Two other examples of chemical change you should know are:
1) Decomposition of hydrogen peroxide to form water and oxygen.
2) The synthesis reaction when hydrogen burns in oxygen to form water.
We will look at these two in the form of experiments.
AIM: To decompose hydrogen peroxide(H2O2)
MATERIALS AND APPARATUS
hydrogen peroxide;…[Read more]
L. Chitsa started the topic APPLICATION OF BOYLE'S LAW(PHSC GRADE 11: 29/06/2020) in the forum PHYSICAL SCIENCE Grade 11 10 months, 1 week ago
Answer the following questions as an activity to test understanding of Boyle’s law:
1) 246 cubic centimeters(246cm3) of air is under a pressure of 108 pascals. Calculate the volume of the air if the pressure is increased by 54 pascals without any change in temperature.
2) How much energy is represented by 100cm3 of a gas at a pressure of 85…[Read more]
-States that ‘The volume of a fixed mass or amount of gas is INVERSELY proportional to the pressure exerted on it provided the temperature remains constant’
-For all gases the product pV gives a constant value (k) at constant temperature.
-We can therefore represent Boyle’s law by:
pV = k.
This product represents a quantity of…[Read more]
We will look at the formation of the compound iron oxide as a chemical change.
AIM:To form/produce iron sulfide.
APPARATUS: boiling tubes, iron filings, yellow sulfur powder, bunsen burner, tripod stand, tongs.
-Draw a diagram of a boiling tube held by a pair of tongs over a bunsen burner flame. The boiling tube( not test…[Read more]
No real gas is ideal, although some come close to ideal behaviour, eg helium.
-One of the obvious ways that real gases differ from ideal gases is that they liquefy when the temperature is low enough and the pressure is high enough.
-At low temperatures, intermolecular forces can form between gas particles, because their kinetic energy is low and…[Read more]
L. Chitsa started the topic METHODS OF SEPARATING MIXTURES( PHYSICAL CHANGES):PHSC GRADE 10(22/06/2020) in the forum PHYSICAL SCIENCE Grade 10 10 months, 2 weeks ago
Remember last term we discussed mixtures, both homogeneous and heterogeneous. We also mentioned that mixtures are physical changes.
Today we will focus on how we can seperate these mixtures.
-Is the method of separating a mixture of a soluble substance(solute) and an insoluble substance, eg a mixture of sand and salt.
Water is…[Read more]
L. Chitsa started the topic ABSOLUTE ZERO TEMPERATURE(PHSC GRADE 11: 22/06/2020) in the forum PHYSICAL SCIENCE Grade 11 10 months, 2 weeks ago
-Not all ideal gas particles have the same energy, and not all of them move at the same rate. The average kinetic energy and speed of particles is determined by the temperature of the gas.
ABSOLUTE ZERO TEMPERATURE
The collisions between ideal gas molecules and between molecules and the sides of the container are perfectly elastic,…[Read more]
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